Dr. Bledsoe's research focuses on two basic areas:
- The reconstruction of avian phylogenies through analysis of molecular and morphological data
- The use of estimates of phylogeny to gain insight into the ecology and biogeography of birds and basic mechanisms of evolutionary change.
The central goal of the work is to provide the historical framework necessary for analysis of the causal mechanisms responsible for the generation of avian diversity and ecological, anatomical, and geographic variety. A related goal involves contributions to the theory of systematics, particularly with regard to testing historical hypotheses about phylogeny and adaptation.
The term "phylogeny" refers to the historical pattern of branching of lineages through the process of speciation. Often represented in tree form, phylogenies provide hypotheses about evolutionary relationships between taxa and evolutionary transformations in anatomy, macromolecules, behavior, and ecology. My current work focuses on the use of cladistic analysis to infer the phylogeny of two important groups of Neotropical passerine birds: the ovenbirds (Furnariinae) and the tapaculos (Rhinocryptidae). The bulk of the data for these projects is obtained by anatomical dissections of the hindlimb locomotor apparatus, supplemented with behavioral and molecular data. Data obtained by anatomical comparisons in addition shed light on locomotor adaptations, which are diverse in the group of birds to which the ovenbirds and tapaculos belong.
A related interest deals with the extent of within-species variation in locomotor traits, and the degree to which that variation causes potential problems in phylogenetic inference. Current work focuses on one genus of the scansorial (woodpecker-like) birds known as woodcreepers. In members of this genus (Dendrocincla), many hindlimb tendons are converted into bone, and the pattern of conversion is highly variable within-species. This work serves as one avenue into the study of the mechanistic basis of evolutionary change, discussed below.
Causal mechanisms and evolutionary diversification
Phylogenies provide the historical framework within which to study causal mechanisms. My work in this area focuses on the concept of key innovations and their possible relationship to patterns of species diversity among clades, as well as on the role (or lack thereof) that natural selection plays in the process of evolutionary loss. The key innovation work currently involves the use of null models to analyze the levels of species diversity found in passerine birds and their relatives. The evolutionary loss work takes advantage of a phylogeny of the woodcreepers, previously published by my close colleague and collaborator, Robert Raikow, combined with information on within-species variation in evolutionary loss in genus Dendrocincla, to test competing selection and drift hypotheses about the possible mechanisms that give rise to loss.