Ecological and Evolutionary Connections Between Individual Behavior and Population Patterns

As a behavioral and evolutionary ecologist, I am fascinated by relationships among different scales of biological organization. Questions about individual variation (behavior, morphology, and physiology) and population patterns (social and genetic structure, population stability, species boundaries) are usually addressed in isolation from one another, but it is the relationship between these two levels that provides powerful predictive information about the causes and consequences of large scale patterns, such as the generation and loss of biodiversity. To
make explicit links between behavioral ecology and population biology, I test theory-driven hypotheses related to both the function and proximate mechanisms that underlie individual behavior and use multi-level statistical models to explore the relationship between individual-level variation and larger-scale patterns within and among populations. I am currently most busy working on reproductive behavior and its consequences for population structure using the barn swallow Hirundo rustica species complex as an interesting study system. This project is a large, international collaboration with many research opportunities for students at all stages of their careers.


Sexual Selection and Speciation

I am intrigued by the role that sexual selection can play in shaping male and female behavior within populations and how that plays out at a larger scale, for example, by shaping differences in populations that might lead to the evolution of new species. Barn swallows are a wonderful study system because they are nearly everywhere in the Holarctic and throughout their widespread distribution, males look quite different from one another. For example, males in western Europe have very long tail streamers and pale ventral feather color, whereas in North America,
males have much shorter tail streamers and darker feather color.  The overall goal of my research program is to take a close look at how these signals (tail streamers and feather color) work within populations in North America, the UK and Israel, and to find out why females use these traits in different combinations for mate selection decisions in different parts of the world.  We use a variety of different molecular tools to examine how hormones, antioxidants and genetic diversity are affected by behavior and morphology within and among our different study populations. The over-arching goal is to determine the role of sexual selection in the evolution and maintenance of biodiversity. Our research is currently funded by the National Science Foundation, National Geographic Society, and the Israel Science Foundation.

Behavioral and Evolutionary Ecology Research Group

at the University of Colorado - Boulder

Primary Investigator - Rebecca Safran

Decision-making and Social Behavior

Biologists are just beginning to realize and implement the incredible utility of studying individual behavior as a way to predict larger scale ecological and evolutionary dynamics. Traditional approaches to studying group breeding involve identifying population-level patterns in group characteristics and then trying to infer individual-level decisions about the process of group formation.  However, inferring process from pattern can be difficult or even misleading.  Some researchers have begun studying the decisions that individuals make when joining groups, but have rarely used these decisions to predict population patterns, such as breeding group size.  In response to a need for a general framework that will simultaneously explain the individual-level process of group formation and the incredible diversity in population-level patterns of group breeding, in collaboration with Drs. Veronica Doerr, Paul Sherman, Erik Doerr, Sam Flaxman, and David Winkler, I developed an integrated method designed to elucidate the process of group formation by identifying and then employing the cues and decision rules that individuals use when joining groups for understanding patterns of population-level variation in group breeding.  The ideas are contained in an empirical paper that analyzes group size variation as a function of nest-site selection (Safran, 2004) and a conceptual revision for studies of social breeding (Safran et al. 2007).

Our research on the dynamics of physiology and sexual signals is described in this current article in Trends in Ecology and Evolution.

Dynamics between Morphological Signals and their underlying Physiology

Dr. Rebecca Safran, Assistant Professor

University of Colorado at Boulder

Department of Ecology and Evolutionary Biology

CB334, Ramaley N395

Boulder, CO 80309

Office Phone :: (303) 735 - 1495