Evolutionary assembly of the conifer fauna: distinguishing ancient from recent associations in bark beetles

Several shifts from ancestral conifer feeding to angiosperm feeding have be en implicated in the unparalleled diversification of beetle species. The si ngle largest angiosperm-feeding beetle clade occurs in the weevils, and com prises the family Curculionidae and relatives. Most authorities confidently place the bark beetles (Scolytidae) within this radiation of angiosperm fe eders. However, some clues indicate that the association between conifers a nd some scolytids, particularly in the tribe Tomicini, is a very ancient on e. For instance, several fragments of Gondwanaland (South America, New Cale donia, Australia and New Guinea) harbour endemic Tomicini specialized on me mbers of the formerly widespread and abundant conifer family Araucariaceae. As a first step towards resolving this seeming paradox, we present a phylo genetic analysis of the beetle family Scolytidae with particularly intensiv e sampling of conifer-feeding Tomicini and allies. We sequenced and analyse d elongation factor 1 alpha and nuclear rDNAs 18S and 28S for 45 taxa, usin g members of the weevil family Cossoninae as an out-group. Our results indi cate that conifer feeding is the ancestral host association of scolytids, a nd that the most basal lineages of scolytids feed on Araucaria. If scolytid s are indeed nested within a great angiosperm-feeding clade, as many author ities have held, then a reversion to conifer feeding in ancestral scolytids appears to have occurred in the Mesozoic, when Araucaria still formed a ma jor component of the woody flora.