The Fight for Space: Exploring the Role of Competition and Physiological Tolerance in Limiting Elevational Distributions and Structuring Communities in Tropical Birds

PhD Dissertation, Andy Boyce

I am conducting an observational and experimental study to investigate the importance of competition and physiology in limiting species distributions. Groups of closely-related species with abutting, non-overlapping elevational ranges are key components of biodiversity and endemism in the tropics and have been documented across taxa (Cadena et al. 2011). However, the mechanisms underlying this pattern are poorly understood. I will perform playback to determine the degree to which pairs of species compete and possible limit each other’s ranges. I am also measuring physiological tolerance to temperature among closely-related species that exist at different elevations to determine if adaptation to a particular range of temperatures could limit the elevations at which a given species could persist. Additionally, I will be examining phylogenetic community structure across elevationally stratified bird communities. Phylogenetic community structure, or the degree to which species in a community are related to one another, is thought to reflect the relative importance of interspecific competition and environmental filtering in a given community (Losos 1996, Webb 2000, Graham 2009).  

I am currently in the midst of my fourth field season at Kinabalu Park on the island of Borneo. The bulk of my fieldwork at the moment is continuing to gather physiological data on a broad array of species in the lower reaches of the park after having completed  similar work at high elevation. I am also continuing point counts and playback experiments around park headquarters to bolster those datasets. Two side-projects have also cropped up – 1) Working with Dr. Rob Fleischer and the Smithsonian Conservation Genetics lab to examine gene flow on both spatial and elevational gradients, and 2) Gathering metabolic data at a second field site (Arizona) to facilitate comparisons between metabolic rates of tropical and temperate birds.