Phylogeography of southern New Zealand: Implications of Pliocene and Pleistocene Processes and Evolutionary Concordance Across Independent Loci

Abstract

The endemic fauna of the South Island has proven to be an ideal taxonomic group to examine the impact of climatic and geological processes on the evolution of New Zealand's biota since the Pliocene. This thesis examines the phylogeography of McCann's skink (Oligosoma maccanni) in order to provide insight into the relative contribution of Pliocene and Pleistocene processes on patterns of genetic structure in South Island biota. This thesis also investigates the phylogeography of the brown skink (O. zelandicum) to examine whether Cook Strait landbridges facilitated gene flow between the North and South Island in the late-Pleistocene. This thesis also investigates the presence of genealogical concordance across independent loci for the endemic alpine stick insect, Niveaphasma. I obtained mitochondrial DNA (mtDNA) sequence data (ND2 and ND4; 1284 bp) from across the range of both skink species and mtDNA (COI; 762 bp) and nuclear sequence data (EF1 ; 590 bp) from across the range of Niveaphasma. I used DGGE in order to resolve nuclear EF1 alleles and examined phylogeographic patterns in each species using Neighbour-Joining, Maximum Likelihood and Bayesian methods. Substantial phylogeographic structure was found within O. maccanni, with divergences among clades estimated to have occurred during the Pliocene. Populations in the Otago/Southland region formed a well-supported lineage within O. maccanni. A genetic break was evident between populations in east and west Otago, while north-south genetic breaks were evident within the Canterbury region. There was relatively minor phylogeographic structure within O. zelandicum. Our genetic data supports a single colonization of the North Island by O. zelandicum from the South Island, with the estimated timing of this event (0.46 Mya) consistent with the initial formation of Cook Strait. There was substantial genetic structuring identified within Niveaphasma, with a well-supported lineage present in the Otago/Southland region. There was also a genetic break between populations in Canterbury and eastern Otago with those in central Otago and Southland. The genetic data provided strong genealogical concordance between mtDNA haplotypes and nuclear alleles suggesting an accurate depiction of the historical isolation identified between the major clades of Niveaphasma. This finding offers compelling evidence for the use of nuclear gene phylogeography alongside mtDNA for future evolutionary studies within New Zealand