Coleoptera found in marine strandlines on New Zealand beaches: species diversity, seasonal trends and the effect of beach substrate

The terrestrial invertebrates found in association with marine strandlines constitute a world-wide ecological system. This study examined the beetle assemblages (Insecta: Coleoptera) in strandlines on New Brighton beach near Christchurch and at 35 other sites on Banks Peninsula in the South Island of New Zealand. In a total of 535 thirty-minute hand searches, 81 distinct beetle taxa (identified species & recognisable taxonomic units) were recorded, representing 25 coleopteran families. Regular sampling at New Brighton over the course of three years identified a clear seasonal increase in Coleoptera species richness in the summer, and revealed that some of the commoner species (e.g. Haplanister crypticus, Lagrioida brouni and Cafius litoreus) occurred in every calendar month. The collections from Banks Peninsula suggested that sampling strandlines on sandy beaches tended to produce more beetle species than those on shingle or boulder shores. Species accumulation analysis indicated that additional species are still likely to be recorded for this region, although many of these species will be vagrants in the strandline habitat. This study provides an initial catalogue of beetle species for strandlines in this region of New Zealand, along with valuable information on aspects of life history and ecology. Further research is needed to enhance the limited biogeographic data available for these beetle species and, by repeated sampling, determine which species can be considered resident within the strandline habitat.