Abstract
Hybridization between hawksbill (Eretmochelys imbricata) and loggerhead (Caretta caretta) breeding groups is unusually common in Bahia state, Brazil. Such hybridization is possible because hawksbill and loggerhead nesting activities overlap temporally and spatially along the coast of this state. Nevertheless, the destinations of their offspring are not yet known. This study is the first to identify immature hawksbill × loggerhead hybrids (n = 4) from this rookery by analyzing the mitochondrial DNA (mtDNA) of 157 immature turtles morphologically identified as hawksbills. We also compare for the first time modeled dispersal patterns of hawksbill, loggerhead, and hybrid offspring considering hatching season and oceanic phase duration of turtles. Particle movements varied according to season, with a higher proportion of particles dispersing southwards throughout loggerhead and hybrid hatching seasons, and northwards during hawksbill season. Hybrids from Bahia were not present in important hawksbill feeding grounds of Brazil, being detected only at areas more common for loggerheads. The genetic and oceanographic findings of this work indicate that these immature hybrids, which are morphologically similar to hawksbills, could be adopting behavioral traits typical of loggerheads, such as feeding in temperate waters of the western South Atlantic. Understanding the distribution, ecology, and migrations of these hybrids is essential for the development of adequate conservation and management plans.
Highlights
Interspecific hybridization occurs naturally or as a result of anthropogenic actions such as habitat modification and fragmentation, species introduction, and population declines (Rhymer & Simberloff, 1996; Allendorf et al, 2001)
Natural hybridization between Cheloniid sea turtle species has been reported for green Chelonia mydas × hawksbill Eretmochelys imbricata, loggerhead Caretta caretta × hawksbill, green × loggerhead, loggerhead × olive ridley Lepidochelys olivacea, and olive ridley × hawksbill turtles (Wood, Wood & Critchley, 1983; Conceição et al, 1990; Karl, Bowen & Avise, 1995; Seminoff et al, 2003; James, Martin & Dutton, 2004; Lara-Ruiz et al, 2006; Reis, Soares & Lôbo-Hajdu, 2010; Vilaça et al, 2012)
We report for the first time immature hawksbill × loggerhead hybrids in Brazilian waters and show how temporal variability in hatching period leads to differences between the dispersal patterns of loggerhead, hawksbill, and hybrid offspring from Bahia
Summary
Interspecific hybridization occurs naturally or as a result of anthropogenic actions such as habitat modification and fragmentation, species introduction, and population declines (Rhymer & Simberloff, 1996; Allendorf et al, 2001). It is estimated that 25% of plant and 10% of animal species undergo hybridization (Mallet, 2005). This process can contribute to the evolution of many taxa (Barton, 2001), but may lead to lower fitness and fertility, and even genetic extinction of species (Rhymer & Simberloff, 1996). Natural hybridization between Cheloniid sea turtle species has been reported for green Chelonia mydas × hawksbill Eretmochelys imbricata, loggerhead Caretta caretta × hawksbill, green × loggerhead, loggerhead × olive ridley Lepidochelys olivacea, and olive ridley × hawksbill turtles (Wood, Wood & Critchley, 1983; Conceição et al, 1990; Karl, Bowen & Avise, 1995; Seminoff et al, 2003; James, Martin & Dutton, 2004; Lara-Ruiz et al, 2006; Reis, Soares & Lôbo-Hajdu, 2010; Vilaça et al, 2012). Possible sterility and lower fitness of these hybrids is concerning since all sea turtle species are currently threatened (IUCN, 2012); the exact causes and consequences of these hybridizations are not yet understood
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