Can the Fisher-Lande process account for birds of paradise and other sexual radiations?

Models of the Fisher‐Lande process (FLP) have been used successfully to explore many aspects of evolution by sexual selection. Despite this success, quantitative tests of these models using data from sexual radiations are rare. Consequently, we do not know whether realistic versions of the FLP can account for the extent and the rate of evolution of sexually selected traits. To answer this question, we generalize the basic FLP model of sexual coevolution and compare predictions of that basic model with patterns observed in an iconic sexual radiation, birds of paradise. Our model tracks the coevolution of male and female traits (two in each sex) while relaxing some restrictive assumptions. Using computer simulations, we evaluate the behavior of the model and confirm that it is an Ornstein‐Uhlenbeck (OU) process. We also assess the ability of the FLP to account for the quantitative aspects of ornament evolution in the genus Paradisaea using published measurements of display traits and a phylogeny of the genus. Finally, we use the program OUwie to compare model fits to generic OU and Brownian motion processes and to estimate FLP parameters. We show that to explain the sexual radiation of the genus Paradisaea one must either invoke extremely weak stabilizing selection on female mating preferences or allow the preference optimum to undergo Brownian motion at a modest rate.

费希尔-兰德过程（Fisher-Lande Process，FLP）模型已被成功用于探究性选择驱动演化的诸多方面。尽管该类模型已取得诸多成功，但利用性辐射（sexual radiation）数据对其开展的定量检验仍较为少见。因此，我们尚不清楚符合现实场景的FLP模型能否解释性选择性状演化的幅度与速率。为解答这一问题，我们对性协同演化的基础FLP模型进行了推广，并将该基础模型的预测结果与标志性性辐射类群——极乐鸟（birds of paradise）中观测到的演化模式进行了比对。我们的模型追踪雌雄两性各两类性状的协同演化过程，同时放宽了部分限制性假设。借助计算机模拟，我们对该模型的行为特征进行了评估，并证实其属于奥恩斯坦-乌伦贝克过程（Ornstein-Uhlenbeck Process，OU）。我们还使用已发表的展示性状测量数据与该属的系统发育树，评估了FLP模型解释极乐鸟属（Paradisaea）装饰性状演化定量特征的能力。最后，我们使用OUwie软件将模型拟合结果与通用OU过程、布朗运动过程（Brownian Motion Process）进行了比较，并估算了FLP模型的参数。我们的研究表明，若要解释极乐鸟属的性辐射现象，要么需要假定对雌性交配偏好的稳定选择极弱，要么允许偏好最适值以适中的速率发生布朗运动。