Heritable variation in host quality as measured through an ectoparasite's performance

Obligate parasites need one or more hosts to complete their life cycle. However, hosts might show intraspecific variation in quality with respect to the parasites themselves, thus affecting on-host and off-host parasite performance. High heritability in host quality for the parasite may therefore exert long-lasting selective pressures on the parasite and influence host–parasite coevolution. However, the amount of variation and heritability in host quality are unknown for most parasite species, especially in wild populations of hosts. Both measures were estimated in a wild-caught bird Parus major that was experimentally infested by two developmental stages (larva and nymph) of a ectoparasite (the tick Ixodes arboricola). We examined variation in host quality through variation in tick performance, namely the on-host performance (attachment success, feeding time, engorgement weight and feeding success) and the off-host performance (moulting time, moulting success and overall survival). He...