Overarching Theme
Many species live in groups, in which stability is maintained via hierarchies. Social hierarchies generally consist of higher-ranking dominant (DOM) individuals, which have greater access to resources and higher reproductive success than lower-ranking subordinate (SUB) individuals. Social rank has profound effects on physiology and behavior, including changes in hormone production, neural circuitry, and neuromodulatory signaling, and these processes are strikingly different between DOM and SUB individuals in a social group. Interestingly, these hierarchical structures are dynamic and can be altered due to naturally occurring changes in the environment, including both biotic (e.g., social) and abiotic factors. Our lab’s central goal is to identify the neural and molecular mechanisms underlying this remarkable social plasticity in African and Neotropical cichlid fishes. Specifically, we manipulate the social environment and seasonal abiotic factors to uncover the mechanisms underlying naturally occurring neural and behavioral plasticity across species.
Our Study Species
Cichlids (family Cichlidae) are a geographically widespread group of teleost fishes consisting of over 1,700 species divided across African, Neotropical, and Malagasy/Indian clades. These fishes show exceptional diversity in their life-history strategies, social structures, and reproductive systems. For example, the African cichlid Astatotilapia burtoni exhibits male-only hierarchies and lives in social groups consisting of multiple breeding pairs. Conversely, the cooperatively breeding African cichlid Neolamprologus pulcher exhibits all-individual hierarchies, in which SUB males and females stratify along the same hierarchical structure, and lives in social groups consisting of SUB helpers and one dominant breeding pair. Although A. burtoni and N. pulcher reproduce year-round, some species breed seasonally, including the South American cichlid Cichlasoma dimerus. C. dimerus exhibits same-sex hierarchies, in which males and females form separate social hierarchies, and lives in social groups consisting of one dominant breeding pair. By studying these species in tandem, our research provides a powerful framework for examining the regulation and evolution of social plasticity in group-living animals.
Current Projects
Neural and Molecular Bases of Subordination
SUB behaviors are essential for preserving stability within social groups, yet we know remarkably little about the specific mechanisms in the brain that modulate a SUB social status. We are characterizing the role of the neurotransmitter serotonin, as well as other neuromodulators and signaling pathways, in regulating social subordination in the African cichlid A. burtoni.
Image credit: Karen Maruska, Louisiana State University.
Seasonal Regulation of Social Status
Seasonality is a critical factor that regulates behavior in many animals; however, seasonal plasticity in social rank is relatively understudied. We are investigating how seasonal abiotic factors (e.g., photoperiod, food availability, temperature) control social status in the South American cichlid C. dimerus and identifying their underlying neuroendocrine mechanisms.
Image credit: phils1stpix on iNaturalist (CC BY-NC).
Evolution of Social
Plasticity
We are examining the neural and physiological mechanisms of social plasticity in male and female cichlids using a comparative approach. By studying the three cichlid species in our lab, which represent diverse hierarchical structures, we are discovering conserved and evolved mechanisms that regulate social status across species and sex.
Figure: Říčan et al. 2016 (Vertebrate Zoology).