Evolutionary processes driving spatial patterns of intraspecific genetic diversity in river ecosystems

Abstract

Describing, understanding and predicting the spatial distribution of genetic diversity is a central issue in biological sciences. In river landscapes, it is generally predicted that neutral genetic diversity should increase downstream, but there have been few attempts to test and validate this assumption across taxonomic groups. Moreover, it is still unclear what are the evolutionary processes that may generate this apparent spatial pattern of diversity. Here, we quantitatively synthesized published results from diverse taxa living in river ecosystems, and we performed a meta-analysis to show that a downstream increase in intraspecific genetic diversity (DIGD) actually constitutes a general spatial pattern of biodiversity that is repeatable across taxa. We further demonstrated that DIGD was stronger for strictly waterborne dispersing than for overland dispersing species. However, for a restricted data set focusing on fishes, there was no evidence that DIGD was related to particular species traits. We then searched for general processes underlying DIGD by simulating genetic data in dendritic-like river systems. Simulations revealed that the three processes we considered (downstream-biased dispersal, increase in habitat availability downstream and upstream-directed colonization) might generate DIGD. Using random forest models, we identified from simulations a set of highly informative summary statistics allowing discriminating among the processes causing DIGD. Finally, combining these discriminant statistics and approximate Bayesian computations on a set of twelve empirical case studies, we hypothesized that DIGD were most likely due to the interaction of two of these three processes and that contrary to expectation, they were not solely caused by downstream-biased dispersal.

Genetic changes caused by restocking and hydroelectric dams in demographically bottlenecked brown trout in a transnational subarctic riverine system

“…However, in the stocked river Theoretical and simulation studies (Morrissey & de Kerckhove, 2009;Paz-Vinas, Loot, Stevens, & Blanchet, 2015) predict that population sizes and genetic diversity might be naturally higher in downstream than in upstream river sections. However, in the stocked river Theoretical and simulation studies (Morrissey & de Kerckhove, 2009;Paz-Vinas, Loot, Stevens, & Blanchet, 2015) predict that population sizes and genetic diversity might be naturally higher in downstream than in upstream river sections.…”

Riverscape genetic variation, migration patterns, and morphological variation of the threatened Round Rocksnail, Leptoxis ampla

“…We assessed whether L. ampla displays a downstream increase in genetic diversity with linear regressions of network position against allelic richness, observed heterozygosity, expected heterozygosity and nucleotide diversity. Following Paz‐Vinas et al (), network position was measured as distance from Centreville, which is the most downstream point in the Cahaba River that we sampled and all sites pass through Centreville by river network path (Figure ). All response variables of both data sets met assumptions of normality except observed heterozygosity.…”

“…Recently, Minton, McGregor, Hayes, Paight, and Inoue () used inter‐simple sequence repeats to examine population structure in Elimia potosiensis , but resolution across its range was limited. Research is needed to inform management decisions (Allendorf, ; McMahon, Teeling, & Höglund, ) and assess whether predictions of genetic diversity patterns across riverine landscapes (Finn et al, ; Meffe & Vrijenhoek, ; Paz‐Vinas et al, ; Vannote et al, ) are applicable to low‐dispersing, nonarthropod, invertebrates.…”

Applying gene flow science to environmental policy needs: a boundary work perspective

“…; Paz‐Vinas et al. ). With climate change and increasing pressure from habitat loss and fragmentation, information about gene flow will play an increasingly important role in the ability of resource managers to develop practices that enhance the capacity of individuals, populations, species, and communities to cope with their new environments (Crook et al.…”

“…; Morrissey and de Kerckhove ; Paz‐Vinas et al. ). For instance, in dendritic stream networks, the distributions of genetic and species diversity (and, thus, future evolutionary trajectories and community composition, respectively) have been linked to spatially influenced, historical processes of migration and gene flow which tend to be highly constrained by physical stream structure (Hughes et al.…”