Within-population Variation in Free-living Adult and Ectoparasitic Larval Trombiculid Mites on Collared Lizards

We quantified within-population variation in the seasonal abundance of free-living adult trombiculid mites and infestation of collared lizards by parasitic mite larvae at the Arcadia Lake Dam in Edmond, OK, U.S.A. Lizards on one of two habitat patches (front) harbored many more larval mites, and were more rapidly re-infested after mites were removed experimentally. Although female and male lizards and males displaying alternative social tactics had different activity rates, they harbored similar numbers of parasites, which is inconsistent with the hypothesis that the degree of ectoparasitism is positively related to host activity. Heavy mite infestation of front patch lizards was related to greater exposure to vegetation/soil surrounding this habitat patch, and perhaps more favorable physical conditions there for mite reproduction and development. The abundance of free-living adult mites on the rock substrata occupied by collared lizards was temporally dissociated from infestation of lizards by mite larvae. Free-living adult mites were abundant in May, but declined precipitously in June shortly after larvae began to appear on lizards. Larval parasites remained until lizards entered hibernacula in late summer. There was no effect of marked differences in larval mite load on any of the behavioral, and most of the life-historical variables that we measured. The exception was growth rate. First-year males grow faster than any of the other social classes in this population, and their rates were reduced on the front habitat patch suggesting a growth cost of heavy parasitism at a time when lizards exhibit maximal growth.