Botany School Annex
42 Union Street West
Professor Graham Wallis
Department of Zoology, University of Otago
Going under down under?
Molecular data provide no evidence for complete inundation of New Zealand during the Oligocene Marine Transgression.
The last 25 years have seen heated debate over whether there was continuous emergent land through the Oligocene “drowning” of current-day NZ some 25–23 million years ago. Such an event would imply that all terrestrial, freshwater and maybe coastal marine lineages must have dispersed here since. A compilation of 248 phylogeographic splits (i.e. molecular estimates of divergence times between NZ lineages and their closest overseas sister groups) follows a smooth exponential over the last 50 Ma or more. ~74 of these lineages appear to have survived the OMT in situ; some of these major lineages comprise multiple additional lineages as a result of autochthonous speciation prior to the OMT. Although extinction of closer
overseas lineages will cause overestimation of some splits, there is no evidence for a deficit of pre-Oligocene lineages, nor an excess of ones arriving just afterwards. Consequently, this large body of molecular data provides no evidence for complete inundation of NZ during the Oligocene.
