A new species and two new records of Goniothalamus (Annonaceae) from Lao PDR

Abstract Goniothalamus saccopetaloides Y.H. Tan & Bin Yang, a new species is described and illustrated from Laos. This species shows morphological similarities to G. yunnanensis W.T. Wang, but it differs from the latter by having almost fleshy, involute and saccate outer petals, subglobose monocarps, and single seeded monocarps. Goniothalamus cheliensis, and G. calvicarpus are new records for the Flora of Lao PDR. A key to Goniothalamus species indigenous to Laos is provided here.


Introduction
Goniothalamus (Blume) Hook.f. & Thomson, comprising over 130 species of trees and shrubs, are one of the largest palaeotropical genera in the Annonaceae, mainly distributed from India and Sri Lanka to tropical Australia and the South Pacific Islands (Saun-ders and Chalermglin 2008;Nakkuntod et al. 2009;Turner 2014;Thomas et al. 2017). The genus is characterized by flowers with two whorls of petals of which the inner petals are smaller than the outer ones; three inner petals form a distinctive mitriform dome over the reproductive organs acting as a pollination chamber (Saunders and Chalermglin 2008;Tang et al. 2015), and stamens with apical connectives. Although the genus Mitrephora J. D. Hooker & Thomson also shares these similar features, Goniothalamus can be distinguished easily by its linear-oblong stamens, inner petals each with a short claw or stipe (Li et al. 2011). The genus shows considerable diversity in flowers of different size and shape, hairy indumentum, and color usually cream, yellow or red at maturity, and fruit morphology, with fruit of different size and shape (Saunders and Chalermglin 2008;Tang 2014;Tang et al. 2015). Species of the genus are widely distributed in tropical South-East Asian lowland and submontane forests (Tang 2014). Several Goniothalamus species have been described in recent years, including four new species from Thailand (Saunders and Chalermglin 2008), four new species from Borneo (Turner and Saunders 2008), and a new species from Palawan, the Philippines (Tang et al. 2013). In Laos, Goniothalamus are represented by four species (Newman et al. 2007;Lee 2016) (Saunders and Chalermglin 2008) and Goniothalamus gabriacianus (Baill.) Ast (Li et al. 2011).
In recent years, the authors examined the flowering material of Annonaceae cultivated in the living collections of Xishuangbanna Tropical Botanical Garden (XTBG), Chinese Academy of Sciences (CAS) and found an unknown species, which is very distinctive and belongs to the genus Goniothalamus; the records showed that this accession was originally collected in 2002, from Lao PDR (although the exact location remains unknown). Based on the morphological characters, we compared it to all other currently known species and concluded that it is new to science. As part of the botanical inventory of China-Laos transboundary biodiversity conservation, we carried out floristic surveys in the Nam Ha National Biodiversity Conservation Area in Luang Namtha Province and Phou Hin Phee National Biodiversity Conservation Area in Oudomxay Province of the northern Laos. During the fieldwork in March and October of 2018, we encountered two species of Goniothalamus representing new records for the flora of Laos. Therefore, the new and noteworthy species of Goniothalamus from Laos are provided and updated in this study.

Material and methods
Our study of the new taxon was predominantly based on plant material newly collected in XTBG. The records showed that this accession was originally collected in 2002, from Laos, although the exact location remains unknown. Ten individuals cultivated in two living collections were observed. Morphological characterizations were measured in the field. We compared our samples with type specimens of similar species deposited in herbaria. Specimens of Goniothalamus from Laos and neighboring regions were examined from the following herbaria: HITBC, IBSC, SING, A, K, BK, high-resolution digital images of specimens (especially types) from JSTOR Global Plants (https:// plants.jstor.org/) and other virtual herbarium websites (http://www.cvh.ac.cn/), as well as the taxonomic literature for species identification. Diagnosis. Goniothalamus saccopetaloides is morphologically similar to G. yunnanensis W.T. Wang with elliptic-oblong to oblong leaf blades and broadly lanceolate, pinkish orange to reddish brown outer petals, but easily distinguished by having almost fleshy, involute, saccate outer petals, subglobose and single seeded monocarps.
Etymology. The new species is named after its saccate and almost fleshy outer petals.
Phenology. Goniothalamus saccopetaloides has been observed in flowers from the end of March to May and in fruits from July to September.
Distribution and habitat. G. saccopetaloides was originally distributed in Laos; the exact location and its wild habitat remains unknown. Additional collections in the future may help to clarify its full distribution.
Conservation status. Due to insufficient field surveys so far, very limited details about its natural distribution and population status are currently known. Further investigation is required to determine more distribution sites and conservation status of the new species; at this moment we consider it as data deficient (DD) according to the IUCN Red List Categories (IUCN 2012).
Notes. Goniothalamus saccopetaloides is morphologically similar to G. yunnanensis; however, in addition to the description in the diagnosis, the two species can be easily distinguished by other characters. Goniothalamus saccopetaloides has 1 to 7 flowers, often on the main trunk (cauliflory) and on older branches (ramiflory), scarcely on young growth, whereas G. yunnanensis has 1 to 2 flowers, axillary, often on young growth, sometimes from leafless nodes (Li et al. 2011). Moreover, G. saccopetaloides has one ovule per carpel, subglobose monocarps and seeds with rounded apices, and G. yunnanensis has 2 ovules per carpel, ellipsoid monocarps and seeds with acute apices (Li et al. 2011). Fig. 2 (A-D) Goniothalamus calvicarpus Craib, Bull. Misc. Inform. Kew. 1922: 227 (1922  Notes. There has been considerable taxonomic confusion between G. calvicarpus and G. griffithii Hook. f. & Thomson (Saunders and Chalermglin 2008), the Chinese material identified as G. griffithii to be more correctly placed in G. calvicarpus (Saunders and Chalermglin 2008;Li et al. 2011). Goniothalamus calvicarpus is relatively widely distributed in the lower mountain evergreen forest in Xishuangbanna, southern Yunnan, compared with our materials collected in Northern Laos, the characters of flowers and fruits are exactly in line with G. calvicarpus; it is also not very hard to encounter around the adjacent areas in Northern Laos bordering southern Yunnan.  20°43'19.12"N, 102°08'46.61"E, 30 March 2018, Y.H. Tan et al., L0350 (HITBC);ibdem, 1372m, 20°43'18.24"N, 102°08'47.31"E, 30 March 2018.

Goniothalamus cheliensis Hu
Notes. Goniothalamus cheliensis is a very distinctive species, with leaves, flowers and fruits very large and densely rust-colored hirsute (Saunders and Chalermglin 2008), according to our personal observation, the monocarps of G. cheliensis can be up to 15 cm long.
With the addition of Goniothalamus saccopetaloides, Goniothalamus cheliensis, and Goniothalamus calvicarpus, seven species are currently recognized in Laos (Newman et al. 2007;Saunders and Chalermglin 2008;Li et al. 2011;Lee 2016). A key is provided below to further elucidate the morphological differences among the species occurring in Laos.