Amarillo-Suárez Angela R, Fox Charles W
Department of Entomology, University of Kentucky, Lexington, KY 40506, USA.
Oecologia. 2006 Nov;150(2):247-58. doi: 10.1007/s00442-006-0516-y. Epub 2006 Aug 17.
For insects that develop inside discrete hosts, both host size and host quality constrain offspring growth, influencing the evolution of body size and life history traits. Using a two-generation common garden experiment, we quantified the contribution of maternal and rearing hosts to differences in growth and life history traits between populations of the seed-feeding beetle Stator limbatus that use a large-seeded host, Acacia greggii, and a small-seeded host, Pseudosamanea guachapele. Populations differed genetically for all traits when beetles were raised in a common garden. Contrary to expectations from the local adaptation hypothesis, beetles from all populations were larger, developed faster and had higher survivorship when reared on seeds of A. greggii (the larger host), irrespective of their native host. We observed two host plant-mediated maternal effects: offspring matured sooner, regardless of their rearing host, when their mothers were reared on P. guachapele (this was not caused by an effect of rearing host on egg size), and females laid larger eggs on P. guachapele. This is the first study to document plasticity by S. limbatus in response to P. guachapele, suggesting that plasticity is an ancestral trait in S. limbatus that likely plays an important role in diet expansion. Although differences between populations in growth and life history traits are likely adaptations to their host plants, host-associated maternal effects, partly mediated by maternal egg size plasticity, influence growth and life history traits and likely play an important role in the evolution of the breadth of S. limbatus' diet. More generally, phenotypic plasticity mediates the fitness consequences of using novel hosts, likely facilitating colonization of new hosts, but also buffering herbivores from selection post-colonization. Plasticity in response to novel versus normal hosts varied among our study populations such that disentangling the historical role of plasticity in mediating diet evolution requires the consideration of evolutionary history.
对于在离散宿主内发育的昆虫而言，宿主大小和宿主质量都会限制后代的生长，进而影响体型和生活史特征的进化。通过一项两代共同花园实验，我们量化了母体宿主和饲养宿主对以大型种子宿主格雷格金合欢（Acacia greggii）和小型种子宿主瓜查佩莱假萨马尼亚树（Pseudosamanea guachapele）为食的种子取食甲虫边缘定子（Stator limbatus）种群间生长和生活史特征差异的贡献。当甲虫在共同花园中饲养时，所有性状在种群间都存在遗传差异。与局部适应假说的预期相反，无论其原生宿主是什么，所有种群的甲虫在以格雷格金合欢（较大的宿主）的种子饲养时，体型更大、发育更快且存活率更高。我们观察到两种宿主植物介导的母体效应：当母亲在瓜查佩莱假萨马尼亚树上饲养时，后代成熟得更快，无论其饲养宿主是什么（这不是由饲养宿主对卵大小的影响导致的），并且雌性在瓜查佩莱假萨马尼亚树上产下的卵更大。这是第一项记录边缘定子对瓜查佩莱假萨马尼亚树产生可塑性反应的研究，表明可塑性是边缘定子的一种祖先性状，可能在饮食扩展中发挥重要作用。尽管种群间生长和生活史特征的差异可能是对其宿主植物的适应，但宿主相关的母体效应，部分由母体卵大小可塑性介导，影响生长和生活史特征，并且可能在边缘定子饮食广度的进化中发挥重要作用。更普遍地说，表型可塑性介导了使用新宿主的适合度后果，可能促进对新宿主的定殖，但也使食草动物在定殖后免受选择。我们研究的种群对新宿主与正常宿主的可塑性反应各不相同，因此要弄清楚可塑性在介导饮食进化中的历史作用，需要考虑进化历史。
