Phylogeny and historical biogeography of the cynipoid wasp family Ibaliidae (Hymenoptera)

The Ibaliidae are a small family of cynipoid wasps, the members of which parasitize woodboring siricid larvae in hardwoods and conifers. The 19 currently recognized extant species occur mainly in the Northern Hemisphere. No fossils are known despite the presumed old age of the family. We present a cladistic analysis of ibaliid relationships at the species-level, mainly based on external skeletal characters of adults. The results indicate that the three genera (Eileenella, Heteribalia, Ibalia) and two subgenera of Ibalia (Ibalia s. str. and Tremibalia) recognized in the current classification are monophyletic. Three different categories of characters were compared for their phylogenetic usefulness. Homoplasy was found to be lowest for main structures, higher for sculptural characters, and still higher for colour differences. The historical biogeography of the family was reconstructed using dispersal-vicariance analysis in combination with palaeogeographical data. The results suggest that the family primarily diversified within the eastern Palaearctic-northern Oriental region. The nominate subgenus of Ibalia dispersed early to the western Nearctic, where it radiated; two species later spread throughout the Holarctic. The other subgenus of Ibalia shows an early eastern Palaearctic-eastern Nearctic disjunction which presumably dates back to the Eocene-Oligocene transition.