Structural equation modeling as a tool to investigate correlates of extra-pair paternity in birds.

Nicholas M A Crouch,Roberta J Mason-Gamer,Tim A Mousseau

doi:10.1371/journal.pone.0193365

Nicholas M A Crouch, Roberta J Mason-Gamer + Show 1 more

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https://doi.org/10.1371/journal.pone.0193365

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Abstract

Identifying relationships between variables in ecological systems is challenging due to the large number of interacting factors. One system studied in detail is avian reproduction, where molecular analyses have revealed dramatic variation in rates of extra-pair paternity—the frequency with which broods contain individuals sired by different males. Despite the attention the topic has received, identification of ecological predictors of the observed variation remains elusive. In this study we evaluate how structural equation modeling—which allows for simultaneous estimation of covariation between all variables in a model—can help identify significant relationships between ecological variables and extra-pair paternity. We estimated the correlation of eight different variables using data from 36 species of passerines by including them in six different models of varying complexity. We recover strong support for species with lower rates of male care having higher rates of extra-pair paternity. Our results also suggest that testes size, range size, and longevity all potentially have a relationship with rates of extra-pair paternity; however, interpretation of this result is more challenging. More generally, these results demonstrate the utility of applying structural equation modeling to understanding correlations among interacting variables in complex biological systems.

Highlights

Variation in species mating systems can influence a range of ecological and evolutionary processes, including: strength of sexual selection, population demographics and variation in species traits [1,2,3,4,5,6]
The application of molecular techniques to avian mating systems has revealed that socially-monogamous species, with a male and female paired at a nesting site, are infrequently genetically monogamous—chicks from a single brood are frequently sired by multiple males [7,8,9,10]
In this study we evaluate structural equation modeling (SEM) as a method to estimate whether eight important life history and morphological variables are correlated with extra-pair paternity (EPP)

Summary

Introduction

Variation in species mating systems can influence a range of ecological and evolutionary processes, including: strength of sexual selection, population demographics and variation in species traits [1,2,3,4,5,6]. Identifying ecological predictors of why mating systems in some taxa are so variable is a major area of research. Structural equation modeling as a tool to investigate correlates of extra-pair paternity in birds considerable research, identification of ecological predictors of the observed variation remains challenging [9, 10]. Rates of extra-pair paternity (EPP) vary dramatically between avian species. Approximately three-quarters of broods of the Superb fairy-wren (Malurus cyaneus) are associated with multiple males [17]. This variation is not ubiquitously between distantly related taxa, members of the same genus can show disparate rates of EPP [9, 16]

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