Population genetic structure of a three-host tick, Amblyomma dissimile, ineastern Venezuela

Patterns of genetic variation for the tick Amblyomma dissimile were analyze d from a total of 200 ticks collected on 12 toads (Bufo marinus), 14 snakes (Boa constrictor), and 8 lizards (Iguana iguana) at 11 localities. The ana lyses were performed on electrophoretic data from 8 isozyme loci. Mean hete rozygosity per locus was 6% (+/-3.1) per population. Differences in allelic frequencies among ticks from different individual hosts were the major sou rce of genetic variability in this study. Host species was a smaller source of genetic variation. Genetic distances between localities varied accordin g to which host species was present in each locality, and these appeared to be related to the extent of habitat overlap between host species. The smal lest genetic distances between samples from different host species were rec orded for I. iguana and B. constrictor. In contrast, the genetic distances between tick samples from B. marinus and either of the reptile species were significantly larger than between tick samples from this amphibian species . Ecological variables or the geographic distance did not explain the local patterns of differentiation observed in A. dissimile. Major genetic differ ences between island and mainland sites (0.03702) suggested an association between genetic distances and geographic isolation. The consistency between patterns of genetic variation and those of host home range overlap suggest s that host dispersion is the main force structuring the genetic variation within this tick species.