Data from: Competition for hummingbird pollination shapes flower color variation in Andean Solanaceae

One classic explanation for the remarkable diversity of flower colors across angiosperms involves evolutionary shifts among different types of pollinators with different color preferences. However, the pollinator shift model fails to account for the many examples of color variation within clades that share the same pollination system. An alternate explanation is the competition model, which suggests that color divergence evolves in response to interspecific competition for pollinators, as a means to decrease interspecific pollinator movements. This model predicts color overdispersion within communities relative to null assemblages. Here we combine morphometric analyses, field surveys, and models of pollinator vision with a species-level phylogeny to test the competition model in the primarily hummingbird-pollinated clade Iochrominae (Solanaceae). Results show that flower color as perceived by pollinators is significantly overdispersed within sites. This pattern is not simply due to phylogenetic history: phylogenetic community structure does not deviate from random expectations, and flower color lacks phylogenetic signal. Moreover, taxa that occur in sympatry occupy a significantly larger volume of color space than those in allopatry, supporting the hypothesis that competition in sympatry drove the evolution of novel colors. We suggest that competition among close relatives may commonly underlie floral divergence, especially in species-rich habitats where congeners frequently co-occur.

针对被子植物花色所呈现的惊人多样性，学界经典解释之一为：具有不同颜色偏好的各类传粉者之间发生演化更替。然而，传粉者更替模型无法解释同一传粉系统下的演化支内存在的大量花色变异案例。另一种替代性解释为竞争模型：该模型提出，花色分化演化是为响应传粉者的种间竞争，以此降低传粉者在不同物种间的移动频次。该模型预测，相较于零假设群落，自然群落内的花色分布会呈现过度离散特征。本研究结合形态计量分析、野外调查、传粉者视觉模型与物种水平系统发育树，在以蜂鸟传粉为主的茄科Iochrominae演化支中对竞争模型进行检验。结果表明，传粉者所能感知的花色在样地内呈现显著的过度离散分布。这一格局并非单纯由系统发育历史所决定：群落系统发育结构并未偏离随机预期，且花色不存在系统发育信号。此外，同域分布类群的花色空间体积显著大于异域分布类群，这一结果支持"同域竞争推动新花色演化"的假说。我们认为，近缘类群间的竞争可能普遍驱动花部性状分化，尤其在同属物种频繁共存的物种丰富型生境中。