The effect of miniaturization on the evolution of sexual size dimorphism in geckos.

Abstract

The evolution of miniaturization can result in dramatic alterations of morphology, physiology, and behavior; however, the effects of miniaturization on sexual dimorphism remain largely unknown. Here we investigate how miniaturization influences patterns of sexual size dimorphism (SSD) in geckos. Measuring 1,875 individuals from 131 species, we characterized patterns of SSD relative to body size across two families. We found that miniaturized species were more female biased than non-miniaturized species. Additionally, one family that contained many miniaturized species (Sphaerodactylidae) displayed allometric patterns in SSD with body size, where larger species were male biased and smaller species were more female biased. Smaller species in this lineage also produced proportionally larger eggs. By contrast, another family containing few miniaturized species (Phyllodactylidae) displayed a more isometric trend. Together, these observations are consistent with the hypothesis that selection for increased reproductive success in small species of Sphaerodactylidae results in female-biased SSD in these taxa, which in turn drives the positive SSD allometry observed in this lineage. Thus, selection for increased miniaturization in the clade may be offset by selection on maintaining a female size in smaller taxa that ensures reproductive success.