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.

Differential effects of environmental climatic variables on parasite abundances in blue tit nests during a decade

Models on climate change have predicted an increase of temperature over the earth’s surface with potential drastic effects on living organisms.We analyzed the relationships between climatic conditions(temperature,rainfall,and wind speed)and the abundance of blood-sucking flying insects(biting midges and blackflies)and nest-dwelling ectoparasites(mites,fleas,and blowflies)collected from blue tit nests during bird breeding seasons for a period of 10 years.Average temperature,rainfall,and wind speed showed significant differences among years.Temperature and wind speed increased during the period of study while rainfall decreased.Biting midge,blackfly,and blowfly abundances increased across years but not flea and mite abundances.Hatching date decreased and brood size increased across years.Independently of year variation,parasites were related to climatic variables.For example,biting midge,blowfly,mite,and flea abundances were positive and significantly related to average temperature.We also found a positive and significant relationship between abundances of Haemoproteus infections and biting midge abundances during the first year of life of birds out of nests.However,abundance and prevalence of Lankesterella infections in yearlings were positive and significantly related to mite abundances during the year of birth of birds.Leucocytozoon and Lankesterella infections were also significantly related to climatic variables and Haemoproteus and Lankesterella infections increased across years.In addition,body condition of adult females and males were negatively related to flea larvae and blowfly abundance respectively.Nestling body condition was also negatively related to biting midge abundance.Changes in climatic conditions across years could therefore affect several parasites of birds but also to birds themselves.

Manipulation of parasite load induces significant changes in the structural-based throat color of male iberian green lizards

The honesty of structural-based ornaments is controversial. Sexual selection theory predicts that the honesty of a sexual signal relies on its cost of production or maintenance. Therefore, environmental factors with negative impact on individuals could generate high costs and affect the expres- sion of these sexual signals. In this sense, parasites are a main cost for their hosts. To probe the effect of parasites on the structural-based coloration of a lacertid species Lacerta schreiberi, we have experimentally removed ticks from a group of male Iberian green lizards using an acaricide treatment （i.e., the broad-use insecticide fipronil）. All individuals were radio-tracked and recaptured after 15 days to study changes in coloration in both the ultraviolet （UV）-blue （structural-based） and UV-yellow （structural and pigment-based） ornamentations after manipulation, as well as changes in endoand ectoparasitic load and body condition. Additionally, after the experiment, we measured the skin inflammatory response to a mitogen. The fipronil treatment was effective in reducing ticks and it was associated with a significant reduction of hemoparasite load. Throughout the season, individuals treated with fipronil tended to maintain the brightness of the UV-blue throat coloration while control lizards tended to increase it. However, individuals treated with fipronil that were not infected with hemoparasites significantly reduced the brightness of the UV-blue throat color ation. Individuals with a higher initial tick load exhibited a lower UV saturation increment （UV-blue） and a higher brightness increment （UV-yellow） during the experiment. Overall these results experimentally support the idea that parasites adversely influence the expression of the structural-based coloration of male Iberian green lizards. This adds evidence to the hypothesis that sexual ornaments in lizards function as honest signals.