Aggressive sexual behaviour and spatial distribution of the polymorphic lizard Sceloporus minor (Squamata: Phrynosomatidae) from Central Mexico

Intrasexual polychromatism has generally been linked to alternative reproductive and ecological tactics, where different morphs may exhibit differences in their behavioural, morphological, physiological, ecological, and life history characteristics. Therefore, these differences might favour the fitness of a certain morph over others. If multiple morphs are able to persist in the population however, they must have had similar fitness levels over a long period of time. This balance can be achieved via two processes: niche partitioning and negative frequency-dependent selection. The present study describes the aggressive sexual behaviour of the lizard Sceloporus minor and evaluates its possible relationships to ecological and behavioural aspects of two different male morphs (yellow and red) in a population from central Mexico. The results reveal that both the yellow and the red morphs are territorial. The home range (HR) of yellow males was 17 times larger than that of females, whereas the HR of red males was 13 times larger than that of females; however, there was no significant difference in HR size between morphs. Spatial distribution analysis indicated a pattern of regular distribution for adult S. minor. Our results also demonstrated that red males had more females within their HRs than yellow males had; however, yellow males were more aggressive than red males. In addition, both red and yellow morphs were similar in some other behavioural, ecological, and morphological traits, disproving the hypothesis that morphs in this population are maintained by niche partitioning. This leaves open the possibility that frequency-dependent selection maintains the polychromatism in this population.