Herlihy Christopher R, Eckert Christopher G
Department of Biology, Queens' University, Kingston, Ontario, Canada.
Nature. 2002 Mar 21;416(6878):320-3. doi: 10.1038/416320a.
The transition from outcrossing to self-fertilization is one of the most common evolutionary trends in plants. Reproductive assurance, where self-fertilization ensures seed production when pollinators and/or potential mates are scarce, is the most long-standing and most widely accepted explanation for the evolution of selfing, but there have been few experimental tests of this hypothesis. Moreover, many apparently adaptive floral mechanisms that ensure the autonomous production of selfed seed might use ovules that would have otherwise been outcrossed. This seed discounting is costly if selfed offspring are less viable than their outcrossed counterparts, as often happens. The fertility benefit of reproductive assurance has never been examined in the light of seed discounting. Here we combine experimental measures of reproductive assurance with marker-gene estimates of self-fertilization, seed discounting and inbreeding depression to show that, during 2 years in 10 Ontario populations of Aquilegia canadensis (Ranunculaceae), reproductive assurance through self-fertilization increases seed production, but this benefit is greatly outweighed by severe seed discounting and inbreeding depression.
从异花授粉到自花受精的转变是植物中最常见的进化趋势之一。生殖保障是自花受精进化最长期且最广泛被接受的解释，即在传粉者和/或潜在配偶稀缺时，自花受精确保种子产生，但对这一假说的实验验证很少。此外，许多看似适应性的花部机制确保自交种子的自主产生，可能会利用那些原本会用于异花授粉的胚珠。如果自交后代的活力低于其异花授粉的对应后代，这种种子折扣成本就会很高，而这种情况经常发生。生殖保障的育性益处从未从种子折扣的角度进行过研究。在这里，我们将生殖保障的实验测量与自花受精、种子折扣和近亲繁殖衰退的标记基因估计相结合，以表明在安大略省10个加拿大耧斗菜（毛茛科）种群的2年时间里，通过自花受精实现的生殖保障增加了种子产量，但这种益处被严重的种子折扣和近亲繁殖衰退大大超过。
