Past distribution of large weevils (Coleoptera: Curculionidae) in the South Island, New Zealand, based on Holocene fossil remains

Abstract

A survey of 12 fossil sites in North and South Canterbury, where faunal remains were accumulated by the apparently extinct laughing owl (Sceloglaux albifacies Gray) and the New Zealand falcon (Falco novaeseelandiae Gmelin), revealed sediments containing abundant remains of not only bones but also invertebrates. Amongst the latter were several species of large weevils (Curculionidae), including Anagotus stephenensis Kuschel, A. rugosus (Broun), Hadramphus tuberculatus (Pascoe), and Ectopsis ferrugalis Broun. Their current and past distributions are discussed. H. tuberculatus has not been found for 84 years, hence is presumed extinct. The others had their territories greatly reduced, in particular A. stephenensis which now is known only from Stephens I. which it shares with the tuatara (Sphenodon punctaius Gray), a likely natural predator. The clearing of vast areas of native vegetation for pastures and crops might have played a part in the likely extinction of H. tuberculatus because its host plant Aciphylla (Apiaceae) is a prickly pastoral weed. However, the main cause of the drastic reduction in territory and numbers of the large weevils came from rats and mice. Some samples of devastation caused by rodents are presented. In New Zealand, large weevils are now more numerous and diverse on the mountains titan in the lowlands in New Zealand, which could well be attributed to some extent to the introduced predators.