﻿Primulinascutellifolia, a new species of Gesneriaceae from southern Vietnam

﻿Abstract Primulinascutellifolia is described as a new species from Khanh Hoa Province, southern Central Vietnam. It is distinct in the genus in having scutellate leaves that make it a highly potential ornamental plant. The new species looks like P.annamensis in general shapes, sizes and colours of habit, inflorescence, flower, and leaf but is distinguishable by adaxially glabrous and abaxially strigose leaves with serrate margins, scutellate leaf blade and appressed downwards tomentose petiole, sparsely glandular hairs on apical 1/2 of the gynoecium and trapeziform one-lipped stigma with slightly emarginated apex.


Introduction
Primulina Hance (Gesneriaceae) is known to have more than 220 species, with the center of species diversity in south and southwest China and North Vietnam (Weber et al. 2011;Möller and Clark 2013;Möller et al. 2016;Xu et al. 2017;Li et al. 2019;Möller 2019;IPNI 2021). As more than 40 new species have been described over the past five years, we now expect that more species will be discovered for the genus if further explorations are employed (Möller 2019;Ge et al. 2020;Tong et al. 2020;Xin et al. 2021).
In Vietnam, Primulina was last revised to have 23 species (Vu 2017), but this work ignored P. crassirhizoma F.Wen, Bo Zhao & Xin Hong (Zhao et al. 2013). Based on molecular, morphological and cytological characters, Möller et al. (2016) (Yang et al. 2018;Chen et al. 2020;Tong et al. 2020). Therefore, prior to this paper, the total number of Primulina species known in Vietnam is 23.
In 2013, the last author of this paper collected a Primulina species in an evergreen broadleaf forest in Khanh Hoa Province. It was misidentified as P. annamensis (Pellegr.) Mich. Möller & A.Weber (Weber et al. 2011) -a species that grows popularly in many forests in Khanh Hoa Province and the neighbour Bidoup -Nui Ba National Park in Lam Dong Province. During our ongoing study of Gesneriaceae in southern Vietnam, we have carefully examined the plant and found that its scutellate leaves are distinct in the genus, and therefore we describe it here as a new species. Measurements of morphological characters were based on living plants whose photographs were taken with Canon EOS 7D digital camera. Morphological comparison with the close species was based on in situ observation and consultation with published literature. Diagnosis. Primulina scutellifolia differs from other congeners in having scutellate leaves.
Phenology. Flowering was found in August to November and fruiting in September to January.
Etymology. The specific epithet is derived from its special scutellate leaves. Vietnamese names. Báo xuân đón lộc. Distribution and habitat. Primulina scutellifolia is currently only known from the type location. It grows scattered on humid fertile soils in the evergreen broadleaf forest at elevations of 1,450 to 1,950 m. Our surveys throughout forests of Khanh Hoa and Lam Dong Provinces, which have now been ongoing for more than ten years, confirm its distribution is confined to the eastern slopes of the Hon Giao Range. This is a locally endemic plant.
Preliminary conservation status. The plant has been recorded in one population at the type location, with Extent of Occurrence <100 km 2 that is impacted by continued logging and not effectively protected. Therefore, we suggest the species to be categorized as Critically Endangered (A1a or B1a,b) (IUCN Standards and Petitions Subcommittee 2019).

Discussion
Primulina scutellifolia is unique in the genus by its scutellate leaves. It may be confused with P. annamensis (Figure 2) which has similar general shapes, sizes and colours of habit, inflorescence, flower, and leaf (Pellegrin 1930;Wood 1974;Pham-Hoang 1993; Vu 2017). However, the latter taxon can be distinguished from our species in having abaxially and adaxially denser silky leaves with obviously cordate base, flat blade and entire or crenate margins, denser pilose petioles, denser glandular hairs on more than apical 2/3 of the gynoecium, bi-lipped stigma and bifid stigma lips with round lobes (Table 1). Both species sometimes grow sympatrically but the latter is much more abundant. In dried specimens, the leaves of the new species look somehow subpeltate, which may be reminiscent of those in Deinostigma tamiana (B.L.Burtt) D.J.Middleton & H.J.Atkins from northern Vietnam (Burtt 1999;Möller et al. 2016), but the latter is distinguishable by its slightly peltate leaves with hairs on both surfaces, short petioles, hooked hairs on pedicel and 4-9-flowered inflorescences. The scutellate leaf blades, often with yellowish-greenish spots and beautiful flowers of the new taxon, render it an ornamental plant of great potential.