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

以硬草为食的蚱蜢比以软草为食的蚱蜢头部和下颌骨相对较大。这种形态模式源于发育或表型的可塑性，这是一种在不同植物环境中由基因型表达的形态变化。红腿蚱蜢（Melanoplus femurrubrum）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，饮食诱导的头部大小可塑性会影响蚱蜢对不同植物的摄食率。p.i.提出了一系列的生态遗传实验，通过测量头部大小的可塑性变化的遗传力（遗传变异）和测量在两种喂养环境（草和草）中表达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。表型可塑性和蚱蜢适应性之间的关系将通过测量在一种植物环境（草或草）中喂养的蚱蜢的生长、生存和繁殖，然后再转移到不同的喂养环境中来估计。蚱蜢在不同的植物环境中发育不同头部大小的能力提高了它们的存活率，因此，这些破坏性的草食性害虫可以在许多不同的环境中持续存在。了解蚱蜢发育可塑性的进化将提供基本的知识，了解在何种条件下，蚱蜢可能进化出占据多种环境的能力，并有可能将其分布扩大到新的自然和农业栖息地。

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.