Genetic variation in prairie populations of Melanoplus sanguinipes, the migratory grasshopper

Abstract

Genetic variation at two visible loci and 10 electrophoretic loci in populations of the migratory grasshopper, Melanoplus sanguinipes, in the Canadian prairies is described. Tibia colour and femoral stripe loci exhibit considerable geographic variation in frequency. Multiple regression and correlation analyses revealed dma! variation patterns for tibia colour, with minimum annual temperature accounting for about 40 per cent of that variation. The possible direct and indirect effects of this factor are discussed. No spatial patterns were evinced for the femoral stripe locus despite its close linkage to the tibia colour gene. Whatever the nature of selection, coefficients must be large enough to maintain polymorphism and divergence in opposition to the swamping effects of gene flow. This does not appear to be the case for the allozyme loci; frequencies of the most common allele at each locus are high (average heterozygosity =45 per cent) and about the same at each location. Tte mean level of polymorphism, 378 per cent, is well within the range of most insects.

Intraspecific mitochondrial DNA variation in the migratory grasshopper, Melanoplus sanguinipes

“…Alberta, Canada T6G 2E I 547 loci (Chapco & Bidochka, 1986). At one time, parkland and prairie populations were afforded subspecies status (Brooks, 1958) but the allozyme work would appear to confirm Vickery 's (1979) suspicion that the claim is premature.…”

“…In any case, such populations are expected to exhibit low mtDNA diversity and, owing to chronically low numbers in the pre-agricultural past, low nuclear diversities. From the present study, this is clearly true for mtDNA, and from a previous investigation of isozymic variation, true for nuclear genes as well (Chapco & Bidochka, 1986). Based on neutral theory (Nei, 1987) and the assumption of an evolutionary rate of 0.01 substitutions/base pair/lineage/million years (see below), a nucleotide diversity value of 0.26 5 per cent corresponds to an effective population size of = 133,000.…”

“…Widespread panmixia should not, however, be automatically inferred on the basis of a perception of boundless movement as the biology of these organisms, including grasshoppers (Vickery & Kevan, 1983;Pfadt, 1988), would suggest. This point is nicely illustrated by studies of the cosmopolitan D. melanogaster, a species often regarded as a 'high migration' insect but for which populations are significantly differentiated fora variety of traits including mtDNA (Hale & Singh, 1987). In the light of the above, the occurrence of clinal variation in hind tibia colour frequency in the region (Chapco & Bidochka, 1986) is all the more significant.…”

“…reproductive capacity (Pfadt & Smith, 1972) and preference for fields disturbed by human activities (Pfadt, 1988), and given historical accounts (see references in Chapco & Bidochka, 1986), it is reasonable to regard this insect as a recent 'colonist' of the area.…”

Esterase variation among Argentine populations of Trimerotropis pallidipennis (Orthoptera)

“…This requires a parallel study of chromosomal, genetical and ecological variation. In spite of the known usefulness of isozymal studies to population genetics, only a few studies (Moran et al, 1980;Gill, 1981;Halliday et al, 1983;Nevo et al, 1984;Chapco and Bidochka, 1986) (1974). The system of gel and tray buffers was discontinuous Poulik, pH 7.9, modified by Schaal and Anderson (1974).…”