Department of Biology, University of Konstanz, Universitätsstrasse 10, 78457 Konstanz, Germany.
Department of Biology, Trent University, 1600 West Bank Drive, Peterborough, Ontario, Canada K9J 0G2.
Proc Biol Sci. 2020 Nov 25;287(1939):20202323. doi: 10.1098/rspb.2020.2323.
Transitions from outcrossing to selfing have been a frequent evolutionary shift in plants and clearly play a role in species divergence. However, many questions remain about the initial mechanistic basis of reproductive isolation during the evolution of selfing. For instance, how important are pre-zygotic pre-pollination mechanisms (e.g. changes in phenology and pollinator visitation) in maintaining reproductive isolation between newly arisen selfing populations and their outcrossing ancestors? To test whether changes in phenology and pollinator visitation isolate selfing populations of from outcrossing populations, we conducted a common garden experiment with plants from selfing and outcrossing populations as well as their between-population hybrids. Specifically, we asked whether there was isolation between outcrossing and selfing plants and their between-population hybrids through differences in (1) the timing or intensity of flowering; and/or (2) pollinator visitation. We found that phenology largely overlapped between plants from outcrossing and selfing populations. There were also no differences in pollinator preference related to mating system. Additionally, pollinators preferred to visit flowers on the same plant rather than exploring nearby plants, creating a large opportunity for self-fertilization. Overall, this suggests that pre-zygotic pre-pollination mechanisms do not strongly reproductively isolate plants from selfing and outcrossing populations of .
从杂交到自交的转变是植物中经常发生的进化转变，显然在物种分化中起着重要作用。然而，在自交进化过程中，关于生殖隔离的初始机制基础仍有许多问题尚未解决。例如，在新出现的自交种群与其杂交祖先之间，预配子期的授粉前机制（例如物候和传粉者访问的变化）在维持生殖隔离方面有多重要？为了检验物候和传粉者访问是否会使来自自交种群的隔离种群与来自杂交种群的隔离种群分离，我们对来自自交和杂交种群的植物以及它们的种群间杂种进行了共同花园实验。具体来说，我们通过以下差异来询问是否存在自交植物与杂交植物及其种群间杂种之间的隔离：（1）开花的时间或强度；和/或（2）传粉者访问。我们发现，来自杂交和自交种群的植物的物候期基本重叠。在与交配系统相关的传粉者偏好方面也没有差异。此外，传粉者更喜欢访问同一植株上的花朵，而不是探索附近的植株，这为自交提供了很大的机会。总体而言，这表明预配子期的授粉前机制并没有强烈地将自交和杂交种群的植物生殖隔离。
