Three new species of Pilea (Urticaceae) from limestone karst in China

Pileadanxiaensis (Urticaceae), a new species in the Danxia landform from Guangdong, China including a description of the entire chloroplast genome

Pileadanxiaensis L.F.Fu, A.K.Monro & Y.G.Wei, a new species of Urticaceae from Danxia landform, Guangdong, China, is described and photographed. Phylogenetic analyses based on three DNA regions (ITS, trnL-F and rbcL) suggest that the new species belongs to P.sect.Pilea. Within the section, the new species is morphologically most similar to P.sinocrassifolia and P.peploides. Plastid genome and ribosomal DNA (rDNA) sequences of the new species are assembled and annotated. The plastid genome is 151,857 bp in length and comprises two inverted repeats (IRs) of 25,307 bp separated by a large single-copy of 82,836 bp and a small single-copy of 18,407 bp. A total of 113 functional genes are recovered, comprising 79 protein-coding genes, 30 tRNA genes, and four rRNA genes. A global conservation assessment suggests that P.danxiaensis should be classified as of Least Concern (LC).

Comparative plastid genomics of four Pilea (Urticaceae) species: insight into interspecific plastid genome diversity in Pilea

BACKGROUND

Pilea is a genus of perennial herbs from the family Urticaceae, and some species are used as courtyard ornamentals or for medicinal purposes. At present, there is no information about the plastid genome of Pilea, which limits our understanding of this genus. Here, we report 4 plastid genomes of Pilea taxa (Pilea mollis, Pilea glauca 'Greizy', Pilea peperomioides and Pilea serpyllacea 'Globosa') and performed comprehensive comparative analysis.

RESULTS

The four plastid genomes all have a typical quartile structure. The lengths of the plastid genomes ranged from 150,398 bp to 152,327 bp, and each genome contained 113 unique genes, including 79 protein-coding genes, 4 rRNA genes, and 30 tRNA genes. Comparative analysis showed a rather high level of sequence divergence in the four genomes. Moreover, eight hypervariable regions were identified (petN-psbM, psbZ-trnG-GCC, trnT-UGU-trnL-UAA, accD-psbI, ndhF-rpl32, rpl32-trnL-UAG, ndhA-intron and ycf1), which are proposed for use as DNA barcode regions. Phylogenetic relationships based on the plastid genomes of 23 species of 14 genera of Urticaceae resulted in the placement of Pilea in the middle and lower part of the phylogenetic tree, with 100% bootstrap support within Urticaceae.

CONCLUSION

Our results enrich the resources concerning plastid genomes. Comparative plastome analysis provides insight into the interspecific diversity of the plastid genome of Pilea. The identified hypervariable regions could be used for developing molecular markers applicable in various research areas.

Spiradiclis tubiflora (Rubiaceae), a new cave-dwelling species from southern China

Spiradiclis tubiflora, a new Rubiaceae species, is described from a limestone area of southern China. It is similar to Spiradiclis glandulosa and S. umbelliformis, but differs from the latter two in its linear stipule, short peduncle and tubular-funnelform corolla with a distinctively enlarged tube. The colour photograph, illustrations, detailed descriptions and conservation status of the new species are provided.

Discovery of a diverse cave flora in China

Few studies document plants in caves. Our field observations of a widespread and seemingly angiosperm-rich cave flora in SW China lead us to test the following hypotheses, 1) SW China caves contain a diverse vascular plant flora, 2) that this is a relic of a largely absent forest type lacking endemic species, and 3) that the light environment plants occupy in caves is not distinct from non-cave habitats. To do so we surveyed 61 caves and used species accumulation curves (SAC) to estimate the total diversity of this flora and used a subsample of 14 caves to characterise the light environment. We used regional floras and existing conservation assessments to evaluate the conservation value of this flora. We used observations on human disturbance within caves to evaluate anthropogenic activities. Four-hundred-and-eighteen vascular plant species were documented with SACs predicting a total diversity of 529–846. Ninety-three percent of the species documented are known karst forest species, 7% are endemic to caves and 81% of the species are angiosperms. We demonstrate that the light environment in caves is distinct to that of terrestrial habitats and that a subset of the flora likely grow in the lowest light levels documented for vascularised plants. Our results suggest that the proportion of species threatened with extinction is like that for the terrestrial habitat and that almost half of the entrance caverns sampled showed signs of human disturbance. We believe that this is the first time that such an extensive sample of cave flora has been undertaken and that such a diverse vascular plant flora has been observed in caves which we predict occurs elsewhere in SE Asia. We argue that the cave flora is an extension of the karst forest understory present prior to catastrophic deforestation in the 20thC. We suggest that within SW China caves serve as both refuges and a valuable source of germplasm for the restoration of karst forest. We also propose that caves represent a distinct habitat for plants that is most similar to that of the forest understory, but distinct with respect to the absence of trees, leaf litter, root mats, higher levels of atmospheric CO2, and lower diurnal and annual variation in temperature and humidity. We highlight tourism, agriculture and the absence of legislated protection of caves as the main current threats to this flora.

Four new species of Andean Pilea (Urticaceae), with additional notes on the genus in Venezuela

Four new species of Pilea (Urticaceae) from the Andes of Venezuela are described and illustrated: Pileamatthewii sp. nov., Pileamiguelii sp. nov., Pileanicholasii sp. nov., and Pileanidiae sp. nov. The affinities of these species and their positions within the informal classifications of Pilea proposed by Weddell and Killip are discussed. Notes on other species of Pilea found in Venezuela also are presented.