Genetic diversity in Listronotus bonariensis (Kuschel) and geographical origin of the New Zealand population

Abstract

The Argentine stem weevil, Listronotus bonariensis (Kuschel) (Coleoptera: Curculionidae), is an important introduced pasture pest in New Zealand and causes hundreds of millions of dollars in damage annually to pasture and livestock health. Adult L. bonariensis were collected from 9 diverse locations in South America (the species' native habitat), 5 locations in New Zealand and 1 location in Australia (where the species is also an introduced pest). The 15 populations were studied by 2 DNA-based techniques, RAPD and mitochondrial analysis, in an effort to determine the geographical origin of the pest populations in New Zealand. RAPD revealed similarities between populations sampled within New Zealand, as well as polymorphisms between the South American populations. Mitochondrial restriction fragment length analysis revealed the unusually large mitochondrial genome size of approximately 32 kilobases in this species but negligible variation within or between populations. Based on the RAPD results, the Rio de la Plata region on the east coast of South America is thought to be the geographical source for the Listronotus bonariensis (Kuschel) populations in New Zealand. The discrepancy between the levels of genetic variation revealed by RAPD and mitochondrial analysis in the native populations is discussed and hypotheses are presented to reconcile this difference.