Genetic structure in populations of Rattus sordidus in sugarcane-growing districts of Queensland, Australia

Genetic structure in populations of Rattus sordidus was examined to determine if population substructuring was occurring as a result of differential dispersal of genotypes or habitat preference. Animals were sampled from grasslands, woodlands, and sugarcane fields in high dissection areas (high dissection of sugarcane fields by non-crop habitat) and low dissection (crop monoculture) areas in the Ingham and Mackay sugarcane-growing districts in Queensland, Australia. Data from six polymorphic allozyme loci showed no statistical differences in allele frequencies 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 and cluster analysis based on genetic distance could not separate samples from high dissection and low dissection areas indicating that the ability of R. sordidus to reach high densities in some crop areas had no genetic basis and individuals within a single sugarcane-growing district formed a panmictic population, probably due to high mobility of the rodents.