A revised generic classification of the jelly lichens, Collemataceae

Abstract

Phylogenetic studies have shown the need for a revised circumscription of generic boundaries in the jelly lichens (Collemataceae). Using a four-marker dataset from a recently published phylogeny of Collemataceae, we tested the monophyly of ten morphologically well-characterized groups. To achieve this, we performed Bayesian and maximum likelihood analyses. The monophyly of the ten morphological groups was confirmed. In order to reconcile molecular and morphological data into a formal classification, we here propose new generic delimitations in Collemataceae. Collema and Leptogium are re-circumscribed and six old generic names are resurrected to accommodate the Collema Crispum-group (Blennothallia), the Collema Tenax-group (Enchylium), the Collema Cristatum-group (Lathagrium), the Collema Occultatum-group (Rostania), the former small Leptogium species (Scytinium), and Leptogium diffractum (Pseudoleptogium). In addition, two new genera are described to accommodate Collema multipartitum (Callome) and the Collema Italicum-group (Paracollema). The presence/absence of a eucortex, which was earlier used as the cardinal character to define genera in the family, is still useful, but only in combination with other traits such as thallus habit (size), lobe size, ascospore characteristics, thallus anatomical structure, and habitat preference. A key to the genera is provided. Lectotypes are designated for Collema marginale Hoffm., Synechoblastus nigrescens (Huds.) Trevis., Eucollema (Cromb.) Horw., Collema section Enchylium Ach., Collema section Lathagrium Ach., Collema sect. Mallotium Ach., Collema section Scytinium Ach., Collemodium Nyl. ex Lamy, and Homodium Nyl. ex Olivier.