In a contact zone between related taxa, phenotypic variation can result from genetic and/or environmental gradients. This study aimed to clarify the cause of phenotypic variation in leaf morphology of two Quercus crispula varieties—crispula (QCC) and mongolicoides (QCM)—in their contact zone along an altitudinal gradient.

中文翻译：

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环境压力而不是持续的杂交导致了两种橡树形态上的垂直上升趋势

在相关类群之间的接触区中，表型变异可能是由遗传和/或环境梯度引起的。本研究旨在阐明表型变异的原因在两个叶形态栎crispula varieties- crispula（QCC）和mongolicoides（QCM）-in不同海拔它们的接触区域。