Investigating a Northland native: Resolving the phylogeographic structure of Northland, New Zealand’s Paryphanta busbyi land snails
Ward, C.J. (2024). Investigating a Northland native: Resolving the phylogeographic structure of Northland, New Zealand’s Paryphanta busbyi land snails. MSc Thesis. University of Otago: Dunedin. 178 pp.
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Documenttype: Doctoraat/Thesis/Eindwerk
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| Abstract |
Ever-changing landscapes throughout geological history have resulted in high levels of endemism throughout Northland, New Zealand, with one endemic genus being Paryphanta — a threatened and culturally significant land snail. Two morphotypes exist within the genus that have historically been considered distinct species. The larger, green morphotype, P. busbyi, ranges from Auckland to Kaitaia, whereas the smaller, black morphotype, P. watti, occurs only in the northernmost region of Northland. The clear geographic split between the two morphotypes corresponds with Northland’s geological history, therefore, it was originally assumed that the phylogeographic split of genus Paryphanta would also follow a north-south pattern. Contrary to this assumption, previous analysis of the COI gene inferred that the two morphotypes were conspecific. However, genetic differences were identified between eastern and western P. busbyi populations, with P. watti being grouped with P. busbyi east. The discrepancies between molecular data and morphological data, that corresponded to Northland’s geological history, generated uncertainties surrounding the true phylogeographic pattern of the genus. This project aimed to test, through genotyping by sequencing (GBS) of nuclear DNA, the phylogeographic pattern of P. busbyi, and determine if the east-west split of P. busbyi, revealed by COI data, is correct. In doing so, it was aimed that an in-depth understanding of the population structure within P. busbyi would be achieved, translocated populations would be identified, and inferences about the origins of translocations would be made. Analyses revealed three distinct clades (northern, southern, and Waitākere) and an additional intermediate form. A clear north-south phylogeographic pattern was observed, although this pattern did not include the Waitākere clade, presumably due to divergence following its translocative origins. Throughout the project, science was communicated and recommendations were made to increase the accessibility of the knowledge gained, thereby enhancing opportunities for further research and conservation of the genus. This project was the first to successfully identify thousands of SNPs in Paryphanta using GBS, although still highlights the importance of comprehensive assessments, including, where possible, multiple genetic assessments, consideration of morphology, and assessment of phylogeography, regardless of whether multiple species have been identified. It is recommended that these assessments are considered in future management plans to ensure both genetic and morphological variation, as well as phylogeographic patterns, are conserved. |
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