Investigation genetic diversity of Ixodes ricinus based on four microsatellite loci

Abstract

Ixodes ricinus belongs to Ixodes ricinus complex composed of 14 species of ticks distributed worldwide and the most widely spread tick species in Europe I. ricinus is a major ixodid tick, involved in the transmission of a number of diseases to animals and humans in Eurasia. Genetic diversity of these tick populations may have implications on disease transmission. In order to investigate genetic diversity and to characterize the genetic structure of I. ricinus populations in the Baltic countries microsatellite markers described in literature were used. A total of 180 ticks (170 I. ricinus and 10 I. persulcatus) collected from 18 locations in Lithuania, Latvia and Estonia were examined based on four polymorphic microsatellite loci. Genetic diversity of six I. ricinus populations from Lithuania (n  =  60), Latvia (n  =  60), and Estonia (n = 60) were compared. The number of observed alleles between loci ranged from 5 to 11. Observed heterozygosities were lower than expected at most loci. Mean estimates of expected heterozigosities (He) over loci and populations varied from 0.621 to 0.800, and observed heterozygosity (Ho) from 0.304 to 0.634. F statistics were calculated to analyze the differences between observed and expected heterozygosities, and to obtain genetic distances between populations. Two loci deviated significantly from Hardy-Weinberg equilibrium. However, the highest observed heterozygosity (Ho) was found in coastal locations and lowest - in continental parts, which shows the importance of birds as hosts to tick population structure.