Assortative mating in Ixodes scapularis Say, 1821 (Acari: Ixodidae).

Mate choice influences levels of inbreeding and genetic diversity in natural populations. Positive assortative mating (PAM), for instance, has been described in Ixodes ricinus L., but this behavior has yet to be investigated in the closely related Ixodes scapularis Say, 1821. By analyzing nine microsatellite loci of 30 females and 30 males removed in copula from hunter-harvested deer specimens at the Savannah River Site (South Carolina) during the hunting season of fall 2010, we found a weak but significant assortative pairing signature in a population that, otherwise, appeared genetically homogeneous. This indicated that in spite of a low average relative relatedness between members of the same pair, the difference between observed and all other possible male-female pairs was highly significant. The results suggested that our non-coding microsatellite loci were drafted by genes coding for PAM, through genetic hitchhiking. To explain our data, such genes would need to be homogeneously distributed in the genome and span from a few genes with major effects on PAM to many genes with moderate or weak effects on PAM.