目的:风花授粉在开花植物中反复进化,然而,将风授粉综合征鉴定为一组综合的花卉性状可能是难以捉摸的。Thalictrum(Ranunculaceae)包括温带多年生草本植物,这些草本植物反复从昆虫授粉过渡到风授粉,同时还表现出混合授粉,提供了一个理想的系统来测试生物到非生物连续体中的花形态和授粉模式之间的进化相关性。此外,该属中缺乏花器官融合,因此可以在没有此功能的情况下测试对授粉载体的专业化。
方法:我们从先前的研究中使用六个叶绿体基因座扩大了该属的系统发育采样,这使我们能够测试物种是否根据花卉形态聚集成不同的授粉综合征。然后我们对花卉性状进行了多变量分析,然后对新兴的花朵形态进行祖先状态重建,并在布朗运动的贝叶斯框架下确定这些性状是否在进化上相关。
结果:花卉性状分为五个不同的簇,在考虑了系统发育相关性后,它们减少到了三个,并且与花的形态类型和相关的授粉载体基本一致。多变量进化分析发现花卉生殖结构的长度之间存在正相关(样式,柱头,长丝,和花药)。较短的生殖结构跟踪系统发育中昆虫授粉的物种和进化枝,而较长的结构跟踪风授粉的物种和进化枝,与生物与生物施加的选择性压力一致非生物授粉载体,分别。
结论:尽管在形态空间分布的极端情况下,整个Thalictrum中可检测到的综合花卉性状套件与风或昆虫授粉相关,一个假定的中间人,还检测到混合授粉模式形态空间。因此,我们的数据广泛支持在Thalictrum中存在可检测的花朵形态类型,大概是通过祖先混合授粉状态的不同路径。
Wind pollination has evolved repeatedly in flowering plants, yet the identification of a wind pollination syndrome as a set of integrated floral traits can be elusive. Thalictrum (Ranunculaceae) comprises temperate perennial herbs that have transitioned repeatedly from insect to wind pollination while also exhibiting mixed pollination, providing an ideal system to test for evolutionary correlation between floral morphology and pollination mode in a biotic to abiotic continuum. Moreover, the lack of floral organ fusion across this genus allows testing for specialization to pollination vectors in the absence of this feature.
We expanded phylogenetic sampling in the genus from a previous study using six chloroplast loci, which allowed us to test whether species cluster into distinct pollination syndromes based on floral morphology. We then used multivariate analyses on floral traits followed by ancestral state reconstruction of the emerging flower morphotypes and determined whether these traits are evolutionarily correlated under a Bayesian framework with Brownian motion.
Floral traits fell into five distinct clusters, which were reduced to three after considering phylogenetic relatedness and were largely consistent with flower morphotypes and associated pollination vectors. Multivariate evolutionary analyses found a positive correlation between the lengths of floral reproductive structures (styles, stigmas, filaments and anthers). Shorter reproductive structures tracked insect-pollinated species and clades in the phylogeny, whereas longer structures tracked wind-pollinated ones, consistent with selective pressures exerted by biotic vs. abiotic pollination vectors, respectively.
Although detectable suites of integrated floral traits across Thalictrum were correlated with wind or insect pollination at the extremes of the morphospace distribution, a presumed intermediate, mixed pollination mode morphospace was also detected. Thus, our data broadly support the existence of detectable flower morphotypes from convergent evolution underlying the evolution of pollination mode in Thalictrum, presumably via different paths from an ancestral mixed pollination state.