COLLABORATIVE RESEARCH: Understanding how a Hormone-signaling Pathway Modulates Behavioral Phenotype within a Social Network

Smithsonian Institution, Washington DC

Investigators

Abstract

Social networks are a common characteristic of most animal societies. While we know that individual differences in behaviors such as cooperation or aggression influence the role that individuals play within their social network, we know little about the physiological mechanisms underlying those differences. Wire-tailed manakins provide a model system to study the links between hormones, behavior and social networking because males form cooperative partnerships that are the foundation of complex social networks. Using this model system this research will integrate evolutionary, behavioral, endocrine and neurogenetic approaches to understand the physiological and evolutionary basis of individual variation in cooperation and how those individual-level processes scale up to influence an individual's role and position within their social network in a dynamic fashion. Because endocrine function is similar across a wide variety of animals, the outcomes of this work will be broadly applicable. The project will train at least 16 undergraduate students and 1 graduate student in integrative research in the US and at the field site in Ecuador. This research will also be featured in a planned exhibit which will describe the hormonal basis of social behavior and highlight the similarities between human and animal social networks at the National Zoological Park's Amazonia Science Gallery. Research products will be integrated in to tropical ecology courses at the Tipunti Biodiversity Station which hosts the work in Ecuador. This project is jointly supported by the Animal Behavior Program and International Science and Engineering. This project will link hormone-regulatory networks and social networks to transform our understanding of how the endocrine system regulates behavior and influences social dynamics at the individual and population levels. The project will test two alternative hypotheses for how selection has shaped the evolution of hormone-mediated social behaviors involving testosterone: the phenotypic integration hypothesis and the phenotypic independence hypothesis in wire-tailed manakins where males cooperate to perform mating displays on a lek. This highly integrative project will quantify male behaviors in nature (dominance, cooperation, display rate), use nanotags and proximity data loggers to capture all the social interactions and map the social network, measure circulating hormone levels across the year, describe the maximum capacity for testosterone production in males of different status using GnRH challenges, measure the effect of social intrusion on hormone titers, block or increase hormone titers to manipulate phenotype, and measure expression levels of candidate genes for steroidogenic enzymes, steroid receptors and steroid influenced peptide signaling systems in the brains of these males using RT-qPCR. These data from individual birds will then be combined to examine network structures using binary and weighted models and to examine the influence of hormones on network structure and dynamics. All data from the study will be archived at the Smithsonian Migratory Bird Center web site (http://www.si.edu/smbc). The brain transcriptome assembly for the wire-tailed manakin will be posted on NCBI GenBank.