Genetic and morphological variation in three snow pool Aedes mosquito species of the subgenus Ochlerotatus (Diptera : Culicidae)

Thirteen Aedes hexodontus Dyar populations from throughout the western Unit ed States were examined for genetic and morphological variation. Analysis o f allozyme frequencies at 16 loci revealed a pattern of, genetic variation that formed a north-south cline across Washington, Oregon, and California i n the number of alleles per locus, the percent of polymorphic loci, and the frequency of one allele of aconitase-1. Comparison of the genetic profile of Ae. hexodontus populations to two other widely distributed members of th e punctor subgroup, Aedes punctor (Kirby) and Aedes abserratus (Felt & Youn g), revealed only one diagnostic locus for all three species. Seven loci ex hibited frequency differences among species but were not diagnostic. Morpho logical characters also exhibited little variation within and among the thr ee species. The adult females differed only in the scaling of the probasist ernum. This area was extensively scaled in 91% of Ae. hexodontus specimens but bare or only lightly scaled in Ae. puntor and Ae. abserratus. No other differences were observed in the adult females or the male genitalia in any of the three species. The larvae of Be. abserratus could be separated by t he single-branched seta 2-X. Six larval characters differed between As. hex odontus and Ae. punctor but the ranges of each character overlapped and non e were diagnostic. These comparisons indicated that Ae. hexodontus is a sin gle species, at least in the southern part of its range. Also, genetic and morphological comparison of the three species within the punctor subgroup a ttested to the close relationship hypothesized for these mosquitoes.