How river structure and biological traits influence gene flow: a population genetic study of two stream invertebrates with differing dispersal abilities

Abstract

1. Determined by landscape structure as well as dispersal-related traits of species, connectivity influences various key aspects of population biology, ranging from population persistence to genetic structure and diversity. Here, we investigated differences in small-scale connectivity in terms of gene flow between populations of two ecologically important invertebrates with contrasting dispersal-related traits: an amphipod (Gammarus fossarum) with a purely aquatic life cycle and a mayfly (Baetis rhodani) with a terrestrial adult stage. 2. We used highly polymorphic markers to estimate genetic differentiation between populations of both species within a Swiss pre-alpine catchment and compared these results to the broader-scale genetic structure within the Rhine drainage. Landscape genetic approaches were used to test for correlations of genetic and geographical structures and in-stream barrier effects. 3. We found overall very weak genetic structure in populations of B. rhodani. In contrast, G. fossarum showed strong genetic differentiation, even at spatial scales of a few kilometres, and a clear pattern of isolation by distance. Genetic diversity decreased from downstream towards upstream populations of G. fossarum, suggesting asymmetric gene flow. Correlation of genetic structure with landscape topography was more pronounced in the amphipod. Our study also indicates that G. fossarum might be capable of dispersing overland in headwater regions and of crossing small in-stream barriers. 4. We speculate that differences in dispersal capacity but also habitat specialisation and potentially the extent of local adaptation could be responsible for the differences in genetic differentiation found between the two species. These results highlight the importance of taking into account dispersal-related traits when planning management and conservation strategies.

A salt bath will keep you going? Euryhalinity tests and genetic structure of caridean shrimps from Iberian rivers

“…The absence of free larval stages in D. valentina could have contributed to the low genetic interchange observed between geographically close populations. Strong genetic differentiation at spatial scales of a few kilometres has been previously found in some freshwater species, such as the amphipod Gammarus fossarum (Alp et al, 2012). Furthermore, when a river basin is isolated for a long time, allopatric speciation is likely to occur (e.g., Chícamo population).…”

Genetic diversity and dispersal potential of the stoneflyDinocras cephalotesin a central European low mountain range

“…Therefore, the absence of recombination within mitochondrial genes would lead to the persistence of these historically accumulated differences in secondary contact even under panmixia. Historic isolation has been discussed as a primary force underlying contemporary genetic variation in other aquatic insects (Pauls et al 2006, Lehrian et al 2010, Bálint et al 2011, Alp et al 2012, Theissinger et al 2012. The central question to be addressed with regard to such prominent differences in mitochondrial DNA is whether members of these groups still interbreed successfully in secondary contact.…”

Hidden Biodiversity in an Ecologically Important Freshwater Amphipod: Differences in Genetic Structure between Two Cryptic Species

“…Several population genetic studies have been conducted on G. fossarum , but often focused on limited geographical regions containing only one of the cryptic species and/or were constrained by the limited availability of highly variable and selectively neutral markers [13], [14], [35], [38]–[40]. We here make use of nine recently developed microsatellite markers [41] to examine the intraspecific genetic structure within two cryptic species and potential differences between them.…”