Biogeographic Breaks in Vanuatu, A Nascent Oceanic Archipelago

Abstract

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.

Otolith shape analysis for three Sicyopterus (Teleostei: Gobioidei: Sicydiinae) species from New Caledonia and Vanuatu

“…One would be located on the Western border of Vanuatu, colonising both western Vanuatu locations and New Caledonia using the south Vanuatu and the north and south Caledonian jets (Cillauren et al 2001). It has indeed been shown that there is strong population connectivity between New Caledonia and Vanuatu due to ocean currents (Treml et al 2008;Hamilton et al 2010). The other larval pool would be confined to the "central" location of Vanuatu, representing a sort of internal "sea", at the centre of the archipelago, less penetrable by main ocean currents (Cillauren et al 2001).…”

Avifauna from the Teouma Lapita Site, Efate Island, Vanuatu, including a New Genus and Species of Megapode

“…As noted by Steadman (2006a) and Hamilton et al (2010) the majority of birds found in Vanuatu, especially columbids, are widespread, with most shared with the Solomons or areas of Melanesia to the west such as the Bismarks. Only 12 of the 62 taxa of land and freshwater birds Steadman (2006a) listed for Vanuatu were considered endemic, three of which were columbids (i.e., Ptilinopus tannen sis, Ducula bakeri, and Gallicolumba ferruginea).…”

“…Only three other bird species, in the widespread genera Aythya, Circus, and Artamus, have distributions in both areas, but all range over a much greater geographic area including into Australia. This lack of overlap between the faunas of Vanuatu and New Caledonia contributes to the biotic break long recognized between these landmasses (Gibbons 1985, Bauer 1988, Hamilton et al 2010 ( Hamilton et al 2010), which places Efate with all more northern islands. It was based on diverse data for plants, invertebrates, and vertebrates, particularly squamates.…”

“…The cemetery is thus coeval with the colonization of the Vanuatu / New Caledonia / Fiji region 3,000 yr ago by the Lapita culture (Sand 1997, Clark and Anderson 2001, Galipaud and Swete-Kelly 2007. Therefore the Post-Lapita midden, with a date range of perhaps 2,800 -2,500 calendar ybp, does not sample the period of initial human contact with the Vanuatu fauna, and so it is likely that the most human-susceptible (Chase 1971, Rodda 1994, Grandcolas et al 2008, Neall and Trewick 2008, Murienne 2009, Hamilton et al 2010) allows minimal time for such divergent forms to evolve. In contrast to such flightless avian taxa, endemic meiolaniid turtles in Vanuatu, Viti Levu, and New Caledonia are presumed to be able to readily disperse across the ocean ( White et al 2010).…”

“…This young age and the rapid tectonic evolution of the region explains the absence of frogs (Platymantis) and elapid (Ogmodon) snakes that are present in Fiji ( Hamilton et al 2010). A majority of biota in Vanuatu is considered derived by dispersal from the Solomons to the north, and a distinct biotic break to the south, between Vanuatu and New Caledonia, has long been recognized (Gibbons 1985, Bauer 1988, Hamilton et al 2010.…”