Phylogeography of the Endangered Otago Skink, Oligosoma otagense: Population Structure, Hybridisation and Genetic Diversity in Captive Populations

David G Chapple,Alisha Birkett,Kimberly A Miller,Dianne M Gleeson,Charles H Daugherty,Sergios-Orestis Kolokotronis

doi:10.1371/journal.pone.0034599

Abstract

Climatic cooling and substantial tectonic activity since the late Miocene have had a pronounced influence on the evolutionary history of the fauna of New Zealand's South Island. However, many species have recently experienced dramatic range reductions due to habitat fragmentation and the introduction of mammalian predators and competitors. These anthropogenic impacts have been particularly severe in the tussock grasslands of the Otago region. The Otago skink (Oligosoma otagense), endemic to the region, is one of the most critically endangered vertebrates in New Zealand. We use mitochondrial DNA sequence data to investigate the evolutionary history of the Otago skink, examine its population genetic structure, and assess the level of genetic diversity in the individuals in the captive breeding program. Our data indicate that the Otago skink diverged from its closest relatives in the Miocene, consistent with the commencement of tectonic uplift of the Southern Alps. However, there is evidence for past introgression with the scree skink (O. waimatense) in the northern Otago-southern Canterbury region. The remnant populations in eastern Otago and western Otago are estimated to have diverged in the mid-Pliocene, with no haplotypes shared between these two regions. This divergence accounts for 95% of the genetic diversity in the species. Within both regions there is strong genetic structure among populations, although shared haplotypes are generally evident between adjacent localities. Although substantial genetic diversity is present in the captive population, all individuals originate from the eastern region and the majority had haplotypes that were not evident in the intensively managed populations at Macraes Flat. Our data indicate that eastern and western populations should continue to be regarded as separate management units. Knowledge of the genetic diversity of the breeding stock will act to inform the captive management of the Otago skink and contribute to a key recovery action for the species.

Highlights

Geological and climatic processes have acted to dramatically alter the landscape of the South Island of New Zealand [1,2,3]
Extensive glaciers throughout the South Island were evident during glacial maxima [9], and repeated glacial cycles during the Pleistocene resulted in the continual expansion and contraction of the distribution of the resident biota [3,11]
These samples were obtained from existing collections (National Frozen Tissue Collection [NFTC], housed at Victoria University of Wellington, New Zealand; Te Papa Tongarewa, National Museum of New Zealand, Wellington) and tissues collected by the New Zealand Department of Conservation during population surveys of the species (1998–2003)

Summary

Introduction

Geological and climatic processes have acted to dramatically alter the landscape of the South Island of New Zealand [1,2,3]. Extensive glaciers throughout the South Island were evident during glacial maxima [9], and repeated glacial cycles during the Pleistocene resulted in the continual expansion and contraction of the distribution of the resident biota [3,11]. These processes acted to fragment the range of many species, and led to extensive speciation and phylogeographic structure within the South Island (reviewed in [3,11])

Methods

Results

Discussion

Conclusion