Taxonomic notes on the Piper pedicellatum C. DC. (Piperaceae)

Based on the evidence from morphology, literature survey and specimen examination, Piper curtipedunculum (Piperaceae) is recognized as independent species which is used to be a synonym of Piper pedicellatum. Piper boehmeriifolium var. glabricaule, Piper terminaliflorum and Piper yunnanense are considered as new synonyms of P. pedicellatum to which they are similar by a series of morphological characters. And the morphological differences, similarities and geographical ranges of these plant are clarified.

It is hard to identify the specimens of Piper accurately due to polytypic blades, lack of perianth, only tiny bracts, stamens and pistils in the flowers. Moreover, dependening on the herbarium specimens and the insufficient observation to the population variation pattern, there are still some taxonomic problems in Chinese Piper species, such as misapplication of names, unclear species delimitation and improper taxonomic treatment of some species.
The aim of this paper is to clarify P. pedicellatum, P. curtipedunculum, P. boehmeriifolium var. glabricaule, P. terminaliflorum and P. yunnanense based on our extensive examination of literature studies and detailed observations on the field populations. The related articles of International Code of Nomenclature(ICN) (Turland et al. 2018) were followed for nomenclature changes.
We examined specimens that kept in all the major Chinese herbaria, holotype especially, including IBSC, KUN, NAS and PE, and in some non-Chinese herbaria as well, including A, B, E, G, K, MO, P and US. The size and shape of leaves and inflorescences were studied first. Then the details of flowers and fruits were examined. Through the study of a large number of specimens, the morphological character variation pattern, phenology, habitat and other information of those plants were preliminarily understood, which laid a foundation for field work.
The basic distribution data and photographs of the those plants were collected during our fieldwork from 2012 to 2021 in Yunnan province of China. The habitat was photographed and some of major morphological characters were measured, such as plant life form, size and shape of the leaves and inflorescences, details of flowers and fruits, form of the floral bracts and others.   Tseng (1979) published a new distribution of P. pedicellatum in China, in Acta Phytotaxonomica Sinica, who stated that the species was similar to P.

Piper curtipedunculum
curtipedunculum, but differs from it by leaves 7-9 veins, 3 of which emanate from the base; Pedicels often as long as petioles; bracts large, 1-1.2 mm in diameter (leaves 7-9 veins, 5-7 of which emanate from the base; Pedicels length, often twice as long as petioles; bracts 0.5-1 mm in diameter). M.G. Gilbert and N.H. Xia(1999) considered that the difference was small between the two species and P. curtipedunculum was consdered as a synonym of P. pedicellatum in Flora of China.
In the protologue, we found that both of them were described as liana and no significant characteristic difference by De Candolle. However, P. curtipedunculum can easily be distinguished from P. pedicellatum by several morphological characters. We examined the holotype and origin specimens of both names and found that P. pedicellatum were subshrubs and P. curtipedunculum were woody lianas. Morphology of leaves, inflorescences and fruits were obviously different. Field observation and examination on the different populations of both species showed that P. pedicellatum and P.curtipedunculum were differ significantly in their leaf blade shape (ovate or narrowly ovate to broad elliptic vs. trophophyll leaf blade lanceolate, gonophyll leaf blade broad lanceolate to ovate), leaf blade texture (papery, rough vs. leathery, glossy), infructescence size (length 4-10 cm, 7-11 mm in diameter vs. length 5-10 cm, 3-4 mm in diameter), mature berries (obovate, 4-angled, 2-3 mm in diameter, red vs. globose, 0.8-1.2 mm in diameter, green), and stigmas (3 or 4 vs. 3) (Figure 1, Table 1). FIGURE 1. A-C Type of P. curtipedunculum C. DC., Mengzi Yunnan Province, A holotype, B100294777; B-C isotype, A00005900, E00318488, respectively. D-F Type of P. pedicellatum C. DC., Bangladesh, D lectotype, K000794428; E isolectotype, P01656299; F Syntype, K000794427.   Note. Piper glabricaule C. DC. was designated based on only one specimen in branch with male spike (Fig. 3A) by De Candolle (1917) from Mengzi, altitudes 1524 m, Yunnan province in China. M.G. Gilbert and N.H. Xia (1999) reduced P. glabricaule to a variety of Piper boehmeriifolium mainly because the former is different in leaf morphology and infructescence size. According to the original description, P. glabricaule is more similar to P. pedicellatum with slight differences in leaf morphology. There should be two extremes of a continuum of material and the leaves are often transitional and not well demarcated in the wild.
The type specimens of Piper terminaliflorum Y.Q. Tseng and Piper yunnanense Y. Q. Tseng were both collected from Lincang of Yunnan Province in China by Y.Q. Tseng (1979). Y.Q. Tseng stated that the Piper terminaliflorum was similar to P. glabricaule, but differed by its inflorescences insertion patterns. M.G. Gilbert and N.H. Xia (1999) considered that the difference was small between P. terminaliflorum and P. boehmeriifolium and placed P. terminaliflorum as a synonym of P. boehmeriifolium in Flora of China. During 2012 to 2021, we carried out continuous field investigation of Piper speceis in Lincang and Mengzi, Yunnan Province. And we also compared the type of specimens and protologue of these four plants. The results showed that the life form, leaves shape and texture, finely glandular, base oblique, veins number, inflorescence structure and length, fruit shape and size vary continuously and have no much distinct morphological difference (Table 2，Fig. 3). In addition, the type localities of the four species are not far away from each other. These available evidence indicate that these species are actually conspecific. P. pedicellatum is different from P. boehmeriifolium by its leaf blades ovate or narrowly ovate to elliptic, base broadly cuneate or suborbicular, bilateral difference 2-3 mm, apex acute to acuminate, female spikes 6.5-8 mm thick in fruit ( leaf blades narrowly elliptic, oblong, oblong-lanceolate, base oblique, bilateral difference 5-10 mm, apex acute to long acuminate, female spikes 3-3.5 mm thick in fruit ) (Fig. 1D, Fig. 3E-G).  FIGURE 3. A-C Holotype of P. boehmeriifolium var. glabricaule, P. terminaliflorum and P. yunnanense respectively; D Isotype of P. yunnanense; E-F Habitat and Branch with infructescence of P. boehmeriifolium in the wild (Xishuangbanna, Yunnan); G P. pedicellatum in the wild (Jingdong wuliang mountain, Puer, Yunnan); H Comparison of unripe infructescence between P. pedicellatum(Left) and P. boehmeriifolium (Right)