Role of exotic pine forests in the conservation of the critically endangered New Zealand ground beetle Holcaspis brevicula (Coleoptera : Carabidae)

The Canterbury Plains in the eastern South Island is one of the most modified regions of New Zealand with less than 2% of indigenous vegetation cover remaining. The critically endangered ground beetle Holcaspis brevicula Butcher, a local endemic known only from a small area in that region, is thought to be threatened by the loss and fragmentation of the formerly widespread forest and shrubland habitat. Previously, only the two type specimens, both male, were known to science. From 2000-2005, we conducted a survey for H. brevicula, using pitfall traps and active searching, in four of the largest remnants of the once extensive low forest and shrubland of kanuka, Kunzea ericoides, each covering less than 20 ha. In addition we conducted extensive trapping in an adjacent 7000 ha plantation forest of exotic Pinus radiata, in grassland and pasture areas, exotic shrubland, and in the nearest mountain beech (Nothofagus solandri var. cliffortioides) forest in the foothills of the Southern Alps. A total of 8658 carabids representing 47 species were collected over 57 494 trap-days, including five specimens of H. brevicula, all found in the pine plantation. A search of all major New Zealand collections for this species revealed three additional specimens, bringing the overall total of known specimens to ten, all of which were collected in this plantation forest. We propose that the exotic plantation forest inadvertently provides an important substitute habitat for this forest carabid, whereas the few small and fragmented native kanuka remnants appear to be insufficient to maintain populations of this specie