NEW RECORDS FOR THE LIVERWORT AND HORNWORT FLORA OF VIETNAM, 1

After the examination of the Cryptogam collection in the Herbarium of the University of Science, Vietnam National University Ho Chi Minh City (PHH), 25 species proved to be new to Vietnam, including one hornwort and 24 liverworts. Among them, four genera: De-notarisia Grolle, Gongylanthus Nees, Leiomitra Lindb. and Lepicolea Dumort. are new records for the country. Diagnostic characters and illustrations are given for some taxa, as well as locality notes and habitat descriptions are provided for each collecting area.


INTRODUCTION
The first checklist of bryophytes, also the first checklist of Vietnam liverworts was published by T. Pócs in 1965, including 394 species of mosses and 162 species of liverworts and hornworts (Pócs 1965). Tixier (1966a) gave a detailed account on the epiphytic vegetation (including the bryophytes) of the Central Highlands of southern Vietnam, without floristical novelties. Fifty years later, Bakalin and Nguyen (2016) published the second checklist of 301 Vietnam liverwort and hornwort species (five species of hornworts) based on 45 literature sources. Recently,  added 79 new records for Vietnam liverworts, in which 43 species are new to Indochina. The authors concluded that Vietnam liverwort flora currently has 379 species and infraspecific taxa and predicted that the total number of liverworts in Vietnam should be close to 500 species and infraspecific taxa. In the same year, Shu et al. (2017) revised Bakalin and Nguyen's (2016) checklist and added 100 new records, raising the total number of Vietnam liverwort and hornwort species PÓCS, T., TRAM, N.-K.-T., HE, Q., KATAGIRI, T. and LUONG, T.-T. to 430 (except for 23 infraspecific taxa). There are differences in these author's opinions about the status of some species, which causes some discrepancies in the precise number of liverwort and hornwort taxa of Vietnam.
There has been a gap in liverwort studies in Vietnam for about 20 years since the late 1970s and the majority of publications on Vietnam liverworts and hornworts concentrated on floristical records. Studies on Vietnam liverworts began again in 1999, when Zhu and So reported a new Cololejeunea for Vietnam: C. pseudoplagiophylla P. C. Wu et J. X. Luo (Zhu and So 1999), which was not included in the Bakalin and Nguyen's (2016) checklist. Floristical studies with the participation of local bryologists have been restarted during the 21st century. In 2005, Pócs and Tran published 41 liverwort taxa in Vu Quang Nature Reserve (now it is a national park), of which Cheilolejeunea streimannii Pócs and Cololejeunea vuquangensis Pócs et Ninh were new to science, eight taxa were new to Indochina or Asia, while a further four were new to Vietnam (Pócs and Tran 2005). For the south of Vietnam, Pócs and Tran (2012) reported 21 epiphyllous species in Cat Tien National Park, in which Colura ornata K. I. Goebel were new to Vietnam. In 2013, Pócs, Luong and Ho described a new liverwort, Drepanolejeunea bidoupensis Pócs, among 54 epiphyllous species from 125 samples collected in Bidoup-Nui Ba National Park . Three of them are also new to Vietnam. Bakalin and Vilnet (2018) announced a new Mylia to science: Mylia vietnamica Bakalin et Vilnet, which was also the first record of this genus for Southeast Asia. Recently, in 2019, Borovichev, Bakalin and Nguyen published a paper on the genus Cyathodium, which is poorly known in Vietnam. The authors provided morphological descriptions, ecology and distribution for three Cyathodium species present in the country (Borovichev et al. 2019).
In summary, the liverwort and hornwort floras of Vietnam have been studied for a long time but still insufficiently understood due to many disruptions. This paper belongs to a series of reports of new and noteworthy bryophytes of Vietnam, whereas specimen information is published and available on the Global Biodiversity Information Facility (GBIF) (www.gbif.org) database.

MATERIALS AND METHODS
The samples treated in this article were collected from 2011 to 2018 in 11 locations (1-11) of seven main localities (A-G) (Fig. 1), which are all described below. An overview on habitat and vegetation for each location is provided. Most of the specimens are from the Central Highlands of southern Vietnam and dominated by those in Bidoup-Núi Bà National Park.
The specimens were identified in connection with the project by the University of Science, VNUHCM, which aims to digitise and publish observations of Vietnamese bryophyte and lichen specimens being held in the Herbarium of the University of Science, Vietnam National University Ho Chi Minh City (PHH) in the GBIF database. Until now, the dataset includes 851 records of which three species are hornworts and 154 species of liverworts (Luong et al. 2019). Identifications of specimens were done or confirmed by Tamás Pócs (EGR), Tomoyuki Katagiri (NICH) and Qiang He (PE). All specimens listed below are stored in PHH, with duplicates in EGR, NICH and PE. B). Chư Yang Sin National Park, Đắk Lắk province, NW to Bidoup-Núi Bà National Park. Elevation: 800-2,442 m. The highest peak of the park and also of the province is Chư Yang Sin peak (2,442 m).

RESULTS
A total of 25 species are newly recorded for the flora of Vietnam: one hornwort and 24 liverworts, in which four genera are new for the country: Denotarisia Grolle, Gongylanthus Nees, Leiomitra Lindb. and Lepicolea Dumort.
Lejeunea cf. dipterota (Eifrig) (Lee et al. 2018). -Taxonomic notes: the distinguishing characters are the ovate-oblong leaves with rounded apices, the straight ventral margin of keel, the leaf cells with trigones, the small leaf lobules and the distant, small, suborbicular underleaves (Lee et al. 2018). Eifrig (1937) described it as Taxilejeunea compressiuscula Lindenb. ex Steph. nom. nudum, but did not separate it well from specimens of the later described L. micholitzii Mizut.

DISCUSSION
The greater part of the above species was collected in the Bidoup-Nui Ba National Park in the Lang Bian Mountains, Central Highlands of southern Vietnam. As the area, both in altitudinal regions and in its variable substrates, provides a high diversity of habitats along favourable climatic conditions, it is no wonder that its bryoflora is so rich. Here an important substrate is the acidic bark of Pinus kesiya, occurring both in pure stands or mixed among broadleaved trees. Pine bark is especially rich in members of Lepidoziaceae family. Epiphylls are more common in the broadleaved forests of the area.
As far as the phytogeographical composition of the bryoflora is concerned, the number of Indo-Malesian and Malesian-Pacific elements increases going southward in Vietnam, as was previously shown by Tixier (1966a, b). At the same time the ratio of Sino-Himalayan elements decreases southwards. Belonging to the former group, in our collection, they are for example Acrolejeunea arcuata, Acromastigum herzogii, Bazzania serrulatoides, Colura speciosa, Denotarisia linguifolia, Lepidozia borneensis, Metahygrobiella acuminata and Radula formosa, while to the later group are Asterella mussuriensis and Gongylanthus himalayensis. Southeast Asian species add a special feature to the bryoflora, like Lepicolea yakusimensis and Riccardia nagasakiensis. The rest of species are more widespread Palaeotropical or northern temperate elements.
To gain a more complete knowledge of the flora a more detailed phytogeographical analysis should be done. But currently based on our collection of 103 species, 24 proved to be new to Vietnam and much more species of the area yet to be investigated, we can conclude that the very rich liverwort flora of the country is still very imperfectly known. We can also confirm the statements of Bakalin and Nguyen (2016) and of Shu et al. (2017) in this respect, that to obtain a fairly complete knowledge of the bryoflora of Vietnam further thorough researches are needed. NEW RECORDS FOR THE LIVERWORT AND HORNWORT FLORA OF VIETNAM, 1 *