Dpto de Ecología Funcional y Evolutiva, Estación Experimental de Zonas Aridas (EEZA-CSIC), E-04120, Almería, Spain; Dpto de Ecología, Universidad de Granada, E-18071, Granada, Spain.
New Phytol. 2015 Jan;205(1):440-53. doi: 10.1111/nph.13016. Epub 2014 Sep 23.
It is widely assumed that floral diversification occurs by adaptive shifts between pollination niches. In contrast to specialized flowers, identifying pollination niches of generalist flowers is a challenge. Consequently, how generalist pollination niches evolve is largely unknown. We apply tools from network theory and comparative methods to investigate the evolution of pollination niches among generalist species belonging to the genus Erysimum. These species have similar flowers. We found that the studied species may be grouped in several multidimensional niches separated not by a shift of pollinators, but instead by quantitative variation in the relative abundance of pollinator functional groups. These pollination niches did not vary in generalization degree; we did not find any evolutionary trend toward specialization within the studied clade. Furthermore, the evolution of pollination niche fitted to a Brownian motion model without phylogenetic signal, and was characterized by frequent events of niche convergences and divergences. We presume that the evolution of Erysimum pollination niches has occurred mostly by recurrent shifts between slightly different generalized pollinator assemblages varying spatially as a mosaic and without any change in specialization degree. Most changes in pollination niches do not prompt floral divergence, a reason why adaptation to pollinators is uncommon in generalist plants.
人们普遍认为，花的多样化是通过在授粉小生境之间的适应性转变而发生的。与特化花不同，确定广域花的授粉小生境是一个挑战。因此，广域授粉小生境的进化在很大程度上是未知的。我们应用网络理论和比较方法的工具，来研究属于旱菜属的广域物种的授粉小生境的进化。这些物种具有相似的花。我们发现，所研究的物种可能会被分成几个多维小生境，这些小生境不是通过传粉者的转移来区分的，而是通过传粉者功能组的相对丰度的定量变化来区分的。这些授粉小生境在概括程度上没有变化；我们没有发现所研究的进化枝内有向特化进化的趋势。此外，授粉小生境的进化符合没有系统发育信号的布朗运动模型，其特征是小生境趋同和趋异的频繁事件。我们推测，旱菜属的授粉小生境的进化主要是通过在空间上作为镶嵌体变化的略有不同的广义授粉组合之间的反复转变而发生的，而专业化程度没有任何变化。大多数授粉小生境的变化不会促使花朵的分化，这也是为什么一般植物中对传粉者的适应并不常见的原因。
