Cuticular hydrocarbon composition, phenotypic variability, and geographic relationships in allopatric populations of Amblyomma variegatum (Acari: Ixodidae) from Africa and the Caribbean.

Gas chromatography of cuticular hydrocarbons is used to determine the degree of genetic similarity and heterozygosity among 20 populations of Amblyomma variegatum (F.) collected from Africa and the Caribbean. Twenty-one compounds were detected in at least 90% of the specimens studied; another 57 hydrocarbons were detected in a variable number of specimens, ranging from 50 to 90% of all ticks extracted. Visual inspection of chromatograms revealed prominent differences in the relative abundance of hydrocarbons among the populations. Average heterozygosity was unexpectedly high (41.61%), whereas the average genetic identity among all populations was 0.8397. Principal components analysis for the relative amounts of several compounds did not provide adequate separation of populations according to geographical origin. Our data suggested that A. variegatum ticks are rapidly evolving and, while using several separate pathways, are sharing an undifferentiated genetic pool and retaining features that are typical for each population cluster.