Petrocosmea nanchuanensis (Gesneriaceae), a new species from Chongqing, China

Abstract A new species, Petrocosmea nanchuanensis Z.Y. Liu, Z.Y. Li & Z.J. Qiu from Mt. Jinfo at Banhe valley of Nanchuan District in Chongqing Municipality (China) is described and illustrated for the first time. Even though this new species is similar to Petrocosmea barbata, it has several significant morphological differences, which includes smaller leaves, repand leaf margin, densely appressed longer pubescences on both surfaces of leaves, larger flower with length of its lower lips about three times longer than that of the upper lips, oblong lower lip lobes, shorter pistil, ovate anthers and styles that are shortly pubescent or approximately glabrous above the middle. The distinct features of P. nanchuanensis and four relative species namely, P. barbata, P. longipedicellata, P. cavaleriei and P. xanthomaculata were also represented in depth. However, P. nanchuanensis is most closely related to P. barbata, based on molecular studies.


Materials and methods
Measurements and observations of morphological characters of the new species, based on living individuals and specimens, were carried out in the field or greenhouse and at the herbarium. Hairs and glandular hairs and other tiny morphological characters were observed and measured by using a stereomicroscope (Nikon SMZ18). Morphological comparisons with related species were measured, based on living individuals in the greenhouse and specimens from PE, SZBG and KUN herbaria. Diagnosis. Petrocosmea nanchuanensis is morphologically similar to P. barbata Craib, but is distinguished from the latter by smaller leaves, a repand leaf margin, densely appressed longer pubescences on both surfaces of its leaves, larger flower with the length of its lower lips three times longer than that of the upper lips, oblong lower lip lobes, shorter pistil, ovate anthers and styles that are shortly pubescent or approximately glabrous above the middle.
Habitat and distribution. Petrocosmea nanchuanensis grows on moist shady limestone cliffs or along forest edges at an altitude of 600-650 m on the Mt. Jinfo, Banhe valley, Nanchuan District, Chongqing Municipality, which is adjacent to Guizhou Province in south-western China.
International Union for Conservation of Nature (IUCN) Red List Category. The new species is determined to be Critically Endangered (CR A2c) according to the IUCN Red List of Threatened Species Categories and Criteria (IUCN 2001). About 850 individuals were found in two separate and restricted populations: 300 individuals were found growing in one location with ca. 4 × 2 m 2 and 550 individuals were found at the other location with ca. 8 × 3 m 2 . Petrocosmea nanchuanensis is only known from the type locality, i.e. Nanchuan District and their habitat has been threatened and damaged by deforestation and over-exploitation due to native tourism despite its protection in the Mt. Jinfo National Nature Reserve.
Phenology. The new species was collected with flowers during September-November; fruits were not seen.
Additional specimens studied (

Discussion
In our previous study, molecular phylogenetic analysis of Petrocosmea genus which includes P. nanchuanensis has been studied using six chloroplast DNA regions (atpI-atpH, matK, trnH-psbA, rps16 intron, trnL-F and trnT-L) and two nuclear DNA regions (ITS and PeCYC1D) . The molecular phylogenetic study showed that P. nanchuanensis rests at the base of a clade containing three other species, P. barbata Craib, (1919), P. longipedicellata W.T. Wang, (1985) and P. cavaleriei Levl., (1911), as shown in Fig. 3. In the phylogenetic tree, this clade, which includes four species, P. nanchuanensis, P. barbata, P. longipedicellata and P. cavaleriei, has some morphological synapomorphies, such as two yellow spots at the base of the lower lip lobes, densely villous on the ovary, villous inside corolla tube and glabrous filaments. The phylogenetic tree revealed that P. nanchuanensis is most closely related to P. barbata that also belongs to sect. Barbata.   Table 1 summarises the distinguishing features of P. nanchuanensis and its related species namely, P. barbata, P. longipedicellata, P. cavaleriei and P. xanthomaculata G.Q. Gou & X.Y. Wang (2010). Herein, both morphological and our previous molecular studies support P. nanchuanensis as a new species and being most similar to P. barbata. The foremost morphological differences between P. nanchuanensis and P. barbata include that P. nanchuanensis has smaller leaves than P. barbata and P. nanchuanensis leaves have an undulate-toothed margin, whereas, P. barbata has a crenate margin. Moreover, P. nanchuanensis shows a densely appressed villous on both surfaces of leaves instead of the adaxially puberulent and abaxial slightly and densely puberulent pattern of P. barbata.
Likewise, P. nanchuanensis has larger flowers than P. barbata, in which P. nanchuanensis has flowers about three times longer in lower than in upper lips instead of about two times longer in lower than in upper lips in P. barbata. Additionally, lower lip lobes are oblong in P. nanchuanensis instead of broadly ovate in P. barbata, while P. nanchuanensis has a shorter pistil than P. barbata. Besides, P. nanchuanensis has styles that are shortly pubescent or approximately glabrous above the middle instead of styles with unfolded villous and short glandular hairs under the top and short glandular hairs on the top in P. barbata. The P. nanchuanensis has ovate instead of round-ovate anthers in P. barbata.
We conclude that Petrocosmea nanchuanensis belongs to sect. Barbata due to its floral structure, particularly anthers that are not constricted near the apex, the length of its abaxial corolla lip being twice as long as the adaxial and two yellow spots at the base of the lower lips lobes. Even though, this new species is similar to P. barbata and mostly varies through smaller leaves, a repand leaf margin, densely appressed longer pubescences on both surfaces of its leaves, larger flowers with their lower lips about three times longer than the upper lips, oblong lower lip lobes, shorter pistil, ovate anthers and shortly pubescent styles or approximately glabrous above the middle.
Morphological similarity between P. nanchuanensis and P. barbata has been supported by our previous molecular phylogenetic data . A phylogenetic tree, based on six cpDNA regions and two nrDNA regions, confirmed that P. nanchuanensis is most closely related to P. barbata (Figure 3), which is distributed throughout Kunming County in the east-central portion of Yunnan Province, China.