Clematisguniuensis (Ranunculaceae), a new species from Eastern China

Abstract Clematisguniuensissp. nov., a new narrowly endemic species of Clematis, is described and illustrated from the Huangshan Mountains of Eastern China. A description of C.guniuensis is presented along with illustrations, photographs and diagnostic differences between the new species and its putative close allies.


Introduction
Clematis L. (Ranunculaceae) is a large genus of early diverging eudicots, comprising approximately 280-350 species (Tamura 1987(Tamura , 1995Johnson 1997;Grey-Wilson 2000;Wang and Li 2005), out of which 147 species are reported in China, 93 of them being endemic to the country (Wang and Bartholomew 2001). The species of Clematis are economically important for their chemical properties relating to traditional medicine and also as ornamentals due to their attractive flowers (Grey-Wilson 2000; Wang and Bartholomew 2001). The genus is distributed worldwide, showing a high degree of speciation, with adaptations to a variety of habitats, especially in eastern Asia (Tamura 1993). Clematis species also show considerable morphological diversity and plasticity, making the taxonomy and classifications of the genus notoriously difficult (Brandenburg 2000), with different classifications emphasising different morphological characters (e.g. Prantl 1888 ;Tamura 1995;Johnson 1997;Grey-Wilson 2000;Wang and Li 2005).
During floristic surveys in experimental forestry plots of this Guniujiang National Nature Reserve between 2016 and 2018, a conspicuous species bearing 1-flowered cymes was collected. After thorough comparisons of diagnostic morphological and anatomical features of similar taxa (Lin and Wei 2009;Wang 2004aWang , 2004bWang , 2006aWang , 2006bWang , 2015aWang , 2015bWang and Bartholomew 2001;Wang and Huang 2014;Wang and Li 2016;Wang and Xie 2007), we have concluded that this specimen belongs to a hitherto undescribed species. We describe this specimen as a new species, presenting a morphological description, illustrations and comments on morphologically related species.

Clematis guniuensis
Phenology. Flowering from April to May; fruiting from October to November. Etymology. The specific epithet is derived from the type locality, Guniujiang National Nature Reserve. Vernacular name. Gǖ Niǘ Tiě Xiãn Lián (Chinese pronunciation); 牯牛铁线莲 (Chinese name).

Distribution and habitat.
To date, C. guniuensis is only known from the type locality, Guniujiang National Nature Reserve, Huangshan City, Anhui Province (Fig. 4). Currently the species is known from a few collections and there is only one known population with ca. 20 individuals at the type locality. The species is mostly found in tea plantations or forest edges along valleys of evergreen broad-leaved forests, at an elevation of 1,500 m a.s.l.
Conservation assessment. Based on the present field investigations, C. guniuensis is currently only known from the type locality and with a very small population size (ca. 20 individuals). The species should be given the IUCN status of Critically Endangered (CR) based on criteria D: "Population size estimated to number fewer than 50 mature individuals" (IUCN 2016).
Notes. A morphological comparison between C. guniuensis and morphologically related species, C. florida and C. huchouensis, is provided in Table 1. A total of 17 species of this genus was found in the Anhui province, with this new species being easily distinguished from the other species in this region by its 3-lobed leaflets, 1-flowered cymes, flowers 6-8 cm diam., sepals 4 and light green and glabrous filaments.