Indiana University, Department of Biology, Bloomington, Indiana 47405 USA;
Am J Bot. 2001 Feb;88(2):270-7.
Diploid hybrid lineages often are ecologically distinct from their parental species. However, it is unclear whether this niche divergence is typically achieved via hybrid intermediacy, a mixture of parental traits, and/or the evolution of extreme (transgressive) morphological and ecophysiological features. Here we compare an extensively studied hybrid sunflower species, Helianthus anomalus, with its putative parents, H. annuus and H. petiolaris, for 41 morphological and 12 ecophysiological traits. Helianthus anomalus was morphologically intermediate for one trait (2.4%), parental-like for 23 traits (56.1%), and transgressive for 17 traits (41.5%). For ecophysiological traits, H. anomalus was not significantly different from one or both parents for nine traits (75%), and was transgressive for the remaining three (25%). Thus, H. anomalus appears to be a mosaic of parental-like and transgressive phenotypes. Although the fitness effects of the transgressive characters are not yet known, many of these characters are consistent with adaptations reported for other sand dune plants. Genetic studies are currently underway to ascertain whether these extreme characters arose as a direct byproduct of hybridization or whether they evolved via mutational divergence.
二倍体杂种系通常在生态上与其亲本物种不同。然而，目前尚不清楚这种生态位分化是否通常是通过杂种中间状态、亲本特征的混合以及/或极端（越界）形态和生理生态特征的进化来实现的。在这里，我们比较了一个经过广泛研究的杂种向日葵物种 Helianthus anomalus 与其假定的亲本 H. annuus 和 H. petiolaris 在 41 个形态和 12 个生理生态特征方面的差异。Helianthus anomalus 在一个特征（2.4%）上表现为中间型，在 23 个特征（56.1%）上表现为亲本样，在 17 个特征（41.5%）上表现为越界型。对于生理生态特征，H. anomalus 在 9 个特征（75%）上与一个或两个亲本没有显著差异，而在其余三个特征（25%）上表现为越界型。因此，H. anomalus 似乎是亲本样和越界型表型的混合体。尽管越界特征的适应度效应尚不清楚，但这些特征中的许多与其他沙丘植物的报道适应特征一致。目前正在进行遗传研究，以确定这些极端特征是杂交的直接副产品，还是通过突变分化进化而来。
