After continents divide: comparative phylogeography of reef fishes from the R ed S ea and I ndian O cean

Aim TheRedSea is a biodiversity hotspot characterized by a unique marine fauna and high endemism. This sea began formingc. 24 million years ago with the separation of theAfrican andArabian plates, and has been characterized by periods of desiccation, hypersalinity and intermittent connection to theIndianOcean. We aim to evaluate the impact of these events on the genetic architecture of theRedSea reef fish fauna. Location RedSea andWesternIndianOcean. Methods We surveyed seven reef fish species from theRedSea and adjacentIndianOcean using mitochondrialDNAcytochromecoxidase subunit I and cytochromebsequences. To assess genetic variation and evolutionary connectivity within and between these regions, we estimated haplotype diversity (h) and nucleotide diversity (π), reconstructed phylogenetic relationships among haplotypes, and estimated gene flow and time of population separation usingBayesian coalescent‐based methodology. Results Our analyses revealed a range of scenarios from shallow population structure to diagnostic differences that indicate evolutionary partitions and possible cryptic species. Conventional molecular clocks and coalescence analyses indicated time‐frames for divergence between these bodies of water ranging from 830,000 years to contemporary exchange or recent range expansion. Colonization routes were bidirectional, with some species moving from theIndianOcean to theRedSea compared with expansion out of theRedSea for other species. Main conclusions We conclude that: (1) at least someRedSea reef fauna survived multiple salinity crises; (2) endemism is higher in theRedSea than previously reported; and (3) theRedSea is an evolutionary incubator, occasionally contributing species to the adjacentIndianOcean. The latter two conclusions – elevated endemism and species export – indicate a need for enhanced conservation priorities for theRedSea.