Phylogeny And Taxonomy Of Leptolejeunea(Lejeuneaceae,Marchantiophyta)

Lejeuneaceae is the most speciose family of the liverworts,distributed in the tropical and subtropical areas.Leptolejeunea,a typical epiphyllous group with about 48 species of Lejeuneaceae,is one of the pioneer groups of epiphyllous liverworts,which plays an important role in the global ecology.However,the habitats of epiphyllous liverworts are reducing because of dwindling rainforest areas.There is an urgent need for more studies on these groups.Due to their small and easily degraded ocelli,it is hard to distinguish species of Leptolejeunea from one another.This genus has not been revised around the world until now.The definitions of species,subgenus,and even the circumscription of genera are still unclear.We aims to use integrative taxonomy to address these questions,establish the evolution history of Leptolejeunea and research how the vicariance and dispersion influenced the distribution of Leptolejeunea.Based on supplemented representative samples,a new database including 71 samples from 19 genera with chloroplast genes trnL-trnF,rbcL and nuclear gene ITS was implemented to reconstruct trees by three methods:Maximum Likelihood,Maximum Parsimony and Bayesian inference.The trees afford proofs that Leptolejeunea is a natural monophyletic group.Another phylogentic tree was reconstructed using 183 samples form Leptolejeunea with chloroplast genes trnL-trnF,trnG and nuclear gene ITS,while outgroup samples from Cheilolejeunea.A species tree was estimated with 39 samples of L.maculata.The results are as follows:1)Schuster’s two subgenera of Leptolejeunea(Leptosticta and Leptolejeunea)was supported and two new subgenera Neoleptolejeunea and Subasticta with type species L.nigra and L.exocellata respectively were proposed;2)L.elliptica is not monophyletic and just distributed in America tropics,with the materials form Asia splitting into two species:L.subacuta and L.dapitana and thoses from Australia belonging to L.australis;3)The samples of L.maculata are divided into three species:L.subrotundifolia distributed in Asia and Africa,both L.schiffneri and L.maculata distrbuted in Asia,Africa,Oceanic islands,Australia and New Zealand;4)39 species of Leptolejeunea are recognized and Asia is its distribution center with 27 species;5)Seven new species were discovered and described:L.serrata sp.nov.from Papua New Guinea,L.latilobula sp.nov.from Fiji,L.longifolia sp.nov.and L.subdapitana sp.nov.from Brunei,L.scalpellifolia sp.nov.from the boundary areas of China and Vietnam,L.nigra sp.nov.from Himalayas and L.herzogii sp.nov.from tropical Asia;6)Fourteen new synonyms were suppported:L.diversilobulata Bischl.was proposed as a synonym of L.exocellata(Spruce)A.Evans,L.lancifolia Mitt.ex Steph.as L.maculata(Mitt.)Schiffn.,L.borneensis Herzog as L.vitrea(Nees)Schiffn.,L.micronesica Inoue et H.A.Mill.and L.lepinii Gottsche ex Steph.as L.schiffneri(Steph.)Steph.,L.serrulata Herzog,L.minima Herzog and L.rhombifolia Steph.as L.tripuncta(Mitt.)Steph.,L.dolabriformis Pearson as L.epiphylla(Mitt.)Steph.,L.udarii M.Dey et D.K.Singh as L.latifolia Herzog,L.foliicola Steph.and L.ligulata Herzog as L.subacuta Steph.ex A.Evans,L.jamaicensis R.M.Schust.as L serratifolia Schiffn.,L.himalayensis Pande et R.N.Misra as Lejeunea cocoes Mitt.;7)Four species names were resurrected:L.sikkimensis,L.schiffneri,L.dapitana and L.subacuta.In addition,the consequence of molecular dating using BEAST V1.8.2 with chloroplast genes trnL-trnF,trnG,rbcL and nuclear gene ITS from 71 samples,reconstructing the ancestral areas by RASP and ancestral states performed in Bayes Traits V2 indicates that:the ancestor of Leptolejeunea is obligate epiphyllous and trends to increase the reproduction efficiency by vegetative propagation when facing environment stress;Current distribution of Leptolejeunea is decided both by vicariance and dispersion;Leptolejeunea went through extinction events during the initial period,which leads to two ancestral areas,Asia and Americas;The subgenus Leptolejeunea was originated from Asia and dispersed to Oceania and Africa from which some species spread to the Americas.The collision between Indian Subcontinent and Eurasia,Australia plate and Pacific plate changed the terrain and provided more habitats for epiphyllous liverworts.Meanwhile,the climate change from Eocene epoch to Miocene epoch promoted the diversification of Leptolejeunea in the Southeast Asia and Oceanic Islands.This paper comprehensively elaborates the circumscription of Leptolejeunea,elucidates subgenera and species,and recounts discovery of seven new species.By exploring the history of Leptolejeunea,it is found that global warming event could result in mass extinction of Leptolejeunea,suggesting that protection of these epiphyllous liverworts is uegent today.