Abstract
Specialization for the use of different resources can lead to ecological speciation. Accordingly, there are numerous examples of ecologically specialized pairs of fish “species” in postglacial lakes. Using a polymorphic panel of single nucleotide variants, we tested for genetic footprints of within‐lake population stratification in nine‐spined sticklebacks (Pungitius pungitius) collected from three habitats (viz. littoral, benthic, and pelagic) within a northern Swedish lake. Analyses of admixture, population structure, and relatedness all supported the conclusion that the fish from this lake form a single interbreeding unit.
Highlights
Environmental heterogeneity and intraspecific competition provide the opportunity and motivation for individuals to maximize their fitness by taking advantage of the resources that are most exploited given their specific phenotypes (Rainey and Travisano 1998; Schluter 2001; Nosil and Reimchen 2005; Reid and Peichel 2010; Siwertsson et al 2010; Araujo et al 2011; Faulks et al 2015)
On the other hand, when comparing the empirically derived Fst with a simulated population with three subpopulations having Fst % 0.0025, the empirical Fst was not significantly different than what could be expected from a random sample from this population. These results suggest that the lake population is genetically very weakly structured, most likely at a level no greater than Fst % 0.0025
Our analyses did not detect any form of population or kin structuring, suggesting that nine-spined sticklebacks from the different habitats in the study lake were all members of a single panmictic population
Summary
Environmental heterogeneity and intraspecific competition provide the opportunity and motivation for individuals to maximize their fitness by taking advantage of the resources that are most exploited given their specific phenotypes (Rainey and Travisano 1998; Schluter 2001; Nosil and Reimchen 2005; Reid and Peichel 2010; Siwertsson et al 2010; Araujo et al 2011; Faulks et al 2015). Individuals living in sympatry can segregate into different habitats to exploit dissimilar resources; this may provide a starting point for ecological speciation, in which reproductive isolation evolves as consequence of contrasting selection pressures between different resource environments (Schluter 1996a, 2001). Genetically divergent sympatric forms of fishes in postglacial freshwater habitats provide numerous potential examples of ecological speciation Well-studied examples include different trophic forms of whitefishes (Coregonus clupeaformis; Bernatchez and Dodson 1990; Bernatchez et al 1996), arctic charrs (Salvelinus alpinus; Hartley et al 1992; Malmquist et al 1992), and three-spined sticklebacks (Gasterosteus aculeatus; Schluter and Conte 2009). Additional examples of trophic specialization and intrapopulation divergence within relatively young Fennoscandian lakes have been emerging, including the case of Eurasian perch (Perca fluviatilis; Bartels et al 2012)
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