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Population divergence at small spatial scales: – theoretical and empirical investigations in perch
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Zooekologi.
2009 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Genetically structured populations arise when gene flow between groups of individuals is hindered by geographical, behavioural or temporal barriers. The identification of such groups is important for understanding evolution and has large implications for conservation concern. The field of population subdivision has received a lot of interest throughout the years and gained empirical support from a number of species. However, very little is known about population structure at small spatial scales, especially in a highly mobile species such as fish. The main object for my thesis was to further investigate population differentiation, explicitly at small spatial scales in the Eurasian perch. My results show that in this species, genetic differentiation occurs, even at very small spatial scales, both within lakes and in the Baltic Sea. Additionally, the differentiation can be stable over years and thus have a large impact in the evolution of adaptation to different environments. I also found barriers to gene flow that overlapped with the largest change in spring temperature, suggesting a temporal difference in spawning. Morphological differences were found at these small scales as well which indicates that a difference in food resources might be an underlying cause of change. My thesis work shows that the aquatic environment might not be as homogenous as widely thought and that there could be barriers or adaptations to different environments that hinder the fish from genetic panmixia. Slight patterns of isolation by distance (IBD) were found in the Baltic Sea, implying that the distance (i.e. currents) effect the level of differentiation via drifting of larvae and/or small fish. However, I have also theoretically investigated the IBD model of and seen that it is no longer correct when differences in population sizes are introduced. The pattern of IBD can mean high levels of gene flow or no gene flow at all, solely dependent on population size differences and fluctuations. My thesis has resulted in new and important findings regarding the existence and cause of genetic differentiation at very small spatial scales and thus added new knowledge into the field of evolution and speciation. In addition, my results also give insights into the contemporary state of the Eurasian perch and future evolutionary potential.

sted, utgiver, år, opplag, sider
Uppsala: Acta Universitatis Upsaliensis , 2009. , s. 33
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 659
Emneord [en]
Perca fluviatilis L., Perch, Small scale genetic differentiation, Morphometrics, Isolation by distance, Dispersal, Gene flow, Microsatellites, Spatiotemporal stability, Barriers
HSV kategori
Forskningsprogram
zooekologi
Identifikatorer
URN: urn:nbn:se:uu:diva-107223ISBN: 978-91-554-7573-4 (tryckt)OAI: oai:DiVA.org:uu-107223DiVA, id: diva2:228359
Disputas
2009-09-18, Zootissalen, Villavägen 9, Uppsala, 10:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2009-08-28 Laget: 2009-07-29 Sist oppdatert: 2017-07-12bibliografisk kontrollert
Delarbeid
1. Cryptic barriers to dispersal within a lake allow genetic differentiation of Eurasian perch
Åpne denne publikasjonen i ny fane eller vindu >>Cryptic barriers to dispersal within a lake allow genetic differentiation of Eurasian perch
2007 (engelsk)Inngår i: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 61, nr 8, s. 2035-2041Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Gene flow between coexisting or nearby populations normally prevents genetic divergence and local adaptation. Despite this, there are an increasing number of reports of sympatric sister taxa, indicating potential divergence and speciation in the face of gene flow. A large number of such reported cases involve lake-dwelling fish, which are expected to run into few physical barriers to dispersal within their aquatic habitat. However, such cases may not necessarily reflect sympatric speciation if cryptic dispersal barriers are common in lakes and other aquatic systems. In this study, we examined genetic differentiation in perch (Perca fluviatilis L.) from nine locations in a single, small lake (24 km(2)), using microsatellites. We detected significant genetic differentiation in all but two pairwise comparisons. These patterns were not consistent with divergence by distance or the existence of kin groups. Instead, they suggest that cryptic barriers to dispersal exist within the lake, allowing small-scale genetic divergence. Such an observation suggests that allopatric (or parapatric) divergence may be possible, even in small, apparently homogenous environments such as lakes. This has important consequences for how we currently view evidence from nature for sympatric speciation.

sted, utgiver, år, opplag, sider
Oxford: Wiley-Blackwell, 2007
Emneord
Allopatric speciation, Geographic reproductive barriers, Microsatellites, Perca fluviatilis L., Small-scale genetic divergence, sympatric speciation
HSV kategori
Forskningsprogram
Zooekologi
Identifikatorer
urn:nbn:se:uu:diva-107227 (URN)10.1111/j.1558-5646.2007.00163.x (DOI)000248600300022 ()
Tilgjengelig fra: 2009-07-30 Laget: 2009-07-30 Sist oppdatert: 2017-12-13bibliografisk kontrollert
2. Spatiotemporal analysis shows stable genetic differentiation and barriers to dispersal in the Eurasian perch (Perca fluviatilis L.)
Åpne denne publikasjonen i ny fane eller vindu >>Spatiotemporal analysis shows stable genetic differentiation and barriers to dispersal in the Eurasian perch (Perca fluviatilis L.)
2009 (engelsk)Inngår i: Evolutionary Ecology Research, ISSN 1522-0613, E-ISSN 1937-3791, Vol. 11, nr 5, s. 827-840Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Background: Recently, unexpected or cryptic barriers to gene flow causing genetic discontinuities have been found in a number of animal taxa, even in apparently highly connected areas such as aquatic environments. 

Goal: Investigate the temporal stability of previously documented microgeographic genetic structure in a fish.

Organism: Eurasian perch (Perca fluviatilis L.)

Method: We sampled four locations over a period of 2 years. We used six microsatellites to investigate population differentiation. We compared within-year to between-year differentiation.

Results: The significant genetic differentiation found between locations in 2004 was still present in 2006. The strongest barriers to gene flow in the lake were consistent over both sampling periods. Furthermore, temporal differentiation existed within each site between the years. Populations of perch appear to cluster in different patches in the lake that harbour genetically differentiated groups of fish. Hence, limited migration and barriers to dispersal can persist over time, even at a very small geographical scale and in an open aquatic environment.

sted, utgiver, år, opplag, sider
Tucson: Evolutionary Ecology Ltd., 2009
Emneord
Barriers to gene flow, Microsatellites, Perca fluviatilis L, Small-scale genetic divergence, Spatiotemporal stability
HSV kategori
Forskningsprogram
Zooekologi
Identifikatorer
urn:nbn:se:uu:diva-107228 (URN)000269674500009 ()
Tilgjengelig fra: 2009-07-30 Laget: 2009-07-30 Sist oppdatert: 2018-05-31bibliografisk kontrollert
3. Genetic and morphological divergence reveals local subdivision of perch (Perca fluviatilis L.)
Åpne denne publikasjonen i ny fane eller vindu >>Genetic and morphological divergence reveals local subdivision of perch (Perca fluviatilis L.)
2009 (engelsk)Inngår i: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 96, nr 4, s. 746-758Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The level of gene flow is an important factor influencing genetic differentiation between populations. Typically, geographic distance is considered to be the major factor limiting dispersal and should thus only influence the degree of genetic divergence at larger spatial scales. However, recent studies have revealed the possibility for small-scale genetic differentiation, suggesting that the spatial scale considered is pivotal for finding patterns of isolation by distance. To address this question, genetic and morphological differentiation were studied at two spatial scales (range 2–13 km and range 300 m to 2 km) in the perch (Perca fluviatilis L.) from the east coast archipelago of Sweden, using seven microsatellite loci and geometric morphometrics. We found highly significant genetic differentiation between sampled locations at both scales. At the larger spatial scale, the distance not affecting the level of divergence. At the small scale, however, we found subtle patterns of isolation by distance. In addition, we also found morphological divergence between locations, congruent with a spatial separation at a microgeographic scale, most likely due to phenotypic plasticity. The present study highlights the importance of geographical scale and indicates that there might be a disparity between the dispersal capacity of a species and the actual movement of genes. Thus, how we view the environment and possible barriers to dispersal might have great implications for our ability to fully understand the evolution of genetic differentiation, local adaptation, and, in the end, speciation.

sted, utgiver, år, opplag, sider
Wiley-Blackwell, 2009
Emneord
Differentiation, Dispersal, Gene flow, Isolation by distance, Microsatellites, Morphometrics
HSV kategori
Forskningsprogram
Zooekologi
Identifikatorer
urn:nbn:se:uu:diva-107229 (URN)10.1111/j.1095-8312.2008.01149.x (DOI)000264730400004 ()
Tilgjengelig fra: 2009-07-30 Laget: 2009-07-30 Sist oppdatert: 2017-12-13bibliografisk kontrollert
4. Population differentiation in perch Perca fluviatilis: environmental effects on gene flow?
Åpne denne publikasjonen i ny fane eller vindu >>Population differentiation in perch Perca fluviatilis: environmental effects on gene flow?
2010 (engelsk)Inngår i: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 76, nr 5, s. 1159-1172Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Environmental parameters were used to investigate barriers to gene flow and genetic differentiation in the Eurasian perch (Perca fluviatilis L.) at a small geographical scale in an archipelago system. Significant genetic differentiation was found among locations. Distance per se did not play a major role in the reduction of gene flow. Instead, the largest genetic differences between populations correlated with major changes in environmental conditions, such as temperature at time of spawning. The results show that genetic divergence can arise between populations in habitats thought to be highly connected, and that environmental variables can influence the level of gene flow between populations, including those that are at small spatial scales (tens of kilometres). The importance of a landscape approach when investigating genetic differentiation and defining barriers to gene flow is highlighted.

Emneord
barriers to gene flow; landscape genetics; microsatellite DNA; Perca fluviatilis L; population differentiation
HSV kategori
Forskningsprogram
Zooekologi
Identifikatorer
urn:nbn:se:uu:diva-107244 (URN)10.1111/j.1095-8649.2010.02565.x (DOI)000276403000006 ()
Tilgjengelig fra: 2009-07-30 Laget: 2009-07-30 Sist oppdatert: 2017-12-13bibliografisk kontrollert
5. The effect of local population dynamics on patterns of isolation by distance
Åpne denne publikasjonen i ny fane eller vindu >>The effect of local population dynamics on patterns of isolation by distance
2010 (engelsk)Inngår i: Ecological Informatics, ISSN 1574-9541, Vol. 5, nr 3, s. 167-172Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Isolation-by-distance (IBD) is a widely used model explaining population structure and how gene flow decreases with increasing distances. It is biologically intuitive that populations which rarely exchange individuals should drift apart genetically. However, the model is based on the assumptions that populations are large, equal in size and stable over time - conditions that are unlikely to occur in natural conditions. The model has been challenged in the past, for example, in the light of metapopulations or variance in reproductive success. However, an appraisal of the assumption of a large and stable population size per se is lacking. We investigate the robustness of the results concerning IBD patterns when smaller and fluctuating population sizes, or differences in population size are allowed. Through computer simulations we show that allowing for different population sizes and randomly fluctuations leads to unpredictable patterns regarding the results concerning gene flow and IBD. A pattern of IBD could be the result of high gene flow or no gene flow at all, depending on how populations differ in size and how they fluctuate. Adding environmental noise (white, red and blue noise corresponding to random, positive and negative autocorrelation respectively) gives even more unpredictable results concerning patterns of IBD. Our results have important implications for genetic and conservation research. Interpreting an IBD pattern, or lack thereof, is not as easy as earlier thought and needs to be more thoroughly explored.

 

Emneord
Isolation-by-distance, Wright’s Island model, effective population size, stepping stone model, FST, computer simulations
HSV kategori
Forskningsprogram
Zooekologi
Identifikatorer
urn:nbn:se:uu:diva-107249 (URN)10.1016/j.ecoinf.2009.12.003 (DOI)000277916000002 ()
Tilgjengelig fra: 2009-07-30 Laget: 2009-07-30 Sist oppdatert: 2016-04-18bibliografisk kontrollert

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