Wang Hui, Liu Pei-Liang, Li Jian, Yang Han, Li Qin, Chang Zhao-Yang
College of Life Sciences, Northwest A&F University, Yangling, China.
Key Laboratory of Resource Biology and Biotechnology in Western China, Northwest University, Xi'an, China.
Front Plant Sci. 2021 Aug 19;12:681962. doi: 10.3389/fpls.2021.681962. eCollection 2021.
Leaf shape exhibits tremendous diversity in angiosperms. It has long been argued that leaf shape can affect major physiological and ecological properties of plants and thus is likely to be adaptive, but the evolutionary evidence is still scarce. (Fabaceae) is polymorphic for leaf shape (1 leaflet, 1-3 leaflets, and 3 leaflets) and exhibits clinal variation in steppes of Nei Mongol, China. With two close relatives predominantly fixed for one phenotype as comparison ( with 1 leaflet and with 5-13 leaflets), we used a comprehensive cline-fitting approach to assess the role of natural selection in shaping the spatial pattern of leaf-shape variation in this system. For 551 individuals sampled from 22 populations, we quantified leaf-morphological differentiation, evaluated patterns of neutral genetic variation using five chloroplast DNA intergenic regions and 11 nuclear microsatellite loci, and performed microhabitat and macroclimatic-association analyses. We found that 1-leaflet proportions in populations significantly increased from west to east, and three phenotypes also differed in leaflet-blade size. However, compared with the other two species, populations of showed little neutral genetic differentiation, and no population structure was detected at either marker. We further revealed that the leaf-shape cline could largely be explained by three macroclimatic variables, with leaflet number decreasing and leaflet-blade size increasing with annual precipitation and showing the reverse trends with temperature seasonality and isothermality. Our results suggest that spatially varying abiotic environmental factors contribute to shape the leaf-shape cline in , while the interspecific pattern may be due to both local adaptation and historical events.
叶片形状在被子植物中表现出极大的多样性。长期以来，人们一直认为叶片形状会影响植物的主要生理和生态特性，因此很可能具有适应性，但进化证据仍然很少。（豆科）的叶片形状具有多态性（1片小叶、1 - 3片小叶和3片小叶），并且在中国内蒙古草原呈现渐变变异。以两个主要固定为一种表型的近缘种作为对照（一个有1片小叶，另一个有5 - 13片小叶），我们采用了一种综合的渐变拟合方法来评估自然选择在塑造该系统中叶片形状变异空间模式方面的作用。对于从22个种群中采样的551个个体，我们量化了叶片形态分化，使用五个叶绿体DNA基因间隔区和11个核微卫星位点评估中性遗传变异模式，并进行了微生境和宏观气候关联分析。我们发现，种群中1片小叶的比例从西向东显著增加，并且三种表型在小叶叶片大小上也存在差异。然而，与其他两个物种相比，种群的中性遗传分化很小，并且在任何一个标记上都未检测到种群结构。我们进一步揭示，叶片形状渐变在很大程度上可以由三个宏观气候变量来解释，随着年降水量的增加，小叶数量减少，小叶叶片大小增加，而随着温度季节性和等温性呈现相反的趋势。我们的结果表明，空间上变化的非生物环境因素有助于塑造的叶片形状渐变，而种间模式可能是由于局部适应和历史事件共同导致的。
