Abstract
Th. maderense was regarded either as synonymous with Th. alopecurum, as a variety of the latter and also as a good species. A morphological study revealed that it clearly distinguished from Th. alopecurum by four ranked instead of eight-ranked leaves and thus deserves full rank of a species. Th. fernandesii has eight-ranked leaves and is therefore more related to Th. alopecurum than to Th. maderense. A comparison of the sequences of the Internal Transcribed Spacer of the nuclear ribosomal DNA region in the tree species supports the morphological evidence. Previous molecular studies of Th. maderense (showing almost no differences to Th. alopecurum) were based on misidentifications.
The status of Th. fernandesii is not clear. The multistratose leaves with broad costa indicate that it is a mutant as proved in several other cases by molecular methods. It differs, however, genetically too much from Th. alopecurum that it cannot be interpreted as a mutant of the latter.