INTRASPECIFIC MITOCHONDRIAL-DNA VARIATION IN THE MIGRATORY GRASSHOPPER, MELANOPLUS-SANGUINIPES

Restriction fragment analysis of mitochondrial DNA (mtDNA) was used to examine genetic variation and population structure of the migratory grasshopper, Melanoplus sanguinipes. The total DNA of 89 individuals was digested with 10 restriction enzymes and probed with three cloned EcoRI fragments representing the entire mitochondrial genome (total length 16.1 kb). Five endonucleases revealed polymorphism, yielding 12 haplotypes in combination. Nucleotide diversity indices (delta) between haplotypes ranged from 0.18 to 0.92 per cent with an average value (pi) of 0.27 per cent, a comparatively low figure that possibly reflects a history of chronically small population numbers prior to the species' colonization of a suitable habitat engendered by agricultural settlement. Little, if any, differentiation was evident among locations or between prairie and parkland regions, areas spanned by a colour trait cline. Selective forces with respect to the latter must, therefore, be sufficiently powerful to withstand the attenuating effects of widespread gene flow, implied by the mtDNA data.