Molecular phylogeny and evolution of world Tachinidae (Diptera).

We reconstructed phylogenetic relationships within the diverse parasitoid fly family Tachinidae using four nuclear loci (7800 bp) and including an exceptionally large sample of more than 500 taxa from around the world. The position of the earthworm-parasitizing Polleniinae (Calliphoridae s.l.) as sister to Tachinidae is strongly supported. Our analyses recovered each of the four tachinid subfamilies and most recognized tribes, with some important exceptions in the Dexiinae and Tachininae. Most notably, the tachinine tribes Macquartiini and Myiophasiini form a clade sister to all other Tachinidae, and a clade of Palpostomatini is reconstructed as sister to Dexiinae + Phasiinae. Although most nodes are well-supported, relationships within several lineages that appear to have undergone rapid episodes of diversification (basal Dexiinae and Tachininae, Blondeliini) were poorly resolved. Reconstructions of host use evolution are equivocal, but generally support the hypothesis that the ancestral host of tachinids was a beetle and that subsequent host shifts to caterpillars may coincide with accelerated diversification. Evolutionary reconstructions of reproductive strategy using alternative methods were incongruent, however it is most likely that ancestral tachinids possessed unincubated, thick shelled eggs from which incubated eggs evolved repeatedly, potentially expanding available host niches. These results provide a broad foundation for understanding the phylogeny and evolution of this important family of parasitoid insects. We hope it will serve as a framework to be used in concert with morphology and other sources of evidence to revise the higher taxonomic classification of Tachinidae and further explore their evolutionary history and diversification.

Explosive radiation or uninformative genes? Origin and early diversification of tachinid flies (Diptera: Tachinidae).

Molecular phylogenetic studies at all taxonomic levels often infer rapid radiation events based on short, poorly resolved internodes. While such rapid episodes of diversification are an important and widespread evolutionary phenomenon, much of this poor phylogenetic resolution may be attributed to the continuing widespread use of "traditional" markers (mitochondrial, ribosomal, and some nuclear protein-coding genes) that are often poorly suited to resolve difficult, higher-level phylogenetic problems. Here we reconstruct phylogenetic relationships among a representative set of taxa of the parasitoid fly family Tachinidae and related outgroups of the superfamily Oestroidea. The Tachinidae are one of the most species rich, yet evolutionarily recent families of Diptera, providing an ideal case study for examining the differential performance of loci in resolving phylogenetic relationships and the benefits of adding more loci to phylogenetic analyses. We assess the phylogenetic utility of nine genes including both traditional genes (e.g., CO1 mtDNA, 28S rDNA) and nuclear protein-coding genes newly developed for phylogenetic analysis. Our phylogenetic findings, based on a limited set of taxa, include: a close relationship between Tachinidae and the calliphorid subfamily Polleninae, monophyly of Tachinidae and the subfamilies Exoristinae and Dexiinae, subfamily groupings of Dexiinae+Phasiinae and Tachininae+Exoristinae, and robust phylogenetic placement of the somewhat enigmatic genera Strongygaster, Euthera, and Ceracia. In contrast to poor resolution and phylogenetic incongruence of "traditional genes," we find that a more selective set of highly informative genes is able to more precisely identify regions of the phylogeny that experienced rapid radiation of lineages, while more accurately depicting their phylogenetic context. Although much expanded taxon sampling is necessary to effectively assess the monophyly of and relationships among major tachinid lineages and their relatives, we show that a small number of well-chosen nuclear protein-coding genes can successfully resolve even difficult phylogenetic problems.