Scree weta phylogeography: surviving glaciation and implications for Pleistocene biogeography in New Zealand

The Pleistocene glaciation is thought to have had a profound impact on the distribution of endemic biota. The intraspecific phylogeography of the alpine-adapted scree weta, Deinacrida connectens Ander, was surveyed throughout its range in the South Island, New Zealand using mitochondrial cytochrome oxidase I DNA sequence data. Seven distinct genetic lineages were evident from mtDNA haplotypes, with each occupying mountain ranges in discrete geographic regions. Genetic distances among lineages were up to 8.2%, whereas within-lineage distances reached only 2.8%. The inferred age of lineages and the striking phylogeographic structure exhibited by D. connectens indicates that it radiated in response to Pliocene mountain building. Maintenance of this structure is likely to relate to the combined effects of mountain-top isolation during Pleistocene interglacials and ice barriers to dispersal during glacials. Two lineages are endemic to the central South Island, an area regarded as species poor due to glacial-extirpation of much of the biota. It appears that D. connectens survived across much of the South Island in a mosaic of ecological, rather than one or few, regional refugia. The Pleistocene biogeography of New Zealand in general is discussed in the light of this hypothesis.