﻿Ficusmotuoensis (Moraceae), a new species from southwest China

﻿Abstract A new climbing species, Ficusmotuoensis Zhen Zhang & Hong Qing Li in Moraceae from southwest China has been described and illustrated in this paper. The new species resembles F.disticha, F.diversiformis and F.hederacea, but differs from these in the medium-sized acrophylls, shorter peduncle, as well as larger and spotted syconium. According to the morphological traits and phylogenetic placement, the new species belongs to Ficussubg.Synoeciasect.Apiosycea. Besides, the new species deviates from the common distribution pattern compared to the other members of sect. Apiosycea, indicating that it could be very useful for exploring the biogeography of sect. Apiosycea.


Introduction
Ficus L. is an extremely species-rich woody genus in the family Moraceae, mainly distributed in tropical and subtropical regions (Berg and Corner 2005;Pederneiras et al. 2018;Zhang et al. 2020). As the largest genus in Moraceae, Ficus features the syconium and mutualism relationship to fig wasps (Janzen 1979;Wiebes 1979;Bronstein and McKey 1989). To date, the number of species in Ficus has grown to almost 800 after recent frequent descriptions from South America, Southeast Asia and so on (Chantarasuwan and Thong-Aree 2006;Berg and Homeier 2010;Whitfeld and Weiblen 2010;Berg 2012;Medina 2014;Machado and de Queiroz 2017;Pederneiras et al. 2017;Ezedin and Weiblen 2019;Rivera et al. 2020). Southwest China, especially the Himalaya-Hengduan Mountains, is one of twenty-five biodiversity hotspots worldwide and possesses abundant endemic species (Myers et al. 2000). Meantime, many gynodioecious fig trees are endemically distributed in the Himalaya-Hengduan Mountains or the Sino-Himalaya Region in Ficus subg. Ficus and subg. Synoecia (Miq.) Miq. However, relatively few species in Ficus have been described from these regions in two decades (Chen et al. 2020), indicating a possible underestimate of biodiversity.
Through two field investigations with an interval of seven years in Motuo County, Tibet, in China, we found an unrecorded climbing fig tree. The climbing species is rather distinct in the aspects of small leaves and spotted syconia compared to the other Chinese climbing figs. Based on specimen examination and phylogenetic analyses, we confirmed that it is a new species in subg. Synoecia and provided its taxonomical description and illustration.

Morphological observations
The novel species was surveyed in Motuo County, Tibet, in China. The morphological characteristics were measured and then photographed by digital camera (Canon, D80) or stereomicroscope (SMZ25, Nikon). The type specimens have been stored in the Herbarium of the East China Normal University (HSNU). The morphological comparison between the new species and its congeners has also been examined.

Phylogenetic inference
Three samples represented the new species and three nuclear loci, internal transcribed spacer (ITS), external transcribed spacer (ETS) and glyceraldehyde 3-phosphate dehydrogenase (G3pdh) were used to verify its phylogenetic placement in Ficus. Simultaneously, two samples of its morphologically related species F. hederacea Roxb. were supplemented. The other taxa and sequences in subg. Synoecia were selected according to the work of Zhang et al. (2020) and their GenBank accession numbers can be found in Suppl. material 1: Table S1. In total, twenty-eight samples were involved in phylogenetic analyses together with two extra samples of F. laevis Blume as the outgroups.
Bayesian Inference (BI) and Maximum Likelihood (ML) analysis were implemented to reconstruct the phylogenetic trees. Bayesian Inference was carried out by MrBayes 3.2.6 (Ronquist et al. 2012) with 5,000,000 generations, sampling every 1,000 generations to ensure the convergence (average deviation of split frequencies less than 0.01 and the effective sample sizes over 200). The first 25% of sampling trees were treated as burn-in and the remainder were used to prepare the consensus tree and posterior probabilities. The IQ-TREE 2.1.3 (Nguyen et al. 2015) was used to reconstruct the Maximum Likelihood tree with 10,000 ultrafast bootstrap to assess the confidence of the nodes. The nucleotide substitution models for both BI and ML were selected by ModelFinder (Kalyaanamoorthy et al. 2017) with the respective commands. The ML tree was chosen to show the topology after visualisation by Figtree 1.4 (http://tree.bio.ed.ac.uk/software/figtree/).

Morphological observations
The novel species is a gynodioecious root-climbing taxon with obvious dimorphic leaves, thus it should belong to subg. Synoecia. Some key traits, including leaf dimorphy, rather small leaves, spotted syconia and sessile flowers, make the new species fairly distinct in subg. Synoecia. Four climbing fig trees, including F. laevis, F. pubigera var. pubigera, F. pubigera var. maliformis and F. sarmentosa Buch.-Ham. ex Sm., were sympatric with the new species in Motuo County, based on our field investigation. However, none of them resembles the new species. The bathyphylls of the new species are similar to those of F. disticha Blume (subg. Synoecia), except for the symmetric lamina and its round apex. Besides, the acrophylls (4.5-6.5 cm in length) and syconia (8-10 mm in diameter) of the new species are obviously larger than those of F. disticha. The new species also resembles F. hederacea and F. diversiformis in the aspect of acrophylls, whereas its syconia are different from these. The syconia of F. hederacea is globose with a 10-12 mm peduncle in length and those of F. diversiformis is basal constricted with a 3-12 mm peduncle. Both of them are clearly longer than the new species (1-2 mm). From a geographical point of view, the new species is also allopatric to F. disticha, F. hederacea and F. diversiformis. A comparison between the new species and its morphological allies are shown in Table 1.

Phylogenetic Inference
The phylogenetic tree indicates that three samples of the new species comprised a wellsupported monophyletic group (posterior probability = 1 and ultrafast bootstrap value = 100, Fig. 1). The new species is phylogenetically sister to another widely distributed  species F. hederacea and both of them form a sister relationship to the Sri Lankan endemic species F. diversiformis. The closely-related genetic relationship amongst these three species is also supported by their morphological similarity. Another morphologically related species F. disticha is far from the new species in the phylogenetic tree. Diagnosis. Ficus motuoensis is similar to F. disticha in the shape and texture of the bathyphylls, but differs from the latter by its larger acrophylls (4.5-6.5 cm in F. motuoensis versus 2.5-5 cm in F. disticha) and larger syconia (8-10 mm in F. motuoensis versus 3-6 mm in F. disticha). The new species also resembles F. hederacea and F. diversiformis in the aspect of the acrophylls, but can be distinguished from these by its globose and spotted syconia (versus without spots in F. hederacea and F. diversiformis) with a shorter peduncle (1-2 mm in F. motuoensis versus 10-12 mm in F. hederacea and 3-12 mm in F. diversiformis).
Distribution and habitat. Only found in the type locality, i.e. China: Tibet, Linzhi, Motuo County. However, considering that Motuo is close to Assam in India, the new species probably also exists in India. The new species develops very well in the type locality, as it has been recorded in five different villages (Bari, Yarang, Gelin, Deergong and Maniweng). The individuals of the new species are rather abundant without the risk of extinction. The new species grows in the tropical monsoon forest climbing on substrates, such as soils and tree trunks, whereas its fertile branches often break away from the substrate at the time of reproduction. It is located at an altitude of 700-2000 m. Note. Based on the morphological traits and phylogenetic placement, the new species is related to F. disticha, F. diversiformis and F. hederacea. In the latest division framework of Ficus, these three species were assigned to sect. Apiosycea (Miq.) Pedern. & Romaniuc (Zhang et al. 2020). However, the taxa in sect. Apiosycea are mainly distributed in Malesia (Zhang et al. 2020). In total, six Chinese taxa belong to sect. Apiosycea, including F. hederacea, F. laevis, F. punctata Thunb., F. sagittata Vahl, F. trichocarpa Blume and F. villosa Blume, but south China is only the northern limit of their distribution range (Chang et al. 1998;Berg and Corner 2005). Therefore, the new species, which is endemic to southwest China, could be very useful for exploring the biogeography of sect. Apiosycea.