Abstract
Neutral genetic structure of natural populations is primarily influenced by migration (the movement of individuals and, subsequently, their genes) and drift (the statistical chance of losing genetic diversity over time). Migration between populations is influenced by several factors, including individual behavior, physical barriers, and environmental heterogeneity among populations. However, drift is expected to be stronger in populations with low immigration rate and small effective population size. With the technological advancement in geological information systems and spatial analysis tools, landscape genetics now allows the development of realistic migration models and increased insight to important processes influencing diversity of natural populations. In this study, we investigated the relationship between landscape connectivity and genetic distance of threespine stickleback (Gasterosteus aculeatus) inhabiting a pond complex in Belgjarskógur, Northeast Iceland. We used two landscape genetic approaches (i.e., least-cost-path and isolation-by-resistance) and asked whether gene flow, as measured by genetic distance, was more strongly associated with Euclidean distance (isolation-by-distance) or with landscape connectivity provided by areas prone to flooding (as indicated by Carex sp. cover)? We found substantial genetic structure across the study area, with pairwise genetic distances among populations (DPS) ranging from 0.118 to 0.488. Genetic distances among populations were more strongly correlated with least-cost-path and isolation-by-resistance than with Euclidean distance, whereas the relative contribution of isolation-by-resistance and Euclidian distance could not be disentangled. These results indicate that migration among stickleback populations occurs via periodically flooded areas. Overall, this study highlights the importance of transient landscape elements influencing migration and genetic structure of populations at small spatial scales.
Highlights
Much evidence exists on how natural selection and mutations shape population structure (Darwin 1859; Coyne and Orr 2004; Schluter 2009; Roesti et al 2012)
We investigated the relationship between landscape connectivity and genetic distance of threespine stickleback (Gasterosteus aculeatus) inhabiting a pond complex in Belgjarskogur, Northeast Iceland
We used two landscape genetic approaches and asked whether gene flow, as measured by genetic distance, was more strongly associated with Euclidean distance or with landscape connectivity provided by areas prone to flooding? We found substantial genetic structure across the study area, with pairwise genetic distances among populations (DPS) ranging from 0.118 to 0.488
Summary
Much evidence exists on how natural selection and mutations shape population structure (Darwin 1859; Coyne and Orr 2004; Schluter 2009; Roesti et al 2012). Neutral processes such as migration and drift are important (Hartl and Clark 1997; Neiva et al 2012). The further apart two populations are in space, the less likely migration between the two populations will occur, thereby increasing their genetic differentiation due to isolation-by-distance (IBD) (Wright 1951).
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