Dissertation Research: Origin and Evolution of Adaptations as Revealed by a Study of Proximate Developmental Mechanisms

适应性表型可塑性从根本上说是一种发育现象；发育途径的表达随着环境的变化而改变，产生连续的性状变异或离散的、可选择的形态。了解这种可塑性的近似发育基础可以揭示出许多关于发育在进化中的一般作用。本研究将利用四种掌足蟾蜍蝌蚪的实验操作来研究产生衍生的、可诱导的幼虫形态的近似发育基础。当典型的，杂食性幼虫在这个分支中某些物种消耗高甲状腺激素（TH）的猎物时，它们可能会过渡到适应性的肉食性蝌蚪。操纵这些物种的幼虫的TH水平测试了TH在诱导替代形态中的作用的假设。对非食肉物种的幼虫进行类似的操作，验证了环境因素（高TH饮食）如何干扰共同祖先的发育，从而引发了今天在更多衍生物种中看到的完全适应的可塑性反应的进化。这样一种综合的方法可以阐明近一清二楚的发育机制如何影响新性状产生的途径，使某些表型的产生易感性，并影响进化变化的途径。

Sinervo 9702033 Adaptive phenotypic plasticity is fundamentally a developmental phenomenon; expression of developmental pathways is modified in response to environmental cues, generating continuous trait variation or discrete, alternative morphologies. Understanding the proximate developmental basis of such plasticity can reveal much about the general role of development in evolution. Experimental manipulation of four species of spadefoot toad tadpoles will be used to investigate the proximate developmental basis underlying the production of a derived, inducible larval morphology. When typical, omnivorous larvae of some species in this clade consume prey high in thyroid hormone (TH), they may undergo transition to an adaptive, carnivorous tadpole. Manipulating TH levels in larvae from these species tests hypotheses addressing the role of TH in inducing the alternative morph. Similar manipulations of larvae from species that do not naturally become carnivorous tests hypotheses addressing how environmental factors (diet high in TH) may have perturbed development in the common ancestor, initiating evolution of the fully adapted plastic response seen today in the more derived species. Such an integrative approach may elucidate how proximate developmental mechanisms influence the route by which novel traits are produced, predisposing the production of certain phenotypes and influencing the path of evolutionary change.