Abstract
BackgroundColor polymorphisms are a conspicuous feature of many species and a way to address broad ecological and evolutionary questions. Three potential major evolutionary fates of color polymorphisms are conceivable over time: maintenance, loss, or speciation. However, the understanding of color polymorphisms and their evolutionary implications is frequently impaired by sex-linkage of coloration, unknown inheritance patterns, difficulties in phenotypic characterization, and a lack of evolutionary replicates. Hence, the role of color polymorphisms in promoting ecological and evolutionary diversification remains poorly understood. In this context, we assessed the ecological and evolutionary consequences of a color polymorphic study system that is not hampered by these restrictions: the repeated adaptive radiations of the gold/dark Midas cichlid fishes (the Amphilophus citrinellus species complex) from the great lakes and crater lakes of Nicaragua, Central America.ResultsWe conducted multi-trait morphological and ecological analyses from ten populations of this young adaptive radiation (<6,000 years old), which revealed sympatric ecological differentiation associated with the conspicuous binary (gold/dark) color polymorphism. Varying degrees of intraspecific ecological divergence were observed across the ten color morph pairs, but most pairs exhibited a consistently parallel ecological and evolutionary trajectory across populations. Specifically, gold Midas cichlids are frequently deeper-bodied, have more robust pharyngeal jaws, and feed at a lower trophic level compared to conspecific, sympatric dark individuals. A common garden experiment suggests there is a genetic correlation of color and eco-morphological traits.ConclusionsWe demonstrate unprecedented ecological and evolutionary consequences of color polymorphism in this adaptive radiation. Across the species complex, sympatric conspecific individuals differed in eco-morphology depending on color morph (gold/dark) and the axis of differentiation tended to be consistent across replicates. The consistent divergence across wild populations and the common garden experiment suggests that color is genetically correlated to ecology. Because Midas cichlids are known to mate color assortatively, the putative genetic correlation of this color polymorphism with an eco-morphological divergence suggests an innate potential to promote ecological and evolutionary divergence across this species complex. However, there are to date no examples of speciation based on color in this radiation, suggesting long-term maintenance of this color polymorphism.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-015-0192-7) contains supplementary material, which is available to authorized users.
Highlights
IntroductionThe role of color polymorphisms in promoting ecological and evolutionary diversification remains poorly understood
Color polymorphisms are a conspicuous feature of many species and a way to address broad ecological and evolutionary questions
This was shown by a geometric morphometric analysis across the ten populations pooled (Procrustes distance = 0.01, Hotelling’s T2 = 248.06, p < 0.0001) (Fig. 2a). This pattern was generally consistent across populations examined individually; in most cases a discriminant function analysis clearly separated body shapes by color, variable in extent and significance given the small sample sizes in some groups (Additional file 1: Table S1 and S2)
Summary
The role of color polymorphisms in promoting ecological and evolutionary diversification remains poorly understood. The occurrence of two or more genetically determined color morphs within an interbreeding population [1], occur in animals and plants alike. They potentially have a great impact on various intra- and interspecific processes such as communication, mating systems, and vulnerability to predation [2,3,4], and, may accelerate speciation [5]. For example in complex animal systems, color polymorphisms tend to have unknown inheritance mechanisms, exhibit continuous or intermediate variation, result from assortative mating under natural conditions, and/or be sex-linked [3] as seen in the African cichlid fishes [7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
