GENETIC-STRUCTURE IN POPULATIONS OF RATTUS-SORDIDUS IN SUGARCANE-GROWING DISTRICTS OF QUEENSLAND, AUSTRALIA

Genetic structure in populations of Rattus sordidus was examined to de termine if population substructuring was occurring as a result of diff erential dispersal of genotypes or habitat preference. Animals were sa mpled from grasslands, woodlands, and sugarcane fields in high dissect ion areas (high dissection of sugarcane fields by non-crop habitat) an d low dissection (crop monoculture) areas in the Ingham and Mackay sug arcane-growing districts in Queensland, Australia. Data from six polym orphic allozyme loci showed no statistical differences in allele frequ encies among populations from the three habitat types, suggesting that sugarcane crops were colonized by a random sample of individuals from the refuge (grassland) populations. Standardized genetic variances an d cluster analysis based on genetic distance could not separate sample s from high dissection and low dissection areas indicating that the ab ility of R. sordidus to reach high densities in some crop areas had no genetic basis and individuals within a single sugarcane-growing distr ict formed a panmictic population, probably due to high mobility of th e rodents.