Isolation and characterization of new polymorphic microsatellite markers for the tick Ixodes ricinus (Acari, Ixodidae)

Nine microsatellite markers were isolated from unfed larvae of Ixodes ricinus and were tested on two populations of nymphs collected on roe deer (N=21) and birds (N=39) in a French suburban forest. All markers were polymorphic, with limited evidence for deviations from linkage equilibrium. In accordance with previous markers developed for this species, we found large heterozygote deficits for six of the nine loci. Deficits were of the same order of magnitude within a tick infrapopulation, suggesting that population-level estimates were not due to a Wahlund effect among individual hosts, but more likely to technical problems (i.e., null alleles due to mutations in the flanking regions of the microsatellites). Although micro-geographic substructure (e.g., homogamy within infrapopulations) can not be ruled out, it is possible that null alleles could be an inherent problem associated with this tick species and specific genome-level studies are called for. Despite the possible presence of null alleles, the precision of population genetic estimates was improved by the addition of the newly-developed markers making them a useful addition for studying the population ecology of I. ricinus.