Cryptic female choice mediated by oviductal fluid in a model lizard

Abstract

Cryptic female choice (CFC) involves female-mediated morphological, behavioral, or physiological mechanisms that bias fertilization toward the sperm of specific males. Therefore, the sperm of certain notype. Female reproductive tract fluids offer significant potential for CFC, for instance by modifying sperm swimming performance. Moreover, the temperature of pre-fertilization environments to which the sperm cells are exposed can have many fundamental effects on sperm performance. Tropidurus spinulosus, the spiny lava lizard, is a suitable ectotherm model for studying CFC in relation to temperature because reproductive individuals have specific thermal requirements according to their preferred temperatures. Furthermore, due to the fact that color ornamentation is highly male-biased and it is related to male reproductive potential, we hypothesized that male color might be a cue over which the fluid of the reproductive female tract acts. We also predict that temperature might influence CFC patterns. We found that reproductive female fluid enhanced sperm velocity of males with high yellow extension in their flanks at the species' preferred temperature, however, when temperature increased, sperm velocity did not vary among males. These results suggest that females exert CFC mediated by reproductive fluid discriminating among color phenotype of males and that environmental temperature is an important factor. Postcopulatory selection on male phenotype and environmental factors adds complexity to the sexual selection scenarios.