Comparison of reproductive output of hybrid sea turtles and parental species
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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.
KeywordsClutch Size Reproductive Output Parental Species Hybrid Zone Generalize Additive Model
We are very grateful to Projeto TAMAR biologists and trainees for their help collecting the data, especially L. Verissímo, B. Canal, P. Luz, R. Machado and D. Mora. We thank A. Santos and G. Maurutto for assisting with extracting data from Projeto TAMAR dataset and for their help with Fig. 1. We are also grateful to R. Lo and M. Schlig for the indispensable help processing the genetic samples. S. McDaniel and A. Payton for providing equipment and expertise on the preparation and analyses of the genetic samples. We also thank three anonymous reviewers for comments that improved this manuscript. Our studies were supported by the following funding sources: Archie Carr Center for Sea Turtle Research general funds, Tropical Conservation and Development Grant, PADI Foundation, Maturo Excellence Fund, Lerner-Gray Memorial Fund, Beckmam Foundation and the Michael L. May Research Grants.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed in studies involving animals were in accordance with the ethical standards of the University of Florida and Projeto TAMAR-ICMBio at which the studies were conducted. This research was approved by the Institutional Animal Care and Use Committees at the University of Florida (201101985) and conducted under SISBIO permit 28938-3 from the Brazilian Ministry of the Environment. Samples were exported under CITES permit 13BR010456/DF and were imported into the USA under CITES permits 13US724540/9 (Archie Carr Center for Sea Turtle Research).
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