Abstract Understanding how ecological processes affect phenotypic evolution has been and continues to be an important goal of ecology and evolutionary biology. Interspecific competition for resources can be a selective force driving phenotypic differentiation that reduces competition among sympatric species (character divergence), enabling closely-related species to coexist. However, although patterns of character divergence are well documented in both empirical and theoretical researches, how local adaptation to abiotic environment affects trait evolution in the face of interspecific competition is less known. Here, we investigate how patterns in morphological traits of 2 parapatric frog species, Feirana quadranus and F. taihangnica, vary among allopatric and sympatric regions using range-wide data derived from extensive field surveys. Feirana quadranus was overall larger than F. taihangnica in body size (i.e., snout–vent length [SVL]), and the difference between SVL of both species in sympatry was larger than that in allopatry. From allopatry to sympatry, the 2 species diverged in foot and hand traits, but converged in eye size and interorbital span, even when we controlled for the effects of geographic gradients. Sympatric divergence in SVL, hand and foot traits is likely acting as a case of evolutionary shift caused by interspecific competition. In contrast, sympatric convergence of eye-related traits may derive at least partly from adaptation to local environments. These results imply the relative roles of interspecific competition and local adaptation in shaping phenotypic diversification. Our findings illustrate how traits evolve in parapatric species pair due to sympatric divergent and convergent evolution. It thus provides insights into understanding underlying evolutionary processes of parapatric species, that is, competition and local adaptation.

中文翻译：

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揭示种间竞争和局部适应在旁系蛙表型分化中的作用

摘要 了解生态过程如何影响表型进化一直并将继续成为生态学和进化生物学的重要目标。种间对资源的竞争可以是驱动表型分化的选择性力量，减少同域物种之间的竞争（特征分歧），使密切相关的物种能够共存。然而，尽管在实证研究和理论研究中都很好地记录了性状差异的模式，但在面对种间竞争时，对非生物环境的局部适应如何影响性状进化却鲜为人知。在这里，我们使用从广泛的实地调查中获得的范围广泛的数据，研究了 2 种旁系蛙种 Feirana quadranus 和 F. taihangnica 的形态特征模式如何在异域和同域区域之间变化。Feirana quadranus 在体型（即口鼻长度[SVL]）上总体上比F. taihangnica 大，并且两种物种的SVL 在同域中的差异大于异域中的差异。从同种异域到同种异域，这 2 个物种在足部和手部特征上存在差异，但在眼睛大小和眶间跨度上趋于一致，即使我们控制了地理梯度的影响。SVL、手足特征的同域差异很可能是种间竞争引起的进化转变的一个例子。相比之下，眼睛相关特征的同域收敛可能至少部分源于对当地环境的适应。这些结果意味着种间竞争和局部适应在塑造表型多样化中的相对作用。我们的研究结果说明了由于同域发散和趋同进化，旁系物种对的特征如何演变。因此，它为理解准外来物种的潜在进化过程提供了见解，即竞争和局部适应。