Reproductive and genetic evidence for a reticulate evolutionary history ofmass-spawning corals

Reef-building corals, which reproduce through simultaneous multispecies spa wning, are thought to hybridize frequently, and it is hypothesized that the y have evolved in repeated rounds of species separation and fusion. We cond ucted cross-fertilization experiments and molecular analyses with a number of mass-spawning coral species in the genus Acropora. A high rate of inters pecific fertilization occurred between some species despite very different morphologies. The hybrid larvae developed normally and contained an allelic sequence transmitted from each parent, suggesting common diploid hybridiza tion. Molecular phylogenetic analyses provided strong evidence for a gene p ool shared between the hybridizing species. These reproductive and genetic characteristics are consistent with a species complex formed under the sepa ration/fusion processes predicted for a reticulate evolutionary history.