Acaulospora alpina, a new arbuscular mycorrhizal fungal species characteristic for high mountainous and alpine regions of the Swiss Alps

Abstract

Acaulospora alpina sp. nov. forms small (65–85 μm diam), dark yellow to orange-brown spores laterally on the neck of hyaline to subhyaline sporiferous saccules. The spores have a three-layered outer spore wall, a bi-layered middle wall and a three-layered inner wall. The surface of the second layer of the outer spore wall is ornamented, having regular, circular pits (1.5–2 μm diam) that are as deep as wide and truncated conical. A “beaded” wall layer as found in most other Acaulospora spp. is lacking. The spore morphology of A. alpina resembles that of A. paulinae but can be differentiated easily by the unique ornamentation with the characteristic pits and by the spore color. A key is presented summarizing the morphological differences among Acaulospora species with an ornamented outer spore wall. Partial DNA sequences of the ITS1, 5.8S subunit and ITS2 regions of ribosomal DNA show that A. alpina and A. paulinae are not closely related. Acaulospora lacunosa, which has similar color but has generally bigger spores, also has distinct rDNA sequences. Acaulospora alpina is a characteristic member of the arbuscular mycorrhizal fungal communities in soils with pH 3.5–6.5 in grasslands of the Swiss Alps at altitudes between 1800 and 2700 m above sea level. It is less frequent at 1300–1800 m above sea level, and it so far has not been found in the Alps below 1300 m or in the lowlands of Switzerland.

• Alps
• Acaulosporaceae
• Acaulospora paulinae
• Acaulospora lacunosa
• Glomeromycetes
• key
• molecular identification
• mycorrhiza
• spore morphology
• phylogeny
• taxonomy

This study has been supported by the Swiss National Science Foundation with grants to A. Wiemken and D. Redecker within the Programme NFP48 Landscapes and habitats of the Alps. We thank V. Gianinazzi-Pearson and BEG (International Bank for the Glomeromycota) for providing spores of A. lacunosa (BEG78). The excellent technical support by Sue Furler, Teresa Hostettler and David Schneider is highly acknowledged.