Partitioning of herbivore hosts across time and food plants promotes diversification in the Megastigmus dorsalis oak gall parasitoid complex. Issue 2 (25th December 2017)

• Record Type: Journal Article
• Authors: Nicholls, James A.; Schönrogge, Karsten; Preuss, Sonja; Stone, Graham N.
• Is Part Of: Ecology and evolution. Volume 8:Issue 2(2018)
• Page Start: 1300
• Page End: 1315
• Publication Date: 2017-12-25
• Subjects: community evolution -- Cynipidae -- ecological speciation -- host race -- Megastigmus dorsalis -- specialization; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.3712
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: Communities of insect herbivores and their natural enemies are rich and ecologically crucial components of terrestrial biodiversity. Understanding the processes that promote their origin and maintenance is thus of considerable interest. One major proposed mechanism is ecological speciation through host‐associated differentiation (HAD), the divergence of a polyphagous species first into ecological host races and eventually into more specialized daughter species. The rich chalcid parasitoid communities attacking cynipid oak gall wasp hosts are structured by multiple host traits, including food plant taxon, host gall phenology, and gall structure. Here, we ask whether the same traits structure genetic diversity within supposedly generalist parasitoid morphospecies. We use mitochondrial DNA sequences and microsatellite genotypes to quantify HAD for Megastigmus ( Bootanomyia ) dorsalis, a complex of two apparently generalist cryptic parasitoid species attacking oak galls. Ancient Balkan refugial populations showed phenological separation between the cryptic species, one primarily attacking spring galls, and the other mainly attacking autumn galls. The spring species also contained host races specializing on galls developing on different host‐plant lineages (sections Cerris vs. Quercus ) within the oak genus Quercus . These results indicate more significant host‐associated structuring within oak gall parasitoid communities than previously thought and support ecological theory predicting the evolution of specialist lineages within generalist parasitoids. In contrast, UK populations of the autumn cryptic species associated with both native and recently invading oak gall wasps showed no evidence of population differentiation, implying rapid recruitment of native parasitoid populations onto invading hosts, and hence potential for natural biological control. This is of significance given recent rapid range expansion of the economically damaging chestnut gall wasp, Dryocosmus kuriphilus, in Europe. Abstract : Genetic data show that the oak gall parasitoid Megastigmus dorsalis comprises two cryptic species that are ecologically differentiated in time, with one species primarily attacking spring oak galls and the other attacking autumn galls. Within the spring‐attacking species, there are also host races, specializing on galls induced on either section Quercus oaks or section Cerris oaks. Such ecological specialization may have contributed to speciation processes among other Megastigmus species attacking oak galls.