A study of aedeagal and genetic variation among host-specific forms of Melanoplus bowditchi (Orthoptera: Acrididae)

The sagebrush grasshopper, Melanoplus bowditchi Scudder (Orthoptera: Acrididae), is a phytophilous species that is widely distributed in the western United States on sagebrush species. Two reported subspecies of this grasshopper, M. bowditchi bowditchi  Scudder and M. bowditchi canus Hebard were described based on their feeding preference to different sagebrush species. The geographical distribution of M. bowditchi is very similar to the range of its host plants and its feeding preference varies in relation to sagebrush distribution.  Two unnamed forms “frigidus” and “tridentatus” along with the described forms of M. bowditchi were studied for their morphological and genetic differences. We observed no consistent difference among the aedeagal parameres or basal rings of the four forms studied.  Using Amplified Fragment Length Polymorphism markers, we examined the genetic relationships among M. bowditchi individuals. Although these four forms show behavioral and morphological differences, the Analysis of Molecular Variance and the distance-based Unweighted Pair Group Method with Arithmetic mean dendrogram did not reveal significant differences among forms. Further, the genetic data showed all forms under study to be one breeding population, which would support them as a single species instead of four subspecies.