Bowen B W, Clark A M, Abreu-Grobois F A, Chaves A, Reichart H A, Ferl R J
Dept. of Fisheries and Aquatic Sciences, University of Florida, Gainesville 32653-3071, USA.
Genetica. 1997;101(3):179-89. doi: 10.1023/a:1018382415005.
The Kemp's ridley sea turtle (Lepidochelys kempi) is restricted to the warm temperate zone of the North Atlantic Ocean, whereas the olive ridley turtle (L. olivacea) is globally distributed in warm-temperate and tropical seas, including nesting colonies in the North Atlantic that nearly overlap the range of L. kempi. To explain this lopsided distribution, Pritchard (1969) proposed a scenario in which an ancestral taxon was divided into Atlantic and Pacific forms (L. kempi and L. olivacea, respectively) by the Central American land bridge. According to this model, the olive ridley subsequently occupied the Pacific and Indian Oceans and recently colonized the Atlantic Ocean via southern Africa. To assess this biogeographic model, a 470 bp sequence of the mtDNA control region was compared among 89 ridley turtles, including the sole L. kempi nesting population and 7 nesting locations across the range of L. olivacea. These data confirm a fundamental partition between L. olivacea and L. kempi (p = 0.052-0.069), shallow separations within L. olivacea (p = 0.002-0.031), and strong geographic partitioning of mtDNA lineages. The most divergent L. olivacea haplotype is observed in the Indo-West Pacific region, as are the central haplotypes in a parsimony network, implicating this region as the source of the most recent radiation of olive ridley lineage. The most common olive ridley haplotype in Atlantic samples is distinguished from an Indo-West Pacific haplotype by a single nucleotide substitution, and East Pacific samples are distinguished from the same haplotype by two nucleotide substitutions. These shallow separations are consistent with the recent invasion of the Atlantic postulated by Pritchard (1969), and indicate that the East Pacific nesting colonies were also recently colonized from the Indo-West Pacific region. Molecular clock estimates place these invasions within the last 300,000 years.
肯氏丽龟（Lepidochelys kempi）局限于北大西洋的暖温带海域，而榄蠵龟（L. olivacea）则全球分布于暖温带和热带海域，包括北大西洋的筑巢群体，其分布范围几乎与肯氏丽龟的分布范围重叠。为了解释这种不均衡的分布情况，普里查德（1969年）提出了一种设想，即一个祖先分类单元被中美洲陆桥分隔成了大西洋和太平洋两种形态（分别为肯氏丽龟和榄蠵龟）。根据这个模型，榄蠵龟随后占据了太平洋和印度洋，并最近通过非洲南部殖民到了大西洋。为了评估这个生物地理模型，对89只丽龟的线粒体DNA控制区的470个碱基对序列进行了比较，其中包括肯氏丽龟唯一的筑巢群体以及榄蠵龟分布范围内的7个筑巢地点。这些数据证实了榄蠵龟和肯氏丽龟之间存在基本的分化（p = 0.052 - 0.069），榄蠵龟内部存在较浅的分化（p = 0.002 - 0.031），以及线粒体DNA谱系存在强烈的地理分化。在印度 - 西太平洋地区观察到了最具分歧的榄蠵龟单倍型，简约网络中的中心单倍型也是如此，这表明该地区是榄蠵龟谱系最近辐射的来源。大西洋样本中最常见的榄蠵龟单倍型与印度 - 西太平洋单倍型通过一个单核苷酸替换区分开来，东太平洋样本与同一单倍型通过两个单核苷酸替换区分开来。这些较浅的分化与普里查德（1969年）假设的大西洋近期入侵情况一致，并表明东太平洋筑巢群体也是最近从印度 - 西太平洋地区殖民而来的。分子钟估计这些入侵发生在过去30万年之内。
