Multiple lineages of hyper-diverse Zopheridae beetles survived the New Zealand Oligocene Drowning

Aim During the late Oligocene (23 mya) the New Zealand landmass was reduced to approximately 18% of its current area. It has been hypothesized that this event, known as the Oligocene Drowning, caused population bottlenecking and mass extinction. Using phylogenetic methods, we examine the effect of this and other environmental events on the hyper-diverse Zopheridae beetles (162 morphospecies), which largely inhabit leaf litter and dead wood. Location New Zealand. Taxon Zopheridae, Coleoptera. Methods Here we use a fossil-calibrated phylogenetic tree estimated from mitochondrial cytochrome c oxidase subunit I and nuclear large subunit rRNA genes to identify monophyletic New Zealand zopherid lineages and date the age of these lineages. We used Bayesian diversification models (compound Poisson process on mass extinction times) to test the hypothesis that the New Zealand zopherids underwent a mass extinction in the late Oligocene followed by an increase in speciation rate in the Miocene. We also used these data to estimate the age of these lineages in New Zealand. Results We demonstrate that 15-20 zopherid lineages survived the Oligocene Drowning depending on the calibration scheme. Of these lineages from 3 to 11 have posterior intervals that encompass the rifting of New Zealand from Gondwana in the late Cretaceous, again depending on the calibration scheme. The diversification model shows no evidence of an increase in extinction rate during the Oligocene Drowning or during any other period since the Cretaceous. Furthermore, rather than recovering an increase in speciation rate during the Miocene and Pliocene, due to environmental changes, we instead recovered a large drop in the speciation rate during this time. Main conclusions The New Zealand zopherid fauna is a combination of lineages, some of which may have existed on New Zealand since the rifting from Gondwana and other more recent arrivals. The late Oligocene reduction in land area was insufficient to cause a mass extinction in the Zopheridae. This suggests the amount of emergent land was great enough to support a diverse invertebrate fauna. Our study demonstrates the different biogeographic patterns evident in cryptic, hyper-diverse, and poorly dispersing invertebrate species relative to more mobile plants and animals.