Genea, Genabea and Gilkeya gen. nov.: ascomata and ectomycorrhiza formation in a Quercus woodland

Abstract

Genea and Genabea are considered ectomycorrhizal (EM) symbionts of higher plants, but because of their hypogeous habit, dark coloration and the small size of their ascomata, relatively little is known about these genera. Ascomata of six morphological species of Genea and one of Genabea were frequently collected at a single site in xeric Quercus woodlands of California's Sierra Nevada foothills. While most collections were easily referred to known species, those putatively identified as Genea harknessii and Genea arenaria were problematic. Genea harknessii collections appeared relatively homogenous based on morphology, but significant ITS variation revealed by rDNA sequencing suggested cryptic species diversity. Specimens of G. arenaria approximated the brief, original species description except for abundant clumps of septate setae formed at the apex of peridial warts. To verify the identity of this species we reexamined the holotype and analyzed morphology and ITS sequences of G. arenaria ascomata from a wide geographic range. To authenticate the EM status of Genea and Genabea with Quercus we collected healthy EM of Quercus douglasii and Quercus wislizenii and compared their ITS sequences to those from ascomata. We detected nine distinct ITS types of Genea and Genabea on roots. Two new species described here as Genea bihymeniata sp. nov. and Genea cazaresii sp. nov., were discovered during study of herbarium specimens. A phylogenetic analysis of 28 s rDNA from Genea and Genabea indicated three distinct lineages: Genea, Genabea and a third represented by Genea intermedia. For the latter we propose Gilkeya gen. nov. to accommodate the single known species, Gilkeya compacta comb. nov. A dichotomous key to all known Genea, Genabea and Gilkeya spp. from western North America is presented.