Abstract
A well-recorded and tumultuous geographic history makes New Zealand a useful system for testing hypotheses in phylogeography. Within New Zealand’s unique fauna is a relict genus, Latia, the world’s only bioluminescent freshwater pulmonate which is endemic to freshwater streams in the North Island. Individuals of the Latia genus were independently characterised with morphology characters, with recognition of three species: Latia lateralis (Northland), L. climoi (Wellington) and L. neritoides (Auckland). To investigate taxonomy of the Latia genus, a molecular investigation was done, utilising three markers: mitochondrial Cytochrome oxidase 1 (COI), 16S and nuclear internal transcribed spacer 1 (ITS-1). Baysesian trees were produced from singular and concatenated gene datasets. The mitochondrial trees were broadly congruent with each other, whereas the ITS-1 tree lacked structure, which neither supported nor disputed the mitochondrial topologies. Based on the tree topologies, the Latia genus contains a single species, L. neritoides, conspecific with L. lateralis and L. climoi. There was a high level of mitochondrial intraspecific diversity, notably in Northland, with an average pairwise distance of 14.3% and a consistent pattern of phylogeographic structuring in the Bay of Plenty and ‘Southern’ populations. Structuring occurred to a lesser extent in West Auckland populations, where a few individuals grouped with samples from other localities. Several processes and events were suggested to account for the above patterns. Greater genetic diversity in Northland could be attributed to better environmental conditions to support Latia populations and larger effective population sizes. Past events such as the Pleistocene glaciations and volcanism in the Taupo Volcanic Zone could have reduced genetic diversity in the Southern populations through population bottlenecks and founder effects, for instance. This leads on to future investigation around elucidating the genetic processes behind the phylogeographic structure.