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  • 1.
    Andersson, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Berga, Mercè
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    The spatial structure of bacterial communities is influenced by historical environmental conditions2014In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 95, no 5, p. 1134-1140Article in journal (Refereed)
    Abstract [en]

    The spatial structure of ecological communities, including that of bacteria, is often influenced by species sorting by contemporary environmental conditions. Moreover, historical processes, i.e., ecological and evolutionary events that have occurred at some point in the past, such as dispersal limitation, drift, priority effects, or selection by past environmental conditions, can be important, but are generally investigated much less. Here, we conducted a field study using 16 rock pools, where we specifically compared the importance of past vs. contemporary environmental conditions for bacterial community structure by correlating present differences in bacterial community composition among pools to environmental conditions measured on the same day, as well as to those measured 2, 4, 6, and 8 d earlier. The results prove that selection by past environmental conditions exists, since we were able to show that bacterial communities are, to a greater extent, an imprint of past compared to contemporary environmental conditions. We suggest that this is the result of a combination of different mechanisms, including priority effects that cause rapid adaptation to new environmental conditions of taxa that have been initially selected by past environmental conditions, and slower rates of turnover in community composition compared to environmental conditions.

  • 2. Baker, Kate L.
    et al.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Nicol, Graeme W.
    Ricketts, Dean
    Killham, Kenneth S.
    Campell, Colin D.
    Prosser, James I.
    Environmental and spatial characterisation of microbial community composition to inform sampling strategies2009In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 41, no 11, p. 2292-2298Article in journal (Refereed)
    Abstract [en]

    Soil physicochemical properties and microbial communities are highly heterogeneous and vary widely over spatial scales, necessitating careful consideration of sampling strategies to provide representative and reproducible soil samples across field sites. To achieve this, the study aimed to establish appropriate sampling methodology and to determine links between the variability of parameters, utilising two sampling strategies. The first (design 1) involved extracting 25 cores from random locations throughout the field and pooling them into five sets of five cores. The second (design 2) involved a further 25 cores within five 1 m2 sub-plots. Sub-samples from each sub-plot were pooled in order to determine between and within sub-plot variability. All samples were analysed independently and as pooled sub-samples. Results indicate that pooling spatially separated samples significantly reduced the variability in pH, compared to individual samples. Pooling samples from a small area resulted in lower within sub-plot variability than between sub-plots for pH and bacterial community composition assessed by terminal-restriction fragment length polymorphism analysis. Following multivariate statistical analysis, a large amount of variation in community composition was explained by soil pH, which is remarkable given the relatively small size of the sampling area and minor differences in pH. Moisture content was also important in determining bacterial communities in the random design (design 1). In the 1 m2 sub-plot design (design 2), the spatial location of the plots explained a large degree of the variation in bacterial community composition between plots, which was due to spatial autocorrelation of pH and possible additional environmental parameters. This study emphasises the importance of sampling design for obtaining representative samples from soil.

  • 3.
    Berga, Mercè
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Biological Oceanography, Leibniz Institute for Baltic Sea Research Warnemünde, Germany.
    Zha, Yinghua
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Székely, Anna J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Functional and Compositional Stability of Bacterial Metacommunities in Response to Salinity Changes2017In: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 8, article id 948Article in journal (Refereed)
    Abstract [en]

    Disturbances and environmental change are important factors determining the diversity,composition, and functioning of communities. However, knowledge about how naturalbacterial communities are affected by such perturbations is still sparse. We performeda whole ecosystem manipulation experiment with freshwater rock pools where weapplied salinity disturbances of different intensities. The aim was to test how thecompositional and functional resistance and resilience of bacterial communities,alpha- and beta-diversity and the relative importance of stochastic and deterministiccommunity assembly processes changed along a disturbance intensity gradient.We found that bacterial communities were functionally resistant to all salinity levels (3, 6, and 12 psu) and compositionally resistant to a salinity increase to 3 psu andresilient to increases of 6 and 12 psu. Increasing salinities had no effect on local richnessand evenness, beta-diversity and the proportion of deterministically vs. stochasticallyassembled communities. Our results show a high functional and compositional stabilityof bacterial communities to salinity changes of different intensities both at localand regional scales, which possibly reflects long-term adaptation to environmentalconditions in the study system.

  • 4.
    Berga, Mercè
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Östman, Örjan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Combined effects of zooplankton grazing and dispersal on the diversity and assembly mechanisms of bacterial metacommunities2015In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 17, no 7, p. 2275-2287Article in journal (Refereed)
    Abstract [en]

    Effects of dispersal and the presence of predators on diversity, assembly and functioning of bacterial communities are well studied in isolation. In reality, however, dispersal and trophic interactions act simultaneously and can therefore have combined effects, which are poorly investigated. We performed an experiment with aquatic metacommunities consisting of three environmentally different patches and manipulated dispersal rates among them as well as the presence or absence of the keystone species Daphnia magnaDaphnia magnareduced both local and regional diversity, whereas dispersal increased local diversity but decreased beta-diversity having no net effect on regional diversity. Dispersal modified the assembly mechanisms of bacterial communities by increasing the degree of determinism. Additionally, the combination of the D. magna and dispersal increased the importance of deterministic processes, presumably because predator-tolerant taxa were spread in the metacommunity via dispersal. Moreover, the presence of D. magna affected community composition, increased community respiration rates but did not affect bacterial production or abundance, whereas dispersal slightly increased bacterial production. In conclusion, our study suggests that predation by a keystone species such as D. magna and dispersal additively influence bacterial diversity, assembly processes and ecosystem functioning.

  • 5.
    Berga, Mercé
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Székely, Anna J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Effects of Disturbance Intensity and Frequency on Bacterial Community Composition and Function2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 5, p. e36959-Article in journal (Refereed)
    Abstract [en]

    Disturbances influence community structure and ecosystem functioning. Bacteria are key players in ecosystems and it is therefore crucial to understand the effect of disturbances on bacterial communities and how they respond to them, both compositionally and functionally. The main aim of this study was to test the effect of differences in disturbance strength on bacterial communities. For this, we implemented two independent short-term experiments with dialysis bags containing natural bacterial communities, which were transplanted between ambient and 'disturbed' incubation tanks, manipulating either the intensity or the frequency of a salinity disturbance. We followed changes in community composition by terminal restriction fragment analysis (T-RFLP) and measured various community functions (bacterial production, carbon substrate utilization profiles and rates) directly after and after a short period of recovery under ambient conditions. Increases in disturbance strength resulted in gradually stronger changes in bacterial community composition and functions. In the disturbance intensity experiment, the sensitivity to the disturbance and the ability of recovery differed between different functions. In the disturbance frequency experiment, effects on the different functions were more consistent and recovery was not observed. Moreover, in case of the intensity experiment, there was also a time lag in the responses of community composition and functions, with functional responses being faster than compositional ones. To summarize, our study shows that disturbance strength has the potential to change the functional performance and composition of bacterial communities. It further highlights that the overall effects, rates of recovery and the degree of congruence in the response patterns of community composition and functioning along disturbance gradients depend on the type of function and the character of the disturbance.

  • 6. Besemer, Katharina
    et al.
    Peter, Hannes
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Logue, Jürg B.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Battin, Tom J.
    Unraveling assembly of stream biofilm communities2012In: The ISME Journal: multidisciplinary journal of microbial ecology, ISSN 1751-7362, Vol. 6, no 8, p. 1459-1468Article in journal (Refereed)
    Abstract [en]

    Microbial biofilms assemble from cells that attach to a surface, where they develop into matrix-enclosed communities. Mechanistic insights into community assembly are crucial to better understand the functioning of natural biofilms, which drive key ecosystem processes in numerous aquatic habitats. We studied the role of the suspended microbial community as the source of the biofilm community in three streams using terminal-restriction fragment length polymorphism and 454 pyrosequencing of the 16S ribosomal RNA (rRNA) and the 16S rRNA gene (as a measure for the active and the bulk community, respectively). Diversity was consistently lower in the biofilm communities than in the suspended stream water communities. We propose that the higher diversity in the suspended communities is supported by continuous inflow from various sources within the catchment. Community composition clearly differed between biofilms and suspended communities, whereas biofilm communities were similar in all three streams. This suggests that biofilm assembly did not simply reflect differences in the source communities, but that certain microbial groups from the source community proliferate in the biofilm. We compared the biofilm communities with random samples of the respective community suspended in the stream water. This analysis confirmed that stochastic dispersal from the source community was unlikely to shape the observed community composition of the biofilms, in support of species sorting as a major biofilm assembly mechanism. Bulk and active populations generated comparable patterns of community composition in the biofilms and the suspended communities, which suggests similar assembly controls on these populations.

  • 7.
    Comte, Jerome
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lindström, Eva
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Eiler, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Can marine bacteria be recruited from freshwater sources and the air?2014In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 8, no 12, p. 2423-2430Article in journal (Refereed)
    Abstract [en]

    There is now clear evidence that microorganisms present biogeographic patterns, yet the processes that create and maintain them are still not well understood. In particular, the contribution of dispersal and its exact impact on local community composition is still unclear. For example, dispersing cells may not thrive in recipient environments, but may still remain part of the local species pool. Here, we experimentally tested if marine bacteria can be retrieved from freshwater communities (pelagic and sediment) and the atmosphere by exposing bacteria from three lakes, that differ in their proximity to the Norwegian Sea, to marine conditions. We found that the percentage of freshwater taxa decreased with increasing salinities, whereas marine taxa increased along the same gradient. Our results further showed that this increase was stronger for lake and sediment compared with air communities. Further, significant increases in the average niche breadth of taxa were found for all sources, and in particular lake water and sediment communities, at higher salinities. Our results therefore suggests that marine taxa can readily grow from freshwater sources, but that the response was likely driven by the growth of habitat generalists that are typically found in marine systems. Finally, there was a greater proportion of marine taxa found in communities originating from the lake closest to the Norwegian Sea. In summary, this study shows that the interplay between bacterial dispersal limitation and dispersal from internal and external sources may have an important role for community recovery in response to environmental change.

  • 8.
    Comte, Jérôme
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Environm & Climate Change Canada, Canada Ctr Inland Waters, Watershed Hydrol & Ecol Res Div, Water Sci & Technol, Burlington, ON L7S 1A1, Canada..
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Berga, Mercè
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Leibniz Inst Balt Sea Res, Biol Oceanog, Seestr 15, D-18119 Rostock, Germany..
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Contribution of different dispersal sources to the metabolic response of lake bacterioplankton following a salinity change2017In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 19, no 1, p. 251-260Article in journal (Refereed)
    Abstract [en]

    Dispersal can modify how bacterial community composition (BCC) changes in response to environmental perturbations, yet knowledge about the functional consequences of dispersal is limited. Here we hypothesize that changes in bacterial community production in response to a salinity disturbance depend on the possibility to recruit cells from different dispersal sources. To investigate this, we conducted an in situ mesocosm experiment where bacterial communities of an oligotrophic lake were exposed to different salinities (0, 18, 36 psu) for two weeks and subjected to dispersal of cells originating from sediments, air (mesocosms open to air deposition), both or none. BCC was determined using 454 pyrosequencing of the 16S rRNA gene and bacterial production was measured by 3H leucine uptake. Bacterial production differed significantly among salinity treatments and dispersal treatments, being highest at high salinity. These changes were associated with changes in BCC and it was found that the identity of the main functional contributors differed at different salinities. Our results further showed that after a salinity perturbation, the response of bacterial communities depended on the recruitment of taxa, including marine representatives (e.g. Alphaproteobacteria Loktanella, Erythrobacter and the Gammaproteobacterium Rheiheimera) from dispersal sources, in which atmospheric deposition appeared to play a major role.

  • 9. Eiler, Alexander
    et al.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    Bertilsson, Stefan
    Tranvik, Lars J.
    Heterotrophic bacterial growth efficiency and community structure at different natural organic carbon concentrations2003In: Applied and Environmental Microbiology, Vol. 69, p. 3701-3709Article in journal (Refereed)
  • 10.
    Eiler, Alexander
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. limnologi.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. limnologi.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. limnologi.
    Tranvik, Lars J
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. limnologi.
    Heterotrophic bacterial growth efficiency and community structure at different natural organic carbon concentrations.2003In: Appl Environ Microbiol, ISSN 0099-2240, Vol. 69, no 7, p. 3701-9Article in journal (Refereed)
  • 11. Hillebrand, Helmut
    et al.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lebret, Karen
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Östman, Örjan
    Striebel, Maren
    Decomposing multiple dimensions of stability in global change experiments2018In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 21, no 1, p. 21-30Article in journal (Refereed)
    Abstract [en]

    Ecological stability is the central framework to understand an ecosystem's ability to absorb or recover from environmental change. Recent modelling and conceptual work suggests that stability is a multidimensional construct comprising different response aspects. Using two freshwater mesocosm experiments as case studies, we show how the response to single perturbations can be decomposed in different stability aspects (resistance, resilience, recovery, temporal stability) for both ecosystem functions and community composition. We find that extended community recovery is tightly connected to a nearly complete recovery of the function (biomass production), whereas systems with incomplete recovery of the species composition ranged widely in their biomass compared to controls. Moreover, recovery was most complete when either resistance or resilience was high, the latter associated with low temporal stability around the recovery trend. In summary, no single aspect of stability was sufficient to reflect the overall stability of the system.

  • 12. Jezberova, Jitka
    et al.
    Jezbera, Jan
    Brandt, Ulrike
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Hahn, Martin W.
    Ubiquity of Polynucleobacter necessarius ssp asymbioticus in lentic freshwater habitats of a heterogenous 2000 km2 area2010In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 12, no 3, p. 658-669Article in journal (Refereed)
    Abstract [en]

    We present a survey on the distribution and habitat range of Polynucleobacter necessarius ssp. asymbioticus (PnecC), a numerically and functionally important taxon in the plankton of freshwater systems. We systematically sampled stagnant freshwater habitats in a heterogeneous 2000 km2 area, together with ecologically different habitats outside this area. In total, 137 lakes, ponds and puddles were investigated, which represent an enormous diversity of habitats differing, e.g. in depth (< 10 cm - 171 m) and pH (3.9-8.5). PnecC bacteria were detected by cultivation-independent methods in all investigated habitats, and their presence was confirmed by cultivation of strains from selected habitats representing the whole studied ecological range. The determined relative abundance of the subspecies ranged from values close to the detection limit of FISH (0.2%) to 67% (average 14.5%), and the highest observed absolute abundance was 5.3 x 106 cells ml-1. Statistical analyses revealed that the abundance of PnecC bacteria was partially controlled by factors linked to concentrations of humic substances, which support the hypothesis that these bacteria utilize photodegradation products of humic substances. Based on the revealed statistical relationships, an average relative abundance of this subspecies of 20% in global freshwater habitats was extrapolated. Our study provides important implications for the current debate on ubiquity and biogeography in microorganisms.

  • 13. Kritzberg, Emma S.
    et al.
    Langenheder, Silke
    Limnologi. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Lindström, Eva S.
    Limnologi. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Influence of dissolved organic matter source on lake bacterioplankton community structure and function: implications for seasonal dynamics of community structure.2006In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 56, no 3, p. 406-417Article in journal (Refereed)
    Abstract [en]

    It has been suggested that autochthonous (internally produced) organic carbon and allochthonous (externally produced) organic carbon are utilized by phylogenetically different bacterioplankton. We examined the relationship between the source of organic matter and the structure and function of lake bacterial communities. Differences and seasonal changes in bacterial community composition in two lakes differing in their source of organic matter were followed in relation to environmental variables. We also performed batch culture experiments with amendments of various organic substrates, namely fulvic acids, leachates from algae, and birch and maple leaves. Differences in bacterial community composition between the lakes, analysed by terminal restriction fragment length polymorphism, correlated with variables related to the relative loading of autochthonous and allochthonous carbon (water colour, dissolved organic carbon, nutrients, and pH). Seasonal changes correlated with temperature, chlorophyll and dissolved organic carbon in both lakes. The substrate amendments led to differences in both structure and function, i.e. production, respiration and growth yield, of the bacterial community. In conclusion, our results suggest that the source of organic matter influences community composition both within and among lakes and that there may be a coupling between the structure and function of the bacterial community.

  • 14.
    Langenheder, S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Kisand, V.
    Wikner, J.
    Tranvik, L. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Salinity as a structuring factor for the composition and performance of bacterioplankton degrading riverine DOC2003In: FEMS Microbiology Ecology, Vol. 45, p. 189-202Article in journal (Refereed)
  • 15.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Berga, Mercé
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Östman, Örjan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Population and Conservation Biology.
    Székely, Anna J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Temporal variation of beta-diversity and assembly mechanisms in a bacterial metacommunity2012In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 6, no 6, p. 1107-1114Article in journal (Refereed)
    Abstract [en]

    The turnover of community composition across space, beta-diversity, is influenced by different assembly mechanisms, which place varying weight on local habitat factors, such as environmental conditions and species interactions, and regional factors such as dispersal and history. Several assembly mechanisms may function simultaneously; however, little is known about how their importance changes over time and why. Here, we implemented a field survey where we sampled a bacterial metacommunity consisting of 17 rock pools located at the Swedish Baltic Sea coast at 11 occasions during 1 year. We determined to which extent communities were structured by different assembly mechanisms using variation partitioning and studied changes in beta-diversity across environmental gradients over time. beta-Diversity was highest at times of high overall productivity and environmental heterogeneity in the metacommunity, at least partly due to species sorting, that is, selection of taxa by the prevailing environmental conditions. In contrast, dispersal-driven assembly mechanisms were primarily detected at times when beta-diversity was relatively low. There were no indications for strong and persistent differences in community composition or beta-diversity between permanent and temporary pools, indicating that the physical disturbance regime is of relatively minor importance. In summary, our study clearly suggests that there are temporal differences in the relative importance of different assembly mechanisms related to abiotic factors and shows that the temporal variability of those factors is important for a more complete understanding of bacterial metacommunity dynamics.

  • 16.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Bulling, Mark T.
    Prosser, James I.
    Solan, Martin
    Role of functionally dominant species in varying environmental regimes: evidence for the performance-enhancing effect of biodiversity2012In: BMC Ecology, ISSN 1472-6785, E-ISSN 1472-6785, Vol. 12, p. 14-Article in journal (Refereed)
    Abstract [en]

    Background: Theory suggests that biodiversity can act as a buffer against disturbances and environmental variability via two major mechanisms: Firstly, a stabilising effect by decreasing the temporal variance in ecosystem functioning due to compensatory processes; and secondly, a performance enhancing effect by raising the level of community response through the selection of better performing species. Empirical evidence for the stabilizing effect of biodiversity is readily available, whereas experimental confirmation of the performance-enhancing effect of biodiversity is sparse. Results: Here, we test the effect of different environmental regimes (constant versus fluctuating temperature) on bacterial biodiversity-ecosystem functioning relations. We show that positive effects of species richness on ecosystem functioning are enhanced by stronger temperature fluctuations due to the increased performance of individual species. Conclusions: Our results provide evidence for the performance enhancing effect and suggest that selection towards functionally dominant species is likely to benefit the maintenance of ecosystem functioning under more variable conditions.

  • 17.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Bulling, Mark T.
    Solan, Martin
    Prosser, James I.
    Bacterial biodiversity-ecosystem function relations are modified by environmental complexity2010In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 5, no 5, p. e10834-Article in journal (Refereed)
    Abstract [en]

    Background

    With the recognition that environmental change resulting from anthropogenic activities is causing a global decline in biodiversity, much attention has been devoted to understanding how changes in biodiversity may alter levels of ecosystem functioning. Although environmental complexity has long been recognised as a major driving force in evolutionary processes, it has only recently been incorporated into biodiversity-ecosystem functioning investigations. Environmental complexity is expected to strengthen the positive effect of species richness on ecosystem functioning, mainly because it leads to stronger complementarity effects, such as resource partitioning and facilitative interactions among species when the number of available resource increases.

    Methodology/Principal Findings

    Here we implemented an experiment to test the combined effect of species richness and environmental complexity, more specifically, resource richness on ecosystem functioning over time. We show, using all possible combinations of species within a bacterial community consisting of six species, and all possible combinations of three substrates, that diversity-functioning (metabolic activity) relationships change over time from linear to saturated. This was probably caused by a combination of limited complementarity effects and negative interactions among competing species as the experiment progressed. Even though species richness and resource richness both enhanced ecosystem functioning, they did so independently from each other. Instead there were complex interactions between particular species and substrate combinations.

    Conclusions/Significance

    Our study shows clearly that both species richness and environmental complexity increase ecosystem functioning. The finding that there was no direct interaction between these two factors, but that instead rather complex interactions between combinations of certain species and resources underlie positive biodiversity ecosystem functioning relationships, suggests that detailed knowledge of how individual species interact with complex natural environments will be required in order to make reliable predictions about how altered levels of biodiversity will most likely affect ecosystem functioning.

  • 18.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Jurgens, K
    Regulation of bacterial biomass and community structure by metazoan and protozoan predation2001In: LIMNOLOGY AND OCEANOGRAPHY, ISSN 0024-3590, Vol. 46, no 1, p. 121-134Article in journal (Refereed)
    Abstract [en]

    We performed food web manipulation experiments in three eutrophic Daphnia-dominated ponds, to compare the predation impact on planktonic bacteria exerted by metazoan and protozoan bacterial consumers. We analyzed the bacterial morphological composition by

  • 19.
    Langenheder, Silke
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Kisand, Veljo
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Lindström, Eva S
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Wikner, Johan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Tranvik, Lars
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Growth dynamics within bacterial communities in riverine and estuarine batch cultures2004In: Aquatic Microbial Ecology, Vol. 37, p. 137-148Article in journal (Refereed)
  • 20.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    Kisand, Veljo
    Lindström, Eva S.
    Wikner, Johan
    Tranvik, Lars J.
    Growth dynamics within bacterial communities in riverine and estuarine batch cultures2004In: Aquatic Microbial Ecology, Vol. 37, p. 137-148Article in journal (Refereed)
  • 21.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    Kisand, Veljo
    Wikner, Johan
    Tranvik, Lars J.
    Salinity as a structuring factor for the composition and performance of bacterioplankton degrading riverine DOC2003In: FEMS Microbiology Ecology, Vol. 45, p. 189-202Article in journal (Refereed)
  • 22.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Factors influencing aquatic and terrestrial bacterial community assembly2019In: Environmental Microbiology Reports, ISSN 1758-2229, E-ISSN 1758-2229, Vol. 11, no 3, p. 306-315Article, review/survey (Refereed)
    Abstract [en]

    During recent years, many studies have shown that different processes including drift, environmental selection and dispersal can be important for the assembly of bacterial communities in aquatic and terrestrial ecosystems. However, we lack a conceptual overview about the ecological context and factors that influence the relative importance of the different assembly mechanisms and determine their dynamics in time and space. Focusing on free-living, i.e., nonhost associated, bacterial communities, this minireview, therefore, summarizes and conceptualizes findings from empirical studies about how (i) environmental factors, such as environmental heterogeneity, disturbances, productivity and trophic interactions; (ii) connectivity and dispersal rates (iii) spatial scale, (iv) community properties and traits and (v) the use of taxonomic/phylogenetic or functional metrics influence the relative importance of different community assembly processes. We find that there is to-date little consistency among studies and suggest that future studies should now address how (i)-(v) differ between habitats and organisms and how this, in turn, influences the temporal and spatial-scale dependency of community assembly processes in microorganisms.

  • 23.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    Lindström, Eva S.
    Tranvik, Lars J.
    Do environmental conditions determine bacterial community composition and functioning? A test of the ubiquity of aquatic bacteriaIn: Article in journal (Refereed)
  • 24.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. limnologi.
    Lindström, Eva S
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. limnologi.
    Tranvik, Lars J
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. limnologi.
    Structure and function of bacterial communities emerging from different sources under identical conditions.2006In: Applied and Environmental Microbiology, Vol. 72, p. 212-220Article in journal (Refereed)
  • 25.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    Weak coupling between community composition and functioning of aquatic bacteria2005In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 50, no 3, p. 957-967Article in journal (Refereed)
    Abstract [en]

    We performed a batch culture experiment with a factorial design in which sterile water from four lakes and bacterial assemblages (size-fractionated lake water) from the same lakes were set up in all possible combinations. The functional performance (biomass yield, respiration, growth rates, and growth efficiency) of bacterial communities growing in the cultures depended primarily on the type of the medium and to a much lesser extent on the origin of the bacterial assemblage. Functional changes were only partly paralleled by changes in community composition, as indicated by terminal restriction fragment length polymorphism analysis. Similar bacterial communities developed in different cultures as a result of receiving either the same medium or the same inoculum, indicating that bacterial communities are comprised of populations of generalists that can grow under most conditions as well as populations with the life strategy of specialists. However, bacteria originating from a slightly acidic polyhumic lake failed to grow, grew unsteadily, or exhibited an extended lag phase when exposed to media originating from other lakes, indicating that the bacterial community in the polyhumic lake was not able to adapt rapidly to changes in environmental conditions.

  • 26.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Prosser, James I.
    Resource availability influences the diversity of a functional group of heterotrophic soil bacteria.2008In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 10, no 9, p. 2245-2256Article in journal (Refereed)
    Abstract [en]

    Resource availability is a key factor regulating biodiversity and ecosystem functioning, but the relationship between resource availability and diversity has only been rarely investigated in microbial communities. The aim of this study was to determine how diversity and community structure of a functional group of soil bacteria are influenced by resource concentration. To achieve this, we used soil microcosms to investigate degradation of benzoate, which served as a model compound, by soil bacterial communities. Microcosms were supplied with 13C-labelled benzoate at four concentrations and RNA-stable isotope probing followed by molecular fingerprinting analysis of 16S rRNA genes was employed to identify bacteria able to assimilate benzoate at different concentrations. The composition of the benzoate degrader community differed at different concentrations and there was a significant decrease in taxa evenness at the highest substrate concentration. Active organisms could be grouped into generalists, occurring at all substrate concentrations, specialists, active at one particular benzoate concentration only, and taxa that were active at either the two lowest or two highest concentrations. The study comprises the first explicit demonstration that resource availability has an effect on the diversity of a functional group of heterotrophic soil bacteria.

  • 27.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Ragnarsson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    The role of environmental and spatial factors for the composition of aquatic bacterial communities2007In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 88, no 9, p. 2154-2161Article in journal (Refereed)
    Abstract [en]

    This study investigates the importance of local vs. spatial factors on bacterial community composition of 35 rock pools at the Baltic Sea coast. The pools were located in five distinct spatial clusters over a total scale of <500 m and differed widely in terms of water chemistry. To determine the fractions of the variance in bacterial community composition (BCC) between rock pools that are explained by local environmental vs. spatial factors, a variance partitioning procedure using partial canonical correspondence analysis was performed. Three environmental variables (salinity, chlorophyll a concentration, and water color) had a significant effect on BCC, irrespective of the spatial location of the pools. Vice versa, there was a significant effect of spatial factors on BCC irrespective of any of the environmental factors included in this study. Hence, the patchy spatial distribution of the pools was partly reflected in the composition of the bacterial communities in the pools, which might be caused by congruent colonization events of adjacent pools, such as simultaneous sea-spray inputs or direct exchange of bacteria via connecting rivulets. This study shows that the composition of planktonic bacteria can show provincialism at small spatial scales, which is likely to be caused by -environmental conditions as well as historical events.

  • 28.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Sobek, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Tranvik, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Changes in bacterial community composition along a solar radiation gradient in humic waters2006In: AQUATIC SCIENCES, Vol. 68, no 4, p. 415-424Article in journal (Refereed)
  • 29.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Szekely, Anna J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Species sorting and neutral processes are both important during the initial assembly of bacterial communities2011In: The ISME Journal, ISSN 1751-7362, Vol. 5, no 7, p. 1086-1094Article in journal (Refereed)
    Abstract [en]

    Many studies have shown that species sorting, that is, the selection by local environmental conditions is important for the composition and assembly of bacterial communities. On the other hand, there are other studies that could show that bacterial communities are neutrally assembled. In this study, we implemented a microcosm experiment with the aim to determine, at the same time, the importance of species sorting and neutral processes for bacterial community assembly during the colonisation of new, that is, sterile, habitats, by atmospheric bacteria. For this we used outdoor microcosms, which contained sterile medium from three different rock pools representing different environmental conditions, which were seeded by rainwater bacteria. We found some evidence for neutral assembly processes, as almost every 4th taxon growing in the microcosms was also detectable in the rainwater sample irrespective of the medium. Most of these taxa belonged to widespread families with opportunistic growth strategies, such as the Pseudomonadaceae and Comamonadaceae, indicating that neutrally assembled taxa may primarily be generalists. On the other hand, we also found evidence for species sorting, as one out of three media selected a differently composed bacterial community. Species sorting effects were relatively weak and established themselves via differences in relative abundance of generalists among the different media, as well as media-specific occurrences of a few specific taxa. In summary, our results suggest that neutral and species sorting processes interact during the assembly of bacterial communities and that their importance may differ depending on how many generalists and specialists are present in a community.

  • 30.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Wang, Jianjun
    Department of Geosciences and Geography, University of Helsinki, Helsinki FIN-00014, Finland; State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academic of Sciences, Nanjing 210008, China.
    Karjalainen, Satu Maaria
    Finnish Environment Institute, Freshwater Centre, FI-90570 Oolu, Finland.
    Laamanen, Tiina M.
    Finnish Environment Institute, Freshwater Centre, FI-90570 Oolu, Finland.
    Tolonen, Kimmo T.
    Finnish Environment Institute, Natural Environment Centre, Biodiversity, FI-90570 Oulu, Finland.
    Vilmi, Annika
    Finnish Environment Institute, Natural Environment Centre, Biodiversity, FI-90570 Oulu, Finland.
    Heino, Jani
    Finnish Environment Institute, Natural Environment Centre, Biodiversity, FI-90570 Oulu, Finland.
    Bacterial metacommunity organization in a highly connected aquatic system2017In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 93, no 4, article id fiw225Article in journal (Refereed)
    Abstract [en]

    The spatial structure and underlying assembly mechanisms of bacterial communities have been studied widely across aquatic systems, focusing primarily on isolated sites, such as different lakes, ponds and streams. Here, our main aim was to determine the underlying mechanisms for bacterial biofilm assembly within a large, highly connected lake system in Northern Finland using associative methods based on taxonomic and phylogenetic alpha- and beta-diversity and a large number of abiotic and biotic variables. Furthermore, null model approaches were used to quantify the relative importance of different community assembly processes. We found that spatial variation in bacterial communities within the lake was structured by different assembly processes, including stochasticity, species sorting and potentially even dispersal limitation. Species sorting by abiotic environmental conditions explained more of the taxonomic and particularly phylogenetic turnover in community composition compared with that by biotic variables. Finally, we observed clear differences in alpha diversity (species richness and phylogenetic diversity), which were to a stronger extent determined by abiotic compared with biotic factors, but also by dispersal effects. In summary, our study shows that the biodiversity of bacterial biofilm communities within a lake ecosystem is driven by within-habitat gradients in abiotic conditions and by stochastic and deterministic dispersal processes.

  • 31.
    Lebret, Karen
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Colinas, Noemi
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Östman, Örjan
    Swedish Univ Agr Sci, Dept Aquat Resources, Öregrund, Sweden.
    Lindström, Eva
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Increased water colour affects freshwater plankton communities in a mesocosm study2018In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 81, no 1, p. 1-17Article in journal (Refereed)
    Abstract [en]

    Increases in water colour (brownification) have been observed in aquatic systems in the Northern Hemisphere, partly caused by increased loading of organic carbon from terrestrial origins. We investigated the effect of increase in water colour on the composition, structure and function of lake plankton communities (bacteria, phytoplankton and zooplankton) conducting a mesocosm experiment in 3 medium-coloured lakes (average absorbance at 420 nm: 0.034 cm(-1)), with different nutrient concentrations and phytoplankton community composition. To simulate an increase in water colour, we added humic substances (HuminFeed) at 3 different concentrations. The additions significantly affected the water colour of the mesocosms, but had no measurable effect on total organic carbon concentration, thus change in light conditions was the main effect of our treatment on the plankton communities. The increase in water colour did not significantly affect the measured functions (productivity, respiration) and biomass of the plankton communities (bacteria, phytoplankton and zooplankton), but led to changes in the relative abundance of some phytoplankton taxa and, to a lesser extent, the bacterial community (differences in relative abundance). The treatments had no significant effect on zooplankton biomass or composition. Our study suggests that increases in water colour favour low-light-adapted phytoplankton species, which in turn also can affect bacterial composition, whereas the change in light climate had no clear impact on the functioning of plankton communities in weakly humic lakes.

  • 32.
    Lebret, Karen
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Centre for Ecology and Evolution in Microbial model Systems - EEMiS, Department of Biology and Environmental Science, Linnæus University, SE-391 82, Kalmar, Sweden.
    Östman, Örjan
    Department of Aquatic Resources, Swedish University of Agricultural Sciences, Skolgatan 6, SE-742 42, Öregrund, Sweden.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Drakare, Stina
    Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences - SLU, PO Box 7050, SE-750 07, Uppsala, Sweden.
    Guillemette, François
    Research Center on Watershed – Aquatic Ecosystem Interactions (RIVE), Department of Environmental Sciences, Université du Québec à Trois-Rivières, Québec, Canada.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    High abundances of the nuisance raphidophyte Gonyostomum semen in brown water lakes are associated with high concentrations of iron2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, no 1, article id 13463Article in journal (Refereed)
    Abstract [en]

    Algal blooms occur frequently in lakes and oceans and the causes and consequences of those are often studied. In this study, we focus on a less well known type of algal bloom by the freshwater raphidophyte Gonyostomum semen. This species’ abundance and occurrence is increasing, especially in brown water lakes, the most abundant lake type in the boreal zone. The aim of the study was to investigate which environmental factors are associated with G. semen by statistical evaluation of field data of 95 Swedish lakes over five years. Although we found G. semen to be associated with dark waters it was, contrary to our expectations, mainly high concentrations of iron, and only to a lesser extent high TOC (total organic carbon) concentrations, that were associated with blooms of G. semen. In addition, high phosphorus concentrations and low pH also appear to facilitate G. semen blooms. We suggest that browning of lakes caused by increased iron concentrations may decrease net heterotrophy by fostering heavy algal blooms, i.e. the opposite to commonly assumed effects of increased DOM (dissolved organic matter).

  • 33.
    Lindström, Eva S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Eiler, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Drakare, Stina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Ragnarsson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Does ecosystem size determine aquatic bacterial richness? Comment2007In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 88, no 1, p. 252-253Article in journal (Refereed)
  • 34.
    Lindström, Eva S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Local and regional factors influencing bacterial community assembly2012In: Environmental Microbiology Reports, ISSN 1758-2229, E-ISSN 1758-2229, Vol. 4, no 1, p. 1-9Article, review/survey (Refereed)
    Abstract [en]

    The classical view states that microbial biogeography is not affected by dispersal barriers or historical events, but only influenced by the local contemporary habitat conditions (species sorting). This has been challenged during recent years by studies suggesting that also regional factors such as mass effect, dispersal limitation and neutral assembly are important for the composition of local bacterial communities. Here we summarize results from biogeography studies in different environments, i.e. in marine, freshwater and soil as well in human hosts. Species sorting appears to be the most important mechanism. However, this result might be biased since this is the mechanism that is easiest to measure, detect and interpret. Hence, the importance of regional factors may have been underestimated. Moreover, our survey indicates that different assembly mechanisms might be important for different parts of the total community, differing, for example, between generalists and specialists, and between taxa of different dispersal ability and motility. We conclude that there is a clear need for experimental studies, first, to clearly separate regional and local factors in order to study their relative importance, and second, to test whether there are differences in assembly mechanisms depending on different taxonomic or functional groups.

  • 35.
    Logares, Ramiro
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Logue, Jürg Brendan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Paterson, Harriet
    Laybourn-Parry, Johanna
    Rengefors, Karin
    Tranvik, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Biogeography of bacterial communities exposed to progressive long-term environmental change2013In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 7, no 5, p. 937-948Article in journal (Refereed)
    Abstract [en]

    The response of microbial communities to long-term environmental change is poorly understood. Here, we study bacterioplankton communities in a unique system of coastal Antarctic lakes that were exposed to progressive long-term environmental change, using 454 pyrosequencing of the 16S rDNA gene (V3-V4 regions). At the time of formation, most of the studied lakes harbored marine-coastal microbial communities, as they were connected to the sea. During the past 20 000 years, most lakes isolated from the sea, and subsequently they experienced a gradual, but strong, salinity change that eventually developed into a gradient ranging from freshwater (salinity 0) to hypersaline (salinity 100). Our results indicated that present bacterioplankton community composition was strongly correlated with salinity and weakly correlated with geographical distance between lakes. A few abundant taxa were shared between some lakes and coastal marine communities. Nevertheless, lakes contained a large number of taxa that were not detected in the adjacent sea. Abundant and rare taxa within saline communities presented similar biogeography, suggesting that these groups have comparable environmental sensitivity. Habitat specialists and generalists were detected among abundant and rare taxa, with specialists being relatively more abundant at the extremes of the salinity gradient. Altogether, progressive long-term salinity change appears to have promoted the diversification of bacterioplankton communities by modifying the composition of ancestral communities and by allowing the establishment of new taxa. The ISME Journal (2013) 7, 937-948; doi:10.1038/ismej.2012.168; published online 20 December 2012

  • 36.
    Logue, Jürg Brendan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Andersson, Anders F.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Drakare, Stina
    Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences (SLU).
    Lanzén, Anders
    Centre for Geobiology and Department of Biology, University of Bergen.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Freshwater bacterioplankton richness in oligotrophic lakes depends on nutrient availability rather than on species-area relationships2012In: The ISME Journal, ISSN 1751-7362, Vol. 6, no 6, p. 1127-1136Article in journal (Refereed)
    Abstract [en]

    A central goal in ecology is to grasp the mechanisms that underlie and maintain biodiversity and patterns in its spatial distribution can provide clues about those mechanisms. Here, we investigated what might determine bacterioplankton richness (BR) in lakes by means of 454 pyrosequencing of the 16S rRNA gene. We further provide a BR estimate based upon a sampling depth and accuracy, which, to our knowledge, are unsurpassed for freshwater bacterioplankton communities. Our examination of 22 669 sequences per lake showed that freshwater BR in fourteen nutrient-poor lakes was positively influenced by nutrient availability. Our study is, thus, consistent with the finding that the supply of available nutrients is a major driver of species richness; a pattern that may well be universally valid to the world of both micro- and macro-organisms. We, furthermore, observed that BR increased with elevated landscape position, most likely as a consequence of differences in nutrient availability. Finally, BR decreased with increasing lake and catchment area that is negative species-area relationships (SARs) were recorded; a finding that re-opens the debate about whether positive SARs can indeed be found in the microbial world and whether positive SARs can in fact be pronounced as one of the few “laws” in ecology.

  • 37.
    Peter, Hannes
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Beier, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Function-specific response to depletion of microbial diversity2011In: The ISME Journal, ISSN 1751-7362, Vol. 5, no 2, p. 351-361Article in journal (Refereed)
    Abstract [en]

    Recent meta-analyses suggest that ecosystem functioning increases with biodiversity, but contradictory results have been presented for some microbial functions. Moreover, observations of only one function underestimate the functional role of diversity because of species-specific trade-offs in the ability to carry out different functions. We examined multiple functions in batch cultures of natural freshwater bacterial communities with different richness, achieved by a dilution-to-extinction approach. Community composition was assessed by molecular fingerprinting of 16S rRNA and chitinase genes, representing the total community and a trait characteristic for a functional group, respectively. Richness was positively related to abundance and biomass, negatively correlated to cell volumes and unrelated to maximum intrinsic growth rate. The response of chitin and cellulose degradation rates depended on the presence of a single phylotype. We suggest that species identity and community composition rather than richness matters for specific microbial processes.

  • 38.
    Roger, Fabian
    et al.
    Univ Gothenburg, Dept Marine Sci, Box 461, SE-40530 Gothenburg, Sweden.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Osman, Omneya
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Gamfeldt, Lars
    Univ Gothenburg, Dept Marine Sci, Box 461, SE-40530 Gothenburg, Sweden.
    Effects of multiple dimensions of bacterial diversity on functioning, stability and multifunctionality2016In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 97, no 10, p. 2716-2728Article in journal (Refereed)
    Abstract [en]

    Bacteria are essential for many ecosystem services but our understanding of factors controlling their functioning is incomplete. While biodiversity has been identified as an important driver of ecosystem processes in macrobiotic communities, we know much less about bacterial communities. Due to the high diversity of bacterial communities, high functional redundancy is commonly proposed as explanation for a lack of clear effects of diversity. The generality of this claim has, however, been questioned. We present the results of an outdoor dilution-to-extinction experiment with four lake bacterial communities. The consequences of changes in bacterial diversity in terms of effective number of species, phylogenetic diversity, and functional diversity were studied for (1) bacterial abundance, (2) temporal stability of abundance, (3) nitrogen concentration, and (4) multifunctionality. We observed a richness gradient ranging from 15 to 280 operational taxonomic units (OTUs). Individual relationships between diversity and functioning ranged from negative to positive depending on lake, diversity dimension, and aspect of functioning. Only between phylogenetic diversity and abundance did we find a statistically consistent positive relationship across lakes. A literature review of 24 peer-reviewed studies that used dilution-to-extinction to manipulate bacterial diversity corroborated our findings: about 25% found positive relationships. Combined, these results suggest that bacteria-driven community functioning is relatively resistant to reductions in diversity.

  • 39. Shade, Ashley
    et al.
    Peter, Hannes
    Allison, Steven D.
    Baho, Didier L.
    Berga, Mercé
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Bürgmann, Helmut
    Huber, David H.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lennon, Jay T.
    Martiny, Jennifer B.H.
    Matulich, Kristin L.
    Schmidt, Thomas M.
    Handelsman, Jo
    Fundamentals of microbial community resistance and resilience2012In: Frontiers in Microbiology, ISSN 1664-302X, Vol. 3, p. 417-Article in journal (Refereed)
    Abstract [en]

    Microbial communities are at the heart of all ecosystems, and yet microbial community behavior in disturbed environments remains difficult to measure and predict. Understanding the drivers of microbial community stability, including resistance (insensitivity to disturbance) and resilience (the rate of recovery after disturbance) is important for predicting community response to disturbance. Here, we provide an overview of the concepts of stability that are relevant for microbial communities. First, we highlight insights from ecology that are useful for defining and measuring stability. To determine whether general disturbance responses exist for microbial communities, we next examine representative studies from the literature that investigated community responses to press (long-term) and pulse (short-term) disturbances in a variety of habitats. Then we discuss the biological features of individual microorganisms, of microbial populations, and of microbial communities that may govern overall community stability. We conclude with thoughts about the unique insights that systems perspectives – informed by meta-omics data – may provide about microbial community stability.

  • 40.
    Shen, Dandan
    et al.
    Leibniz Inst Balt Sea Res, Sect Biol Oceanog, Warnemunde, Germany.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Juergens, Klaus
    Leibniz Inst Balt Sea Res, Sect Biol Oceanog, Warnemunde, Germany.
    Dispersal Modifies the Diversity and Composition of Active Bacterial Communities in Response to a Salinity Disturbance2018In: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 9, article id 2188Article in journal (Refereed)
    Abstract [en]

    Dispersal can influence the response of bacterial communities to environmental changes and disturbances. However, the extent to which dispersal contributes to the community response in dependence of the character and strength of the disturbance remains unclear. Here, we conducted a transplant experiment using dialysis bags in which bacterioplankton originating from brackish and marine regions of the Saint Lawrence Estuary were reciprocally incubated in the two environments for 5 days. Dispersal treatments were set-up by subjecting half of the microcosms in each environment to an exchange of cells between the marine and brackish assemblages at a daily exchange rate of 6% (v/v), and the other half of microcosms were kept as the nondispersal treatments. Bacterial 16S rRNA sequencing was then used to examine the diversity and composition of the active communities. Alpha diversity of the marine communities that were exposed to the brackish environment was elevated greatly by dispersal, but declined in the absence of dispersal. This indicates that dispersal compensated the loss of diversity in the marine communities after a disturbance by introducing bacterial taxa that were able to thrive and coexist with the remaining community members under brackish conditions. On the contrary, alpha diversity of the brackish communities was not affected by dispersal in either environment. Furthermore, dispersal led to an increase in similarity between marine and brackish communities in both of the environments, with a greater similarity when the communities were incubated in the brackish environment. These results suggest that the higher initial diversity in the brackish than in the marine starting community made the resident community less susceptible to dispersing bacteria. Altogether, this study shows that dispersal modifies the diversity and composition of the active communities in response to a salinity disturbance, and enables the local adjustment of specific bacteria under brackish environmental conditions.

  • 41.
    Sjöstedt, Johanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Department of Biology/Aquatic Ecology, Lund University, Lund, Sölvegatan 37, SE 22362, Sweden.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Kritzberg, Emma
    Department of Biology/Aquatic Ecology, Lund University, Lund, Sölvegatan 37, SE 22362, Sweden.
    Karlsson, Christofer M. G.
    Centre for Ecology and Evolution in Microbial model Systems ‐ EEMiS, Linnaeus University, Kalmar, SE 39231, Sweden.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Repeated disturbances affect functional but not compositional resistance and resilience in an aquatic bacterioplankton community2018In: Environmental Microbiology Reports, ISSN 1758-2229, E-ISSN 1758-2229, Vol. 10, no 4, p. 493-500Article in journal (Refereed)
    Abstract [en]

    Disturbances are believed to be one of the main factors influencing variations in community diversity and functioning. Here we investigated if exposure to a pH press disturbance affected the composition and functional performance of a bacterial community and its resistance, recovery and resilience to a second press disturbance (salt addition). Lake bacterial assemblages were initially exposed to reduced pH in six mesocosms whereas another six mesocosms were kept as reference. Seven days after the pH disturbance, three tanks from each treatment were exposed to a salt disturbance. Both bacterial production and enzyme activity were negatively affected by the salt treatment, regardless if the communities had been subject to a previous disturbance or not. However, cell-specific enzyme activity had a higher resistance in communities pre-exposed to the pH disturbance compared to the reference treatment. In contrast, for cell-specific bacterial production resistance was not affected, but recovery was faster in the communities that had previously been exposed to the pH disturbance. Over time, bacterial community composition diverged among treatments, in response to both pH and salinity. The difference in functional recovery, resilience and resistance may depend on differences in community composition caused by the pH disturbance, niche breadth or acquired stress resistance.

  • 42.
    Suarez, Carolina
    et al.
    Univ Gothenburg, Dept Chem & Mol Biol Microbiol, SE-40530 Gothenburg, Sweden;Chalmers Univ Technol, Dept Architecture & Civil Engn, Water Environm Technol, SE-41296 Gothenburg, Sweden.
    Piculell, Maria
    Veolia Water Technol AB AnoxKaldnes, SE-22647 Lund, Sweden.
    Modin, Oskar
    Chalmers Univ Technol, Dept Architecture & Civil Engn, Water Environm Technol, SE-41296 Gothenburg, Sweden.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Persson, Frank
    Chalmers Univ Technol, Dept Architecture & Civil Engn, Water Environm Technol, SE-41296 Gothenburg, Sweden.
    Hermansson, Malte
    Univ Gothenburg, Dept Chem & Mol Biol Microbiol, SE-40530 Gothenburg, Sweden.
    Thickness determines microbial community structure and function in nitrifying biofilms via deterministic assembly2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 5110Article in journal (Refereed)
    Abstract [en]

    Microbial biofilms are ubiquitous in aquatic environments where they provide important ecosystem functions. A key property believed to influence the community structure and function of biofilms is thickness. However, since biofilm thickness is inextricably linked to external factors such as water flow, temperature, development age and nutrient conditions, its importance is difficult to quantify. Here, we designed an experimental system in a wastewater treatment plant whereby nitrifying biofilms with different thicknesses (50 or 400 mu m) were grown in a single reactor, and thus subjected to identical external conditions. The 50 and 400 mu m biofilm communities were significantly different. This beta-diversity between biofilms of different thickness was primarily caused by deterministic factors. Turnover (species replacement) contributed more than nestedness (species loss) to the beta-diversity, i.e. the 50 mu m communities were not simply a subset of the 400 mu m communities. Moreover, the two communities differed in the composition of nitrogen-transforming bacteria and in nitrogen transformation rates. The study illustrates that biofilm thickness alone is a key driver for community composition and ecosystem function, which has implications for biotechnological applications and for our general understanding of biofilm ecology.

  • 43.
    Svoboda, Pavel
    et al.
    Charles Univ Prague, Fac Sci, Dept Bot, Prague 2, Czech Republic..
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Osman, Omneya Ahmed
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Dispersal timing determines the importance of priority effects in bacterial communities2018In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 12, no 2, p. 644-646Article in journal (Refereed)
    Abstract [en]

    The order and timing of species arrival during community assembly can have long term effects on community structure due to priority effects. The importance of such processes in complex bacterial communities where dispersal involves mixing of entire communities is currently not known. Here we used a transplant experiment with two bacterioplankton communities of different origin (freshwater and brackish). Sterile medium of each origin was initially inoculated with a bacterial community of different ('alien') origin, followed by dispersal of the respective 'home' community at different time points after initial inoculation. We found that the later the dispersal with the 'home' community occurred the smaller the effect on the final community composition. This suggests that priority effects by the initially inoculated community reduce the establishment success of taxa from the later arriving community and that this effect depends on dispersal timing.

  • 44.
    Székely, Anna J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Berga, Mercé
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Mechanisms determining the fate of dispersed bacterial communities in new environments2013In: ISME Journal, ISSN 1751-7362, Vol. 7, no 1, p. 61-71Article in journal (Refereed)
    Abstract [en]

    Recent work has shown that dispersal has an important role in shaping microbial communities. However, little is known about how dispersed bacteria cope with new environmental conditions and how they compete with local resident communities. To test this, we implemented two full-factorial transplant experiments with bacterial communities originating from two sources (freshwater or saline water), which were incubated, separately or in mixes, under both environmental conditions. Thus, we were able to separately test for the effects of the new environment with and without interactions with local communities. We determined community composition using 454-pyrosequencing of bacterial 16S rRNA to specifically target the active fraction of the communities, and measured several functional parameters. In absence of a local resident community, the net functional response was mainly affected by the environmental conditions, suggesting successful functional adaptation to the new environmental conditions. Community composition was influenced both by the source and the incubation environment, suggesting simultaneous effects of species sorting and functional plasticity. In presence of a local resident community, functional parameters were higher compared with those expected from proportional mixes of the unmixed communities in three out of four cases. This was accompanied by an increase in the relative abundance of generalists, suggesting that competitive interactions among local and immigrant taxa could explain the observed functional overachievement. In summary, our results suggest that environmental filtering, functional plasticity and competition are all important mechanisms influencing the fate of dispersed communities.

  • 45.
    Székely, Anna J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Dispersal timing and drought history influence the response of bacterioplankton to drying–rewetting stress2017In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 11, no 8, p. 1764-1776Article in journal (Refereed)
    Abstract [en]

    The extent and frequency of drought episodes is expected to increase in the following decades making it a crucial stress factor for smaller water bodies. However, very little is known about how bacterioplankton is affected by increased evaporation and how these communities reassemble after rewetting. Here, we present results from a microcosm experiment that assessed the effect of drying–rewetting stress on bacterioplankton in the light of the stress history and the rate and timing of dispersal after the rewetting. We found that the drying phase resulted mainly in a change of function, whereas the complete desiccation and rewetting processes strongly affected both composition and function, which were, however, influenced by the initial conditions and stress history of the communities. Effects of dispersal were generally stronger when it occurred at an early stage after the rewetting. At this stage, selective establishment of dispersed bacteria coupled with enhanced compositional and functional recovery was found, whereas effects of dispersal were neutral, that is, predictable by dispersal rates, at later stages. Our studies therefore show that both the stress history and the timing of dispersal are important factors that influence the response of bacterial communities to environmental change and stress events.

  • 46.
    Székely, Anna J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    The importance of species sorting in bacterial communities differs between habitat generalists and specialists2014In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 87, no 1, p. 102-112Article in journal (Refereed)
    Abstract [en]

    Recent studies have shown that the spatial turnover of bacterial communities, that is, beta-diversity, is determined by a combination of different assembly mechanisms, such as species sorting, that is, environmental filtering, and dispersal-related mechanisms. However, it is currently unclear to what extent the importance of the different mechanisms depends on community traits. Here, we implemented a study using a rock pool metacommunity to test whether habitat specialization of bacterial taxa and groups or their phylogenetic identity influenced by which mechanisms communities were assembled. Ingeneral, our results show that species sorting was the most important assembly mechanism. However, we found that a larger fraction of the variation in bacterial community composition between pools could be explained by environmental factors in case of habitat generalists, that is, taxa that were widespread and abundant in the metacommunity, compared with habitat specialists, that is, taxa that had a more restricted distribution range and tended to be rare. Differences in assembly mechanisms were observedbetween different major phyla and classes. However, also here, a larger fraction of the variation incommunity composition among pools could be explained for taxonomic groups that contained on average more habitat generalists. In summary, our results show that species sorting is stronger for themost common taxa, indicating that beta-diversity along environmental gradients can be adequately described without considering rare taxa.

  • 47.
    Vass, Mate
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    The legacy of the past: effects of historical processes on microbial metacommunities2017In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 79, p. 13-19Article, review/survey (Refereed)
    Abstract [en]

    Distinguishing the importance of different community assembly mechanisms is an emerging topic in microbial ecology and much focus has been placed in recent years on investigating how contemporary environmental conditions, dispersal and stochastic processes influence the spatial turnover of communities. However, historical events, such as past environmental conditions or dispersal events, can be important as well. We provide a short summary of the processes that can lead to so-called legacy effects, where past biotic or abiotic factors influence the composition of present-day communities. Priority effects, which arise if early colonizers gain advantage over later-arriving species, can lead to persistent legacy effects. In contrast, time-lags in environmental selection can lead to transient legacy effects. Dispersal rates as well as factors that influence the adaptability of species to changing environmental conditions should be important factors that determine the relative importance of contemporary selection versus historical processes and whether legacy effects are likely to be permanent or temporary. Working with microbial communities offers the advantage of feasible time series studies and multi-generation experiments, and can therefore make important contributions to a novel systematic framework on how historical processes shape complex metacommunities in nature.

  • 48.
    Zha, Yinghua
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Berga, Mercè
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Comte, Jérôme
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Effects of Dispersal and Initial Diversity on the Composition and Functional Performance of Bacterial Communities2016In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 5, article id e0155239Article in journal (Refereed)
    Abstract [en]

    Natural communities are open systems and consequently dispersal can play an important role for the diversity, composition and functioning of communities at the local scale. It is, however, still unclear how effects of dispersal differ depending on the initial diversity of local communities. Here we implemented an experiment where we manipulated the initial diversity of natural freshwater bacterioplankton communities using a dilution-to-extinction approach as well as dispersal from a regional species pool. The aim was further to test whether dispersal effects on bacterial abundance and functional parameters (average community growth rates, respiration rates, substrate utilisation ability) differ in dependence of the initial diversity of the communities. First of all, we found that both initial diversity and dispersal rates had an effect on the recruitment of taxa from a regional source, which was higher in communities with low initial diversity and at higher rates of dispersal. Higher initial diversity and dispersal also promoted higher levels of richness and evenness in local communities and affected, both, separately or interactively, the functional performance of communities. Our study therefore suggests that dispersal can influence the diversity, composition and functioning of bacterial communities and that this effect may be enhanced if the initial diversity of communities is depleted.

  • 49.
    Östman, Örjan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Population and Conservation Biology.
    Drakare, Stina
    Kritzberg, Emma S.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Logue, Jürg B.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Importance of space and the local environment for linking local and regional abundances of microbes2012In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 67, no 1, p. 35-45Article in journal (Refereed)
    Abstract [en]

    It is frequently observed that the local relative abundances of aquatic microbial taxa are correlated with their average relative abundance at the regional scale, which results in the composition of different communities being more similar than expected by chance or invariant. The degree to which communities within a region match the regional average community is variable and likely depends on several different mechanisms that control the process of microbial community assembly. Here, we show that environmental variables were associated with the community specific degree of regional invariance in 9 of 10 datasets of microbial communities in aquatic systems, being the main set of variables explaining differences in regional invariance in 5 of them. This indicates that variation in local environmental conditions across a region reduces the degree of regional invariance amongst communities. Spatial distances between communities were not related to the degrees of regional invariance, but in 7 of the datasets, regional invariance differed among different parts of the regions, particularly for phytoplankton communities. This suggests an influence of spatial or historical processes on the community specific degree of regional invariance. We conclude that both local environmental conditions and spatial/historical processes cause between-site differences in the degree of invariance between local and regional abundances in aquatic microbial metacommunities. We argue that studies of regional invariance can be an important complement to other statistical methods due to its propensity to detect variation in stochastic processes along gradients.

  • 50.
    Östman, Örjan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Population and Conservation Biology.
    Drakare, Stina
    Kritzberg, Emma S.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Logue, Jürg Brendan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Regional invariance among microbial communities2010In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 13, no 1, p. 118-127Article in journal (Refereed)
    Abstract [en]

    Microbial ecology has focused much on causes of between-site variation in community composition. By analysing five data-sets each of aquatic bacteria and phytoplankton, we demonstrated that microbial communities show a large degree of similarity in community composition and that abundant taxa were widespread, a typical pattern for many metazoan metacommunities. The regional abundance of taxa explained on average 85 and 41% of variation in detection frequency and 58 and 31% of variation in local abundances for bacteria and phytoplankton, respectively. However, regional abundance explained less variation in local abundances with increasing environmental variation between sites within data-sets. These findings indicate that the studies of microbial assemblages need to consider similarities between communities to better understand the processes underlying the assembly of microbial communities. Finally, we propose that the degree of regional invariance can be linked to the evolution of microbes and the variation in ecosystem functions performed by microbial communities.

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