Biogeographic Breaks in Vanuatu, a Nascent Oceanic Archipelago

The study of distinct biogeographic demarcations has played a pivotal role in our understanding processes responsible for patterns of species distributions and, importantly, the role of geologic processes in promoting biotic diversification. Biogeographic barriers such as Wallace's line have been shown to be the result of old geologic processes shaping ancient faunal or floral diversification events. Based on distributions of birds, bats, reptiles, plants, and invertebrates we identify a distinct biogeographic disjunction in Vanuatu, a geologically nascent oceanic archipelago. We discuss mechanisms contributing to this concordant pattern across these disparate taxonomic groups in light of geologic history, ocean currents, vegetation, soil, and bioclimatic data, and propose the name Cheesman's line to indicate the faunal and floral discontinuity between the northern and southern islands of Vanuatu.