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- Bergek, Sara, 1979-
(author)
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Population divergence at small spatial scales : – theoretical and empirical investigations in perch
- 2009
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Doctoral thesis (other academic/artistic)abstract
- 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.
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| 2. |
- Poulet, Nicolas, et al.
(author)
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Genetic structure and dynamics of a small introduced population : the pikeperch, Sander lucioperca, in the Rhone delta
- 2009
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In: Genetica. - : Springer Science and Business Media LLC. - 0016-6707 .- 1573-6857. ; 135:1, s. 77-86
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Journal article (peer-reviewed)abstract
- Genetic data on introduced populations may help us to understand how these species succeed in colonising new territories. The pikeperch is a predatory fish widely introduced in Europe and has at times been considered as an invasive species. However, little is known about the genetics of both native and introduced populations. In the present study, we surveyed an introduced pikeperch population from the Rhone River delta, a habitat that has been highly modified for agricultural purposes. Using six microsatellites, we genotyped 93 individuals distributed among four hydraulically connected water bodies: the Rhone River, an irrigation canal, a drainage canal and a brackish lagoon. Population isolation were revealed by significant genetic distances and bottleneck highlighted by population monitoring. However, values of allelic richness and unbiased expected heterozygosity observed in these populations were similar, or even higher, compare to 18 native populations from the Baltic Sea drainage. It may be explained by multiple introductions in the Rhonee drainage but also by demographic strategy that would have facilitated population persistence in this fragmented habitat. Similarly, heterozygote deficits (revealed by F-IS values) have been detected, but were also found in native populations suggesting that mating among relatives could also result from a mating behavior of the species, maybe reinforce here by the reduced carrying capacity of the artificial canals and their respective isolation. Despite harsh environmental conditions and suspected inbreeding, the pikeperch has successfully maintained viable populations in the Rhone delta. Our study suggests that one of the factors in this invasive success, apart from its ecology, could be the maintenance of a good level of genetic diversity in introduced pikeperch populations. This genetic diversity probably stem from both its popularity as game fish and food resource which led to numerous stocking and an increasing propagule pressure and the reproductive strategy of the species.
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