Research

Developmental Programming: Physiological Mechanisms and Adaptive Significance

Adult phenotypic expression is a product of genes, the environment, and indirect genetic and environmental effects, also known as maternal or, more broadly, parental effects. My early research focused on the physiological mechanisms and potential ecological and evolutionary consequences of maternal effects. However, at least for some traits, the early environment experienced by offspring themselves had a much larger effect on the phenotype over the long-term than maternal effects (e.g., Merrill, Naylor, Dalimonte, McLaughlin, Stewart, and Grindstaff 2017). These results emphasize the formative role that early environmental conditions can have on phenotypic expression by canalizing, and sometimes even inducing, the developmental process. An understanding of the mechanisms through which environmental cues are transduced into phenotypic expression and the potential adaptive value of changes to the phenotype is critical to delineate the limits to the capacities of organisms to adaptively respond to rapid environmental changes. Moreover, knowledge of the physiological mechanisms and environmental conditions that favor increased plasticity is necessary to identify resilient and vulnerable individuals and species. Knowledge of the physiological mechanisms that convey sensitivity to the environment should inform conservation, provide insight and novel treatment approaches for a number of animal and human diseases with their origins firmly rooted in development, and advance basic biological understanding.

 

Current Research

Environmental and endocrine factors underlying behavioral plasticity in response to adversity.

Early life adversity can reprogram the developing brain and endocrine system with consequences for behavior. However, some individuals are resilient to early adversity, whereas others are vulnerable. We lack fundamental understanding of how individual differences in plasticity arise. This critically impairs our ability to predict the individuals and species most vulnerable to adverse developmental conditions. Our research goal here is to define the mechanisms that contribute to variation within and  among individuals in behavioral plasticity. Specifically, we will:

 

1. Determine the effects of the number of stressors encountered during different developmental periods on adult behavioral plasticity
2. Quantify the consistency of behavioral plasticity and physiological reactivity across the lifespan
3. Test for relationships between behavioral plasticity and physiological reactivity
4. Experimentally manipulate physiological state to test for a causal role in behavioral plasticity; and
5. Determine if hormone receptor concentrations across tissues contribute to the capacity for plasticity.

We are grateful to the National Institutes of Health for funding this research.

 

Long-term effects of simulated early infection.

When young vertebrates are exposed to novel pathogens, the subsequent immune response is dominated by the inflammatory response, which can impede growth and impact later immune responses and behavior, but existing research is focused primarily on immediate effects of infection. Longer term studies have mostly tested the consequences of bacterial infection. Viral early life immune challenge has particular ecological relevance due to the susceptibility of young vertebrates to arthropod-borne pathogens and the potential for many of these diseases (e.g., Avian Influenza, West Nile Virus) to impact humans. In a captive population of zebra finches (Taeniopygia guttata), we are testing the effects of early simulated viral infection on the ontogeny of antibody and cytokine production, developmental trajectories and the adult behavioral phenotype. This research has broad implications for both wildlife conservation and human health.

 

This research is led by Sierra Williams, Ph.D. candidate.

 

Effects of paternal deprivation on stress physiology and behavioral expression.

Disruption of parental care during early development acts as a chronic stressor with long-lasting effects on offspring physiology and behavior. Despite 80% of birds providing bi-parental care, few studies have investigated the importance of paternal care on offspring development. Zebra finches are socially monogamous birds in which both parents provide equal amounts of parental care. Because of this bi-parental care, paternal  removal may have similar impacts on offspring development to those resulting from maternal separation. We are manipulating the presence of fathers during nestling and fledgling periods in captive zebra finches to test for long-term effects on behavior and stress physiology. Zebra finches are a novel, biologically relevant model for the study of pair bond disruption and reduced paternal investment. This research with a tractable, captive model species informs our understanding of the consequences of adverse childhood experiences in humans.

 

This research is led by Angela Goff-Riley, Ph.D. candidate.