Individual variation in an ectoparasite-host system

Ondertitel:life history, fitness and evolutionary potential

Parasites and hosts are dynamic interactions exerting reciprocal selective pressures. Thus, host-parasite interactions are ideal systems for the study of ecological and coevolutionary processes. However, while the effects of parasites on hosts have been extensively investigated, host-induced parasite evolution and parasite life history have been neglected. In particular, knowledge on the amount of among- and within-individual variation between parasite traits is mostly unknown despite its fundamental importance to understand parasite performance and evolution. In this dissertation, I report four experimental studies investigating several aspects of parasite individual variation in a tick-songbird system, namely the bird-specialized tree-hole tick Ixodes arboricola and its main host, the great tit Parus major. First, I investigated the behavioural preferences for tick attachment sites on the host body. Experiments were carried out using three tick species differing in ecology and host specificity both with and without grooming restrictions. The experimental findings as well as the literature evidence suggest that ticks prefer to attach to the host head and actively move to this area. I hypothesize that this pattern is consistent throughout ixodid ticks feeding on birds. Second, I report how fundamental life-history traits affect individual tick success at every stage, and estimate their phenotypic and genetic correlation between and within stages as well as the trait evolutionary potential (using animal models) for feeding time, engorgement weight, moulting time, and number of hatched eggs. Additionally, I account for the effect on the abovementioned traits of tick sex, maternal effect, host identity, fasting time and batch. Results suggest differences in tick individual quality, for which engorgement weight seems to be a good proxy. Third, I report a study investigating variation and heritability of host quality from the parasite perspective. Here, I measured to what extent hosts can affect tick performance and life history of larvae and nymphs both on- and off-host. I show that host individual characteristics significantly influenced larva and nymph attachment success. Additionally, hosts had an heritable effect on tick feeding time and, to a lower extent, on several other traits and success parameters. Lastly, I investigated whether I. arboricola males prefer to mate with heavier engorged females in order to obtain a higher fitness. Surprisingly, male mate choice experiments carried out in two different setups showed a lack of preference for heavier females. However, males seem to remember and avoid the mating partners they previously met.

Jaar van publicatie:2022

Trefwoorden:Doctoral thesis

Toegankelijkheid:Open