Female-limited colour polymorphism in the crab spiderSynema globosum(Araneae: Thomisidae)

Helena Ajuria Ibarra,Tom Reader

doi:10.1111/bij.12338

Helena Ajuria Ibarra, Tom Reader

Open Access

https://doi.org/10.1111/bij.12338

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Abstract

Conspicuous colour variation, caused by the influence of the environment on phenotype, or by genetic differences among individuals, is frequently observed in nature. If genetic in origin, colour variation can facilitate the study of the mechanisms that contribute to the maintenance of true polymorphisms. Here, we describe for the first time the female-limited colour polymorphism in the crab spider Synema globosum. We look for associations between life history traits and female colour morph, and identify potential agents of selection that could influence the maintenance of the polymorphism. Our results show that the polymorphism is discrete and heritable, and that differences in colour among morphs are likely to be detectable by honeybees, birds, and conspecifics. We found limited evidence of differences among morphs in morphology and ecology, and found no differences in components of reproduction. Based on the lines of evidence obtained in this study, we suggest that selection exerted by prey, predators and/or mates is likely to influence the maintenance of the polymorphism observed in S. globosum.

Highlights

Polymorphism is a widespread phenomenon in nature that occurs in a broad range of taxa
The results of this study suggest that the colour variation among females of S. globosum morphs is discrete and heritable, and can be considered to be a true polymorphism
We found limited evidence that colour morphs differ in morphology and ecology

Summary

Introduction

Polymorphism is a widespread phenomenon in nature that occurs in a broad range of taxa It is the presence of multiple genetically and phenotypically distinct forms in a population, which do not respond to changes in the environment or body condition and can interbreed to produce fertile hybrids (Roulin, 2004). Polymorphisms have been a subject of great interest in biological research because determining the mechanisms that generate and maintain them can shed light on how natural selection and other evolutionary processes shape both genotypes and phenotypes (Brockmann, 2001; Gray & McKinnon, 2007; Mitchell-Olds, Willis & Goldstein, 2007). Continuous colour variation has often been observed to be condition- or environment dependent and may not reflect a true (genetic) polymorphism (Hill & Montgomerie, 1994; Fitze, Kolliker & Richner, 2003). Polymorphisms can be maintained if different morphs exhibit alternative strategies that result in equal mean fitness values (Roulin et al, 2003)

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