Meeting Abstract
P1.88 Friday, Jan. 4 Form and Function in the Avian Caudal Skeleton: A Phylogenetic Comparative Investigation FELICE, R.F.; Ohio University ryanfelice@gmail.com
The tail apparatus in birds serves an important role in aerial locomotion, assisting the wings by contributing to lift, stability, and maneuverability, as well as reducing whole-body drag. Previous research has indicated that tail feather morphology in many birds corresponds to flight behavior (i.e., long distance migrants have tails that reduce drag, increasing efficiency). This study examined how caudal skeletal morphology correlates with flight mode (e.g., flap, soar) in the diverse “waterbird” clade (e.g., Ciconiiformes, Pelecaniformes, Procellariiformes, Sphenisciformes). Caudal skeletal morphology was quantified in two ways. The dimensions (e.g., length, width and height of the centrum, neural spine, transverse process, and ventral process) of the free caudal vertebrae were characterized using linear metrics. Pygostyle shape was quantified using Elliptical Fourier Analysis (EFA). EFA is a geometric morphometric method used for analyzing shape variation in complex structures that have few clearly delineated homologous landmarks, like the pygostyle. Preliminary analyses indicate that waterbird taxa differ in free caudal vertebra morphology primarily in the relative size of the transverse process and ventral process. Pygostyle shape varies among taxa in anteroposterior elongation, pointedness, and dorsoventral orientation. However, there is not a significant difference in caudal skeletal morphology among flight mode groups. Phylogenetic relatedness has a significant effect on caudal skeletal morphology as tested using Multivariate Phylogenetic Eigenvector Regression. These results suggest that evolutionary history, rather than flight mode, explains caudal skeletal variation in waterbirds. Thus, whereas caudal integument varies among flight mode groups, the underlying skeletal system does not, suggesting that the integument may be more labile in the face of selective pressures than is the skeleton.
