Two new species of Henckelia (Gesneriaceae) from Southeastern Yunnan, China

Abstract Two new species of Gesneriaceae, Henckelia nanxiheensis Lei Cai & Z.L.Dao, sp. nov. and H. multinervia Lei Cai & Z.L.Dao, sp. nov. from southeastern Yunnan, China, are described with color photos. The diagnostic characters of the two new species, together with photographs, detailed descriptions, distribution and habitat, as well as comparisons with morphologically similar species, are also provided.


Introduction
The circumscription of the genus Henckelia Spreng. (Gesneriaceae) has been redefined by Weber et al. based on molecular and morphological evidence (Weber and Burtt 1998;Weber et al. 2011). Henckelia s.l. consists of more than 60 species, mainly distributed across south and east Asia and the adjacent Himalayan regions (Weber et al. 2011;Manudev et al. 2012;Janeesha and Nampy 2015;Sinha and Datta 2016;Ranasinhe et al. 2016;Krishna and Lakshminarasimhan 2018;Sirimongkol et al. 2019).
Southwest China harbors a high diversity of Henckelia, and more than 20 species of Henckelia, which were originally described under the names of Hemiboeopsis W.T. Wang and Chirita Buch.-Ham. ex D. Don, are recorded from China (Wang et al. 1990(Wang et al. , 1998Weber et al. 2011;Li and Wang 2005;Möller et al. 2016;Xu et al. 2017).

Henckelia nanxiheensis
Phenology. Flowering from March to April. Etymology. The specific epithet 'nanxiheensis' refers to the type locality in the regions near the Nanxi River, which is a tributary of the Red River.
Vernacular name. The Chinese mandarin "nan xi he han ke ju tai" (南溪河汉 克苣苔) Distribution and habitat. The new species is currently known only from the type locality with a small population of ca. 150 individuals growing on moist rocks of the entrance to the valley near the banana plantation. The population of Henckelia nanxiheensis was first discovered in 2014 (without flowers) by Lei Cai; individuals in blossom were collected in 2017. The disturbance of the population has been observed with ca. 15% loss of the original habitat, due to human activities which are not limited to the expansion of banana plantations. An urgent preservation scheme is required to rescue this species from further disturbances or wipe-out from the type locality.

Henckelia multinervia
Phenology. Flowering from March to April; fruiting from April to May. Etymology. The specific epithet 'multinervia' is Latin, and refers to the relatively large number veins of this species.
Vernacular name. The Chinese mandarin "duo mai han ke ju tai" (多脉汉克苣苔) Distribution and habitat. This species is currently known only from the type locality, where ca. 80 individuals were found on moist rocks beside a river in a rainforest valley. More field work is required to assess the conservation status. Notes. The new species is most similar to H. ceratoscyphus in its habitat and floral characteristics, but can easily be distinguished from the latter by having long-elliptic to broadly lanceolate leaf blade (vs. narrowly to broadly elliptic); more lateral veins up to 12-22 pairs (vs. 7-11 pairs); the horn-like apex up to 1/4-1/3 of the length of calyx (vs. 1/2-2/3 of the length of calyx); the corolla glandular pubescent outside (vs. sparsely puberulent outside), the glandular pubescent style (vs. puberulent); and the ca. 2 mm long stigma (vs. ca. 6 mm long).

Discussion
Based on the field observation and field notes of historical herbarium collections of Henckelia, most species of Henckelia were found on soil and rocks (non-limestone), with only four species, H. auriculate, H. dimidiata (Wall. ex C.B. Clarke) D.J. Middleton & Mich. Möller, H. campanuliflora Sirim. and H. candida Sirim. (Sirimongkol et al. 2019) were recorded from limestone areas. We believe that the habitat driven speciation is worthy of further investigation. Although a large number of new species of Gesneriaceae have been reported from China in recent years, until now, no new members of Henckelia have been published after the revision (Weber et al. 2011) from China, and a few new species of the genus have been described from India, Sri Lanka, Myanmar and Thailand (Manudev et al. 2012;Janeesha and Nampy 2015;Ranasinhe et al. 2016;Krishna and Lakshminarasimhan 2018;Sirimongkol et al. 2019). The two new species in this paper were all discovered in Dawei Mountain area, a locality with several different vegetation types and abundant plant diversity; therefore, we will continue to pay more attention to the Gesneriaceae species diversity in this area and adjacent region.
According to the first-hand field investigation, the two new species described here also fit the criterion of Plant Species with Extremely Small Populations (Ma et al. 2013), with unique topography and habitat, extremely limited distribution range, the population and the habitat being susceptible to human activities, e.g. collection, crop planting or deforestation. The development of a conservation strategy and action plan is urgently needed to protect the two new species.