The Life History - Physiology Nexus Constraints on the Evolutionary Diversification of Avian Life Histories
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Project description

This project is an integrated, multidisciplinary effort to understand variation in the life histories of temperate and tropical birds, and thereby the diversification of life histories more generally. Although differences in reproductive success and adult survival over latitudinal gradients have attracted the attention of ecologists and evolutionary biologists for more than 50 years, relatively little effort has been devoted to the adaptive physiological and behavioral responses of birds to their environments in a life-history context. Our project brings together a team of population biologists and physiologists from a variety of disciplines to work together at the intersection of environmental factors and physiological mechanisms that influence demographic patterns of populations—what we refer to as the “life history-physiology nexus.” The central prediction of the evolutionary theory of life histories is that the balance between parental investment and self-maintenance is related to annual adult survival rate. Furthermore, adaptive responses of individuals and populations to their surroundings are constrained. Time, resources, and body tissues are limited, and they must be allocated optimally among different functions. Specific physiological constraints on variation in life histories have received little attention but may nonetheless shape life histories in significant ways. We propose to compare small, altricial, terrestrial birds with varied life styles and living in contrasting environments to address physiological and behavioral mechanisms associated with variation in adult survival and related life-history variables.

understory habitat along Pipeline Road, Panama

Objectives

This project will produce the most significant comparison to date of physiology and behavior between tropical and temperate organisms. These data will allow us to test a fundamental prediction of life history theory, that the high adult survival rates and long breeding seasons typical of tropical environments select for a slower pace of life, including reduced reproductive investment and greater allocation of resources to adult maintenance. In addition to comparing demographic components of life histories in 10 phylogenetically matched pairs of tropical and temperate species, individual components of the project will address different aspects of behavior and physiology. These include activity and metabolic rate in the field and in controlled environments, condition and health status, immune responses, stress responses, and endocrine control mechanisms. Although the components of the life history are complex, we expect to find correlated patterns among these measurements that tie physiology and behavior to ecology and demography. These patterns overlaid on an environmental and phylogenetic framework will provide an integrated perspective on life-history evolution that includes physiological mechanisms and constraints.

Spotted Antbird, female (left) and male (right), from the inner rain forest in Panama

©Marie Read

Integrated nature of the project The project directly involves eight senior personnel at seven institutions. The participants are a mixture of established researchers and new investigators, each of whom has an active research program that addresses one or more components of the overall project, spanning life-history theory, demographics, endocrinology, behavior, immunology, field ecology, energetics, and aging. We also have a history of collaborative research with each other. The University of Missouri-St. Louis will serve as the lead institution for the grant, handling its financial aspects. Twice-yearly coordinating meetings of the senior personnel will facilitate program planning and the integration of projects. The investigators also will spend substantial periods together in the field in Panama and Michigan.

This large-scale study will be the first to synthesize demography and physiology in order to characterize and interpret avian life histories. It will significantly contribute to our understanding of avian longevity and life history adaptation, and it will highlight species with contrasting life histories and physiological makeup for future, more in-depth studies. Long-term benefits of this project include the establishment of a lasting, multidisciplinary network of collaborators, the development of a large, publicly available, comparative database of behavioral and physiological information, and the training of a new generation of biologists who are able to integrate disciplines crucial to understanding the diversity of life.