Department of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA.
Department of Biology, McMaster University, Hamilton, Ontario, Canada L9H 6X9.
Integr Comp Biol. 2019 Nov 1;59(5):1411-1428. doi: 10.1093/icb/icz135.
Artificial selection offers a powerful tool for the exploration of how selection and development shape the evolution of morphological scaling relationships. An emerging approach models the expression and evolution of morphological scaling relationships as a function of variation among individuals in the developmental mechanisms that regulate trait growth. These models posit the existence of genotype-specific morphological scaling relationships that are unseen or "cryptic." Within-population allelic variation at growth-regulating loci determines how these individual cryptic scaling relationships are distributed, and exposure to environmental factors that affect growth determines the size phenotype expressed by each individual on their cryptic, genotype-specific scaling relationship. These models reveal that evolution of the intercept and slope of the population-level static allometry is determined, often in counterintuitive ways, largely by the shape of the distribution of these underlying individual-level scaling relationships. Here we review this modeling framework and present the wing-body size individual cryptic scaling relationships from a population of Drosophila melanogaster. To determine how these models might inform interpretation of published work on scaling relationship evolution, we review studies where artificial selection was applied to alter the parameters of population-level static allometries. Finally, motivated by our review, we outline areas in need of empirical work and describe a research program to address these topics; the approach includes describing the distribution of individual cryptic scaling relationships across populations and environments, empirical testing of the model's predictions, and determining the effects of environmental heterogeneity on realized trait distributions and how this affects allometry evolution.
人工选择为探索选择和发育如何塑造形态比例关系的进化提供了强有力的工具。一种新兴的方法将形态比例关系的表达和进化建模为调节特征生长的发育机制中个体之间变异的函数。这些模型假设存在特定于基因型的形态比例关系，这些关系是看不见的或“隐藏的”。生长调节基因座的群体内等位基因变异决定了这些个体隐藏的比例关系如何分布，而暴露于影响生长的环境因素决定了每个个体在其隐藏的、特定于基因型的比例关系上表达的大小表型。这些模型表明，群体水平静态异速生长的截距和斜率的进化通常以违反直觉的方式，主要由这些基础个体水平比例关系的分布形状决定。在这里，我们回顾了这个建模框架，并介绍了一个黑腹果蝇群体的翅膀-身体大小个体隐性比例关系。为了确定这些模型如何为解释关于比例关系进化的已发表工作提供信息，我们回顾了应用人工选择来改变群体水平静态异速生长参数的研究。最后，受我们的综述启发，我们概述了需要实证工作的领域，并描述了一个解决这些主题的研究计划；该方法包括描述个体隐性比例关系在群体和环境中的分布、对模型预测的实证检验，以及确定环境异质性对实现特征分布的影响以及这如何影响异速生长进化。
