Reproduction and sexual dimorphism in two populations of the polymorphic spiny lizard <i><scp>S</scp>celoporus minor</i> from <scp>H</scp>idalgo, <scp>M</scp>éxico

Abstract

Abstract Male‐biased sexual dimorphism is extensive in N ew W orld spiny lizards ( S celoporus : P hrynosomatidae) and is particularly prominent in the polymorphic minor lizard S celoporus minor . However, the possible relationship between patterns of sexual dimorphism and gonadal development is little known for most species. In this study, we explored aspects of sexual dimorphism in noncolor morphological traits in S . minor and characterized the gonadal cycle in males and females from each of two sites ( E l E nzuelado and L a M anzana) in H idalgo, M éxico, differing in key ecological aspects linked to life‐history trait expression in other lizards. Males were generally larger than females in each population and expressed larger forms of several other morphological traits, although not all comparisons attained statistical significance. Both sexes attained reproductive maturity at a larger size in E l E nzuelado relative to L a M anzana, and females from E l E nzuelado had larger litters. Gonadal cycles differed substantially between the two populations and suggest that reproductive activity of males and females was synchronous at E l E nzuelado and asynchronous at L a M anzana, an unusual pattern. Geographic variation in sex‐specific responses to environmental variables may be at least partly responsible for the exceptional species diversity of spiny lizards in M éxico.