Campbell Diane R, Crawford Matthew, Brody Alison K, Forbis Tara A
Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, 92697, USA.
Rocky Mountain Biological Laboratory, Crested Butte, CO, 81224, USA.
Oecologia. 2002 May;131(3):436-443. doi: 10.1007/s00442-002-0900-1. Epub 2002 May 1.
Plant hybrids can be more, less, or equally resistant to herbivores compared to their parental species. These patterns in resistance can be critical determinants of the fitness of plant hybrids and may also influence distribution of the herbivore. We examined resistance to a pre-dispersal seed predator by natural and experimental hybrids between Ipomopsis aggregata and I. tenuituba. These species and their hybrid offspring differed primarily in ability to avoid oviposition by Hylemya sp. (Diptera: Anthomyiidae) rather than in reducing damage to seeds by a developing larva. Plants of I. tenuituba had the lowest frequency of fly eggs and were thus the most successful at avoiding damage. Hybrids were either intermediate to or less resistant than both parental species. Because these patterns persisted in experimental arrays of interspersed potted plants, they cannot be attributed to ongoing differences in the environment between hybrid and parental sites. In experimental arrays, the frequency of fly eggs correlated positively with corolla width, a dimension of flower size that also influences the rate of pollination, suggesting seed predators can generate selection on reproductive traits of hybrids. Furthermore, in one of the arrays, oviposition on F2 hybrids exceeded the average for the F1 and the midparent. Our results underscore the need to consider genetic background of hybrids in assessing plant responses to herbivores.
与亲本物种相比，植物杂种对食草动物的抗性可能更强、更弱或相同。这些抗性模式可能是植物杂种适合度的关键决定因素，也可能影响食草动物的分布。我们研究了聚花茑萝（Ipomopsis aggregata）和细筒茑萝（I. tenuituba）之间的自然杂种和实验杂种对一种种子传播前捕食者的抗性。这些物种及其杂种后代的主要差异在于避免被Hylemya sp.（双翅目：花蝇科）产卵的能力，而不是减少发育中的幼虫对种子的损害。细筒茑萝植株上蝇卵的频率最低，因此在避免损害方面最成功。杂种的抗性要么介于两个亲本物种之间，要么比两个亲本物种都弱。由于这些模式在盆栽植物相间排列的实验阵列中持续存在，因此不能将其归因于杂种和亲本生长地点之间环境的持续差异。在实验阵列中，蝇卵的频率与花冠宽度呈正相关，花冠宽度是花大小的一个维度，也会影响授粉率，这表明种子捕食者可以对杂种的生殖性状产生选择作用。此外，在其中一个阵列中，F2杂种上的产卵量超过了F1杂种和中亲值的平均值。我们的结果强调在评估植物对食草动物的反应时需要考虑杂种的遗传背景。
