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

Abstract

Aim The R ed S ea is a biodiversity hotspot characterized by a unique marine fauna and high endemism. This sea began forming c . 24 million years ago with the separation of the A frican and A rabian plates, and has been characterized by periods of desiccation, hypersalinity and intermittent connection to the I ndian O cean. We aim to evaluate the impact of these events on the genetic architecture of the R ed S ea reef fish fauna. Location Red S ea and W estern I ndian O cean. Methods We surveyed seven reef fish species from the R ed S ea and adjacent I ndian O cean using mitochondrial DNA cytochrome c oxidase subunit I and cytochrome b sequences. 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 using B ayesian 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 the I ndian O cean to the R ed S ea compared with expansion out of the R ed S ea for other species. Main conclusions We conclude that: (1) at least some R ed S ea reef fauna survived multiple salinity crises; (2) endemism is higher in the R ed S ea than previously reported; and (3) the R ed S ea is an evolutionary incubator, occasionally contributing species to the adjacent I ndian O cean. The latter two conclusions – elevated endemism and species export – indicate a need for enhanced conservation priorities for the R ed S ea.

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