H. Griffith, BODY ELONGATION AND DECREASED REPRODUCTIVE OUTPUT WITHIN A RESTRICTEDCLADE OF LIZARDS (REPTILIA, SCINCIDAE), Journal of zoology, 233, 1994, pp. 541-550
Relationships between body shape and relative abdominal size were comp
ared among differentially elongate species within the scincid lizard g
enus Brachymeles, to investigate how morphological evolution affects t
he proportion of body volume available to hold eggs and offspring. Rel
ative abdominal size is inversely related to elongation, suggesting th
at relative clutch mass decreases with addition of abdominal body segm
ents. Shape-volume relationships contradict trends seen in comparisons
among distantly related limbed and limbless squamates (lizards and sn
akes), in which snakes have relatively more abdominal volume. Comparis
on within a phylogenetically restricted group allows the identificatio
n of functional and ontogenetic factors potentially limiting reproduct
ive output. In Brachymeles, constraining factors include retention of
anterior body segments bearing parasternal ribs, which prevents extens
ion of the clutch anteriorly within the body, and reduction of allomet
ry of abdominal segments, which provides extended series of uniformly-
sized vertebrae for limbless locomotion, but reduces the relative size
of the abdomen. The latter trait is associated with overall size redu
ction, which affects relative egg-size and packing. Factors constraini
ng abdominal volume in this genus are probably common to other elongat
e lizards, a morphological group that has been rarely represented in c
omparative studies of life history.