Molecular phylogenetics and piercer evolution in the bug-killing flies (Diptera: Tachinidae: Phasiinae)

Phasiinae (Diptera: Tachinidae) are endoparasitoid flies that attack Heteroptera, including a multitude of agricultural pests. A phylogenetically informed classification of Phasiinae has eluded systematists for over a century, primarily because of the conflicting character states and confusing morphology of certain taxa that indicate potential placement within other subfamilies. The unstable nature of phasiine taxonomy discourages important research into their classification, life history and potential use in biological control. In hopes of resolving several longstanding taxonomic debates and encouraging future research into this important group of parasitoids, the first molecular systematic analysis of Phasiinae is presented, including 128 worldwide taxa (80 genera) and approximately 7.6 kb of nuclear data representing four genes. Special emphasis is placed on the resolution of taxonomically ambiguous groups. The resulting robustly supported phylogenetic trees [maximum-likelihood (ML)/Bayesian] were used to trace the evolution of significant adaptive traits within Tachinidae and test hypotheses about the classification of Phasiinae. Subfamily placements of certain taxa are confidently resolved including Eutherini, Epigrimyiini, Litophasia Girschner within Dexiinae, and Strongygastrini and Parerigonini within Phasiinae. The members of tribe Phasiini are redistributed: Cistogaster Latreille, Clytiomya Rondani, Ectophasia Townsend, Eliozeta Rondani and Euclytia Townsend transferred to Gymnosomatini; Opesia Robineau-Desvoidy to Strongygastrini; and Xysta Meigen to Xystini. Similarly, members of Parerigonini are treated as belonging to Parerigonini (Parerigone Brauer, Zambesomima Walker), Cylindromyiini (Australotachina Curran, Pygidimyia Crosskey, Neobrachelia Townsend) or new tribe Zitini (Zita Curran, Leverella Baranov). Penthosia van der Wulp is transferred from Cylindromyiini to Hermyini. Ancestral state reconstruction suggests that piercing structures used to insert eggs directly into host tissues have evolved separately in a number of groups, but have also been lost or reduced in several lineages. A single potentially unequivocal morphological synapomorphy of Phasiinae, an elongated medial plate of the hypandrium in males, is identified.