Aim: To use recently published phylogenies of three major reef fish families to explore global patterns of species origin and dispersal over the past 65 million years. The key questions are: when and where did reef fishes arise, and how has this shaped current biodiversity patterns?Location: Biogeographic reconstructions were performed on globally distributed reef fish lineages. Patterns of lineage origination and dispersal were explored in five major biogeographic regions: the East Pacific, the Atlantic, the Indian Ocean, the Indo‐Australian Archipelago hotspot, and the Central Pacific.Methods: A dispersal, extinction and cladogenesis (DEC) model implemented in Lagrange was used to infer the most likely biogeographic scenarios at nodes on chronograms of three diverse reef fish families (Labridae, Pomacentridae, Chaetodontidae). For the terminal branches ANOVA was used to compare patterns of origination on a regional and global scale. Patterns of origination and dispersal were examined within discrete time periods for the five biogeographic regions.Results: Temporal examination of hypothetical ancestral lineages reveal a pattern of increasing isolation of the East Pacific and Atlantic regions from the Eocene, and the changing role of the Indo‐Australian Archipelago from a location of accumulating ranges in the Palaeo/Eocene, a centre of origination in the Miocene, to extensive expansion of lineages into adjacent regions from the Pliocene to Recent.Main conclusions: While the East Pacific and Atlantic have a history of isolation, the Indo‐Australian Archipelago has a history of connectivity. It has sequentially and then simultaneously acted as a centre of accumulation (Palaeocene/Eocene onwards), survival (Eocene/Oligocene onwards), origin (Miocene onwards), and export (Pliocene/Recent) for reef fishes. The model suggests that it was the proliferation and expansion of lineages in the Indo‐Australian Archipelago (the Coral Triangle) during the Miocene that underpinned the current biodiversity in the Indian and Pacific Oceans.

The evolutionary dissimilarity between communities (phylogenetic beta diversity PBD) has been increasingly explored by ecologists and biogeographers to assess the relative roles of ecological and evolutionary processes in structuring natural communities. Among PBD measures, the PhyloSor and UniFrac indices have been widely used to assess the level of turnover of lineages over geographical and environmental gradients. However, these indices can be considered as ‘broad-sense’ measures of phylogenetic turnover as they incorporate different aspects of differences in evolutionary history between communities that may be attributable to phylogenetic diversity gradients. In the present study, we extend an additive partitioning framework proposed for compositional beta diversity to PBD. Specifically, we decomposed the PhyloSor and UniFrac indices into two separate components accounting for ‘true’ phylogenetic turnover and phylogenetic diversity gradients, respectively. We illustrated the relevance of this framework using simple theoretical and archetypal examples, as well as an empirical study based on coral reef fish communities. Overall, our results suggest that using PhyloSor and UniFrac may greatly over-estimate the level of spatial turnover of lineages if the two compared communities show contrasting levels of phylogenetic diversity. We therefore recommend that future studies use the ‘true’ phylogenetic turnover component of these indices when the studied communities encompass a large phylogenetic diversity gradient.

Ancient reefs provided fishy refuges: Climate fluctuations have occurred repeatedly in Earth's history, and so there is much to be learned from examining the responses of past systems. Pellessier et al. reconstructed paleoenvironments over the past 3 million years from sediment cores collected across coral reef systems to explore the impacts of past conditions on reef fish diversity. Coral reefs survived in the Indo-Australian regions during times of otherwise extensive habitat loss. These robust reefs can explain much of the diversity found in present-day reef fish species. Science , this issue p. 1016