Animals display a remarkable amount of variation in their behavior, however, the genetic and neural underpinnings of behavioral diversity are poorly understood. My research program seeks to address this by examining two main questions: What are the genetic, developmental and neural mechanisms that underlie differences in behavior? Further, how do behaviors evolve? To do so, we use the blind cavefish, Astyanax mexicanus. A. mexicanus exists in a river-dwelling surface form, as well as in multiple populations that have been trapped in, and have adapted to life in subterranean caves. Cavefish have adapted to survive and thrive in the cave environment through the modification of morphological, physiological and behavioral traits. While surface fish and cavefish have strikingly divergent phenotypes, they are interfertile, and are therefore a powerful genetic model of behavioral evolution. Furthermore, many of these cave populations have evolved from independent colonization events, allowing for the examination of repeated evolution. Many of the strengths of model organisms, including genetic manipulation and brain imaging, are now feasible in A. mexicanus, allowing for examination of the genetic and neural mechanisms that underlie these differences in behavior. In addition, the small size, ability to live and breed in the laboratory, and short generation time of these fish make Astyanax an extraordinary system for genetic and behavioral studies.
My laboratory currently focuses on four research programs:
Examining how natural genetic variation alters developmental processes to produce phenotypic change
Genetic changes can alter developmental processes, leading to differences in sensory systems and brains and ultimately, behavior. My laboratory is interested in investigating the developmental changes that lead to changes in the central nervous system that underlie morphological and behavioral evolution. For example, cavefish initially develop small eyes that subsequently degenerate. Further, eye regression has evolved in multiple cave populations. My laboratory is currently examining the developmental and genetic basis of eye loss in cavefish from populations that have evolved following independent colonization events to identify the alterations to development that contribute to these evolved changes in eye morphology and to determine if there are multiple ways A. mexicanus cavefish can lose eyes.
Understanding the role of pleiotropy in the evolution of behavior
While trait loss is common in evolution, the mechanisms by which traits are lost remain relatively unknown. Cave animals present important opportunities for understanding the evolutionary processes that contribute to trait loss, as multiple species of cave animals have repeatedly evolved reductions in pigmentation and regression or loss of eyes. My lab has been examining albinism, the complete loss of melanin pigmentation, to understand how evolution of pigmentation is related to evolution of other traits, and ultimately, how and why regressive traits evolve. We are currently testing the hypothesis the gene oca2 underlies the adaptive evolution of both albinism and behavior in cavefish.
Examining how and why behavioral plasticity evolves
Identical genotypes can produce different phenotypes in the context of different environmental conditions. This ability to alter traits in response to environmental conditions, known as phenotypic plasticity, is crucial for survival in a variable environment. While it is widely accepted that plasticity itself has a genetic basis, the genetic underpinnings of plasticity and how plasticity evolves are poorly understood. One striking example of phenotypic plasticity is the change in sleep observed in individuals under different nutrient availability conditions. While many organisms reduce sleep in response to a food-poor environment, presumably to increase time available for foraging, other organisms increase the amount they sleep under these conditions. Sleeping more is thought to conserve energy when food is not available. We are currently evaluating how plasticity in sleep has evolved in A. mexicanus by examining the genetic underpinnings of sleep and sleep plasticity in the lab. Further, we are examining sleep, feeding, and food availability in the field to define these behaviors in natural populations of fish and to identify the environmental conditions under which these behaviors have evolved.
Evolutionary approaches to identify genetic architecture regulating social behavior
Effectively engaging with other individuals of the same species is important for survival, and extreme social behaviors can have negative consequences for both individuals and social groups. While a significant body of research has contributed to our understanding of the genetic and neural bases of social behaviors like aggression and parental care, much less is known about how natural genetic variation alters neural circuits to produce differences in social behaviors between individuals, or how social behaviors evolve. A. mexicanus surface fish are highly social, whereas cavefish from multiple populations have evolved reductions in multiple social behaviors, including aggression and schooling. We are exploring the genetic and neural mechanisms that contribute to these differences in social behaviors.