Hemipenial Allometry in Anolis grahami
In animals with internal fertilization, the male genitalia often vary greatly, have complex morphology, and show fast rates of evolution. In studies of the evolution of such male genitalia, static allometric relationships have been used extensively. Static allometry is an intraspecific measure of proportional size of a particular structure with respect to the body size. We examined the static allometric pattern of the genitalia of two allopatric subspecies of a Jamaican Anolis lizard, Anolis grahami grahami and A. grahami aquarum, and compared our findings to observed patterns in nongenitalian traits: limbs and the dewlap. Limb and dewlap traits showed similar allometric slopes, with some variation in the intercept, whereas hemipenial traits showed different slopes. The hemipenial traits of Anolis g. grahami exhibited a statistically significant negative allometry, while A. g. aquarum showed slope values that were not statistically different from isometry. Our results corroborate the idea that genital traits evolve faster than other morphological body traits.Abstract
(A) Anolis grahami aquarum and (B) A. g. grahami. Photo credit: Brent Berger.
Hemipenis in sulcate view of A. g. grahami (MCZR-192575): (1) measure of hemipenial total length; (2) measure of hemipenial width at the lobes; and (3) measure of hemipenial width at the body.
Regressions of log-transformed traits vs. log-transformed body size (SVL): (A) dewlap; (B) thigh; (C) shank; (D) hemipenis total length; (E) hemipenis width at the lobes; and (F) hemipenis width at the body.
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