Community composition and cold tolerance of soil Collembola in a collapse karst doline with strong microclimate inversion

The study compared communities of soil Collembola along the inversed microclimatic gradient of the collapse doline of the Silicka ľadnica Ice Cave (Slovakia) in spring and autumn of 2005. Kruskal-Wallis ANOVA and the Mann- Whitney test revealed significant differences in abundance between sites and both seasons. Significantly higher abundance means and species richness were observed at most sites during the spring compared with the autumn. NMS ordination documented a clear delimitation of communities with remarkably different soil microclimates. The community pattern of the coldest section of the gradient, with low species richness and high mean abundance, was analogous to communities living in the harsh alpine and polar soils. The collapse doline with inversed microclimate hosted a high number of species (72) and a broad variety of montane forms (13), thus documenting that these karst landforms enhance local diversity of edaphic Collembola and serve as local refugia of specialized cold-tolerant species. The cold tolerance of the four abundant species at the doline cold sites, namely Ceratophysella sigillata, Tetrodontophora bielanensis, Protaphorura armata and Desoria tigrina, was tested in the laboratory using one-hour exposition survival tests. Within a temperature range from -2.4 to -7.8◦C, T. bielanensis was the most cold-sensitive species, with a lethal dose LD50 of -4.4◦C, while D. tigrina was the most cold-resistant, showing LD50 of -5.8◦C.

Selective foraging of fungi by collembolans in soil

Soils contain highly diverse communities of microorganisms and invertebrates. The trophic interactions between these species are largely unknown. Collembolans form an abundant part of the invertebrate community in soils. A prevailing view is that soil collembolans are generalist feeders on fungi, lichens, fragmented litter and bacteria. However, in laboratory food choice experiments, it has been shown that collembolans preferentially select certain taxa of fungi. To examine this apparent contradiction, we developed a molecular technique based on the analysis of 18S ribosomal DNA (rDNA) sequences to explore the diversity of fungi in soils and in the guts of collembolans. We report that the diversity of fungi found in the natural soil was 33 times higher than that in the guts of the collembolan Protaphorura armata . The data support the view that collembolan species can be highly selective when foraging on fungi in soils.