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Shallow but striking genetic structure in the highly connected New Zealand sand dollar (Fellaster zelandiae)

Ian Dixon-Anderson , Miles Lamare, Ceridwen Fraser

Abstract

CONTEXT: Phylogeographic patterns can reveal the physical environmental processes that shape biodiversity. Marine species often have dispersive larval stages, but might not be well-connected over large distances. Sand dollars, for example, often show regional isolation but local connectivity. AIMS: This study sought to quantify the population genomic structure of the New Zealand sand dollar, Fellaster zelandiae. METHODS: Sequencing of the cytochrome c oxidase I (COI) gene fragment determined the phylogenetic relationship of Fellaster to other sand dollars globally, and genotyping-by-sequencing (40,725 SNPs) revealed the phylogeography of this species around New Zealand. KEY RESULTS: The genus was resolved as sister to its Australian counterpart, Arachnoides placenta, and showed evidence of strong connectivity among populations. CONCLUSIONS: Small-scale genetic variation between northern and southern populations appears consistent with biogeographic patterns seen in other coastal species in New Zealand and is probably driven by isolation of some regions by oceanographic features including the East Auckland Current, East Cape Current and Southland Current. IMPLICATIONS: While the strong connectivity of many contemporary populations is likely the result of a relatively long-lived larval stage, gene flow may reduce in the future as larval development times are expected to decrease.

MF25016  Accepted 19 August 2025

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