Dissecting an island radiation: systematic revision of endemic land snails on Lord Howe Island (Gastropoda: Stylommatophora: Microcystidae)

Abstract

AbstractThe Lord Howe Island Microcystidae currently comprise two endemic genera containing nine species. We revise their taxonomy comprehensively using comparative morphology and phylogenetic analyses of the mitochondrial genes COI and 16S and demonstrate that the Lord Howe Island microcystids probably represent a single radiation. Based on our findings, we recognize Melloconcha, Tribocystis and Annacharis as junior synonyms of Innesoconcha and provide a revised generic diagnosis of Innesoconcha and redescriptions for all species. In addition, we reinstate Innesoconcha segna from synonymy and describe Innesoconcha doppelganger sp. nov., bringing the total number of accepted species in the genus to 11. Most species are well differentiated, in terms of both morphological differences and basal branch lengths in the mitochondrial trees. However, members of the Innesoconcha catletti species complex reveal lower levels of genetic and morphological differentiation and are likely to represent examples of more recent, perhaps even ongoing, speciation which might be driven by reinforcement. We recommend conservation assessments of all species, particularly Innesoconcha aberrans and Innesoconcha grata, which are rare species that have declined in abundance over the past 50 years, and note that Innesoconcha rosacea and Innesoconcha delecta appear to have become geographically more restricted. Innesoconcha miranda and I. segna are probably extinct.