Photoreceptors stained for different opsin mRNA in the retinas of Neotropical cichlids
Molecular evolution of visual sensitivity in cichlid fishes
Vision plays a fundamental role in the life of many organisms, influencing their capabilities to avoid predators and to locate food, shelter, and mates. However, performing these activities highly depends on the visual properties of the environment –as anyone who ever drove in fog can attest. The light conditions of aquatic environments are highly variable, both across space and time, providing a great opportunity to study adaptive variation in the visual system of aquatic organisms. This environmental variation in light conditions is mirrored in the large amount of diversity found in the visual system of teleost fish. Combined with a good understanding of the adaptive value of such variation, vision in fishes provides a tractable system to study the molecular mechanisms underlying adaptive divergence in the wild. Our research in this area focuses on color vision in fishes and address three different issues: (i) identifying the molecular and developmental mechanisms that underlie phenotypic variation in freshwater fishes, (ii) determining the molecular mechanisms involved in the response of the visual system to their internal and external environment, and (iii) understanding the contribution of genetic parallelisms to convergent evolution across species.
Adaptive phenotypic variation along environmental gradients
Phenotypes vary in space and time as a result of both, genetic divergence across populations (e.g., due to local adaptation, drift, bottlenecks, etc.) and environmental effects (e.g., plasticity). However, it remains unclear how closely organisms track environmental changes and how genetic and environmental effects on phenotypic variation affect population demography. We explore these issues taking advantage of replicated natural populations. Our research combines field surveys, manipulative common garden experiments, and behavioral assays to address questions such as how closely do organisms track environmental changes? Is phenotypic variation along gradients the result of plastic responses or genetic differences? If populations have the potential to closely track environmental changes, then what prevents them from adaptively evolving and expanding to environments beyond their current range? We explore the role of trade-offs, both at the genetic and phenotypic levels, in driving divergence along gradients and contributing to the emergence of distribution limits.
Phenotypic variation within populations: maintenance of polymorphisms in nature
Extensive work has been conducted to understand the maintenance of phenotypic variation within populations. Nonetheless, several interesting questions regarding the evolutionary ecology of polymorphisms are yet unresolved. We are particularly interested in understanding selection pressures that are more conducive to the maintenance of such polymorphisms. We have used breeding experiments and genome-wide association analyses (GWAS) to determine if polymorphisms are genetically determined. Still, the long-term stability of genetically determined polymorphisms in natural populations is intriguing. Under simple scenarios, genetic variation is expected to be eroded by natural selection. However, disruptive selection can also increase variation within populations. One mechanism proposed to explain the maintenance of polymorphisms is frequency-dependent selection. These selection pressures might result from interactions with other biotic agents, such as predators and resources, but also from within-population patterns of reproductive success. We combine field and laboratory experiments to understand how these agents contribute to the maintenance of polymorphisms.