Widespread positive but weak assortative mating by diet within stickleback populations.

Travis Ingram,Yuexin Jiang,Daniel I Bolnick,Racine Rangel

doi:10.1002/ece3.1609

Abstract

Assortative mating – correlation between male and female traits – is common within populations and has the potential to promote genetic diversity and in some cases speciation. Despite its importance, few studies have sought to explain variation in the extent of assortativeness across populations. Here, we measure assortative mating based on an ecologically important trait, diet as inferred from stable isotopes, in 16 unmanipulated lake populations of three-spine stickleback. As predicted, we find a tendency toward positive assortment on the littoral–pelagic axis, although the magnitude is consistently weak. These populations vary relatively little in the strength of assortativeness, and what variation occurs is not explained by hypothesized drivers including habitat cosegregation, the potential for disruptive selection, costs to choosiness, and the strength of the relationship between diet and body size. Our results support recent findings that most assortative mating is positive, while suggesting that new approaches may be required to identify the environmental variables that drive the evolution of nonrandom mating within populations.

Highlights

Assortative mating is a form of nonrandom mating that occurs when male–female mated pairs are more similar or more dissimilar to one another than expected by chance (Cezilly 2004)
Ecology and Evolution published by John Wiley & Sons Ltd
We find an average tendency toward positive assortative mating on the littoral–pelagic axis, but magnitudes are weak and not predictable from measured lake properties

Summary

Introduction

Assortative mating is a form of nonrandom mating that occurs when male–female mated pairs are more similar (positive assortative mating) or more dissimilar (negative assortative mating) to one another than expected by chance (Cezilly 2004). Positive assortative mating often occurs between species or differentiated populations, reducing hybridization rates and contributing to the maintenance of reproductive isolation (McKinnon et al 2004; Vines and Schluter 2006; Puebla et al 2007). Assortative mating can occur within single undifferentiated populations, where correlations between the traits of male–female pairs have been detected in a wide range of organisms (McLain 1982; Olson et al 1986; Arnqvist et al 1996; Roulin 2004; Snowberg and Bolnick 2008).

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