Spawning and fertility of F1 hybrids of the coral genus Acropora in the Indo-Pacific

The role of hybridization through multi-specific synchronous spawning in the evolution of reef-building corals has been discussed since the 1990s, particularly for the genus Acropora. However, F-1 hybrids have been reported as common in only one case in the Caribbean, with no evidence of mechanisms that would allow continuous reproduction of the hybrids. In this study, we report for the first time the fecundity of two F-1 hybrid colonies produced experimentally from two Indo-Pacific species, A. intermedia and A. florida. These F-1 hybrids spawned at the same time as the parental corals. Backcrossing and F-1 hybrid crossing were successful in both directions. Furthermore, more than 90% self-fertilization was achieved in an F-1 hybrid, although it was negligible in the parental corals. While it is possible that the F-1 hybrid was a chimera, these results suggest that some products of interspecific hybridization may persist as the offspring of self-fertilizing F-1 hybrids.