Morphology-based phylogenetic binning to assess a taxonomic challenge: a case study in Graphidaceae ( Ascomycota) requires a new generic name for the widespread L eptotrema wightii.

Molecular phylogenetic analysis presents two challenges when it is transformed into formal classifications: the taxonomic challenge (whether and how to distinguish monophyletic sister clades or how to deal with paraphyletic grades) and the nomenclatural challenge (naming clades, i.e. placing name-giving types accurately on a tree). One approach to the latter is morphology-based phylogenetic binning, which places specimens based on phenotypic features on a molecular tree and assigns uncertainty values to alternative placement options. Here, we use the example of the lichenized fungal genus L eptotrema to demonstrate how morphology-based phylogenetic binning can help to clarify taxonomic and nomenclatural issues when naming phylogenetically defined entities. L eptotrema is known for a common and widespread species, L . wightii, and phylogenetic analyses have been based exclusively on this species, including the recognition of a separate tribe, Leptotremateae. However, the genus name L eptotrema and the tribal name Leptotremateae are based on the name L . zollingeri, which was initially considered to be a synonym of L . wightii, but has recently been shown to represent a distinct species. As L . zollingeri differs considerably in phenotypic features from L . wightii, it can be questioned whether the two are at all related or whether L . zollingeri is actually closer to the genera M yriotrema and O cellularia in tribe Ocellularieae. The solution to this problem is not trivial, as it affects the correct use of the names Leptotrema and Leptotremateae. Morphology-based phylogenetic binning indeed demonstrated that L . zollingeri clusters with the M yriotrema album group in tribe Ocellularieae with high support. Hence, in contrast with current use, the name L eptotrema becomes available for the M . album group and Leptotremateae becomes a synonym of Ocellularieae. As a consequence, the new names S anguinotrema and Sanguinotremateae are introduced to accommodate L . wightii and the tribe including this species and the genus R eimnitzia. Although the studied case is specific to lichen fungi, the approach can be used in a much broader context with any kind of taxon or organism. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179, 436-443. [ABSTRACT FROM AUTHOR]