Friar Elizabeth A, Prince Linda M, Roalson Eric H, McGlaughlin Mitchell E, Cruse-Sanders Jennifer M, De Groot Sarah J, Porter J Mark
Rancho Santa Ana Botanic Garden, 1500 North College Avenue, Claremont, California 91711, USA.
Evolution. 2006 Sep;60(9):1777-92.
Adaptive diversification can be viewed as a balance between the conservative force of interpopulation gene flow and selection for differential environments. In this paper, we examine ecological, morphological, and genetic differentiation in a small clade consisting of four East Maui-endemic species of Dubautia: D. menziesii, D. platyphylla, D. reticulata, and D. waianapanapaensis, in the Hawaiian silversword alliance (Asteraceae). The East Maui clade is apparently recently derived (less than 1 million years ago) and is geographically restricted yet displays significant ecological and morphological differences. We used geographic data from historical herbarium specimens, measurements of plant architecture and leaf morphometrics, and measures of genetic differentiation in both microsatellite and nuclear coding loci to examine the correlation of different forms of divergence in this small species flock. We found overlap in large-scale geographic distributions, significant differentiation in most habitat factors, significant microsatellite differentiation, and many shared alleles at nuclear coding loci suggesting on-going lineage sorting. Despite the presence of apparent hybrids in some populations, microsatellite variation is consistent with isolation among species. Using Mantel tests, we compared the direction and extent of diversification among different datasets, to determine whether ecological/morphological divergence was correlated with genetic divergence. Correlations among different datasets showed that habitat was strongly correlated with plant architecture but not leaf morphology. Taken together, these results indicate that ecological and morphological diversification has driven genetic divergence at rapidly evolving microsatellite loci, whereas there is continuing lineage sorting at neutral sites in nuclear coding loci.
适应性分化可被视为种群间基因流的保守力量与对不同环境的选择之间的一种平衡。在本文中，我们研究了夏威夷银剑菊科（菊科）中一个由四种东毛伊岛特有植物杜氏菊组成的小分支的生态、形态和遗传分化：门氏杜氏菊、阔叶杜氏菊、网脉杜氏菊和怀阿奈帕纳帕杜氏菊。东毛伊岛分支显然是最近演化而来的（不到100万年前），地理分布受限，但却表现出显著的生态和形态差异。我们利用历史标本馆标本的地理数据、植物结构和叶片形态测量数据，以及微卫星和核编码位点的遗传分化测量数据，来研究这个小物种群中不同形式分化的相关性。我们发现它们在大规模地理分布上存在重叠，在大多数栖息地因素上有显著分化，微卫星有显著分化，并且在核编码位点有许多共享等位基因，这表明正在进行谱系分选。尽管在一些种群中存在明显的杂交种，但微卫星变异与物种间的隔离是一致的。我们使用曼特尔检验来比较不同数据集之间分化的方向和程度，以确定生态/形态分化是否与遗传分化相关。不同数据集之间的相关性表明，栖息地与植物结构密切相关，但与叶片形态无关。综合来看，这些结果表明，生态和形态分化在快速演化的微卫星位点上推动了遗传分化，而在核编码位点的中性位点上仍在继续进行谱系分选。
