Matsuoka Yoshihiro, Takumi Shigeo, Kawahara Taihachi
Fukui Prefectural University, Matsuoka, Eiheiji, Yoshida, Fukui, Japan.
Laboratory of Plant Genetics, Graduate School of Agricultural Science, Kobe University, Nada-ku, Kobe, Japan.
BMC Evol Biol. 2015 Sep 30;15:213. doi: 10.1186/s12862-015-0496-9.
How species ranges form in landscapes is a matter of long-standing evolutionary interest. However, little is known about how natural phenotypic variations of ecologically important traits contribute to species range expansion. In this study, we examined the phylogeographic patterns of phenotypic changes in life history (seed production) and phenological (flowering time) traits during the range expansion of Aegilops tauschii Coss. from the Transcaucasus and Middle East to central Asia.
Our comparative analyses of the patterns of natural variations for those traits and their association with the intraspecific lineage structure showed that (1) the eastward expansion to Asia was driven by an intraspecific sublineage (named TauL1b), (2) high seed production ability likely had an important role at the initial dispersal stage of TauL1b's expansion to Asia, and (3) the phenological change to early flowering phenotypes was one of the key adaptation events for TauL1b to further expand its range in Asia.
This study provides for the first time a broad picture of the process of Ae. tauschii's eastward range expansion in which life history and phenological traits may have had respective roles in its dispersal and adaptation in Asia. The clear association of seed production and flowering time patterns with the intraspecific lineage divergence found in this study invites further genetic research to bring the mechanistic understanding of the changes in these key functional traits during range expansion within reach.
物种分布范围在景观中如何形成是一个长期以来备受进化关注的问题。然而，对于具有生态重要性的性状的自然表型变异如何促进物种分布范围扩张，我们知之甚少。在本研究中，我们研究了节节麦（Aegilops tauschii Coss.）从外高加索和中东向中亚分布范围扩张过程中，生活史（种子产量）和物候（开花时间）性状的表型变化的系统地理学模式。
我们对这些性状的自然变异模式及其与种内谱系结构的关联进行的比较分析表明：（1）向亚洲的东扩是由一个种内亚谱系（命名为TauL1b）驱动的；（2）高种子生产能力可能在TauL1b向亚洲扩张的初始扩散阶段发挥了重要作用；（3）物候变化为早花表型是TauL1b在亚洲进一步扩大其分布范围的关键适应事件之一。
本研究首次全面描绘了节节麦向东分布范围扩张的过程，其中生活史和物候性状在其在亚洲的扩散和适应过程中可能分别发挥了作用。本研究中发现的种子产量和开花时间模式与种内谱系分化的明确关联，促使进一步开展遗传学研究，以便深入了解分布范围扩张过程中这些关键功能性状变化的机制。
