Crawford A J
Committee on Evolutionary Biology, University of Chicago, Chicago, IL 60637, USA.
Mol Ecol. 2003 Oct;12(10):2525-40. doi: 10.1046/j.1365-294x.2003.01910.x.
Molecular genetic data were used to investigate population sizes and ages of Eleutherodactylus (Anura: Leptodactylidae), a species-rich group of small leaf-litter frogs endemic to Central America. Population genetic structure and divergence was investigated for four closely related species surveyed across nine localities in Costa Rica and Panama. DNA sequence data were collected from a mitochondrial gene (ND2) and a nuclear gene (c-myc). Phylogenetic analyses yielded concordant results between loci, with reciprocal monophyly of mitochondrial DNA haplotypes for all species and of c-myc haplotypes for three of the four species. Estimates of genetic differentiation among populations (FST) based upon mitochondrial data were always higher than nuclear-based FST estimates, even after correcting for the expected fourfold lower effective population size (Ne) of the mitochondrial genome. Comparing within-population variation and the relative mutation rates of the two genes revealed that the Ne of the mitochondrial genome was 15-fold lower than the estimate of the nuclear genome based on c-myc. Nuclear FST estimates were approximately 0 for the most proximal pairs of populations, but ranged from 0.5 to 1.0 for all other pairs, even within the same nominal species. The nuclear locus yielded estimates of Ne within localities on the order of 105. This value is two to three orders of magnitude larger than any previous Ne estimate from frogs, but is nonetheless consistent with published demographic data. Applying a molecular clock model suggested that morphologically indistinguishable populations within one species may be 107 years old. These results demonstrate that even a geologically young and dynamic region of the tropics can support very old lineages that harbour great levels of genetic diversity within populations. The association of high nucleotide diversity within populations, large divergence between populations, and high species diversity is also discussed in light of neutral community models.
分子遗传学数据被用于研究细趾蟾属（无尾目：细趾蟾科）的种群大小和年龄，该属是中美洲特有的一个物种丰富的小型落叶蛙类群。对在哥斯达黎加和巴拿马的9个地点调查的4个近缘物种的种群遗传结构和分化进行了研究。从一个线粒体基因（ND2）和一个核基因（c-myc）收集了DNA序列数据。系统发育分析在基因座之间产生了一致的结果，所有物种的线粒体DNA单倍型以及4个物种中的3个的c-myc单倍型都呈现出相互单系性。基于线粒体数据的种群间遗传分化估计值（FST）总是高于基于核数据的FST估计值，即使在纠正了线粒体基因组预期的四倍低有效种群大小（Ne）之后也是如此。比较种群内变异和两个基因的相对突变率发现，线粒体基因组的Ne比基于c-myc的核基因组估计值低15倍。对于最接近的种群对，核FST估计值约为0，但对于所有其他种群对，其范围为0.5至1.0，即使在同一标称物种内也是如此。核基因座得出的局部种群Ne估计值约为105。这个值比之前从蛙类得出的任何Ne估计值大两到三个数量级，但仍然与已发表的人口统计数据一致。应用分子钟模型表明，一个物种内形态上无法区分的种群可能有107年的历史。这些结果表明，即使是热带地区一个地质上年轻且动态的区域也能支持非常古老的谱系，这些谱系在种群中蕴藏着高水平的遗传多样性。还根据中性群落模型讨论了种群内高核苷酸多样性、种群间大分化和高物种多样性之间的关联。
