Phylogeography, historical factors and hostparasite specificity: Comparative study of the communities of acorn feeding insects (Curculio spp.) in the Iberian Peninsula and California

Hostparasite specificity constitutes one of the main speciation engines in phytophagous insects. The isolation of populations and its temporal persistence may promote local adaptations at the intraspecific level, in the same way that local extinctions and intense geneflow among populations eliminate them. These adaptations may be the stage previous to speciation. In this study we compare the trophic specificity patterns of the coleoptera of the genus Curculio (specialist parasites of Quercus seeds) between California and the Iberian Peninsula. These two zones have nowadays a very similar climate, however, their past climate histories differ. Using DNA taxonomy techniques we found a potential cryptic species of Curculio in the Iberian Peninsula, although trophic specialization does not underlay this possible speciation event. At the intraspecific level, californian Curculio showed a much more marked population genetic structure compared to iberian ones, in which genetic depauperation and a posterior intense interpopulation geneflow can be appreciated. These differences, very similar to those found when the Quercus spp. of both zones were compared, point at the existence of a higher number of glacial refugia in California. Despite that a lower interpopulation geneflow prolonged in time could have promoted a higher specialization in California, there were not differences with the Iberian Peninsula in this sense. The marked interannual variability of the trophic source (fluctuations of acorn crops not always coincident among Quercus species) may have favoured the lack of a very strict specificity.