Nuclear markers reveal a complex introgression pattern among marine turtle species on the Brazilian coast

Abstract

Surprisingly, a high frequency of interspecific sea turtle hybrids has been previously recorded in a nesting site along a short stretch of the Brazilian coast. Mitochondrial DNA data indicated that as much as 43% of the females identified as Eretmochelys imbricata are hybrids in this area (Bahia State of Brazil). It is a remarkable find, because most of the nesting sites surveyed worldwide, including some in northern Brazil, presents no hybrids, and rare Caribbean sites present no more than 2% of hybrids. Thus, a detailed understanding of the hybridization process is needed to evaluate natural or anthropogenic causes of this regional phenomenon in Brazil, which could be an important factor affecting the conservation of this population. We analysed a set of 12 nuclear markers to investigate the pattern of hybridization involving three species of sea turtles: hawksbill (E. imbricata), loggerhead (Caretta caretta) and olive ridley (Lepidochelys olivacea). Our data indicate that most of the individuals in the crossings L. olivacea × E. imbricata and L. olivacea × C. caretta are F1 hybrids, whereas C. caretta × E. imbricata crossings present F1 and backcrosses with both parental species. In addition, the C. caretta × E. imbricata hybridization seems to be gender and species biased, and we also found one individual with evidence of multispecies hybridization among C. caretta × E. imbricata × Chelonia mydas. The overall results also indicate that hybridization in this area is a recent phenomenon, spanning at least two generations or ~40 years.

Hybridization betweenMauremys japonicaandMauremys reevesiiInferred by Nuclear and Mitochondrial DNA Analyses

“…Most of the studies published to date on hybridization of various taxa have described unidirectional hybridization or the disappearance of one of the two parental mtDNA types after reciprocal hybridization (Karl et al, 1995;Wirtz, 1999; see the review of Wirtz, 1999; but see also Vila¸ca et al 2012). However, we observed that in both types of hybrid individuals with heterozygous C-mos, the number of a M. japonica maternal lineage was slightly higher than in those of a M. reevesii maternal lineage.…”

Hawksbill × loggerhead sea turtle hybrids at Bahia, Brazil: where do their offspring go?

“…, 2003; James, Martin & Dutton, 2004; Lara-Ruiz et al. , 2006; Reis, Soares & Lôbo-Hajdu, 2010; Vilaça et al. , 2012).…”

“…Interestingly, the hawksbill × loggerhead hybrids are reproductively viable and produce hatchlings, possibly due to an ongoing introgression process (Lara-Ruiz et al. , 2006; Vilaça et al. , 2012).…”

Origin and dispersal routes of foreign green and Kemp’s ridley turtles in Spanish Atlantic and Mediterranean waters

“…Only an hybridisation with an olive Ridley could explain the extra number of scutes, an unlikely possibility considering the very different distribution of both species and the inexistence of common feeding areas (table 3). Thus, the analysis of nuclear markers is needed to completely discard this remote possibility (Bowen and Karl, 2007;Vilaca et al, 2012). It is worth to mention that this putative hybridisation would have no consequences for the maternally inherited mtDNA, and thus the question of the orphan haplotype remains unanswered.…”