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.

此前在巴西沿岸一段狭长区域的筑巢位点中，已记录到比例异常偏高的种间海龟杂交个体。线粒体DNA（mitochondrial DNA）数据显示，在巴西巴伊亚州的该区域，被鉴定为玳瑁（Eretmochelys imbricata）的雌性个体中，多达43%为杂交个体。这是一项极具研究价值的发现，因为全球范围内经调查的多数筑巢位点（包括巴西北部的部分区域）均未发现杂交个体，即便罕见的加勒比地区筑巢点，其杂交个体占比也不超过2%。因此，为厘清巴西该区域出现这一区域性现象的自然或人为成因，亟需深入解析其杂交过程——这或许是影响该种群保护工作的关键因素。本研究针对12组核标记（nuclear markers）开展分析，以探究涉及3种海龟的杂交模式：玳瑁（Eretmochelys imbricata）、蠵龟（Caretta caretta）以及榄蠵龟（Lepidochelys olivacea）。数据表明，榄蠵龟与玳瑁、榄蠵龟与蠵龟的杂交后代中，绝大多数为第一代杂交种（F1 hybrids）；而蠵龟与玳瑁的杂交后代则同时存在第一代杂交种与两个亲本物种的回交个体。此外，蠵龟与玳瑁的杂交似乎存在性别与物种偏向性，我们还在蠵龟×玳瑁×绿海龟（Chelonia mydas）的组合中发现了1例多物种杂交个体。整体结果还显示，该区域的杂交现象属于新近发生的事件，至少已延续两代，即约40年时间。