The contributions of direct and indirect selection to the evolution of mating preferences

Many influential mathematical models of sexual selection have stressed
that mating preferences evolve due to correlations that build between
mating preferences and preferred display traits – that is, through
indirect selection. Nevertheless, there is a perception that indirect
selection should generally be overwhelmed by direct selection, for example
in the form of search costs. Recent work by Fry has used quantitative
genetic models to argue that in many cases, including when there are
direct benefits (a fecundity advantage to mating with the preferred male),
direct and indirect selection may be of similar magnitude. Here I use
population genetic models, in which the strength of the genetic
correlation is an emergent property of evolution at mating preference and
display trait loci, to assess the relative contributions of direct and
indirect selection to the evolution of mating preferences. For the cases
of direct benefits and of indirect benefits with fixed and
frequency-dependent search costs, I outline parameter values of fecundity
benefits, preference strengths, and search costs for which indirect
selection on female preferences can potentially predominate. I also
analyze male mate choice under polygyny, showing that direct selection
will always outweigh indirect selection except when there are direct
benefits.

许多具有影响力的性选择（Sexual Selection）数学模型强调，交配偏好（Mating Preferences）的演化源于交配偏好与偏好展示性状（Display Traits）之间形成的相关性——即通过间接选择（Indirect Selection）实现。然而，存在一种观点认为，间接选择通常应被直接选择（Direct Selection）所掩盖，例如以搜索成本（Search Costs）的形式。Fry近期的研究采用数量遗传模型（Quantitative Genetic Models）指出，在多种情况下（包括存在直接收益（Direct Benefits）——与偏好雄性交配可获得繁殖优势时），直接选择与间接选择的量级可能相近。本文使用群体遗传模型（Population Genetic Models）评估直接选择与间接选择对交配偏好演化的相对贡献；在该模型中，遗传相关（Genetic Correlation）的强度是交配偏好与展示性状基因座（loci）演化的涌现特性。针对存在直接收益的情况，以及存在固定及频率依赖型搜索成本的间接收益情况，本文概述了繁殖收益、偏好强度及搜索成本的参数值范围——在此范围内，雌性偏好所受的间接选择可能占据主导地位。此外，本文分析了一夫多妻制（Polygyny）下的雄性配偶选择，结果表明，除存在直接收益的情况外，直接选择始终会超过间接选择。