Abstract

Complex colouration facilitates evolutionary investigations in nature because the interaction between genotype, phenotype and environment is relatively accessible. In a landmark set of studies, Endler addressed this complexity by demonstrating that the evolution male Trinidadian guppy coloration is shaped by the local balance between selection for mate attractiveness versus crypsis. This became a textbook paradigm for how antagonistic selective pressures shape evolutionary trajectory. However, the paradigm's generality was recently questioned by two studies seeking to use Trinidadian guppy populations to test the concept of parallel evolution. Both applied new and more sophisticated colour pattern analysis but these studies neither adequately address the question of evolutionary parallelism nor actually challenge the paradigm. As a guide to future work we review five main underappreciated factors contributing to colour pattern evolution: (1) inter-population variation in female preference, (2) differences in how predators versus conspecifics view males, (3) biased assessment of pigmentary versus structural colouration, (4) the importance of accounting for multi-species predator communities, and (5) the importance of considering the multivariate genetic architecture and multivariate context of selection. We elaborate upon these points and emphasize the depth of consideration necessary for testing evolutionary hypotheses using complex multi-trait phenotypes such as guppy colour patterns. 2