Natural parasites in conjunction with behavioral and color traits explain male agonistic behaviors in a lizard

Male competition conforms to a cost-benefit model,because while aggression may increase reproductive prospects,it can also increase the risk of injury.We hypothesize that an additional cost in aggressive males would be an increase in parasite load associated with a high energy investment into sexual competition.Some of these infections,in turn,may downmodulate the level of host aggression via energetic trade-offs.We staged dyadic male contests in the lab to investigate the relationships of multiple parasites with the agonistic behavior of lizard hosts,Sceloporus occidentalis.We also included both color and behavioral traits from opponents in the analyses because(1)color patches of lizards may serve as intraspecific signals used by conspecifics to assess the quality of opponents,and(2)contests between male lizards fit classical models of escalated aggression,where lizards increase aggression displays in response to an opponent's behavior.The results conform to our hypothesis because male lizards displayed more pushups when they had more ticks.Moreover,some parasites may modulate the levels of aggression because lizards infected by hematic coccidians performed fewer pushups.Interestingly,lizards also displayed fewer pushups when both the chroma and size of the opponent's blue patch were greater.The results thus also supported the role of the blue patch of s.occidentalis as a sexual armament,because it contributed to the deterrence of aggression from opponent lizards.We revealed that natural parasitic infections in lizard hosts can contribute to their agonistic behavior.We encourage future studies to account for parasites in behavioral testswithlizards.

Multiple color patches and parasites in Sceloporus occidentalis:differential relationships by sex and infection

Parasites generally have a negative influence on the color expression of their hosts.Sexual selection theory predicts resistant high-quality individuals should show intense coloration,whereas susceptible low-quality individuals would show poor coloration.However,intensely colored males of different species of Oid and New World lizards were more often infected by hemoparasites.These results suggest that high-quality males,with intense coloration,would suffer higher susceptibility to hemoparasites.This hypothesis remains poorly understood and contradicts general theories on sexual selection.We surveyed a population of Sceloporus occidentalis for parasites and found infections by the parasite genera Lankesterella and Acroeimeria.In this population,both males and females express ventral blue and yellow color patches.Lankesterella was almost exclusively infecting males.The body size of the males significantly predicted the coloration of both blue and yellow patches.Larger males showed darker (lower lightness)blue ventral patches and more saturated yellow patches that were also orange-skewed.Moreover,these males were more often infected by Lankesterella than smaller males.The intestinal parasite Acroeimeria infected both males and females.The infection by intestinal parasites of the genus Acroeimeria was the best predictor for the chroma in the blue patch of the males and for hue in the yellow patch of the females.Those males infected by Acroeimeria expressed blue patches with significantly lower chroma than the uninfected males.However,the hue of the yellow patch was not significantly different between infected and uninfected females.These results suggest a different effect of Lankesterella and Acroeimeria on the lizards.On the one hand,the intense coloration of male lizards infected by Lankesterella suggested high-quality male lizards may tolerate it.On the other hand,the low chroma of the blue coloration of the infected males suggested that this coloration could honestly express the infection by Acroeimeria.