South Pacific biogeography, tectonic calibration, and pre-drift tectonics: cladogenesis in Abrotanella (Asteraceae)




Abrotanella is the basal genus in the large tribe Senecioneae (Asteraceae) and has a disjunct distribution in Australasia and South America. A recent molecular phylogeny of the genus was used to investigate whether the main biogeographical patterns in the group could be related to the region's tectonic history in a coherent way. The phylogenetic/biogeographical breaks and overlaps in the genus imply a series of vicariance and range expansion events. Each of these can be related to one of the main tectonic events in the region, including assembly of the New Zealand terranes, crustal extension, and magmatism in Gondwana that preceded seafloor spreading, opening of the Tasman and Pacific basins, and transcurrent movement on the New Zealand Alpine fault. The coincident sequence indicates that pre-drift tectonics and magmatism have been more important for the origin of trans-Tasman and trans-Pacific groups than the final rifting of Gondwana that led to their disjunction. For example, during the pre-drift phase of break-up, the Whitsunday volcanic province of Australia and the Median Batholith of New Zealand formed a large, active igneous belt. Its distribution is aligned with the break between New Zealand–south-eastern Australia clades, and New Zealand–New Guinea clades. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ••, ••–••.