﻿Impatienschenmoui (Balsaminaceae), a new species from southern Yunnan, China

﻿Abstract Impatienschenmoui (Balsaminaceae), a new species from southern Yunnan, China, was described and illustrated based on morphological and molecular evidence. This new species is morphologically most similar to Impatiensoblongata Ruchis. & Niet, but can be distinguished by 7–9 pairs of leaf veins, glabrous perianth, obovate upper petal, and capsule with trichome.

In September 2019, during fieldwork in Mengla County, Yunnan, an unfamiliar Impatiens species was collected and transplanted to Shanghai Chenshan Botanical Garden. The flower blossomed in December 2020, indicating its unusual identity which may be new to science. In November 2021, we made a botanical trip back to Mengla County to collect flowers and fruit specimens. After careful comparison of relevant species from the adjacent area, we finally concluded that these specimens represent a species new to science, and described it here.

Morphology study
Morphological characters of the new species and related ones were compared based on living plants and herbarium specimens, including the digital resource of type specimens from JSTOR Global Plants (https://plants.jstor.org/). Herbarium specimens were examined in Chenshan Botanical Herbarium (CSH, index herbarium, http:// sweetgum.nybg.org/science/ih/herbarium-list/?NamOrganisationAcronym=CSH), original protologues and relevant literature were also investigated.

Datasets preparation
To resolve the phylogenetic position of the putative new species, two molecular markers ITS (ITS1-5.8S-ITS2) and atpB-rbcL were used in this study. Leaf material of the putative new species was collected from the field and stored with silica. Total genomic DNA was extracted with the modified CTAB method (Doyle and Doyle 1987) for library construction at Benagen (https://www.benagen.com). Paired-end sequencing of the whole sequences from both ends of 150 bp fragments was performed on the DNBSEQ T7, and about 2 Gb clean data were produced. The plastome and nrDNA were de novo assembled using the GetOrganelle pipeline 1.7.6.1 (Jin et al. 2020). Sequences of atpB-rbcL were extracted from the plastome annotated in Geneious Prime 2021.2.2 (https:// www.geneious.com) with comparison to the published plastome of Impatiens balsamina L. (GenBank accession: MW411292) as reference. Sequences of ITS1-5.8s-ITS2 were extracted with ITSx 1.1.3 (Bengtsson-Palme et al. 2013). The ITS dataset and the atpB-rbcL dataset were respectively aligned using MAFFT v7.450 by default setting. (Katoh and Standley 2013) and concatenated for phylogenetic analysis (Chen et al. 2020). Species sampling was based on previous studies (Yu et al. 2015;Ruchisansakun et al. 2018). All the sequence GenBank accession numbers were listed in Appendix 1.

Phylogenetic analysis
Maximum Likelihood estimation (ML) and Bayesian inference analysis (BI) were performed on Phylosuite v1.2.2 . For ML, GTR+F+R4 was selected as the best fit model for the ITS dataset, and GTR+F+R5 was selected as the best fit model for the atpB-rbcL dataset according to AICc by Modelfinder (Kalyaanamoorthy et al. 2017). Maximum likelihood was estimated using IQ-TREE (Nguyen et al. 2015) under the Edge-linked partition model for 2000 ultrafast (Minh et al. 2013) bootstraps. For BI, GTR+I+G was selected as the best fit model for both datasets according to AICc by PartitionFinder2 (Lanfear et al. 2017). Bayesian Inference phylogeny analysis was inferred using MrBayes 3.2.6 (Ronquist et al. 2012) under the partition model (2 parallel runs, 10,000,000 generations), in which the initial 25000 sampled data were discarded as burn-in. Tree files were visualized and annotated in Figtree v1.4.4 (http://tree.bio.ed.ac.uk/software/figtree/). Bootstrap (BS) and Posterior Probability (PP) values were used as an estimate of nodal robustness.
Phenology. Flowering and fruiting from October to December. Distribution and ecology. This new species was found under evergreen broadleaved forest at an elevation of 1500-1700 m on the limestone mountain ridge, and was currently known as only one population in Mengla County, Yunnan, China. This distribution area is very close to the border with Myanmar and Laos. We assume that this species should be also distributed in Myanmar and Laos due to their similar habitat.
Etymology. The specific epithet "Chenmoui" was dedicated to the famous Chinese collector and botanist, Chen Mou (陈谋)  who was one of the founders of the first botanical garden cataloged by the Classification System of Plants in China, and died during the collection trip through southern Yunnan, China. The Chinese name was given as "陈谋凤仙花".
Conservation status. This species is currently known only from one population in the type locality. The population is located in the tourist area of Kongming Mountain, where it could be easily disturbed by human activities, such as road construction and illegal mining. The IUCN status proposed is Vulnerable(VU) based on IUCN (2022) guidelines.
Additional specimens examined (Paratype   Note. New species of sect. Uniflorae discovered from Southeast Asia in recent years were mostly found distributed on mountain summits in an evergreen forest, which indicated that the stone mountain in this area was likely to be one of the speciation centers of this section. Impatiens species exhibited interspecific and even intraspecific variation in spur length, at least from our observation of the same population of I. davidii Franchet, I. platysepala Y. L. Chen, and I. chenmoui, which may be considered as retaining of a bimodal pollinated system of bee and lepidopteran (Ruchisansakun et al. 2016). Floristic survey and pollination ecology study in these regions' Impatiens species is still insufficient, and more fieldwork is urgently needed.