An ultrastructural study of spore wall development and septal pores in species of the Pachyphlodes (Pezizaceae, Pezizales) lineage, with a description of the new species Pachyphlodes annagardnerae

Abstract

Pachyphlodes (Pezizaceae) is a genus of truffle-like fungi that is distributed across the Northern Hemisphere. These fungi form ectomycorrhizae primarily with trees in the Fagaceae family, and occasionally with other host plants. The genus Plicariella (= Scabropezia) is phylogenetically inferred as an ally of, or within, the Pachyphlodes lineage. Despite molecular phylogenetic analyses that show the close relationships of species in these two genera, morphological differences in ascomata shape and color, spore ornamentation, and ascus shape are profound. Here, we studied spore wall development to better understand affinities within the Pachyphlodes–Plicariella lineages. Electron microscopy studies indicate that the initial spore wall development is similar across six Pachyphlodes species and a Plicariella species, despite striking differences in mature spore ornamentation among species. Ultrastructural analyses reveal that differences in spore ornamentation among Pachyphlodes species are due to unique developmental events at the final stages of spore wall deposition. Septal pore ultrastructure in Pachyphlodes species is similar to other Pezizaceae that have been studied. Molecular analyses of the five species studied indicate that four of them have not been previously described. The new species Pachyphlodes annagardnerae is here described, and the ultrastructural features of species of Pachyphlodes, Plicariella, and other Pezizales are compared and discussed.