Pérez Fernanda, Arroyo Mary T K, Armesto Juan J
Center for Advanced Studies in Ecology and Biodiversity and Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile.
Am J Bot. 2009 Jun;96(6):1168-76. doi: 10.3732/ajb.0800306. Epub 2009 May 12.
The co-occurrence of elaborate flowers visited by specific groups of pollinators and capacity for autonomous selfing in the same plant species has puzzled evolutionary biologists since the time of Charles Darwin. To examine whether autonomous selfing and floral specialization evolved in association, we quantified the autofertility level (AFI) in nine Schizanthus species characterized by a wide range of pollination specialization, revealing AFI values of 0.02 to complete selfing. An independent contrasts analysis conducted on AFIs and number of functional pollinator groups showed that autonomous selfing evolved from an ancestral outcrossing system as plants became increasingly specialized (r = -0.82). To assess whether autonomous selfing together with specialization acts as a reproductive assurance mechanism, we estimated spatial and interannual variation in fruit set due to pollinator failure in two closely related high Andean Schizanthus species differing in their specialization levels. Variation in pollinator failure rate was more pronounced and autonomous selfing increased fruit production over biotically assisted pollination in the more specialized species. Our study suggests that specialized pollination deems species more vulnerable to pollinator fluctuation thus promoting the evolution of delayed autonomous selfing.
自查尔斯·达尔文时代以来，特定传粉者群体访问的精致花朵与同一植物物种的自主自花授粉能力同时出现，这一直困扰着进化生物学家。为了研究自主自花授粉和花的特化是否协同进化，我们对9种蛾蝶花属植物的自育水平（AFI）进行了量化，这些植物具有广泛的授粉特化特征，其AFI值从0.02到完全自花授粉不等。对AFI和功能性传粉者群体数量进行的独立对比分析表明，随着植物变得越来越特化，自主自花授粉从祖先的异交系统进化而来（r = -0.82）。为了评估自主自花授粉与特化是否共同作为一种生殖保障机制，我们估计了两种亲缘关系密切、特化水平不同的安第斯高地蛾蝶花属植物因传粉者失败导致的坐果空间和年际变化。传粉者失败率的变化更为明显，在更特化的物种中，自主自花授粉比生物辅助授粉增加了果实产量。我们的研究表明，特化授粉使物种更容易受到传粉者波动的影响，从而促进了延迟自主自花授粉的进化。
