Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada.
J Evol Biol. 2024 Aug 1;37(8):935-946. doi: 10.1093/jeb/voae078.
Pollinators are thought to be the main drivers of floral evolution. Flowers are also colonized by abundant communities of microbes that can affect the interaction between plants and their pollinators. Very little is known, however, about how flower-colonizing microbes influence floral evolution. Here we performed a 6-generation experimental evolution study using fast-cycling Brassica rapa, in which we factorially manipulated the presence of pollinators and flower microbes to determine how pollinators and microbes interact in driving floral evolution. We measured the evolution of 6 morphological traits, as well as the plant mating system and flower attractiveness. Only one of the 6 traits (flower number) evolved in response to pollinators, while microbes did not drive the evolution of any trait, nor did they interact with pollinators in driving the evolution of morphological traits. Moreover, we did not find evidence that pollinators or microbes affected the evolution of flower attractiveness to pollinators. However, we found an interactive effect of pollinators and microbes on the evolution of autonomous selfing, a trait that is expected to evolve in response to pollinator limitations. Overall, we found only weak evidence that microbes mediate floral evolution. However, our ability to detect an interactive effect of pollinators and microbes might have been limited by weak pollinator-mediated selection in our experimental setting. Our results contrast with previous (similar) experimental evolution studies, highlighting the susceptibility of such experiments to drift and to experimental artefacts.
传粉者被认为是花部进化的主要驱动因素。大量的微生物也会在花朵上定殖，这些微生物会影响植物与其传粉者之间的相互作用。然而，人们对定殖在花朵上的微生物如何影响花部进化知之甚少。在这里，我们使用快速循环的 Brassica rapa 进行了 6 代实验进化研究，在该研究中，我们通过因子实验操纵传粉者和花部微生物的存在，以确定传粉者和微生物如何相互作用以推动花部进化。我们测量了 6 个形态特征的进化，以及植物的交配系统和花的吸引力。只有 6 个特征中的一个（花的数量）对传粉者有反应，而微生物没有驱动任何特征的进化，也没有与传粉者相互作用来驱动形态特征的进化。此外，我们没有发现证据表明传粉者或微生物影响花对传粉者的吸引力的进化。然而，我们发现传粉者和微生物之间存在相互作用，会影响自主自交的进化，而自主自交是一种预计会因传粉者限制而进化的特征。总的来说，我们只发现了微生物介导花部进化的微弱证据。然而，我们检测到传粉者和微生物相互作用的能力可能受到实验设定中传粉者介导的选择较弱的限制。我们的结果与之前的（类似的）实验进化研究形成对比，突出了此类实验容易受到漂移和实验假象的影响。
