SREL Reprint #1863
BEHAVIORAL AND MORPHOLOGICAL
CORRELATES OF HETEROCHRONY IN
HISPANIOLAN PALM-TANAGERS
MARA A. McDONALD
Department of Zoology, University of Florida, Gainesville, FL 32611 and
University of Georgia-Savannah River Ecology Laboratory, P. 0. Drawer E, Aiken, SC
29802
MICHAEL H. SMITH
University of Georgia-Savannah River Ecology Laboratory, P. 0. Drawer E, Aiken, SC
29802
Abstract. We documented the occurrence of heterochrony for morphological
and behavioral characters in two species of Hispaniolan Palm-Tanager.
Phaenicophilus palmarum is age-dimorphic in morphology and foraging
behavior with 55% (n = 126) of specimens classified as juveniles. Juveniles
differed from adults of their own species in five of eight foraging variables,
average flight distance during a foraging bout, foraging height, use of broadleaf
instead of pine substrates, and the presence of a gray instead of black crown.
Phaenicophilus poliocephalus have gray crowns similar to those of P.
palmarum juveniles and do not differ significantly from them for any of the eight
foraging variables measured, choice of substrate, or average flight distance. They
do differ from adult P. palmarum for four of eight foraging variables, average
flight distance, and use of substrates. Phaenicophilus poliocephalus lacks a
significant age-dimorphism in all behavioral and morphological characters
measured. We classified only 15% (n = 66) of the specimens examined as
juveniles based on morphology. This species tends to form groups of four to six
individuals in the non-breeding season, in contrast to P. palmarum occurring
singly or in pairs. Phaenicophilus poliocephalus is also smaller than adult P.
palmarum for seven of 11 size-related features. We assessed the degree of
gene flow across the narrow hybrid zone we documented and concluded, based
on morphological variance analysis, that there was little introgression. The
resemblance of P. poliocephalus to juvenile P. palmarum in general
morphology and behavior, their smaller body size, and the increased tendency to
form groups is consistent with a paedomorphic derivation of P. poliocephalus
from P. palmarum.
Keywords: Age-dimorphism; foraging behavior; heterochrony, -Hispaniolan
Palm-Tanagers; morphology,- paedomorphosis; progenesis.
SREL Reprint #1863
McDonald, M.A. and M.H. Smith. 1994. Behavioral and morphological correlates of heterochrony in Hispaniolan Palm-Tanagers. The Condor 96:433-446.
