Towards a monograph of Dothideomycetes: Studies on Diademaceae

The family Diademaceae presently comprises the genera Clathrospora, Comoclathris, Diadema, Diademosa and Graphyllium and is characterized by ascomata opening as a flat circular lid, bitunicate asci and ascospores with three or more transverse septa, with or without longitudinal septa. The ascospores are fusiform, brown, mostly applanate and usually have a mucilaginous sheath. The type species of Clathrospora, Comoclathris and Graphyllium are revisited in this paper and re-described and illustrated with light micrographs based on examination of holotype specimens. The status of the family is discussed based on morphology and sequence data. Comoclathris is excluded from the family based on morphology and phylogenetic analysis, and should be accommodated in Pleosporaceae. Clathrospora is tentatively placed in Pleosporaceae pending molecular studies. Graphyllium has hysterothecial ascomata with a slit-like ostiole and should be excluded from Diademaceae. It can be accommodated in Hysteriaceae, but with uncertainty as species with hysterothecia have now been accommodated in at least five families. Molecular work is needed on Graphyllium to establish its familial placement. The status of Diadema and Diademosa as a distinct family Diademaceae based on ascomata opening as a flat circular lid is thought to be doubtful, but awaits molecular study.