Reproductive strategies of ectoparasites on small mammals

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Abstract
A model of ectoparasitic reproductive strategies is presented. To be successful, an ectoparasite must either disperse to find a new host or stay on one host and produce its progeny during the lifetime of the host. Dispersion is facilitated by utilizing many host species and by waiting for the next host; these strategies prolong the generation time. Staying on the host is facilitated by shortening the generation time. Ectoparasites that repeatedly move on and off hosts are thus expected to have wide host preference spectra and long generation times while sedentary ectoparasites are expected to have narrow host preference spectra and short generation times. Population parameters of 27 ectoparasitic species (fleas, lice, mesostigmatic mites, and one ixodid tick species) on cyclic small mammal populations were investigated and a cluster analysis was performed. Three population parameters proved to be important and could be used to form a base for life-trait grouping of the ectoparasites: (i) the host preference spectra; (ii) the time lag between host and parasite peak abundance; and (iii) the intensity of the infestation. Three groups of ectoparasitic life traits were discernible: (i) species with narrow host preference spectra, no time lag (short ectoparasitic generation time), and major infestation: the Anoplura–Laelapinae group; (ii) species with moderate to wide host preference spectra, 1-year time lag (long parasitic generation time), and minor infestation: the Siphonaptera–Haemogamasinae group; (iii) one species, Ixodes trianguliceps, had moderate host preference spectrum, 2-year time lag, and moderate infestation. Ectoparasites, such as trombiculid mites and the tick Ixodes ricinus, which are not confined to small mammals, were missing or very rare on the cyclic small mammal populations. This was predicted by the model.