Phylogeny and systematics of the longhorn beetle genus Rhytiphora (Coleoptera: Cerambycidae)

Abstract

The classification and phylogenetic relationships of longhorn beetles, a diverse and ecologically important group, have been debated for decades, with neither morphological nor molecular data achieving a satisfactory resolution. Rhytiphora, the largest Australian genus of the subfamily Lamiinae, is no exception. The current concept of the genus encompasses around 200 species (from nearly 40 former genera), united by a putative apomorphy: setose 'sex patches' on the male abdomen, probably involved in dispersing pheromones. However, these sex patches are not unique to Rhytiphora. In this thesis, multiple nuclear loci were sequenced from museum specimens to produce the first molecular phylogeny of the Australasian Lamiinae, using fossil calibration data to estimate the branch lengths in real time. This phylogeny indicates that the tribal classification of the Australasian Lamiinae is largely incorrect, and the Australian genera form two clades: an older clade containing the Australian endemics and all the New Zealand taxa; and a younger clade with close ties to Asia, including the focal genus Rhytiphora. Many of the genera in this younger clade have male sex patches. The tribal classification of the sampled genera was revised, moving many Australian endemics to Lamiinae incertae sedis and reinstating the tribe Niphonini for Rhytiphora and five other Asian-Australian genera. Mitochondrial sequences were then used to reconstruct the phylogeny of Rhytiphora and examine patterns of morphological evolution and biome distributions. The Australian Rhytiphora species form two distinct clades. Nine morphological traits are correlated with these clades, including sex patches, body size and eye emargination. Clade 1 has mostly tropical species, while clade 2 has more mesic and arid zone species; both clades show evidence of multiple biome shifts between species groups. On the basis of these results, the morphological definition of the genus was revised, providing diagnostic features to distinguish Rhytiphora from related genera. Both molecular results and examination of type material were used to revise the collaris group, describe a new species, and construct an updated checklist of 162 Australian species (involving many new synonymies). These results shed light on an important part of Australia's insect fauna, improving the tribal classification of Lamiinae and providing insight into the previously unknown biogeographic history of the Australian longhorn beetles. They also improve our understanding of the phylogeny, morphology, biogeography and species-level taxonomy of the diverse genus Rhytiphora.