The Evolution of Diet-Induced Development Plasticity in HeadMorphology of Grasshoppers

与以软草本植物为饲料饲养的蝗虫相比，以硬草饲养的蝗虫发育出相对较大的头部和下颌。这种形态模式是发育可塑性或表型可塑性的结果，即在不同的植物环境中，一个基因所表达的形态的变化。红腿蝗虫非常适合研究适应性表型可塑性的进化，因为初步实验表明，食物诱导的头部大小可塑性会影响蝗虫在不同植物上的取食率。P.I.提出了一系列生态遗传实验，通过测量头部大小可塑性变化的遗传率(遗传变异)，以及测量在两种取食环境(草和草)中表现出来的相同性状的自然选择强度，来测试表型可塑性进化的理论。表型可塑性和蝗虫适合度之间的关系将通过测量在一种植物环境(草或杂草)中饲养的蝗虫的生长、存活和繁殖，然后转移到不同的摄食环境来估计。蝗虫在不同的植物环境中发育出不同大小的头部的能力提高了它们的生存能力，从而使这些破坏性的食草性害虫在许多不同的环境中持续存在。了解蝗虫发育可塑性的演化将提供有关种群在什么条件下可能进化出占据多种环境的能力并潜在地将其分布扩展到新的自然和农业生境的基本知识。

Grasshoppers raised on hard grass diets develop relatively larger heads and mandibles than those raised on diets of soft herbaceous plants. This morphological pattern results from developmental or phenotypic plasticity, a change in the morphology expressed by a genotype in different plant environments. The red-legged grasshopper (Melanoplus femurrubrum) is ideally suited to studies of the evolution of adaptive phenotypic plasticity since preliminary experiments indicate that diet-induced plasticity in head size influences grasshopper feeding rates on different plants. The P. I. has proposed a series of ecological genetic experiments that will test theories of the evolution of phenotypic plasticity by measuring the heritability (genetic variation) of plastic shifts in head size and by measuring the intensity of natural selection on the same characters as they are expressed in two feeding environments (grass and forb). The relationship between phenotypic plasticity and grasshopper fitness will be estimated from measurements of growth, survival, and reproduction of grasshoppers fed in one plant environment (grass or forb) and then, later, shifted to a different feeding environment. The ability of grasshoppers to develop different head sizes in different plants environments enhances their survivorship and, hence, allows these destructive herbivorous pests to persist in many different environments. An understanding of the evolution of grasshopper developmental plasticity will provide basic knowledge about the conditions under which populations are likely to evolve the ability to occupy multiple environments and to potentially expand their distributions into new natural and agricultural habitats.