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Factors influencing the biogeography of bacteria in fresh waters - a metacommunity approach
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

One of ecology’s primary goals is to comprehend biodiversity and its patterns of distribution over space and time. Since microorganisms play a pivotal role in key ecological processes, the diversity of microbial communities may have important implications for the stability and functioning of Earth’s ecosystems. Thus, it is of utmost importance to develop a theoretical foundation but also a conceptual understanding for the mechanisms that generate and maintain microbial diversity.

The aim of this thesis is to investigate to what extent local freshwater bacterioplankton diversity, i.e. richness and community composition, is structured by local environmental interactions and/or regional processes. The key objective is to identify ecological linkages between lake bacterioplankton and bacterial communities in connected streams and the surrounding terrestrial landscape, thereby applying a metacommunity approach. To do so, I studied several natural lake bacterioplankton assemblies within different regions of Sweden and assessed both local environmental properties and regional parameters (e.g. dispersal, landscape position). The genetic composition of freshwater bacterioplankton diversity was determined by means of terminal-restriction fragment length polymorphism or 454 pyrosequencing.

From the review on the biogeography of bacterioplankton in inland waters it became clear that microbial diversity and its spatial distribution are governed by a complex interplay of both local and regional drivers. In one case, freshwater bacterioplankton communities were structured by local environmental conditions rather than by regional dispersal processes. These local environmental conditions seemed to be equally important in controlling both the total bacterioplankton community and its active fraction. In a study of bacterioplankton communities from five different regions, locally abundant aquatic bacteria were shown to be also regionally widespread, a pattern predicted by neutral theory. Yet, this degree of similarity decreased with increasing environmental heterogeneity. In another study, bacterioplankton richness was controlled mostly by nutrient content, indicating that productivity exerted influence on bacterioplankton richness. However, landscape position and productivity covaried, suggesting that the landscape dictates environmental properties, which then directly structure local bacterioplankton richness. Finally, a review synthesising results from empirical metacommunity approaches and comparing these to theory showed that yet a gap between empirics and theory exists. To conclude, local bacterioplankton diversity appeared to be mainly structured by local environmental properties. However, signatures of neutral processes driving local bacterioplankton community assembly were also recorded.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2010. , p. 52
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 763
Keywords [en]
bacteria, diversity, richness, community composition, dispersal, metacommunity, fresh water, biogeography
National Category
Ecology Microbiology in the medical area
Research subject
Biology with specialization in Limnology
Identifiers
URN: urn:nbn:se:uu:diva-130009ISBN: 978-91-554-7881-0 (print)OAI: oai:DiVA.org:uu-130009DiVA, id: diva2:345756
Public defence
2010-10-08, Ekmansalen, Evolutionary Biology Centre (EBC), Uppsala University, Norbyvägen 18, 752 36 Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2010-09-16 Created: 2010-08-27 Last updated: 2022-01-28
List of papers
1. Biogeography of bacterioplankton in inland waters.
Open this publication in new window or tab >>Biogeography of bacterioplankton in inland waters.
2008 (English)In: Freshwater Reviews, ISSN 1755-084X, Vol. 1, no 1, p. 99-114Article in journal (Refereed) Published
Abstract [en]

Bacteria are among the most abundant groups of organisms.  They mediate key ecological processes.  Recent molecular advances have provided greater insight into bacterial diversity as well as allowing a more thorough examination of patterns in the spatial and temporal distribution of bacteria.  Thus, the study of bacterial biodiversity and biogeographical distribution has stimulated considerable interest and dispute over the last decade. This review summarises the findings obtained from studies on the biogeography of bacterioplankton in inland waters.  We examine factors and processes that may determine and maintain bacterial diversity and biogeography, and relate these to the theoretical metacommunity framework. We conclude that the importance of local environmental factors (such as lake character) for local bacterioplankton community compositions (BCC) is much more intensively studied than the importance of regional factors, such as dispersal.  Further, few attempts have been made to evaluate simultaneously the relative importance of the two types of factors for BCC.  Finally, we summarise gaps in knowledge, delineate challenges and put forward possible future research directions.

National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-107690 (URN)10.1608/FRJ-1.1.9 (DOI)
Available from: 2009-08-24 Created: 2009-08-24 Last updated: 2024-03-14
2. Empirical approaches to metacommunities: a review and comparison with theory
Open this publication in new window or tab >>Empirical approaches to metacommunities: a review and comparison with theory
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Metacommunity theory has advanced our understanding of how spatial dynamics and local interactions shape local community structure and biodiversity. The last decade has seen an increase in implementation of these ideas in empirical ecology to explain and understand the regulation of local community structure and dynamics. Here, we review the different empirical (experimental and observational) approaches to metacommunities to analyse their strengths and weaknesses in comparison to natural ecosystems and theoretical paradigms. Experimental approaches are extremely diverse, ranging from highly controlled laboratory microcosms to large-scale fragmentation studies in the field. The main body of experiments, however, favours downscaled, artificial designs, avoiding physical complexity. These approaches are often successful in mechanistically addressing local and regional species interactions but the preponderance of artificial dispersal treatments via transfer neglects the importance of species’ differences in dispersal ability for community structure. Observational approaches mainly focus on investigating smaller organisms in aquatic communities, which are predominantly assembled by local environmental processes. However, observational approaches often lack actual measurements of dispersal rates, which hamper the distinction of local and regional effects on community composition. More generally, empirical metacommunity data deviate from theory as – with the exception of the most artificial experimental systems – the data rarely reflect specific paradigms. Thus, the paradigms capture only parts of the observed spatial dynamics. Metacommunity theory has emerged as a highly successful framework to understand the assembly of local communities but we conclude that empirical and theoretical approaches need thorough harmonisation to utilise the potential of this framework in guiding our understanding of spatial dynamics in ecological communities.

Keywords
metacommunity, community ecology, experimental, observational, empirical, theory, review, literature survey
National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:uu:diva-129366 (URN)
Available from: 2010-08-12 Created: 2010-08-12 Last updated: 2011-11-15
3. Species sorting affects bacterioplankton community composition as determined by 16S rDNA and 16S rRNA fingerprints
Open this publication in new window or tab >>Species sorting affects bacterioplankton community composition as determined by 16S rDNA and 16S rRNA fingerprints
2010 (English)In: The ISME Journal, ISSN 1751-7362, Vol. 4, no 6, p. 729-738Article in journal (Refereed) Published
Abstract [en]

To understand the mechanisms determining community composition, it is essential to distinctively unravel the importance of local from that of regional processes. In this effort, the mechanisms underlying bacterioplankton community assembly were analysed in eight lakes of short water residence time (WRT) during a four-season sampling campaign. Bacterioplankton community composition (BCC) was determined using terminal-restriction fragment length polymorphism (t-RFLP) on the 16S rRNA gene (16S rDNA) and 16S rRNA. The relationship between similarity in BCC between a lake and its major inlet on the one hand and cell import per cell production rate from the inlet to the lake epilimnion on the other was used as a measure of the importance of cell dispersal (mass effects) for community assembly. Low similarities in BCC between lakes and their inlets were observed even at short WRTs, and the degree of similarity correlated better with the environmental conditions in lakes and streams than with cell import per cell production rates. Thus, mass effects seemed less important for local lake BCC in comparison to environmental habitat characteristics (species sorting). Analyses of 16S rDNA and 16S rRNA community fingerprints yielded similar results, indicating that species-sorting dynamics exerted an equally important effect on both the abundant and active fraction within the studied bacterioplankton communities.

Place, publisher, year, edition, pages
Nature Publishing Group, 2010
Keywords
16S rDNA, 16S rRNA, biogeography, mass effects, metacommunity, species sorting
National Category
Biological Sciences
Research subject
Biology with specialization in Limnology
Identifiers
urn:nbn:se:uu:diva-129364 (URN)10.1038/ismej.2009.156 (DOI)000278104800002 ()20130658 (PubMedID)
Available from: 2010-08-12 Created: 2010-08-12 Last updated: 2010-12-13Bibliographically approved
4. Freshwater bacterioplankton richness in oligotrophic lakes depends on nutrient availability rather than on species-area relationships
Open this publication in new window or tab >>Freshwater bacterioplankton richness in oligotrophic lakes depends on nutrient availability rather than on species-area relationships
Show others...
2012 (English)In: The ISME Journal, ISSN 1751-7362, Vol. 6, no 6, p. 1127-1136Article in journal (Refereed) Published
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.

Keywords
bacterial richness, biogeography, freshwater, landscape position, productivity, species-area relationship
National Category
Microbiology Ecology
Research subject
Biology with specialization in Limnology
Identifiers
urn:nbn:se:uu:diva-130008 (URN)10.1038/ismej.2011.184 (DOI)000304047800005 ()
Available from: 2010-08-26 Created: 2010-08-26 Last updated: 2013-01-14Bibliographically approved
5. Regional invariance among microbial communities
Open this publication in new window or tab >>Regional invariance among microbial communities
Show others...
2010 (English)In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 13, no 1, p. 118-127Article in journal (Refereed) Published
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.

Keywords
Abundance-occupancy, dispersal, freshwater, generalists, neutral models, species sorting, Sweden
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-121206 (URN)10.1111/j.1461-0248.2009.01413.x (DOI)000272996200013 ()19968693 (PubMedID)
Available from: 2010-03-19 Created: 2010-03-19 Last updated: 2017-12-12Bibliographically approved

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