Yasumoto Akiko A, Yahara Tetsukazu
Department of Biology, Faculty of Sciences, Kyushu University, 6-10-1, Hakozaki, Fukuoka, Japan.
J Plant Res. 2006 Nov;119(6):617-23. doi: 10.1007/s10265-006-0028-1. Epub 2006 Sep 6.
To examine whether floral and post-pollination isolation develops independently or not, we conducted a crossing experiment between Hemerocallis fulva and Hemerocallis citrina that shows large floral divergence adapted for diurnal and nocturnal pollinators that have been believed to be fully cross-fertile. Flowers of the two species from sympatric populations were hand-pollinated with conspecific pollen from the same population (control), interspecific pollen from the same area (sympatric cross), and interspecific pollen from the different area (allopatric cross). After capsule dehiscence, the fruit set, seed set per fruit and seed set per flower were determined among three cross categories. The seed sets per flower were 32 and 77% lower in sympatric and allopatric crosses than in the control when H. fulva was the pollen recipient. There was no difference in three reproductive measures among the cross categories when H. citrina was the pollen recipient. This finding indicates that post-pollination isolation does exist between H. fulva and H. citrina, although it is partial, asymmetric, and weakened in sympatry. Our result suggests that floral and post-pollination isolation may develop independently, and reinforcement may not be a general phenomenon in plants.
为了研究花期隔离和授粉后隔离是否独立发展，我们对黄花菜和黄花菜进行了杂交实验，这两种植物表现出较大的花部差异，分别适应白天和夜间传粉者，一直以来人们认为它们完全可以杂交结实。对同域种群的这两个物种的花朵进行人工授粉，分别用来自同一种群的同种花粉（对照）、来自同一地区的异种花粉（同域杂交）和来自不同地区的异种花粉（异域杂交）。在蒴果开裂后，测定三种杂交类型的坐果率、单果种子数和单花种子数。当黄花菜作为花粉接受者时，同域杂交和异域杂交的单花种子数分别比对照低32%和77%。当黄花菜作为花粉接受者时，三种杂交类型的生殖指标没有差异。这一发现表明，黄花菜和黄花菜之间确实存在授粉后隔离，尽管这种隔离是部分的、不对称的，并且在同域中有所减弱。我们的结果表明，花期隔离和授粉后隔离可能独立发展，强化现象在植物中可能并非普遍存在。
