Hybridization, the breeding of two separate and distinct species, has the potential to merge two species into one when hybrids are fairly healthy, or keep the species separate when hybrids fare poorly. In western Panama, where the species ranges of the tropical shorebirds known as Northern Jacanas and Wattled Jacanas meet, they form a hybrid zone. Jacanas exhibit mating role reversal where females control access to mates by competing for territories encompassing a harem of males, and males provide all parental care. The unusual circumstance of hybridization between species with such a unique mating system offers a window into examining why and how species-specific boundaries to mating fail, from a female perspective. Genetic and experimental evidence suggests that differences in aggressive behavior between the species may explain patterns of hybridization. Females of the more aggressive species produce the majority of hybrid offspring. The proposed research employs techniques to assess the expression of genes to examine variation in aggressive behavior between the hybridizing species. This research addresses a fundamental question in ecology, evolution, and behavior what is the genetic basis of behavioral differences? This can 1) improve our understanding of the behavioral mechanisms important in species formation, and 2) provide insight into the genetic mechanisms underlying behavioral differences between males and females. Understanding of science and research will be communicated through workshops with local school aged children and ecotourists at the Panamanian field site.
Between recently diverged species, mating behavior can either impede or promote reproductive isolation. Theoretical and empirical evidence demonstrates this for female mate choice and male competition, but little is known about the relative roles of each. Female aggression has only recently been recognized as an adaptive behavior, and how its underlying mechanisms compare to those of males is not well understood. A key step towards understanding the evolutionary significance of the competitive phenotype in females is determining its underlying genomic mechanisms. The goal of the proposed research is to elucidate the molecular basis of the female competitive phenotype by identifying clusters of candidate genes whose differential expression is responsible for consistent variation in aggressive behavior. This study combines aggression assays with a transcriptomic approach to address this question in role reversed, hybridizing Northern Jacanas (Jacana spinosa)and Wattled Jacanas (J. jacana) in Central America. This project is novel with respect to understanding the mechanisms by which phenotypes change as role reversed species diverge, which could advance our understanding of how organisms respond and adapt to changing environmental selection. By identifying how the genes underlying aggression are differentially expressed between role reversed females and males, the proposed research will expand upon general principles in sexual selection theory that have been developed in well-known male-dominant systems. Furthermore, this project investigates the genetic underpinnings of complex behavioral traits in wild, free-living, non-model organisms, which is vital for understanding the evolution of ecologically relevant phenotypes under natural conditions.
