The Genetic Analysis of Lasaea hinemoa: The Story of an Evolutionary Oddity

• Main Author: Lockton, Katherine
• Other Authors: Spencer, Hamish
• Format: Thesis
• Language: English
• Published: University of Otago 2019
• Subjects: Phylogeography; New Zealand; Lasaea; Mollusc; Genetic Analysis; Antarctic; Kerguelen; Kerguelen Islands; The Antarctic; Antarc*; Antipodes Island
• Online Access: http://hdl.handle.net/10523/9580

Lasaea is a genus of molluscs that primarily consists of minute, hermaphroditic bivalves that occupy rocky shores worldwide. The majority of Lasaea species are asexual, polyploid, direct developers. However, two Australian species are exceptions: Lasaea australis is sexual, diploid and has planktotrophic development, whereas Lasaea colmani is sexual, diploid and direct developing. The New Zealand species Lasaea hinemoa has not been phylogeographically studied. I investigated the phylogeography of L. hinemoa using mitochondrial and nuclear gene sequencing (COIII and ITS2, respectively). Additionally, I investigated population-level structuring around Dunedin using microsatellite markers that I developed. It was elucidated that the individuals that underwent genetic investigation consisted of four clades (Clade I, Clade II, Clade III and Clade IV). Clade I and Clade III dominated in New Zealand and support was garnered through gene sequencing and microsatellite analysis for these clades to represent separate cryptic species, with biogeographic splitting present. Clade II consisted of individuals that had been collected from the Antipodes Island. The Antipodes Island contained individuals from two clades (Clade I and Clade II), with Lasaea from the Kerguelen Islands being more closely related to individuals from Clade II than Clade I was to Clade II. This genetic distinction between Clade I and Clade II seemed to indicate transoceanic dispersal via the Antarctic Circumpolar Current (ACC) between the Kerguelen Islands and Antipodes Island. Clade IV clustered very distinctly from L. hinemoa, appearing to represent transoceanic dispersal by another Lasaea species.