Fertile Hybrids Could Aid Coral Adaptation

Fertile hybrids can enhance the adaptive capacity and resilience of species under stress by increasing genetic diversity within populations, masking the effects of deleterious recessive alleles, and facilitating the introgression of beneficial genetic variants into parental species. However, many hybrids are infertile. We compared the fertility of aquarium-reared F1 hybrid and purebred corals of the species Acropora loripes and Acropora kenti and examined the viability of early life stages of second-generation (F2) hybrid and back-crossed planula larvae and recruits. The F1 hybrids spawned viable gametes and the F2 hybrid and back-crossed embryos developed into planula larvae and settled to become sessile coral recruits. The F1 hybrids had greater reproductive fitness than the F1 A. loripes purebred stock in an aquarium environment based on their probability of spawning and their fertilization success in crosses using their gametes. Interspecific coral hybrids can therefore be fertile and have high reproductive fitness, which could benefit the persistence of threatened coral reefs.