2bRAD genomics corroborate morphologically defined species and resolve phylogenetic relationships in the pitcher fly genus Fletcherimyia (Sarcophagidae)

Sarcophagidae, a behaviorally diverse dipteran family best known for carrion feeding, alternatively engages in predation, parasitism, and kleptoparasitism. Most kleptoparasitic species exploit hymenopterans, but one entire genus, Fletcherimyia, associates with an unlikely host group: carnivorous pitcher plants (Sarracenia, Sarraceniaceae), in which fly larvae develop and consume pitcher prey. Eight species of Fletcherimyia are recognized—all morphologically defined constructs that have yet to be confirmed genetically or compared phylogenetically. Here we report on two molecular datasets (mitochondrial cox1, 2bRADseq) providing thorough geographic and host plant coverage for each fly species. We used these data to 1) assess species validity; 2) examine phylogeographical structure; 3) construct a phylogeny for the genus; and 4) estimate its temporal origin. All eight species were confirmed unequivocally (cox1, 2bRAD), three of which (Fletcherimyia abdita, F. celarata, and F. papei) exhibited substantive phylogeographical structuring. Maximum likelihood analysis (2bRAD) recovered two major clades, corroborating informal groups previously recognized on the basis of abdominal coloration. Estimated nodal divergence (cox1) between the clades dates to 2.56 Ma, an age comparable to the radiation of Sarracenia (< 3 Ma) that, in turn, suggests symbiosis initiated early in the evolution of both genera. Our results also demonstrate the efficacy of 2bRAD for constructing phylogenies of recently diverged taxa.