Effects of hybridization on sea turtle fitness
Sea turtle hybridization is a common phenomenon in Brazil between loggerheads (Caretta caretta) and hawksbills (Eretmochelys imbricata) as well as between loggerheads and olive ridleys (Lepidochelys olivacea). In a previous study we showed that the reproductive output of loggerhead/hawksbill hybrids is similar to that of parental species, suggesting no negative effect of hybridization at this life stage. In this study, we used pooled amplicon sequencing to assign species identity to dams and their progeny, and to investigate the fitness consequences of hybridization, using hatchling viability as a proxy for fitness. We genotyped 4829 hatchlings from egg clutches laid by 78 loggerheads, 13 hawksbills, seven loggerhead/hawksbill hybrids, and three loggerhead/olive ridley hybrids. The proportion of viable hybrid (heterozygous) hatchlings was similar to that of homozygous hatchlings (based on data at two loci), independent of the dam’s genotype. Multiple species paternity was observed in 35.7% of the nests. Both hybrid males and females were fertile and produced viable offspring, and we found no evidence for hybrid breakdown. We suggest a genome-wide study of the hybrids and parental species to better characterize hybrids, as well as studies on additional demographic and ecological parameters to further assess the effects of hybridization and its consequences for sea turtles and their environment.
KeywordsHybridization Sea turtles Loggerhead Hawksbill Olive ridley Fitness
We are very grateful to Projeto TAMAR biologists and trainees for their help collecting the data, especially L. Verissímo, B. Canal, and D. Mora. We thank G. Maurutto for his help with Fig. 1. We are thankful to J. Wellehan for his contribution and discussions on the design of the genetic assessment on this study. We are also grateful to M. Schlig for the indispensable help processing the genetic samples, and P. Thompson for his help with processing the samples in the NGS Illumina sequencer. 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, Beckman Foundation, the Michael L. May Research Grants, Lalita Shastry, the Cynthia A. Melnick Endowment, and an NSF Grant (DEB 1541005) to SFM.
LSS, KAB, ABB and MLW designed the study with input from MAM. Field work and sampling were conducted by LSS, PBL and RM. Laboratory and data analyses were conducted by LSS, RL and ACP with input from MLW, SFM, TBW, KAB, and ABB. LSS drafted the first version of the manuscript, and all authors contributed to the writing of the final version.
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 United States under CITES permits 13US724540/9 (Archie Carr Center for Sea Turtle Research).
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