Comparative allozyme analysis of Oriental migratory locust Locusta migratoria manilensis from two breeding areas in north China.

ABSTRACT

The allozyme analysis using horizontal starch gel electrophoresis was employed to compare the genetic structure in the population of oriental migratory locust Locusta migratoria manilensis from two breeding areas, Beidagang(Tianjin) and Huanghua(Hebei). The two areas are adjacent but with distinct ecological features, with the recorded locust outbreaks and migration. The zymograms showed that among nineteen loci four (Mdh-1, Pgm, Adk and G3pd) showed extremely low variability level with the frequency of the most common allele higher than 0.95 in the populations from both sites. The rest loci had 2 to 4 alleles but the allele frequencies between the two populations were all similar except Fbp and Got-2 loci. In the 27 chi 2-tests for the genotypes at polymorphic loci only two (Pgi and Got-1) of beidagang population did fit the Hardy-Weinberg's expectations. This is due to high frequencies of the most common homozygotes and the corresponding heterozygote deficiency. The allozyme data demonstrated that the locusts had remarkable genetic variability within each population, but little divergence between the populations. The genetic variability measurements were found similar Percentage of polymorphic loci (P) was between 73.7% and 78.9%; The mean number of alleles per locus (A) was from 2.9 to 3.1; and the mean heterozygosity (Ho) was nearly identical (about 0.138). The F-statistics (FST = 0.053) also showed the genetic uniformity of the populations, corresponding to the high Nei's genetic identity (I = 0.938). These results of the allozyme analysis suggested that the two populations appeared to be a part of a large population. It is reasoned that the genetic polymorphism and differentiation at certain loci between the two populations may depend on at least two agnostic factors that are all related to migration. First, the unusual dispersal capability of L. m. manilensis tends to make a continuous genetic structure distribution. Second, the frequent migration also results in the individuals to be exposed to drastically various environments. Since the broad adaptability is crucial to survive the changing environments, the genetic variation at population level is necessarily required to offer the population resilience for successful survival and reproduction under those ecologically divergent abiotic and biotic conditions. Thus, the migration contributes to the maintenance of dynamic equilibrium of genetic polymorphism in this highly specialized subspecies.