Koski Matthew H, Ashman Tia-Lynn
Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, 15260, USA.
New Phytol. 2016 Jul;211(2):708-18. doi: 10.1111/nph.13921. Epub 2016 Mar 14.
Selection driven by biotic interactions can generate variation in floral traits. Abiotic selection, however, also contributes to floral diversity, especially with respect to patterns of pigmentation. Combining comparative studies of floral pigmentation and geography can reveal the bioclimatic factors that may drive macroevolutionary patterns of floral color. We create a molecular phylogeny and measure ultraviolet (UV) floral pattern for 177 species in the Potentilleae tribe (Rosaceae). Species are similar in flower shape and visible color but vary in UV floral pattern. We use comparative approaches to determine whether UV pigmentation variation is associated with geography and/or bioclimatic features (UV-B, precipitation, temperature). Floral UV pattern was present in half of the species, while others were uniformly UV-absorbing. Phylogenetic signal was detected for presence/absence of pattern, but among patterned species, quantitative variation in UV-absorbing area was evolutionarily labile. Uniformly UV-absorbing species tended to experience higher UV-B irradiance. Patterned species occurring at higher altitudes had larger UV-absorbing petal areas, corresponding with low temperature and high UV exposure. This analysis expands our understanding of the covariation of UV-B irradiance and UV floral pigmentation from within species to that among species, and supports the view that abiotic selection is associated with floral diversification among species.
由生物相互作用驱动的选择可以产生花部性状的变异。然而，非生物选择也有助于花的多样性，特别是在色素沉着模式方面。将花色素沉着与地理的比较研究相结合，可以揭示可能驱动花颜色宏观进化模式的生物气候因素。我们构建了一个分子系统发育树，并测量了委陵菜族（蔷薇科）177个物种的紫外（UV）花部模式。这些物种在花的形状和可见颜色上相似，但在紫外花部模式上有所不同。我们使用比较方法来确定紫外色素沉着变异是否与地理和/或生物气候特征（UV-B、降水、温度）相关。一半的物种存在花部紫外模式，而其他物种则均匀吸收紫外线。检测到模式存在与否的系统发育信号，但在有模式的物种中，紫外线吸收面积的定量变异在进化上是不稳定的。均匀吸收紫外线的物种往往经历更高的UV-B辐照度。在较高海拔地区出现的有模式的物种具有更大的紫外线吸收花瓣面积，这与低温和高紫外线暴露相对应。该分析扩展了我们对UV-B辐照度与花部紫外色素沉着从种内协变到种间协变的理解，并支持非生物选择与物种间花的多样化相关的观点。
