Fine-scale spatial genetic structure and within population male-biased gene-flow in the grasshopper Mioscirtus wagneri

Dispersal is a life history trait that plays a key role in population dynamics, determining gene flow and influencing the size, structure and persistence of populations. For these reasons, the study of the genetic consequences of dispersal can be considered a central topic in both conservation and population genetics. In this study we examine the patterns of fine-scale genetic structure within two populations of the grasshopper Mioscirtus wagneri (Orhoptera: Acrididae). For this purpose, we have used seven species-specific microsatellite markers to type 266 individuals from two populations (Peña Hueca and El Salobral) located in Central Spain. We have found subtle genetic differentiation between some sampling patches and significant kinship structures up to 25 m distance which were particularly patent for females. In Peña Hueca locality, patterns of isolation-by-distance at both the patch scale and the individual level have also revealed an association between genetic differentiation/similarity and geographical distance in females but not in males. Overall, these data suggest a fine-scale spatial genetic substructure in the studied populations which seems to be mainly driven by female philopatry. Such pattern of within population genetic structure together with the inferred restricted dispersal distances is likely to contribute to reduce effective population sizes and inter-population gene flow. This can erode genetic variability and limit the colonization ability of this orthoptera, factors which can ultimately compromise the long-term persistence of their small size and isolated populations.