The Evolution of Color Polymorphisms in Colias Butterflies: Preferences, Learning, and Sensory Limitations
Year: 2017
Type: article
Abstract: Polymorphisms are useful for studying major evolutionary questions, such as how diversity arises and is maintained over time. They are a widespread form of biodiversity and take on a number of different forms, including behavioral, physiological and morphological. The female-limited ‘alba’ color polymorphism in the butterfly family Coliadinae is a widespread polymorphism, yet despite its prevalence, the selective forces that maintain it are not fully understood. In order to better understand the evolutionary mechanisms that maintain this ubiquitous color polymorphism, I first utilized a phylogenetic approach to answer questions about the evolutionary origin and history of the ‘alba’ polymorphism. Ancestral state reconstruction revealed that the ‘alba’ polymorphism is ancestral to the Coliadinae, but is often lost, leaving about half of the current species monomorphic. Next, I asked whether sensory limitations might contribute to polymorphism maintenance via the influence of reproductive interference on male mate preferences. To answer this question, I modeled the male visual system to determine whether males should experience difficulty discriminating between the white female morph (‘alba’ morph) and other co-flying white butterflies. I found that visual limitations may explain a male mate preference for the more discriminable, yellow (non-‘alba’) female morph. I then tested whether such a preference exists and whether males modify their mate preference based on the frequency of each morph in the population. Field observations of natural populations and behavioral experiments in captive populations revealed that males do prefer to court non-‘alba’ females, and that this preference is unaffected by morph frequency. Finally, I used a theoretical model that combined signal detection theory and optimal diet theory to explore optimal decision making in situations where options differ in value and discriminability. This model revealed that the morph ratio, discriminability, and recognition costs should influence optimal mate preference and that mate preferences can affect polymorphism maintenance by affecting morph fitness. Altogether, these studies advance our understanding of the role that the evolutionary history, sensory limitations, and community composition have played in a widespread but poorly understood polymorphism.
Author: Lisa B. Limeri
Language: English
Domain: Life Sciences
Open Access status: green
Funder: University of Pittsburgh
OpenAlex ID: W2773315398