No Concordant Phylogeographies of the Rose Gall Wasp Diplolepis rosae (Hymenoptera, Cynipidae) and Two Associated Parasitoids across Europe

Abstract

According to the Host-tracking Hypothesis, species of higher trophic levels with a close relationship to their hosts, such as parasites or parasitoids, are expected to show spatio-temporal phylogeographic patterns similar to those of their host. Alternatively, with ecological sorting, a subset of the local species pools might shift to a related host species, thereby disengaging common phylogeographic patterns. Here, we compare the phylogeographic structures of the cynipid rose gall wasp Diplolepis rosae across Europe and of two of its most common parasitoids, the wasps Orthopelma mediator and Glyphomerus stigma, by analysing the sequences of two gene fragments (COI and ITS 2). The phylogeographic structures of the three species associated with roses were incongruent. D. rosae had the lowest genetic diversity with one major clade, O. mediator showed the classical phylogeographic structure for Europe with one eastern and one western clade, and G. stigma had the highest diversity but no geographical structuring. This discordance of geographical patterns may be explained by 1) the dispersal propensity of adult parasitoids or 2) the parasitoids having the ability to switch to another host, while the primary host becomes rare or is even not available. Furthermore there was no indication that phylogenetic patterns were affected by Wolbachia infections. Our results document that communities of closely interacting species may be the result of idiosyncratic biogeographic histories.

Biased parasitoid sex ratios:Wolbachia, functional traits, local and landscape effects

“…G. stigma showed in both studies (Schilthuizen et al, 1998; Kohnen et al, 2012) a complete lack of Wolbachia , as it did in our samples. The only difference between our results and literature concerns the species P. bedeguaris : in a study 6 specimens were analysed and they found the Type I strain of Wolbachia (Schilthuizen et al, 1998), while we did not found any evidence for Wolbachia presence (N=36).…”

“…Thus, it seems that although O. mediator is infected, prevalence of Wolbachia is low. T. bedeguaris in the first study (Kohnen et al, 2012) was not a target species, while in the second (Schilthuizen et al, 1998) all its specimens were infected. Our results are in concordance with the previous studies since all T. bedeguaris specimens were infected by Wolbachia also in our samples.…”

“…For O. mediator a study found 10% prevalence of Wolbachia (Kohnen, Richter, & Brandl, 2012), while another showed that out of three analysed localities, only specimens from one were infected by Wolbachia (Schilthuizen & Stouthamer, 1998). Thus, it seems that although O. mediator is infected, prevalence of Wolbachia is low.…”

Incongruent evolutionary histories of two parasitoids in the Mediterranean Basin: influence of host specialization and ecological characteristics

“…Comparative phylogeographical studies aim at testing whether species belonging to the same community responded as a single unit to Quaternary environmental perturbations ('community phylogeography', commonly expected in closed communities; Nicholls et al, 2010) or whether the genetic structure of interacting species results from idiosyncratic biogeographical histories (Kohnen et al, 2012). Incongruent patterns are expected when host switches occur in dependent species, or when their dispersal characteristics and ecological requirements are different.…”

“…When studying interacting species (plant and pollinators, phytophagous or parasite species associated with the same host), comparative phylogeography allows for the testing of the congruence of phylogeographical patterns across trophic levels or between species belonging to the same community. Congruence can be expected when a dependent species is strongly constrained in its migration pathways by its partner and must follow its colonization routes (Nicholls et al, 2010;Borer et al, 2012), while incongruent histories can occur if the species have different dispersal propensities or if the dependent species can switch hosts (Esp ındola & Alvarez, 2011;Kohnen et al, 2012). The level of similarity in phylogeographical patterns is thus expected to be lower in generalist species, which can survive on alternative hosts, than in specialists.…”