Malhotra A, Thorpe R S
School of Biological Sciences, University of Wales, Bangor, Gwynedd, United Kingdom.
Evolution. 2000 Feb;54(1):245-58. doi: 10.1111/j.0014-3820.2000.tb00025.x.
The larger islands of the Lesser Antilles are ecologically and geologically complex and are inhabited by single, but morphologically variable, Anolis species. Although earlier work has indicated that a large part of the morphological variation in Anolis oculatus from Dominica can be attributed to selection, a history of recurrent volcanic activity over the last few million years suggests that vicariance may have also played a significant role. We report a study of variation in the cytochrome b gene of mitochondrial DNA across the island to address this issue. We uncovered a very high degree of polymorphism, with an overall gene diversity of 0.97 and a nucleotide diversity of 0.04. Sequences, on average, differ by 3.82% and the maximum pairwise divergence (corrected for multiple hits) is 9.29%. Most haplotypes are restricted to single localities (a pattern not changed by increasing the sample size). Phylogenetic analysis revealed the presence of two distinct lineages on the island with strong phylogeographic structure. One of these is geographically restricted to a relatively small part of the central Caribbean coast. Sublineages were also discernible within the other more widely distributed lineage, but resolution within and support for these sublineages was poor. The phylogeographic pattern is not congruent with generalized body shape and scalation, but is significantly correlated with color pattern. Even when correcting for this lineage effect with partial Matrix correspondence tests, the relationship between color pattern and vegetation is reaffirmed, suggesting that although both vicariance and selection have played a role in the morphological differentiation of this species, selection for current environmental conditions has been more important. We discuss the causes of the phylogeographic structure in light of the volcanic history of the island and highlight the exceptional instance of congruence between all morphological character systems and lineage boundaries, which occurs at the transition between the northern and southern Caribbean ecotypes.
小安的列斯群岛较大的岛屿在生态和地质方面都很复杂，栖息着单一但形态多变的安乐蜥物种。尽管早期研究表明，多米尼克岛安乐蜥形态变异的很大一部分可归因于选择，但过去几百万年反复的火山活动历史表明，地理隔离可能也起到了重要作用。我们报告了一项关于该岛线粒体DNA细胞色素b基因变异的研究，以解决这一问题。我们发现了非常高的多态性，总体基因多样性为0.97，核苷酸多样性为0.04。序列平均差异为3.82%，最大成对差异（经多重命中校正）为9.29%。大多数单倍型仅限于单个地点（增加样本量并未改变这一模式）。系统发育分析揭示该岛存在两个具有强烈系统地理学结构的不同谱系。其中一个在地理上局限于加勒比海中部海岸相对较小的区域。在另一个分布更广的谱系中也可辨别出亚谱系，但这些亚谱系内部的分辨率和支持度都很差。系统地理学模式与广义的体型和鳞片特征不一致，但与体色模式显著相关。即使通过部分矩阵对应检验校正这种谱系效应，体色模式与植被之间的关系仍得到确认，这表明尽管地理隔离和选择在该物种的形态分化中都发挥了作用，但针对当前环境条件的选择更为重要。我们根据该岛的火山历史讨论了系统地理学结构的成因，并强调了所有形态特征系统与谱系边界之间一致性的特殊实例，这种情况发生在加勒比海北部和南部生态型的过渡地带。
