Adaptive radiation is the diversification of a founding population into multiple taxa that are differentially adapted to diverse ecological niches. The three Callicarpa (Lamiaceae) species endemic to the Bonin Islands are considered to represent an example of adaptive radiation on oceanic islands. All three species are distributed in the Chichijima Island Group and grow in different habitats, while only one species, C. subpubescens, is distributed among other island groups. Particularly, in the Hahajima and Mukojima Island Groups, C. subpubescens grows in various habitats and shows relatively high morphological variation. We investigated genotypes of the three Callicarpa species at 14 microsatellite markers to elucidate genetic differentiation within and between species or island groups and between different habitats or morphologies. We found that genetic differentiation within C. subpubescens in the Hahajima and Mukojima Island Groups was equally as high as that between the three species in the Chichijima Island Group, while differentiation within C. subpubescens in the Chichijima Island Group was much lower. Analyses such as a Bayesian clustering analysis showed that genetically distinct groups were associated with the three species in the Chichijima Island Group, whereas they showed strong genetic structure within C. subpubescens in the Hahajima and Mukojima Island Groups among different habitats and morphologies. These results indicated that ecological diversification occurred in the Hahajima and Mukojima Island Groups. Meanwhile, high genetic differentiation among different island groups was also observed, reflecting isolation by distance. It implies that non-ecological factors such as geographic isolation also played important roles in genetic differentiation in Callicarpa species in the Bonin Islands. These findings suggest that the Callicarpa species in the Bonin Islands are differentiated into multiple genetic groups by both ecological and non-ecological factors.

中文翻译：

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波宁（小gas原）群岛特有的Callicarpa物种的微卫星变异揭示了强大的遗传结构。

适应性辐射是将创始种群多样化为多种分类单元，以适应不同的生态位。波宁群岛特有的三种Callicarpa（唇形科）物种被认为是海洋岛屿上适应性辐射的一个例子。这三种物种均分布在秩父岛群中，并在不同的生境中生长，而只有一种物种，即耻骨梭菌，分布在其他岛群中。特别地，在哈哈岛和穆克岛岛群中，亚毛耻线虫生长在各种生境中，并表现出较高的形态变化。我们研究了三种Callicarpa物种在14个微卫星标记上的基因型，以阐明物种或岛屿群之间以及物种或岛屿群之间以及不同栖息地或形态之间的遗传分化。我们发现，在Hahajima和Mukojima岛群中的耻骨梭状芽胞杆菌内的遗传分化与在Chichijima岛群中的三个物种之间的遗传分化一样高，而在Chichijima岛群中的耻骨梭状芽胞中的遗传分化要低得多。贝叶斯聚类分析等分析表明，在千岛岛群中的三个物种与遗传上不同的群体相关，而在不同生境和形态之间，在哈哈岛和穆岛岛群中的毛竹假单胞菌内却显示出强大的遗传结构。这些结果表明，在Hahajima和Mukojima岛群中发生了生态多样化。同时，还观察到了不同岛屿群之间的高度遗传分化，反映了距离的隔离。这暗示着非生态因素（例如地理隔离）在波宁群岛的卡里卡帕物种的遗传分化中也起着重要作用。这些发现表明，波宁群岛的卡里卡帕物种通过生态和非生态因素被分为多个遗传群。