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

A surprisingly high frequency of interspecific sea turtle hybrids have 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 E. imbricata are hybrids in this area (Bahia State of Brazil). It is a remarkable find, since 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 analyzed a set of 12 nuclear markers to investigate the pattern of hybridization involving three species of sea turtles: hawksbill (Eretmochelys 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.此前在巴西海岸一段狭长区域的筑巢地中，已记录到异常高频率的海龟种间杂交个体。线粒体DNA（mitochondrial DNA）数据显示，在巴西巴伊亚州的该区域内，多达43%被鉴定为玳瑁（Eretmochelys imbricata）的雌性个体为杂交个体。这一发现极具科研价值，因全球范围内已调查的绝大多数筑巢地（包括巴西北部的部分区域）均未发现杂交个体，即便加勒比地区极少数存在杂交的筑巢地，其杂交个体占比也不超过2%。因此，为探明巴西该区域出现此现象的自然或人为成因，亟需深入解析其杂交过程——这或将成为影响该海龟种群保护的关键因素。本研究选用12组核基因标记（nuclear markers），针对3种海龟的杂交模式展开探究，分别为玳瑁（Eretmochelys imbricata）、蠵龟（Caretta caretta）以及橄榄丽龟（Lepidochelys olivacea）。研究数据显示，橄榄丽龟×玳瑁以及橄榄丽龟×蠵龟的杂交组合中，绝大多数后代均为F1代杂交个体；而蠵龟×玳瑁的杂交组合后代则同时存在F1代个体与回交个体，且回交对象涵盖两个亲本物种。此外，蠵龟×玳瑁的杂交似乎存在性别与物种偏向性；本研究还发现1只同时涉及蠵龟、玳瑁与绿海龟（Chelonia mydas）的多物种杂交个体。综合所有结果来看，该区域的杂交事件属于新近发生的现象，其发生至少已历经两代，时长约40年。