Two new species of Paraboea (Gesneriaceae) in Caryota obtusa forests in Southwest China, with compound and simple dichasia, respectively

Abstract Two new species of Gesneriaceae, Paraboea myrianthasp. nov. and P. brevipedunculatasp. nov. are described and illustrated with photos. They grow in the Caryota obtusa forests from Yunnan Province of China. P. myriantha is closely related to P. glutinosa (Hand.-Mazz.) K.Y.Pan, but differs mainly in corolla outside glandular-puberulent, adaxial corolla lobes semicordate, corolla tube obliquely campanulate, and filaments glandular-puberulent. P. brevipedunculata is closely related to P. crassifolia (Hemsley) B. L. Burtt, but different mainly in simple dichasia with 1 and 2 flowers, peduncles 0.5–2 cm long and capsules slightly twisted. The geographical relationship between the two new species and their similar species has been discussed.


Introduction
The genus Paraboea (Clarke) Ridl. (Gesneriaceae), including about 90 species, mainly occurs in Bhutan, China, Indonesia, Malaysia, Myanmar, Philippines, Thailand and Vietnam (Xu et al. 2008). Recently, several new species have been published (Chen et al. 2008(Chen et al. , 2012Kiew 2010;Xu et al. 2012;Wen et al. 2013;He et al. 2018). Most of them are distributed in the karst regions in South China and Indo-China (Li 1987;Wang 1990;Xu 1993;Fang et al. 1995;Zhu et al. 2003;Li and Wang 2004;Shui and Chen 2006;Zhu 2007;Shui et al. 2017). The genus is easily recognised by the thick hairs on the adaxial surface and lax hairs on the abaxial surface of the leaves in the karst regions, especially in Caryota obtusa forest in southwest China . The forest is a special vegetation subtype in the karst regions and harboured numerous endemic species, such as Paraboea hekouensis Y.M. Shui (Chen et al. 2012;Chen et al. 2019).
Long-term surveys of Caryota forests revealed some new findings in the karst regions in Southwest China. From 2001 to 2005, during our botanical exploration to Caryota forests in karst areas in the southeast of Yunnan Province, China, we collected some species of the genus Paraboea in Gesneriaceae in Hekou County of SE Yunnan, China (Figure 1). Amongst them, one species with up to 0.9 m tall habit, produces a compound dichasium with hundreds of flowers (Shui and Chen 2006;Chen et al. 2008). With further observation, it is similar to P. glanduliflora Barnett in glandular hairs outside the corollas and different in the basal leaves (Wang et al. 2012). After careful comparison with the other species of Paraboea in China (Li 1987;Wang 1990;Fang et al. 1995;Li and Wang 2004;Chen et al. 2008Chen et al. , 2012Chen et al. , 2017He et al. 2018) and bordering countries (Thúợngtiền 2000;Xu et al. 2008), we confirmed that the species represents an undescribed species of Paraboea in Gesneriaceae. After a complete examination to the main worldwide herbaria, we confirmed several additional specimens collected in the adjacent karst regions in China during the 2001-2018 period.
In June 2013, on the other hand, we collected one small doubtful species of Paraboea with fruits in Malipo county in the southeast of Yunnan Province (Figure 1). In the field, it grows on cliffs, as well as in the Caryota forest at the border with Vietnam in Malipo county, Yunnan, China. However, we missed the flowering period in 2014 and 2015. In May 2016, we collected the plants with flowers and confirmed that it belonged to the genus Paraboea. After an examination of literatures and related specimens, we determined that it is unique in ca. 5 cm high habit and simple dichasia and should be an undescribed species in the genus. It is possible that it may be collected in Vietnam in the future (Figure 1).

Materials and methods
We confirmed two new species after examination of the specimens preserved in worldwide herbaria (E, IBSC, K, KUN, P, PE). We took photographs of the habit and macro-morphological characters in the field. Subsequently, we carried out morphological observations and measurements of the two new species, based on living plants in the field and Kunming Botanical Garden, together with additional specimens in KUN. All micro-morphological characters were observed and photographed with a Leica S8 APO stereomicroscope and a Nikon D700 microscope camera. Diagnosis. The new species is similar to P. glutinosa (Hand.-Mazz.) K.Y.Pan in winged petioles, leaf-like bracts and compound dichasia, but distinguished by adaxial corolla lobes semicordate (vs. nearly rounded), tube obliquely campanulate (vs. urceolate) outside glandular-puberulent (vs. glabrous or rarely pubescent) and laterally uneven (vs. even), and glandular-puberulent filament (vs. covered by a beard of multicellular hairs); and similar to P. thorelii (Pellegr.) B.L.Burtt in winged petioles and compound dichasia, but distinguished by corolla tubes 9-10 mm long (vs. 3-4 mm long) outside glandular-puberulent (vs. glabrous) and staminodes 2 (vs. inconspicuous).
Etymology  Shui and Chen (2006). However, we de- cided to name it as Paraboea myriantha, after careful comparison of references and type specimens with similar species, P. glutinosa (Hand.-Mazz.) K.Y.Pan and P. thorelii (Pellegr.) B.L.Burtt. The new species is similar to the above two species on winged leaves and compound dichasia, but distinguished by corolla lobes (shape) and tubes (shape and indumenti) and glandular filament, which are described in diagnostics (Figure 2; Xu et al. 2008;Vu et al. 2011). Furthermore, P. glutinosa is distributed in South China, P. thorelii in South Laos (type locality) and North Vietnam, but the new species we proposed seems geographically distributed between the above two similar species. So, the future molecular work in the context of the whole genus may reveal if the above three species become a species complex with obvious geographical replacement. Diagnosis. Paraboea brevipedunculata is similar to P. crassifolia (Hemsley) B. L. Burtt in morphology and indumenti of the leaves, but different in simple dichasia with 1-2 flowers (vs. compound dichasia with many flowers), peduncle 0.5-2 cm (vs. 8-12 cm), 4-5 mm calyx segments (vs. 2-3 mm), capsules slightly twisted (vs. multi-twisted) and 0.6-0.7 mm long when mature (2-2.5 cm long). The new species is also similar to P. velutina (W.T.Wang & C.Z.Gao) B.L.Burtt. in the small plant, short peduncle and simple dichasia, but distinguished by purple corolla (vs. white), calyx 4-5 mm long (vs. ca. 1 mm), lobes of adaxial lip ca. 3 × 5 mm (vs. ca. 1.5 × 1 mm), lobes of abaxial lip ca. 5 × 7 mm (vs. ca. 1.5 × 2.3 mm) and capsule slightly twisted (vs. not twisted).
Etymology. The new species is named after its short peduncle per dichasium.   Hems1.) B.L. Burtt in its linear bracts (Wang et al. 1998;Li and Wang 2004). P. crassifolia is distributed in W Huibei, SE Chongqing, Guizhou, Guangxi and SE Yunnan in China, while P. neurophylla is distributed in China (Central and West Yunnan) and Myanmar. The new species is distributed in SE Yunnan and shares the similar distribution with P. crassifolia, which is considered as the similar species to the new species. Besides, as to the small habit and fruits, it is somewhat similar to P. velutina in West Guangxi, which is next to SE Yunnan, but distinguished by corolla colour, size of calyx and corolla lobes, and twisted capsules (see the above diagnosis). Vu et al. (2011) reported Paraboea neurophylla as a new record in Vietnam. The voucher specimens are collected from Ba Be National Park, Bac Kan province, Vietnam. However, the figure (based on HLF 608 in HN) reveals that it seems to be conspecific with the new species we proposed here. Additionally, the description and geographical distribution of the new record in Vietnam roughly match that of the new species (Vu et al. 2011). Although we are still waiting for further confirmation from the detailed surveys, it is possible that the new species will also occur in North Vietnam. In fact, P. neurophylla grows at ca. 2000 m elevation in China (Yunnan, e.g. B.Y. Qiu 55121 in PE, P. I Mao 1322 in PE, S. E. Liu 831, 13970, 14087, 19713 and 20886 in PE, K.M. Feng 10115 in PE, K.Y. Pan 1 in PE, J. Wu WJ2015010 in PE, Z.J. Qiu QZJ-0936 in PE, C.J. Chen 38 in PE, J.S. Xin 51404 in IBSC) and Myanmar (Shan hills, Collett 804, holotype K and isotype in E), but its habitat is very different from the habitat of the new species at less than 1000 m elevation (Wang 1990;Wang et al. 1998;Xu et al. 2008).