Side by side? Vascular plant, invertebrate, and microorganism distribution patterns along an alpine to nival elevation gradient

Abstract

High mountain areas above the alpine zone are, despite the low-temperature conditions, inhabited by evolutionary and functionally differing organism groups. We compared the abundance and species richness of vascular plants, oribatid mites, springtails, spiders, and beetles, as well as bacterial and methanogenic archaeal prokaryotes (only abundance), at 100 m vertical intervals from 2,700–3,400 m in the Central Alps. We hypothesized that the less mobile microarthropods and microorganisms are more determined by and respond in similar ways to soil properties as do vascular plants. In contrast, we expected the more mobile surface-dwelling groups to forage also in places devoid of vegetation and thus to show patterns that deviate from that of vascular plants. Surprisingly, the observed patterns were diametrically opposed to our expectations: soil-living oribatid mites and springtails showed high individual numbers at high elevations, even where vascular plants barely occurred. Springtails also showed a rather constant species richness throughout the entire gradient. In contrast, patterns of surface-dwelling organisms and of archaeal prokaryotes did not differ significantly from vascular plants, because of either comparable climate sensitivity or their dependency on vegetated habitats. This study may serve as a baseline to estimate the risks of biodiversity losses in response to climate change across different biotic ecosystem components and to explore the potential and limitations of vascular plants as proxy for other organism groups that are far more challenging to monitor.