Large‐scale patterns in genetic variation, gene flow and differentiation in five species of European Coenagrionid damselfly provide mixed support for the central‐marginal hypothesis

Abstract

Recently, an increased effort has been directed towards understanding the distribution of genetic variation within and between populations, particularly at central and marginal areas of a species' distribution. Much of this research is centred on the central-marginal hypothesis, which posits that populations at range margins are sparse, small and genetically diminished compared to those at the centre of a species' distribution range. We tested predictions derived from the centralmarginal hypothesis for the distribution of genetic variation and population differentiation in five European Coenagrionid damselfly species. We screened genetic variation (microsatellites) in populations sampled in the centre and margins of the species' latitudinal ranges, assessed genetic diversity (H S ) in the populations and the distribution of this genetic diversity between populations (F ST ). We further assessed genetic substructure and migration with Bayesian assignment methods, and tested for significant associations between genetic substructure and bioclimatic and spatial (altitude and latitude) variables, using general linearized models. We found no general adherence to the central-marginal hypothesis; instead we found that other factors such as historical or current ecological factors often better explain the patterns uncovered. This was illustrated in Coenagrion mercuriale whose colonisation history and behaviour most likely led to the observation of a high genetic diversity in the south and lower genetic diversity with increasing latitude, and in C. armatum and C. pulchellum whose patterns of low genetic diversity coupled with the weakest genetic differentiation at one of their range margins suggested, respectively, possible range shifts and recent, strong selection pressure.For many species there exists detailed information on distribution ranges, and in some cases also historical distribution records. However, how and why these ranges are maintained, and under what conditions and by which mechanism they change, is highly speculative (Bridle and Vines 2006, Sagarin et al. 2006, Sexton et al. 2009). There has recently been increased interest in range margin dynamics due to global climate change, because species can respond to climate change and ensure their persistence through moving their ranges or adapting in situ (Parmesan et al. 2005). A critical issue in this context is that of population dynamics at range margins, and if they are akin to dynamics in central populations, because of their potential importance for genetic adaptation (Bridle and Vines 2006).The central-marginal hypothesis (Hengeveld and Haeck 1982, Brussard 1984) assumes that populations are most abundant and have higher densities where conditions are optimal for growth, and that populations become smaller and scarcer towards their range margins; since survival and growth becomes more arduous with increasing distance from the environmental optimum (Sagarin and Gaines 2002, Eckert et al. 2008. Based on this, the central-marginal hypothesis makes two pred...

A test of the central–marginal hypothesis using population genetics and ecological niche modelling in an endemic salamander (Ambystoma barbouri)

“…It is possible that other 30% of animal ranges are simply not influenced by CMH predictions (Johansson et al . ), or that this inconsistency among studies has resulted from misidentification of the species' core (Saavedra‐Sotelo et al . ).…”

“…; Johansson et al . ), and in some cases find no support for the CMH (Knopp & Merila ; Vakkari et al . ; Munwes et al .…”

Rapid range expansion increases genetic differentiation while causing limited reduction in genetic diversity in a damselfly

“…It might be that the Swiss SC edge population has experienced less genetic drift compared with the other edge populations due to its relatively older age and vicinity to the historical range, resulting in a similar genetic composition as the core populations. The Spanish SLF core population, on the other hand, might be isolated due to the Pyrenean mountains forming a barrier for gene flow, hence resulting in a deviant genetic composition than the other core populations, as recently shown for another Coenagrion damselfly species (Johansson et al, 2013).…”

Evolution determines how global warming and pesticide exposure will shape predator–prey interactions with vector mosquitoes

“…Moreover, any local adaptation to pesticides would be unlikely in damselflies given the high levels of gene flow (Johansson et al. ).…”