Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, Iowa 50011 USA.
Am J Bot. 2008 Jun;95(6):756-65. doi: 10.3732/ajb.0800049.
The study of recently formed species is important because it can help us to better understand organismal divergence and the speciation process. However, these species often present difficult challenges in the field of molecular phylogenetics because the processes that drive molecular divergence can lag behind phenotypic divergence. In the current study we show that species of the recently diverged North American endemic genus of purple coneflower, Echinacea, have low levels of molecular divergence. Data from three nuclear loci and two plastid loci provide neither resolved topologies nor congruent hypotheses about species-level relationships. This lack of phylogenetic resolution is likely due to the combined effects of incomplete lineage sorting, hybridization, and backcrossing following secondary contact. The poor resolution provided by molecular markers contrasts previous studies that found well-resolved and taxonomically supported relationships from metabolic and morphological data. These results suggest that phenotypic canalization, resulting in identifiable morphological species, has occurred rapidly within Echinacea. Conversely, molecular signals have been distorted by gene flow and incomplete lineage sorting. Here we explore the impact of natural history on the genetic organization and phylogenetic relationships of Echinacea.
研究新近形成的物种很重要，因为它可以帮助我们更好地理解生物的分歧和物种形成过程。然而，这些物种在分子系统发育学领域常常带来困难的挑战，因为驱动分子分歧的过程可能滞后于表型分歧。在本研究中，我们表明，新近分化的北美特有紫锥花属（Echinacea）的物种具有较低水平的分子分歧。来自三个核基因座和两个质体基因座的数据既没有提供解决的拓扑结构，也没有提供关于种级关系的一致假说。这种缺乏系统发育分辨率可能是由于不完全谱系分选、杂交和二次接触后的回交的综合影响。分子标记提供的低分辨率与之前的研究形成对比，后者从代谢和形态数据中发现了分辨率良好且具有分类学支持的关系。这些结果表明，表型管化导致可识别的形态物种在紫锥花属中迅速发生。相反，分子信号受到基因流和不完全谱系分选的扭曲。在这里，我们探讨了自然历史对紫锥花属的遗传组织和系统发育关系的影响。
