Micro Gondwana: soil and litter mesofauna in the subalpine and alpine of North-West Nelson, southern New Zealand

Alpine ecosystems are vulnerable to the warming climate, yet alpine soil mesofauna remains the less studied part of NZ biodiversity. Here we present a survey of soil mesofauna communities of three mountain peaks in the Nelson-Tasman and Marlborough regions of the South Island of New Zealand. We assessed changes in abundance, diversity and trophic composition along the elevational gradient from subalpine forests to alpine herb fields (800-1600 m a.s.l.) and analysed the influence of selected environmental factors on mesofauna. Taxon richness was expected to decrease and the proportion of predators to increase in alpine habitats, as has been observed elsewhere. Sub-alpine beech forests harboured a high diversity of soil mesofauna, many of which are Gondwanan relics. There was a decline in abundance and taxonomic richness of mesofauna with increasing elevation. However, no proportional increase in predators with increasing elevation was seen - alpine mesofauna assemblages had lower predator-to-herbivore ratios than upland forests. Several interesting taxa - harpacticoid copepods, moss bugs (Hemiptera: Peloridiidae), unique-headed bugs (Hemiptera: Enicocephalomorpha), micro-spiders, mite harvestmen, Neelidae springtails and acarifauna are discussed in more detail. Baseline data such as these advance the knowledge of native fauna and provide a baseline for ecological monitoring in the alpine zone.