No evidence of male-biased sexual selection in a snake with conventional Darwinian sex roles: Lack of Sexual Selection in Rattlesnakes

Decades of research on sexual selection have demonstrated that 'conventional' Darwinian sex roles are common in species with anisogamous gametes, with those species often exhibiting male-biased sexual selection. Yet, mating system characteristics such as long-term sperm storage and polyandry have the capacity to disrupt this pattern. Here, these ideas were explored by quantifying sexual selection metrics for the western diamond-backed rattlesnake (Crotalus atrox). A significant standardized sexual selection gradient was not found for males (β SS = 0.588, p = 0.199) or females (β SS = 0.151, p = 0.664), and opportunities for sexual selection (I s) and selection (I) did not differ between males (I s = 0.069, I = 0.360) and females (I s = 0.284, I = 0.424; both p > 0.05). Furthermore, the sexes did not differ in the maximum intensity of precopulatory sexual selection (males: s′ max = 0.155, females: s′ max = 0.080; p > 0.05). Finally, there was no evidence that male snout-vent length, a trait associated with mating advantage, is a target of sexual selection (p > 0.05). These results suggest a lack of male-biased sexual selection in this population. Mating system characteristics that could erode male-biased sexual selection, despite the presence of conventional Darwinian sex roles, are discussed. © 2020 The Authors.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu