The Oligocene bottleneck and New Zealand biota: genetic record of a past environmental crisis.

Mitochondrial DNA (mtDNA) 12S sequences from the two New Zealand ratite orders, the kiwi and moa, indicate that each group represents a separate colonization event. However, the amount of mtDNA genetic diversity observed within each of the New Zealand groups is similar, and limited, which is not consistent with the ratite phylogenetic tree. We examine the Cenozoic (65-0 million years ago) geological history of New Zealand for possible causes and summarize evidence for land area and climatic changes. A genetic bottleneck is hypothesized and tested, by using molecular data from a second mitochondrial locus (ND6) and a further taxon, the New Zealand acanthisittid wrens. The data support the existence of a widespread genetic bottleneck during the mid-Cenozoic in New Zealand and demonstrate the benefits of synthesizing traditional research with new molecular techniques.