A phylogenetic analysis of cooperative breeding in the class Aves

Much of the research on avian cooperative breeding has examined how current ecological factors maintain the behavior. Understanding the evolution of breeding systems provides an additional picture of the ecological factors related to the origin of cooperative breeding. Edwards and Naeem (1994) have previously suggested that the complex behavior of cooperative breeding evolves with difficulty, yet is easily lost in subsequent evolution. I examined the basic pattern of transitions between cooperative and non-cooperative breeding lineages using a variety of character coding assumptions. I tested for a transition bias between these two breeding systems. I found cooperative breeding origins to be more prevalent than losses on the phylogenetic tree. My results at the family level suggest a pattern contrary to the opinions of Edwards and Naeem.