Hodges S A, Arnold M L
Department of Genetics, University of Georgia, Athens 30602.
Proc Natl Acad Sci U S A. 1994 Mar 29;91(7):2493-6. doi: 10.1073/pnas.91.7.2493.
Habitat preference and pollination syndrome have been suggested as major factors in reproductive isolation among plant species. The columbine genus Aquilegia contains species that have been used as classic examples of reproductive isolation due to ecological and floral factors. In this analysis Aquilegia formosa, Aquilegia pubescens, and natural hybrid populations between these two species were assayed for genetic and morphological variation. Clinal variation was evident for three "random amplified polymorphic DNA" loci and five morphological characters along a transect extending from a lower altitude A. formosa population, through an intermediate hybrid population, to a higher altitude A. pubescens population. Similar clinal variation was also discovered for a transect that included A. formosa-like, hybrid, and A. pubescens-like populations at a single elevation. The change in the frequency of both sets of markers was closely associated with change in habitat. The molecular markers indicate the presence of bidirectional introgression between these two species. In contrast, there was apparently selection against introgression of four of the five alternate floral characters. Selection against the incorporation of floral characters from one species into the other species was suggested by the introgression of the DNA markers with little or no introgression of the four floral characters. These findings suggest the importance of adaptations associated with both pollination syndromes and habitat preference on species integrity.
栖息地偏好和传粉综合征被认为是植物物种间生殖隔离的主要因素。耧斗菜属植物包含一些物种，由于生态和花的因素，它们一直被用作生殖隔离的经典例子。在这项分析中，对美丽耧斗菜、柔毛耧斗菜以及这两个物种之间的自然杂交种群进行了遗传和形态变异分析。沿着一条从低海拔的美丽耧斗菜种群，经过中间杂交种群，到高海拔的柔毛耧斗菜种群的样带，三个“随机扩增多态性DNA”位点和五个形态特征呈现出渐变变异。在一条包含单一海拔高度的类似美丽耧斗菜、杂交和类似柔毛耧斗菜种群的样带上也发现了类似的渐变变异。两组标记频率的变化都与栖息地的变化密切相关。分子标记表明这两个物种之间存在双向渐渗。相比之下，五个交替花特征中的四个显然存在对渐渗的选择。DNA标记的渐渗伴随着四个花特征很少或没有渐渗，这表明存在对一个物种的花特征融入另一个物种的选择。这些发现表明与传粉综合征和栖息地偏好相关的适应性对物种完整性的重要性。
