The Role of Heritable and Dietary Factors in the Sexual Signal of a Hispaniolan Anolis Lizard, Anolis distichus

Abstract

The diversity of sexual signals is astounding, and divergence in these traits is believed to be associated with the early stages of speciation. An increasing number of studies also suggest a role for natural selection in driving signal divergence for effective transmission in heterogeneous environments. Both speciation and adaptive divergence, however, are contingent on the sexual signal being heritable, yet this often remains assumed and untested. It is particularly critical that the heritability of carotenoid-based sexual signals is investigated because such traits may instead be phenotypically plastic indicators of an individual's quality that exhibit no or little heritable variation. We present the first study to investigate the relative contribution of genetic and environmental factors to the striking diversity of dewlap color and pattern in Anolis lizards. Using a breeding experiment with Anolis distichus populations exhibiting different dewlap phenotypes, we raise F1 offspring in a common garden experiment to assess whether dewlap color is inherited. We follow this with carotenoid supplementation to investigate the influence of dietary pigments to dewlap color variation. We find significant differences in several aspects of dewlap color and pattern to persist to the F1 generation (fathers: N = 19; F1 males: N = 50; P < 0.01) with no change in dewlap phenotype with carotenoid supplementation (N = 52; P > 0.05). These results strongly support that genetic differences underlie dewlap color variation, thereby satisfying a key requirement of natural selection. Our findings provide an important stepping-stone to understanding the evolution of an incredibly diverse signal important for sexual selection and species recognition.