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

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 with other sand dollars globally, and genotyping-by-sequencing (40,725 single-nucleotide polymorphisms) revealed the phylogeography of this species around New Zealand. Key results The genus Fellaster was resolved as sister to its Australian counterpart, Arachnoides. Fellaster zelandiae showed evidence of strong connectivity among populations. Conclusions Small-scale genetic variation between northern and southern populations appears to be consistent with biogeographic patterns seen in other coastal species in New Zealand and is probably driven by isolation of some regions by oceanographic features incluing the East Auckland Current, East Cape Current and Southland Current. Implications While the strong connectivity of many contemporary Fellaster zelandiae populations is likely to be the result of a long-lived larval stage, gene flow may reduce in the future if larval development times decrease.