Phylogeography and evolutionary dynamism of marine gastropods from the Lord Howe Island Group

Abstract

Context There has been considerable interest in the biogeography of the marine fauna of the Lord Howe Island Group (LHIG) lying ~580 km from continental Australia. Most phylogenetic studies of the group’s marine taxa have included few specimens, limiting their phylogeographic perspective. Aims This investigation was conducted to enhance understanding of the phylogeographic relationships of the LHIG, especially with temperate Australia. Methods The investigation used mitochondrial DNA sequences of the muricid subfamily Ergalataxinae, especially Tenguella, which has a broad distribution in the Indo-West Pacific, and two other gastropod genera, Cellana and Bembicium, each proposed to have endemic species in the LHIG. Key results Most species of LHIG Ergalataxinae have recent genetic connections with tropical landmasses, but Tenguella marginalba is closely related to temperate mainland conspecifics. The endemic taxa Cellana howensis and Bembicium flavescens respectively, have tropical and southern temperate affinities. Conclusions The most recent common ancestors (MCRAs) of LHIG specimens of each of B. flavescens, C. howensis and T. marginalba all date from long after the archipelago’s emergence. Implications The studied species may have arrived only recently on the archipelago. Alternatively, their estimated MCRAs may be due to recent demographic bottlenecks or selective sweeps influenced by Pleistocene environmental changes.