Genetic and morphological characterization of the Aedes (Ochlerotatus) dorsalis (Diptera : Culicidae) group in North America

An examination of the electrophoretically detectable variation among the No rth American members of the Aedes (Ochlerotatus) dorsalis group revealed la rge genetic differences among all 4 species. At least 9 of 18 loci examined (50%) were diagnostic for each species pair. However, morphological variat ion observed among species was low. Only Aedes canadensis (Theobald) was se parated readily from the other members of this group [Aedes dorsalis (Meige n), Aedes melanimon Dyar and Aedes campestris Dyar & Knab] in all life stag es. Characters traditionally used to separate the remaining 3 species were less reliable. Ln the adult female, ae. melanimon may be distinguished from Ae, campestris by the scaling patterns of the wings and abdomen, but Ae. d orsalis could not be distinguished reliably by these characters. Adults of Ae, dorsalis may be separated reliably from those of As. campestris and Ae melanimon only by the length of the subapical tooth relative to the length of the tarsal claw. Ae. melanimon was identified in the larval stage by the short mesothoracic hair 1. Eight larval characters differed between Ae. do rsalis and Ae. campestris. However, the ranges of these characters overlapp ed and no character was truly diagnostic. Genetic variation within species was low as measured by average heterozygosity and Nei's genetic distance co efficients. No allozymes were diagnostic for coastal and inland populations of Ae, dorsalis, and the pattern of genetic differentiation within this sp ecies did not correspond to the geographic location of the populations exam ined. Therefore, the genetic data did not support the hypothesis that Ae. d orsalis represents a complex of 2 or more cryptic species.