﻿Pipermotuoense, a new species of Piperaceae from Xizang, China

﻿Abstract Pipermotuoense X.W.Qin, F.Su & C.Y.Hao, a new species of Piperaceae from Xizang, China, is described and illustrated in this paper. The new species resembles P.yinkiangense and P.anisotis, but it can be readily distinguished from the compared species by several characteristics. Gonophyll leaves are chartaceous and the leaf secondary vein count is 7–9, with the outermost pair being very weak when there are nine veins. Additionally, the apical pair arises 2–4 cm above the base and the leaf base is asymmetrical, with bilateral petioles that cling and heal together. Pistillate floral bracts are sessile, with 3, 4 or 5 stigmas. The description of the new species includes photographs, detailed descriptions, notes on etymology, distribution and habitat, as well as comparisons with morphologically similar species.

Up to the present, more than 60 species have been recorded in China, half of which are endemic (Gilbert and Xia 1999;Cheng et al. 1999;Gajurel et al. 2001;Hao et al. 2012Hao et al. , 2015Hao et al. , 2017Hao et al. , 2020;;Yang et al. 2017;Su et al. 2022 ).Some species are economically important.A typical example is P. nigrum L. (Linnaeus 1753), which is the source of black pepper, the world's most widely used spice (Takooree et al. 2019).A few other species, such P. betle L., P. cubeba L.f., P. longum L., P. magen B.Q.Cheng ex C.L.Long & Jun Yang bis and P. pedicellatum C.DC., are used locally as condiments or medicine (Yang et al. 2017;Salehi et al. 2019 ).
Through two field investigations over an interval of three years in Motuo County, Xizang, China, specimens of a dioecious plant were found and collected.Based on a detailed examination of the morphological characteristics of this plant and its possible relatives (Tseng 1979;Cheng et al. 1999;Gilbert and Xia 1999;Suwanphakdee and Chantaranothai 2011;Suwanphakdee and Chantaranothai 2014;Su et al. 2022;Hao et al. 2012Hao et al. , 2015Hao et al. , 2017Hao et al. , 2020;;Junior and Guimaraes 2015;Mathew et al. 2016;Mukherjee 2016Mukherjee , 2018Mukherjee , 2020)), we concluded that it did not match morphologically with any of the existing species.It exhibits trophophyll blades with an auriculate-cordate and asymmetrical base, with base bilaterally clung to the petiole and overlap together, leaf-blades abaxially densely villous, especially along the mid-vein and flowers with a single stamen.Due to these distinctive morphological features, we confirm that it is a new species, which we describe and illustrate here as Piper motuoense X.W.Qin, F.Su & C.Y.Hao.
Phenology.Flowering from June to October; fruiting from September to November.

Figure 1 .
Figure 1.Piper motuoense X.W.Qin, F.Su & C.Y.Hao, sp.nov.A habit B branch with infructescence C branch with staminate spike D branch with trophophyll leaf E adaxial and abaxial surface of gonophyll leaf F adaxial and abaxial surface of gonophyll leaf base G detail of the indument along the mid-vein of the gonophyll leaf adaxial and abaxial surface H pistillate spike I staminate spike J infructescence K close-up of portion of the staminate spike L close-up of portion of the infructescence M cross-section of infructescence N seed (side view).Photographs by Fan Su.

Figure 2 .
Figure 2. Line drawing of Piper motuoense X.W. Qin, F. Su & C.Y. Hao A branch with infructescence B branch with staminate spike C magnified view of pistillate spike D magnified view of staminate spike E magnified view of infructescence F detail of the indument along the secondary nerves of the abaxial leaf surface G adaxial surface of gonophyll leaf H adaxial surface of gonophyll leaf base I abaxial surface of gonophyll leaf J abaxial surface of gonophyll leaf base K cross-section of infructescence L stamen M carpel N seed.Illustration by Fan Su, based on the holotype.