Biogeographic patterns and diversification dynamics of the genus Cardiodactylus Saussure (Orthoptera, Grylloidea, Eneopterinae) in Southeast Asia.

Southeast Asia harbors an extraordinary species richness and endemism. While only covering 4% of the Earth's landmass, this region includes four of the planet's 34 biodiversity hotspots. Its complex geological history generated a megadiverse and highly endemic biota, attracting a lot of attention, especially in the field of island biogeography. Here we used the cricket genus Cardiodactylus as a model system to study biogeographic patterns in Southeast Asia. We carried out molecular analyses to: (1) infer phylogenetic relationships based on five mitochondrial and four nuclear markers, (2) estimate divergence times and infer biogeographical ancestral areas, (3) depict colonization routes, and summarize emigration and immigration events, as well as in situ diversification, and (4) determine whether shifts in species diversification occurred during the course of Cardiodactylus evolution. Our results support the monophyly of the genus and of one of its species groups. Dating and biogeographical analyses suggest that Cardiodactylus originated in the Southwest Pacific during the Middle Eocene. Our reconstructions indicate that Southeast Asia was independently colonized twice during the Early Miocene (ca. 19-16 Million years ago), and once during the Middle Miocene (ca. 13 Million years ago), with New Guinea acting as a corridor allowing westward dispersal through four different passageways: Sulawesi, the Philippines, Java and the Lesser Sunda Islands. Sulawesi also served as a diversification hub for Cardiodactylus through a combination of high immigration and in situ diversification events, which can be accounted for by the complex geological history of the Wallacea region.