Morphological phylogenetics of Australian gall-inducing thrips and their allies: the evolution of host-plant affiliations, domicile use and social behaviour

A phylogeny for seventy-two species of Australian thrips in the subfamily P hlaeothripinae, based on cladistic analysis of forty morphological adult ch aracters, is presented. We use this phylogeny to infer the evolutionary his tory of host-plant affiliations, gall induction and other types of domicile use, and different forms of social behaviour. Maximum parsimony analysis y ielded forty-eight cladograms of length 316, and the strict consensus of th ese cladograms was well resolved. This phylogeny indicated that: (1) associ ations of thrips with their host plants tend to be evolutionarily conservat ive, with monophyletic groups of thrips on the host-plant genera Acacia, Ca suarina and Geijera, (2) galling has evolved multiple times, on different h ost plants, (3) transitions in domicile use include changes between galling and living in holes or old galls, between living in glued phyllodes and li ving in old galls, and between leaf-feeding and galling, and (4) in three o f five cases, inquiline lineages were not closely related to their host lin eages and the evolution of inquilinism apparently involved a host-plant shi ft. However, in two cases, inquilines were very closely related to their ga ll-inducing hosts. Eusocial behaviour (involving soldier castes) has evolve d in different lineages from those that exhibit communal behaviour (coopera tion in building or defending domiciles), suggesting a lack of direct trans ition between the two social systems. This phylogeny serves as a framework for future molecular systematic studies, and future comparative analysis of ecology and behaviour in the Phlaeothripinae.