Hemithecium Trevisan (1853: 12)

Kalb, Jutarat & Kalb, Klaus, 2017, New lichen species from Thailand, new combinations and new additions to the Thai lichen biota, Phytotaxa 332 (2), pp. 141-156 : 145

Hemithecium Trevisan (1853: 12)

Staiger (2002) described two subgenera for Hemithecium , viz. subgenus Hemithecium and subgenus Leucogramma . The latter was characterized by brown, I+ reddish ascospores and was later elevated to generic level as Pallidogramme Staiger, Kalb & Lücking ( Lücking et al. 2008).

In a subsequent molecular phylogeny of Graphidaceae ( Rivas Plata et al. 2012) , Hemithecium s. str. was found to be nested within Graphis (species with small- and medium-sized ascospores) or within Allographa (species with large ascospores).

Because of this result and the fact that the only difference between Allographa , Graphis and Hemithecium is the absence of carbonization in the exciple of the ascocarps in Hemithecium , we formally transfer the species with small ascospores newly found in Thailand to the genus Graphis and one species with large ascospores to the genus Allographa . Furthermore, there is a continuum from Allographa and Graphis species with a fully carbonized exciple to species with an apically and laterally carbonized exciple or species where the exciple is only carbonized at the tips.