Erickson David L, Fenster Charles B
Department of Biology, University of Maryland, College Park, Maryland 20742, USA.
Evolution. 2006 Feb;60(2):225-33.
Genetic incompatibilities and low offspring fitness are characteristic outcomes of hybridization between species. Yet, the creative potential of recombination following hybridization continues to be debated. Here we quantify the outcome of hybridization and recombination between adaptively divergent populations of the North American legume Chamaecrista fasciculata in a large-scale field experiment. Previously, hybrids between these populations demonstrated hybrid breakdown, suggesting the expression of adaptive epistatic interactions underlying population genetic differentiation. However, the outcome of hybridization ultimately rests on the performance of even later generation recombinants. In experiments that compared the performance of recombinant F6 and F2 generations with nonrecombinant F1 and parental genotypes, we observed that increasing recombination had contrasting effects on different life-history components. Lifetime fitness, defined as the product of survivorship and reproduction, showed a strong recovery of fitness in the F6. The overall gain in fitness with increased recombination suggests that hybridization and recombination may provide the necessary genetic variation for adaptive evolution within species. We discuss the mechanisms that may account for the gain in fitness with recombination, and explore the implications for hybrid speciation and phenotypic evolution.
遗传不亲和性和低后代适合度是物种间杂交的典型结果。然而，杂交后重组的创造潜力仍存在争议。在此，我们在一项大规模田间试验中，对北美豆科植物束花孪叶草适应性分化种群间杂交和重组的结果进行了量化。此前，这些种群间的杂种表现出杂种衰败，这表明种群遗传分化背后存在适应性上位相互作用的表达。然而，杂交的最终结果取决于更晚世代重组体的表现。在比较重组F6和F2代与非重组F1和亲本基因型表现的实验中，我们观察到重组增加对不同生活史组分有不同影响。将寿命适合度定义为存活率和繁殖率的乘积，我们发现F6代的适合度有显著恢复。随着重组增加，适合度总体上升，这表明杂交和重组可能为物种内的适应性进化提供必要的遗传变异。我们讨论了可能解释重组导致适合度增加的机制，并探讨了其对杂交物种形成和表型进化的影响。
