Strong Gene Flow Undermines Local Adaptations in a Host Parasite System

The co-evolutionary pathways followed by hosts and parasites strongly depend on the adaptive potential of antagonists and its underlying genetic architecture. Geographically structured populations of interacting species often experience local differences in the strength of reciprocal selection pressures, which can result in a geographic mosaic of co-evolution. One example of such a system is the boreo-montane social wasp Polistes biglumis and its social parasite Polistes atrimandibularis, which have evolved local defense and counter-defense mechanisms to match their antagonist. In this work, we study spatial genetic structure of P. biglumis and P. atrimandibularis populations at local and regional scales in the Alps, by using nuclear markers (DNA microsatellites, AFLP) and mitochondrial sequences. Both the host and the parasite populations harbored similar amounts of genetic variation. Host populations were not genetically structured at the local scale, but geographic regions were significantly differentiated from each other in both the host and the parasite in all markers. The net dispersal inferred from genetic differentiation was similar in the host and the parasite, which may be due to the annual migration pattern of the parasites between alpine and lowland populations. Thus, the apparent dispersal barriers (i.e., high mountains) do not restrict gene flow as expected and there are no important gene flow differences between the species, which contradict the hypothesis that restricted gene flow is required for local adaptations to evolve

Strong Gene Flow Undermines Local Adaptations in a Host Parasite System

The co-evolutionary pathways followed by hosts and parasites strongly depend on the adaptive potential of antagonists and its underlying genetic architecture. Geographically structured populations of interacting species often experience local differences in the strength of reciprocal selection pressures, which can result in a geographic mosaic of co-evolution. One example of such a system is the boreo-montane social wasp Polistes biglumis and its social parasite Polistes atrimandibularis, which have evolved local defense and counter-defense mechanisms to match their antagonist. In this work, we study spatial genetic structure of P. biglumis and P. atrimandibularis populations at local and regional scales in the Alps, by using nuclear markers (DNA microsatellites, AFLP) and mitochondrial sequences. Both the host and the parasite populations harbored similar amounts of genetic variation. Host populations were not genetically structured at the local scale, but geographic regions were significantly differentiated from each other in both the host and the parasite in all markers. The net dispersal inferred from genetic differentiation was similar in the host and the parasite, which may be due to the annual migration pattern of the parasites between alpine and lowland populations. Thus, the apparent dispersal barriers (i.e., high mountains) do not restrict gene flow as expected and there are no important gene flow differences between the species, which contradict the hypothesis that restricted gene flow is required for local adaptations to evolve

Population diversity in cuticular hydrocarbons and mtDNA in a mountain social wasp

International audienceNestmate recognition is a common phenomenon insocial insects that typically is mediated by cuticular hydrocarbons.Geographical variation in cuticular hydrocarbons hasbeen observed, although the pattern of variation is not consistentacross species and is usually related to the biology andecology of the different species. Polistes biglumis(Hymenoptera: Vespidae) is a social wasp that lives in highmountains where populations are separated by significantgeographical barriers. Here we investigated the level of chemicalvariation among populations of P. biglumis in the Alps,and shed light on the phylogeography of this species.Populations could be discriminated bymeans of their cuticularhydrocarbon profiles, which showed a pattern consistent withthe isolation-by-distance hypothesis. Molecular datahighlighted two areas with different levels of haplotype diversity,although all wasps belonged to the same species. Theseresults suggest that the populations of P. biglumis in the Alpsare geographically isolated from one another, favoring theirgenetic and chemical differentiation