Invertebrate Molecular Phylogeography Steve Trewick Graham Wallis

Since its isolation from Gondwana about 90 million years ago New Zealand has had a complex and turbulent geophysical history with episodes of extensive marine transgression, volcanism, earthquakes, orogenics and glaciation. Identifying how the lottery of extinction, refugiation, dispersal and speciation associated with these events has shaped the present (prehuman) New Zealand biota is the goal of this programme. To reach this objective we are employing a synthesis of molecular techniques, phylogenetic theory and traditional biogeographic methods. We are testing in particular the predicted effects on diversity and distribution of geophysical events including the break up of Gondwana (late Cretaceous), extensive marine transgressions (Oligocene/ Miocene), mountain building and postglacial island formation (Plio-pleistocene). There is good geological evidence for these events with detail of location and timing determined with varying degrees of accuracy. There is also much circumstantial biological evidence for their effects, in the form of congruent distributional patterns among taxa. We are using molecular techniques to tie the various evidence together and place the spatial evidence in a firm temporal framework. Invertebrates with low vagility (dispersal) characteristics and restricted habitat tolerance are of most use to us as they are most likely to carry molecular signals that are informative of phylogenetic events in space and time. Thus we are presently studying the congruence of geographic and phylogenetic relationships of invertebrates including peripatus (velvet worms), weta (endemic crickets), cockroaches, flatworms, leaf-slugs, springless spring-tails and alpine grasshoppers. Peripatus (Onychophora) which are often described as 'living-fossils' have a strictly southern hemisphere distribution and are of particular interest in studies of Gondwanan break-up in which we and our collaborators are engaged.

Flatworm Peripatus (velvet worm)

Associated researchers: Mary Morgan-Richards, Brent Emerson.

Peripatus collaborators: Dave Rowell, Noel Tait, Dave Briscoe.