Histories of host shifts and cospeciation among free‐living parasitoids of Rhagoletis flies

Abstract

Host shifts by specialist insects can lead to reproductive isolation between insect populations that use different hosts, promoting diversification. When both a phytophagous insect and its ancestrally associated parasitoid shift to the same novel host plant, they may cospeciate. However, because adult parasitoids are free living, they can also colonize novel host insects and diversify independent of their ancestral host insect. Although shifts of parasitoids to new insect hosts have been documented in ecological time, the long-term importance of such shifts to parasitoid diversity has not been evaluated. We used a genus of flies with a history of speciation via host shifting (Rhagoletis [Diptera: Tephritidae]) and three associated hymenopteran parasitoid genera (Diachasma, Coptera and Utetes) to examine cophylogenetic relationships between parasitoids and their host insects. We inferred phylogenies of Rhagoletis, Diachasma, Coptera and Utetes and used distance-based cophylogenetic methods (ParaFit and PACo) to assess congruence between fly and parasitoid trees. We used an event-based method with a free-living parasitoid cost model to reconstruct cophylogenetic histories of each parasitoid genus and Rhagoletis. We found that the current species diversity and host-parasitoid associations between the Rhagoletis flies and parasitoids are the primary result of ancient cospeciation events. Parasitoid shifts to ancestrally unrelated hosts primarily occur near the branch tips, suggesting that host shifts contribute to recent parasitoid species diversity but that these lineages may not persist over longer time periods. Our analyses also stress the importance of biologically informed cost models when investigating the coevolutionary histories of hosts and free-living parasitoids.

Barcoding of parasitoid wasps (Braconidae and Chalcidoidea) associated with wild and cultivated olives in the Western Cape of South Africa

“…It has been reported as being more abundant in wild olives than in cultivated olives (Neuenschwander 1982;Mkize et al 2008;Giacalone 2011;Caleca et al 2017), most likely because its short ovipositor is unable to reach fly larvae buried deep inside the pulp of the large fruit of cultivated olives. The genus Utetes was shown to be polyphyletic (Hamerlinck et al 2016), and three main clusters were recovered for U. canaliculatus with an exact correspondence between microsatellite genetic distances and a COI maximum parsimony tree (Hood et al 2015). Our NJ and ML trees also recovered non-monophyly for the genus, the same three U. canaliculatus clusters, and inconsistency between species designations and sequence clustering (e.g., U. tabellariae was positioned within U. canaliculatus in cluster 2).…”

Revisiting the particular role of host shifts in initiating insect speciation

“…Though for two of the species microsatellites do not conclusively reveal which of the differentiated wasp populations was the ancestor of the new apple wasp, phylogenetic study suggests that wasp parasitoids of Rhagoletis flies may often cospeciate with their fly hosts (Hamerlinck et al. ). On the other hand, for D. alloeum microsatellites suggest that populations of the wasp that ancestrally attacked the blueberry wasp R. mendax —and not the wasps attacking hawthorn‐associated R. pomonella flies—were the progenitors of the new apple‐associated population (Forbes et al.…”

“…Another barrier is allochrony in adult emergence timing: wasp emergences track those of their host flies, which in turn track the fruiting times of their associated fruits, and this results in reduction of temporal overlap between populations . Though for two of the species microsatellites do not conclusively reveal which of the differentiated wasp populations was the ancestor of the new apple wasp, phylogenetic study suggests that wasp parasitoids of Rhagoletis flies may often cospeciate with their fly hosts (Hamerlinck et al 2016). On the other hand, for D. alloeum microsatellites suggest that populations of the wasp that ancestrally attacked the blueberry wasp R. mendax-and not the wasps attacking hawthorn-associated R. pomonella flies-were the progenitors of the new apple-associated population (Forbes et al 2009;Feder and Forbes 2010).…”

Unravelling mummies: cryptic diversity, host specificity, trophic and coevolutionary interactions in psyllid – parasitoid food webs

“…However, very few studies have tested for codivergence between insect hosts and their parasitoids (but see [10–14]), and we are aware of none that have investigated cophylogenetic relationships between hosts, primary parasitoids and their hyperparasitoids. Given that hyperparasitoids can be host specific to either the host herbivore (e.g.…”