Abstract
Dispersal is an essential life-history trait crucial to species persistence and diversification. This is particularly important in spatiotemporal fluctuating environments such as freshwater habitats, where species movement is confined to the dendritic network and wetted boundaries. To persist in such fluctuating environments, a species can modify, adaptively and plastically, its phenotypic variation to better match the environment or escape via directed dispersal to a more suitable habitat (i.e., matching habitat choice). We use the invasive smallmouth bass, Micropterus dolomieu, sampled at 10 km intervals, to assess the effect of directed dispersal on the fine scale genetic and phenotypic variation in populations of M. dolomieu along a river course. Gene flow was used as a proxy for dispersal. By comparing population genetic structure, morphological variation (of linear traits and geometric landmarks), and environmental heterogeneity, we discovered a clear correlation between environmental variation and morphological traits. Although isolation by distance seemed to have shaped the overall genetic pattern detected among the populations, the strong genetic structuring observed within the Ratel tributary appeared to be non-random. These results provide novel insights into the potential mechanisms promoting the spread and establishment of invasive species and the possible influence multiple introductions may have on fine scale genetic structuring.
Highlights
Dispersal is a life-history trait essential to the persistence, diversification and evolution of species (Edelaar and Bolnick, 2012; Saastamoinen et al, 2018)
Fish belonging to locality A and D were significantly older (Bonferroni post hoc tests, all P ≤ 0.03) than those of the other localities (Supplementary Figure 2), no significant difference in age was observed among the other populations
The principal component analysis (PCA) conducted on the Procrustes coordinates provided four PCSHAPE axes, jointly explaining 67% of the variation, which were retained for the geometric morphometric data analyses
Summary
Dispersal is a life-history trait essential to the persistence, diversification and evolution of species (Edelaar and Bolnick, 2012; Saastamoinen et al, 2018). No longer thought to occur at random, active dispersal can reflect the response of individual phenotypes to the surrounding environment (Bowler and Benton, 2005; Edelaar et al, 2008; Clobert et al, 2009; Edelaar and Bolnick, 2012; Hui et al, 2012; Jacob et al, 2015). Directed dispersal (associated with matching habitat choice) is thought to promote genetic differentiation and potentially local adaptation when coupled with natural selection (Benkman, 2016), increasing local population genetic structure (Edelaar et al, 2008; Edelaar and Bolnick, 2012). Despite directed dispersal receiving increased attention, few empirical studies have sought to test matching habitat choice (Benkman, 2016; Camacho et al, 2020), especially for introduced species in their invaded ranges
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