Influence of the geography of speciation on current patterns of coral reef fish biodiversity across the Indo-Pacific
Gaboriau Théo, Leprieur Fabien, Mouillot David, Hubert Nicolas
The role of speciation processes in shaping current biodiversity patterns represents a major scientific question for ecologists and biogeographers. Hence, numerous methods have been developed to determine the geography of speciation based on co-occurrence between sister-species. Most of these methods rely on the correlation between divergence time and several metrics based on the geographic ranges of sister-taxa (i.e. overlap, asymmetry). The relationship between divergence time and these metrics has scarcely been examined in a spatial context beyond regression curves. Mapping this relationship across spatial grids, however, may unravel how speciation processes have shaped current biodiversity patterns through space and time. This can be particularly relevant for coral reef fishes of the Indo-Pacific since the origin of the exceptional concentration of biodiversity in the Indo-Australian Archipelago (IAA) has been actively debated, with several alternative hypotheses involving species diversification and dispersal. We reconstructed the phylogenetic relationships between three species-rich families of coral reef fish (Chaetodontidae, Labridae, Pomacentridae) and calculated co-occurrence metrics between closely related lineages of those families. We demonstrated that repeated biogeographic processes can be identified in present-day species distribution by projecting co-occurrence metrics between related lineages in a geographical context. Our study also evidence that sister-species do not co-occur randomly across the Indo-Pacific, but tend to overlap their range within the IAA. We identified the imprint of two important biogeographic processes that caused this pattern in 48% of the sister-taxa considered: speciation events within the IAA and repeated divergence between the Indian and Pacific Ocean, with subsequent secondary contact in the IAA.