Molecular phylogenetics and premating isolation in the punctoid land snails of Belau (Republic of Palau, Oceania)

Pacific island land snails exhibit exceptionally high species diversity, morphological diversity, and endemism. Species within superfamily Punctoidea, which contains the Charopidae and Pacific-endemic family Endodontidae, are among the most morphologically spectacular Pacific endemic land snails. The evolution of Pacific island punctoids remains poorly known, due in part to rampant human-induced extinction within this group of minute ground-dwellers. The Belau archipelago (Republic of Palau) with its relatively intact lowland rainforest and limestone karst Rock Islands, is home to many endemic punctoids and presents a unique opportunity to better understand the diversification of one of the most diverse but also imperiled land snail lineages on Pacific islands. For the first time, the diversification of the endemic Pacific punctoid fauna of Belau was studied using Bayesian Inference (BI) and Maximum Likelihood (ML) methods applied to sequences from mitochondrial (COI) and nuclear (ITS2) gene regions. Evolutionary relationships, molecular divergence, disjunct or complex geographic ranges, and ecological similarity among Belau punctoid species, likely reflect species' long evolutionary history and diversification through geographic isolation. We find no evidence for adaptation in species-level shifts in spire height within Aaadonta endodontids. We also find preliminary evidence for the evolution of premating reproductive isolation in Semperdon species in sympatry, through the study of apertural teeth. In addition, we report the first new endodontid species from living individuals as well the first new genus record from the Belau archipelago in nearly half a century.

Automated summary

Pacific island land snails exhibit high species and morphological diversity, with the Belau archipelago in the Republic of Palau providing a unique opportunity to study this diversity. The study found evolutionary relationships and geographic ranges among endemic Pacific punctoid species, shedding light on their long evolutionary history and diversification through geographic isolation. Additionally, evidence for species-level shifts and reproductive isolation within specific punctoid species was also uncovered.