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.Keywords: phenotypic tango, adaptive radiation, Brownian motion, Ornstein‐Uhlenbeck (OU) process, sexual coevolution

ArnoldCanFisherLandeProcessAppendixB.pdf

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.Keywords: adaptive radiation, phenotypic tango, Brownian motion, Ornstein-Uhlenbeck (OU) process, sexual coevolutio

Experimental analysis of monogamy in the Caribbean cleaner goby, Gobiosoma evelynae

To investigate factors promoting monogamy, we studied the reproductive behaviour and ecology of the monogamous Caribbean cleaner goby at two sites near St Croix, U.S. Virgin Islands. We assessed mate fidelity and the amount of time required to acquire a new mate in experimentally widowed males and females. We also measured behavioural responses of pair members and single females to experimentally introduced conspecific intruders of both sexes. Finally, we evaluated the distribution of suitable habitat relative to existing goby territories. We found that pairs often separated due to males abandoning females\ud and moving to a new territory, that most widowed fish soon acquired a new mate, and that there was strong aggression towards large same-sex intruders. We also found an abundance of suitable, unoccupied habitat. We conclude that pairs are maintained by intrasexual aggression that is related to both mate availability and other resources, such as high-quality, food-rich cleaning stations. Combined with observations of frequent pair separation, interterritory male movement, and relatively rapid remating by both sexes, these results suggest a complex mating system that is best classified as serial monogamy