Taxonomic Revision Of The Genus Drepanolejeunea In The Borneo Island

The genus Drepanolejeunea is the fourth largest genus in the family Lejeuneaceae.It is widely distributed in the tropical rainforest.The tropical island Borneo,which is the third largest island in the world,has previously reported a number of 24 Drepanolejeunea species.Ecologically,the species mostly grows on the leaves,tree trunk and tree branches.Since the rise of the genus in 1893,it has been challenging to study the species delimitation due to its smaller size and hydrophilic nature.Morphologically highly plastic species also led to the difficulty in identifying Drepanolejeunea species.Although there was a number of phylogenetic analyses conducted on the genus in the past,there are still many problems with the morphological characters that explain the monophyletic relationship of the certain species complexes.Therefore,the study aimed 1)to revise the morphological characters of Drepanolejunea species in the Borneo island in relation to its phylogenetic analyses and 2)to establish a morphological framework for investigating species boundaries for Drepanolejeunea complexes and 3)to reveal species diversity and distribution in Borneo.Over 500 specimens were collected from eight investigated locations on the Borneo island.Anatomical-morphological and phylogenetic methods were used in the study.The study confirmed that D.actinogyna,D.blumei,D.elegans,D.grandis and D.pleiodictya are new to the island.However,three species,namely D.longicruris,D.obtriangulata and D.ciliata remained under-collected.Drepanolejeunea brunnea,now named Mohamedia brunnea,has been excluded from the genus.One species,D.intermedia,was mistakenly reported in previous literature.Additionally,the caducity character used in delimiting D.vesiculosa from D.affinis and D.propagulifera was debated based on the physiological development.Instead,more reliably stable characters to delimit aforementioned species were basal ocelli shape and size as well as underleaves middle cells.Drepanolejeunea obliqua and D.teysmanii are regarded as synonyms based on their morphological resemblance on the sexual plants and are further confirmed by molecular studies.The study concluded a total of 25 Drepanolejeunea species present on the island.A key to all known species of the genus in Borneo is presented.