A Preliminary study in Propolis (Fungi, Ascomycota): Propolis farinosa - common, cosmopolitan and plurivorous

Abstract

Propolis farinosa, a member of Ascomycota, is a commonly encountered microfungus in temperate and boreal forests of North America and Western Europe. Southern Hemisphere collections are reported from Chile, Australia and New Zealand. Propolis farinosa, the type species of the genus, is notable for its occurrence on the dead woody parts of many different plants. Its widespread distribution presumably tracks that of its various dicot and gymnosperm hosts. It produces distinctive apothecia that are erumpent and surrounded by ragged flaps of degraded woody tissue, with discs that are covered by a stark-white powdery substance. Ascospores are wind-dispersed, smooth, hyaline and allantoid. That P. farinosa is globally-distributed and plurivorous suggests cryptic speciation. To investigate this, I used 89 sequences from 32 specimens of P. farinosa to generate a three-gene phylogeny. Additionally, I conducted an evolutionary distance analysis using ITS sequences, as well as a statistical analysis of variation in ascospore size. My results elucidate some degree of genetic and morphological variation in P. farinosa, though they do not support a claim of cryptic speciation. In the phylogeny, I also used a wider taxon sampling of Propolis species and representatives of the allied genera Mellitiosporiella and Propolina – generating a total of 152 sequences from 52 specimens. I recovered a sister clade to P. farinosa that consists of four other taxa including Propolina. These constitute a core Propolis clade, with Propolina to be synonymized under Propolis. My discussion concludes with the possible significance of allantoid ascospores in the life-histories of Propolis species, as well as an overview of host species preferences of wood-inhabiting Ascomycota. My work is original research in the systematics of P. farinosa that will serve as the foundation for a monographic study of Propolis. This diverse and understudied genus is an ideal subject with which to investigate questions of biogeography, host-tree associations, and endophytism, as well as colonization and resource capture strategies in Ascomycota.