Acaulospora reducta sp. nov. and A. excavata — two glomeromycotan fungi with pitted spores from Brazil

Acaulospora reducta sp. nov. and A. excavata, both characterized by large pits on their spore surfaces, were found in the semi-humid Atlantic rainforest and semiarid Caatinga biomes of Northeastern Brazil. Phylogenetic analyses of the ITS regions of the ribosomal gene place the two fungi in two distinct clades within the Acaulosporaceae. Acaulospora reducta has whitish yellow, dark yellow to light brown spores (135-205 mu m in diam.) and irregularly shaped, often edged to sometimes dumbbell-shaped pits (5.5-19 x 3.5-8.6 mu m). These large pits have roughened irregular surfaces comprising secondary small pits (c. 0.5 mu m broad and deep) and fine ridges. Spores of A. excavata are ochre to yellow orange (sometimes yellow) and have regular circular to subcircular pits (4-20 x 4-16 mu m) with smooth pit surfaces. Most recently, A. reducta was also found in the Cerrado biome of Minas Gerais, suggesting its wide distribution in tropical Brazil.