Pyxidiophora: life histories and arthropod associations of two species

Abstract

Based on field studies in New Brunswick and Ontario, two species of the genus Pyxidiophora are demonstrated to be of frequent occurrence. Pyxidiophora sp. and Pyxidiophora spinuliformis have complex life cycles involving anamorph formation and sporulation on a phoretic mite host. Pyxidiophora sp., the more common of the two species, appears to be parasitic on the apothecia of coprophilous Pezizales where it forms clusters of synnemata within a week of dung deposition. Later, perithecia develop among the synnemata and produce ascospores. Ascospores attach to mites that are, in turn, carried by beetles and flies to a new substrate. On the new substrate while attached to the mite, ascospores of Pyxidiophora sp. differentiate into linearly arranged or complex and often muriform Thaxteriola thalli, which produce phialoconidia. The phialoconidia appear to be the propagules that inoculate the new substrate. Pyxidiophora spinuliformis has a life cycle similar to that of Pyxidiophora sp. but differs in having a conidial anamorph with a different development and ascospores that never form muriform thalli on the phoretic mite host. The taxonomic, ecological, and evolutionary significance of these findings is discussed.