Beetle (Coleoptera) communities inside and outside the pest-resistant fencing of a New Zealand ecosanctuary

The ecological impacts of invasive mammals are widely documented around the world. In New Zealand, fencing designed to exclude non-native mammals is used for conservation and restoration efforts. The Orokonui Ecosanctuary is a 307-hectare coastal Otago reserve (Dunedin, New Zealand) that is surrounded by mammal-exclusion fencing. The goal of the present study was to investigate how excluding mammals and including (native) animals inside the Orokonui Ecosanctuary fence has influenced ground- and litter-dwelling beetle (Coleoptera) abundance, diversity, and community composition. We hypothesised that beetle abundance, diversity, and community composition would be different whether the beetles sampled were from sites inside the fence or outside the fence. Beetles were extracted from the litter and soil of six sites (three inside, three outside) two times (once in winter, once in summer). The abundance, diversity, species composition, size distribution, and trophic guild distribution of beetles inside and outside the fence and between seasons were compared. Our results suggest that sites inside the fence harbour a greater abundance and diversity of beetles. We found a high abundance of native beetles both inside and outside the Orokonui Ecosanctuary’s fence. Further research may find evidence that the fenced sanctuary is providing a ‘halo effect’ whereby native beetles thriving within the Orokonui Ecosanctuary are spreading out into the surrounding landscape and also outcompeting introduced beetles.