Facultad de Biología, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Mexico.
UBC Botanical Garden & Centre for Plant Research and Department of Botany, University of British Columbia, Vancouver, BC, Canada.
Plant Biol (Stuttg). 2018 Nov;20(6):1075-1082. doi: 10.1111/plb.12874. Epub 2018 Aug 31.
The integrity of species in sympatric contact sites is dependent on the existence of reproductive isolating mechanisms, which restrict gene flow between them. However, we know little about the mechanisms that enable the coexistence of species with similar floral morphologies. Here, we evaluated several reproductive isolation barriers between Salvia elegans and S. fulgens, two sympatric sages with a similar ornithophilous floral syndrome, offering nectar as the main reward. Over 3 years, we evaluated broad-scale geographic isolation, floral phenologies and floral visitors as pre-pollination barriers, and fruit set, seed number and seed germination as post-pollination barriers. We found considerable geographic isolation and significant altitudinal differences between the two sages. The flowering period of both sages always overlapped extensively during the 3 years of this study, but hummingbirds were highly specific, visiting one or the other Salvia species and showing aggressive territorial behaviour. Interspecific experimental crosses revealed that hybrid seeds might be formed although strong asymmetric barriers were found depending on the species acting as the maternal donor. Despite the low level of flowering asynchrony, reproductive isolation was remarkably high in the two sages. Geographic isolation and pollinator fidelity were the main factors responsible for maintaining species integrity. Despite an extensive review, we found very few studies quantifying the efficiency of isolation barriers in Neotropical plants or even the importance of hummingbirds as pollinators.
同域接触点中物种的完整性取决于生殖隔离机制的存在，这些机制限制了它们之间的基因流动。然而，我们对能够使具有相似花形态的物种共存的机制知之甚少。在这里，我们评估了两种同域的鼠尾草属植物，即具有相似传粉鸟综合征的优雅鼠尾草（S. elegans）和繁茂鼠尾草（S. fulgens）之间的几种生殖隔离障碍，它们都以花蜜作为主要的报酬。在 3 年的时间里，我们评估了广泛的地理隔离、花期和花访客作为授粉前的障碍，以及果实结实、种子数量和种子萌发作为授粉后的障碍。我们发现这两个物种之间存在相当大的地理隔离和显著的海拔差异。在这项研究的 3 年中，两个物种的花期总是广泛重叠，但蜂鸟高度专一，只访问一种或另一种鼠尾草属植物，并表现出攻击性的领地行为。种间实验杂交表明，尽管根据作为母本供体的物种，存在强烈的不对称障碍，但可能形成杂种种子。尽管开花的同步性水平较低，但两个物种的生殖隔离非常高。地理隔离和传粉者的保真度是维持物种完整性的主要因素。尽管进行了广泛的审查，但我们发现很少有研究定量评估新热带植物的隔离障碍的效率，甚至很少有研究关注蜂鸟作为传粉者的重要性。
