PARULID HINDLIMB MYOLOGY AND NICHE UTILIZATION

FRANKLYN WAYNE COMMISSO, Fordham University

Abstract

The analysis of parulid warbler pelvic appendicular myology demonstrates an amount of variation between species sufficient to indicate how this body system has aided the adaptive radiation into three or more niche types typified by the genus Seiurus as a ground dweller, the genus Mniotilta as a bark creeper, and the genus Wilsonia as an aerial Flycatcher.^ Seven parulid species were selected for examination, captured by mist-netting, filmed, and placed in myological preservative. Observations of behavior and locomotion in the field were correlated with movement patterns on film. Dissection of the thirty-two important leg elements demonstrated variation in eight important pelvic and leg muscles: Mm. iliotrochantericus posterior, femorotibialis internus, biceps femoris, ischiofemoralis, obturator externus, peroneus longus, and the flexores perforans et perforatus digiti III and II in terms of increase or decrease in fiber length, mass, and cross-sectional area.^ Ancillary evidence was examined in terms of caudal myology, bone ratios, and foot pads, folds, and papillae. Correlations were made to tail-wagging in Seiurus, spreading in Setophaga, and use of the tail as a rudder in hawking. The use of the tail as a brace in Mniotilta is negated. Shortened upper bone ratios are noted for the walking terrestrial forms and enlarged digit ratios are noted for the scansorial foot of Mniotilta. The planter folds are discussed as reduced pads in perching forms and the friction-generating nature of the papillae is examined.^ Biomechanical analysis of foraging positions is presented using free-body diagrams and the differences in two- and three-joint muscle systems are explained. The evolution of fiber pinnation for increased power is examined and nine muscles demonstrating significant fiber pinnation are analyzed. There are Mm. iliotrochantericus posterior, femorotibialis internus, biceps femoris, ischiofemoralis, obturator externus, peroneus longus, flexores perforans et perforatus digiti III and II, and flexor hallucis brevis. Eight of these were muscles exhibiting morphological variation as well.^ All pelvic musculature data was examined statistically and using mean, standard deviation, correlation coefficient, coefficient of variability, and multiple correlation analysis parallels were drawn for significant evolutionary trends. Synergs and aponeurotic musculature demonstrate the greatest tendency to vary directly.^ An analysis of the literature pertaining to parulid ecology reinforces the principle of adaptive radiation by competitive exclusion. The generalist type exemplified by Dendroica coronata is restricted to the spruce forest and typifies insectivorous and frugivorous feeding in the central portions around the larger branches of trees. The speculations in literature concerning a close relationship to Setophaga ruticilla is confirmed by myological parallels with some modification for flycatching, bill-snapping, and beating of prey. Hybrid reports of both Mniotilta and Seiurus noveboracencis with Dendroica indicate a close relationship with modifications for scansorial feeding and aquatic habitat locomotion respectively. Wilsonia is assumed to be a more specialized aerial flycatching form with few myological modifications and Geothylypis is presented as the most aberrant in terms of myology, foot pads, bone ratios, and foraging position. The feeding from a perch on a directly vertical stem necessitates rotational modifications to overcome gravitational and substrate torque vectors unlike that in any other species. ^

Subject Area

Zoology

Recommended Citation

COMMISSO, FRANKLYN WAYNE, "PARULID HINDLIMB MYOLOGY AND NICHE UTILIZATION" (1981). ETD Collection for Fordham University. AAI8111312.
https://fordham.bepress.com/dissertations/AAI8111312

Share

COinS