Comparison of reproductive output of hybrid sea turtles and parental species

Globally, sea turtle hybridization has been reported at very low frequencies. However, in Brazil, a high incidence (>40% of morphologically assigned hawksbills) of hybridization between loggerheads and hawksbills has been reported. To the best of our knowledge, this is the first analysis of the effect of hybridization on the reproductive output of sea turtle hybrids. We used nuclear and mitochondrial markers to assign a status of hawksbill (Eretmochelys imbricata), loggerhead (Caretta caretta), or hybrid to 146 females that deposited 478 nests. Hybrids do not appear to be at either a reproductive advantage or disadvantage relative to their parental species based on the parameters analyzed (female curved carapace length, clutch size, emergence success, incubation period, hatchling production, observed clutch frequency, and observed breeding frequency). Although emergence success is lower in hybrids, hatchling production per clutch, as well as clutch frequency and breeding frequency, is similar among the three groups. These results show that hybrids may persist in this region. Further research on hybrid survival rates at different life stages, as well as growth rates and their ecological roles, will be fundamental to predict the fate of hybrid turtles. Sea turtle populations that overlap with other sea turtle species in space and time on nesting beaches should be screened for hybridization with the appropriate genetic markers.