Wu Carrie A, Campbell Diane R
Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA.
Mol Ecol. 2005 Mar;14(3):781-92. doi: 10.1111/j.1365-294X.2005.02441.x.
Spatial variation in natural selection may play an important role in determining the genetic structure of hybridizing populations. Previous studies have found that F1 hybrids between naturally hybridizing Ipomopsis aggregata and Ipomopsis tenuituba in central Colorado differ in fitness depending on both genotype and environment: hybrids had higher survival when I. aggregata was the maternal parent, except in the centre of the hybrid zone where both hybrid types had high survival. Here, we developed both maternally (cpDNA PCR-RFLP) and biparentally inherited (nuclear AFLP) species-diagnostic markers to characterize the spatial genetic structure of the natural Ipomopsis hybrid zone, and tested the prediction that the majority of natural hybrids have I. aggregata cytoplasm, except in areas near the centre of the hybrid zone. Analyses of 352 individuals from across the hybrid zone indicate that cytoplasmic gene flow is bidirectional, but contrary to expectation, most plants in the hybrid zone have I. tenuituba cytoplasm. This cytotype distribution is consistent with a hybrid zone in historical transition, with I. aggregata nuclear genes advancing into the contact zone. Further, nuclear data show a much more gradual cline than cpDNA markers that is consistent with morphological patterns across the hybrid populations. A mixture of environment- and pollinator-mediated selection may contribute to the current genetic structure of this hybrid system.
自然选择中的空间变异可能在决定杂交种群的遗传结构方面发挥重要作用。先前的研究发现，科罗拉多州中部自然杂交的聚花蛾蝶花（Ipomopsis aggregata）和细管蛾蝶花（Ipomopsis tenuituba）之间的F1杂种在适应性上因基因型和环境而异：当聚花蛾蝶花为母本时，杂种具有更高的存活率，但在杂交区中心除外，在该区域两种杂交类型都有较高的存活率。在这里，我们开发了母系遗传（cpDNA PCR-RFLP）和双亲遗传（核AFLP）的物种诊断标记，以表征自然蛾蝶花杂交区的空间遗传结构，并检验了这样的预测，即除了在杂交区中心附近的区域外，大多数自然杂种具有聚花蛾蝶花的细胞质。对来自杂交区各地的352个个体的分析表明，细胞质基因流是双向的，但与预期相反，杂交区中的大多数植物具有细管蛾蝶花的细胞质。这种细胞型分布与处于历史转变中的杂交区一致，聚花蛾蝶花的核基因正向接触区推进。此外，核数据显示出比cpDNA标记更为渐进的渐变，这与整个杂交种群的形态模式一致。环境和传粉者介导的选择的混合可能有助于这种杂交系统当前的遗传结构。
