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Physiology of environmental coping. Hormones are chemical messengers that transmit information from the environment to the body, ultimately leading to behavioral responses to environmental cues and challenges. Stress hormones have been related to different social phenotypes in a variety of vertebrates, including starlings, but the patterns are inconsistent across different taxa. Because a basic framework for making testable predictions linking stress physiology to social behavior is lacking, we have been developing the first mathematical theory of sociality that considers the physiological and stress-related costs of group-living. This integrative and predictive theory synthesizes three disciplines (evolutionary biology, mathematics, biomedicine) and is grounded in evolutionary theory and physiological mechanisms.

Adaptation along environmental gradients. We are also interested in understanding how all birds adapt to unpredictable environments, not just in terms of their social behavior but also in terms of their stress physiology and immune function. We are examining different suites of birds along ecological gradients across Kenya. This work has important conservation implications because understanding how birds are physiologically adapted to natural environmental uncertainty will allow us to make predictions about how other species will respond to the anthropogenically-induced climatic variability resulting from global warming.

Epigenetics, plasticity and environmental variation. Determining the mechanisms that underlie phenotypic variation is important for understanding not only how organisms cope with environmental challenges, but also how their responses could affect later life stages or even future generations. However, environmentally-induced phenotypic variation resulting from differential gene expression may be regulated by processes that that do not include the DNA sequence itself (i.e., ‘epigenetic mechanisms’). DNA methylation is one such epigenetic mechanisms that allows organisms to respond to environmental change via changes in gene expression that alter the phenotype. DNA methylation during development and early life can have long-term consequences for gene expression, physiology, and behavior in many vertebrates. We are examining how developmental conditions (both social and environmental) influence social phenotypes, stress physiology, and fitness late in life, and we are exploring DNA methylation as one potential mechanisms underlying this relationship.

Social Evolution & Environmental Coping

We take an integrative approach to understand the evolution of animal sociality by combining studies of behavior and ecology with those of the underlying genetic and neuroendocrine mechanisms. We emphasize how environmental uncertainty shapes social-living by examining how behavioral decisions, and other individual level processes influence population level processes and other larger scale phenomenon and patterns. Specifically, we seek to understand how ecology and the environment shapes individual reproductive decisions and interspecific patterns of sociality by trying to unravel the interaction among physiology, life history, and behavior at different scales. In addition to field work, we employ a variety of lab techniques (genetics, genomics, endocrinology, immunology) and statistical and theoretical approaches (comparative analyses, game theory) to answer a range of questions about social complexity in a diversity of vertebrate and invertebrate taxa. Currently, we work on free-living social vertebrate (African starlings) and invertebrate (Synalpheus shrimp) systems in a comparative context to better understand the causes, consequences, and patterns of sociality in a broad array of animal systems.

Environmental uncertainty and social evolution. All organisms—including humans—must cope with uncertainty in their daily lives. Environmental variation in time (environmental uncertainty) can influence social behavior, including dispersal decisions and the adoption of different breeding roles, or social phenotypes. Our work in cooperatively breeding starlings and other birds examines how erratic and variable climatic patterns can also influence social complexity. We are exploring how cooperative breeding behavior may be a bet-hedging strategy that animals use to reduce environmentally-induced fecundity variance using game theoretical models, simulation models, comparative analyses, and empirical tests in the field.

Genomic architecture of social phenotypes. The underlying physiological and genetic bases of sociality and its reproduction division of labor (castes) in most social invertebrates outside of bees and ants remain effectively unknown. We are studying the mechanistic basis of caste differentiation and social complexity and diversity by examining gene expression in closely related species of snapping shrimp that show not only a range of social behaviors, but also a range of levels of physiological and morphological caste differentiation. We are using RNAseq to study the expression of all functional genes in individuals (and species) with different social phenotypes and from varying social and ecological environments.

Sexual selection and social competition. Although cooperation is the critical feature that defines all complex societies, conflict is inherent in any group of genetically different entities. In social species, competition over reproduction may be particularly intense, and this competition has important consequences for the behavior, physiology, and genetics of organisms living in groups. We have shown that competition for reproduction may be intense in both sexes in cooperatively breeding species. The increased competition in females may result in intense selection on traits used in intra-sexual competition, resulting in elaborate ornaments or armaments in both sexes in social species. This intriguing pattern has spurred us to think more about female-female competition in general, particularly in social species. We are studying studying inter and intra-sexual competition and signaling (song, plumage) in starlings. Additionally, living in groups can have important consequences for an individual’s stress physiology. The importance of dominance structure and rank is understudied in many social species, particularly in birds. We are exploring the interactions between dominance rank, social structure and conflict, both theoretically and empirically.

Evolution of social diversity. Arguably one of the most fundamental problems in biology is the evolution of altruism, most clearly manifested as the sacrifice of personal reproduction among social animals. To identify general principles governing social evolution across disparate animal taxa, it is necessary to understand why the within-group distribution of reproduction (i.e., reproductive skew) varies among closely related species and how that variation is maintained. We are examining the evolution of social diversity in Synalpheus sponge-dwelling snapping shrimp. Synalpheus shrimps are one of the most socially diverse group of organisms on earth; approximately 50% of the species in a single clade of 40 species live in social groups ranging in complexity from asocial pairs, to colonies of pairs, to cooperatively breeding families, to eusocial colonies. Our research is attempting to quantify key characteristics common to disparate social taxa and explore the key evolutionary transition—differentiation of castes—suggested to uniquely define eusocial insects and differentiate them from social vertebrates.

Comparative social evolution. In addition to studying the evolution of social diversity in a single group of diverse organisms, we have also been comparing social behaviors across taxonomically diverse animals. Rather than focusing on the ecological, social, and other factors that may select for social living (a top-down approach), we are taking a bottom-up approach to look at the traits and behavioral characteristics that these disparate taxa share. We are examining the distinction between societies with a single reproductive females and those with multiple reproductive females. This distinction exists in both social vertebrates and invertebrates. We are currently compiling data for over a dozen additional traits, as well as exploring ways that social insect and social vertebrate society categorizations are actually more similar than most think.

Social Evolution

Environmental Coping


behavior | ecology | evolution

Columbia University in the City of New York