Phylogeography of Maoricicada Cambelli (Hemiptera: Cicadidae): MtDNA Evidence Interpreted Using Phylogenetics and Nested Clade Analysis

New Zealand, because of its wide range of habitats and rapidly changing, well-studied palaeohistory provides an excellent opportunity to investigate the impact of earth processes on the distribution of taxa. There are now a variety of studies on plants that investigate such patterns, and a growing number of studies on animal taxa. Most studies have supported the hypothesis that current patterns of distribution of New Zealand taxa were created by dispersal, mediated by landscape and climatic conditions over time, and have contradicted the panbiogeographic hypothesis that explained distributions via vicariant landscape changes such as lateral displacement along the Alpine Fault. This thesis presents a detailed phylogeographic history of a widespread, endemic New Zealand cicada, Maoricicada campbelli, that is abundant throughout much of the South Island and is also found in the central volcanic plateau of the North Island. Mitochondrial DNA sequences of 223 individuals from 70 populations of M. campbelli were studied using both traditional phylogenetic methods and nested clade analysis (NCA). As found in a previous study of 35 M. campbelli individuals, geographic structuring was strong, with two main clades (North Island+northern South Island versus Otago) representing diverse lineages that may in fact be different species. Population structuring within the northern South Island clade suggested that the central South Island was mostly uninhabitable during glacial periods and demonstrated a sister-group relationship between northern and southern Southern Alps populations to the exclusion of the more central Southern Alps populations. Population histories estimated from NCA support the hypothesis that most M. campbelli populations were formed through dispersal rather than via fragmentation or Alpine Fault vicariance. Three areas of ring-species-like secondary contact were found between the Otago and northern South Island clades, between lineages that had been isolated for approximately 2.3my. Further study is predicted to confirm the presence of additional suspected contact zones, and will demonstrate whether the different lineages are reproductively isolated or hybridising at these areas of secondary contact.