Code for the population genetic models of the evolution of preference strength

Sexual selection has a rich history of mathematical models that consider why preferences favor one trait phenotype over another (for population genetic models) or what specific trait value is preferred (for quantitative genetic models). Less common is exploration of the evolution of choosiness or preference strength: that is, by how much a trait is preferred. We examine both population and quantitative genetic models of the evolution of preferences, specifically developing “baseline models” of the evolution of preference strength during the Fisher process. Using a population genetic approach based on the classic model of Kirkpatrick (1982), we find selection for stronger and stronger preferences when trait variation is maintained by mutation. However, this force is quite weak and likely to be swamped by drift in moderately-sized populations. In a quantitative genetic model based on Lande (1981), unimodal preferences will generally not evolve to be increasingly strong without bounds when male traits are under stabilizing viability selection, but evolve to extreme values when viability selection is directional. Our results highlight that different shapes of fitness and preference functions lead to qualitatively different trajectories for preference strength evolution ranging from no evolution to extreme evolution of preference strength.

Methods
The dataset consists of Mathematica code used to develop and analyze the two locus model, the three locus model, and the model with finite population sizes in the accompanying paper.  It also contains a the quasi-linkage equilibrium analysis.

性选择拥有悠久的数学模型研究历史，此类模型旨在解答两个核心问题：针对种群遗传学模型，为何择偶偏好会偏向某一性状表型；针对数量遗传学模型，何种具体的性状值会成为偏好对象。而针对择偶挑剔度或偏好强度自身演化的探讨则相对少见，即偏好对某一性状的青睐程度会如何随演化改变。本文同时考察了偏好演化的种群遗传学与数量遗传学模型，专门构建了费希尔过程中偏好强度演化的“基准模型”。基于柯克帕特里克（Kirkpatrick, 1982）的经典种群遗传学模型，研究发现，当性状变异由突变维持时，选择会驱动偏好强度不断增强。但该选择作用力相当微弱，在中等规模种群中极易被遗传漂变所淹没。在基于兰德（Lande, 1981）的数量遗传学模型中，当雄性性状受到稳定存活选择时，单峰型偏好通常不会无限制地向更强偏好演化；但若存活选择为定向选择，偏好则会演化至极端水平。本研究结果表明，适合度函数与偏好函数的不同形状，会使偏好强度的演化呈现出截然不同的定性轨迹，从无演化到偏好强度的极端演化均有可能。

方法
本数据集包含用于开发和分析配套论文中双位点模型、三位点模型以及有限种群规模模型的Mathematica代码，同时涵盖准连锁平衡分析的相关内容。