Combined analysis of metagenome and transcriptome revealed the adaptive mechanism of different golden Camellia species in karst regions.

Camellia sect. Chrysantha is an important rare and protected plant species. Some golden Camellia species grow in karst soil while others grow in acidic soil. In order to study the adaptation mechanism of golden Camellia to the karst environment, four species of golden Camellia growing in the karst soil (Camellia pubipetala, Camellia perpetua, Camellia grandis, and Camellia limonia) and four species growing in the acidic soil (Camellia nitidissima, Camellia euphlebia, Camellia tunghinensis, and Camellia parvipetala) were selected for this study. Combining the metagenome and transcriptome, the structure and function of the rhizosphere microbial communities and the gene expression in roots of golden Camellia were analyzed. The results showed that the rhizosphere microbial communities in different golden Camellia were significantly different in abundance of Acidobacteria, Actinobacteria, Candidatus_Rokubacteria, Nitrospirae, Planctomycetes, and Candidatus_Tectomicrobia. The proportion of Candidatus_Rokubacteria was significantly higher in the rhizosphere soil of four species of golden Camellia grown in karst areas, compared to C. nitidissima, C. euphlebia, and C. tunghinensis. The linear discriminant analysis Effect Size showed that C. parvipetala was similar to karst species in the enrichment of ABC transporters and quorum sensing. During the transcriptome analysis, numerous upregulated genes in four karst species, including CYP81E, CHS, F3H, C12RT1, NAS, and CAD, were found to be enriched in the secondary metabolite synthesis pathway in the KEGG library, when compared to C. tunghinensis. This study provides information for plant adaptation mechanisms on the rhizosphere soil microbial composition and gene expression in secondary metabolic pathways to karst habitats and its distribution in karst areas.

Correlation between Vegetation Structure and Species Diversity in Traditional Villages in Karst Topographic Regions of the Zunyi City, China.

Studying the relationship between vegetation structure and diversity is important in an area having karst topography and unique traditional customs. We selected a total of six traditional villages in Zunyi City, China, to collect vegetation data. Additionally, using one-way ANOVA and the Pearson correlation coefficient analytic method to analyze, the results showed that, overall, plant communities were mostly regularly distributed. The overall differentiation degree was low aggregation, intensity, and the extreme intensity mixed state. Overall, competitive pressure, growth vigor and stability were better than the natural forest. The community stability index at lower altitude was significantly higher than that at higher altitude. The recorded plant communities in the living space were typically aggregated, the plant communities were randomly distributed in the production space, and the plant communities were uniformly distributed in the ecological space. In general, the diversity indexes, except the Jh index, were the highest in the herb layer; the second was in the shrub layer and the lowest was in the tree layer. Species diversity at the middle altitude was higher than that at low and high altitudes (except for the shrub at a high altitude of 1100-1160 m). The overall plant species diversity was highest in the living space, second highest in the ecological space and lowest in the production space. On the whole, there was a significant correlation between the spatial structure of plant communities and the species diversity of plant communities at different altitudes, and in PLE spaces. The main objective of this study was to reveal the plant community structure, species diversity, and their relationship under the dual effects of national traditional culture and karst landform. Additionally, we sought to provide theoretical guidance for the construction of plant community protection and biodiversity conservation in traditional villages in karst areas.

Plant adaptability in karst regions.

Karst ecosystems are formed by dissolution of soluble rocks, usually with conspicuous landscape features, such as sharp peaks, steep slopes and deep valleys. The plants in karst regions develop special adaptability. Here, we reviewed the research progresses on plant adaptability in karst regions, including drought, high temperature and light, high-calcium stresses responses and the strategies of water utilization for plants, soil nutrients impact, human interference and geographical traits on karst plants. Drought, high temperature and light change their physiological and morphological structures to adapt to karst environments. High-calcium and soil nutrients can transfer surplus nutrients to special parts of plants to avoid damage of high nutrient concentration. Therefore, karst plants can make better use of limited water. Human interference also affects geographical distribution of karst plants and their growing environment. All of these aspects may be analyzed to provide guidance and suggestions for related research on plant adaptability mechanisms.

Bacterial Communities Are More Sensitive to Water Addition Than Fungal Communities Due to Higher Soil K and Na in a Degraded Karst Ecosystem of Southwestern China.

Precipitation is predicted to become more intense in Southern China in the context of climate change; however, the responses of microbial communities to variations in soil moisture have not been well documented for karst areas. The climate is typically in a subtropical monsoon category with two different seasons: a dry season (December-May) and a wet season (June-November). Based on a randomized complete block design (RCBD), a water addition experiment (0, +20, +40, and +60% relative to local precipitation) was established in April 2017, with five replicates, in a degraded grass-shrub community. Sampling was performed in May and at the end of August of 2017. Macroelements (C, H, N, P, K, Ca, Mg, and S), microelements (Mn, Fe, Zn, and Cu), and non-essential elements (Na, Al, and Si) were quantified in the soil. The total DNA of the soil samples was analyzed through 16S rRNA amplicon by Illumina Miseq. Subsequent to the addition of water during both the dry and wet seasons, the concentrations of non-metal elements (C, H, N, S, and P, except for Si) in the soil remained relatively stable; however, metal elements (K, Na, Fe, and Mg, along with Si) increased significantly, whereas Zn and Ca decreased. During the dry season, fungal and bacterial communities were significantly distinct from those during the wet season along the PC axis 1 (p < 0.001). Water addition did not alter the compositions of bacterial or fungal communities during the dry season. However, during the wet season, water addition altered the compositions of bacterial rather than fungal community based on principal component analysis. At the phylum level, the relative abundance of Actinobacteria increased with water addition and had a significantly positive correlation with K+ (r 2 = 0.70, p < 0.001) and Na+ (r 2 = 0.36, p < 0.01) contents, whereas that of Acidobacteria, Planctomycetes, and Verrucomicrobia decreased and showed negative correlation with soil K and Na content, and no changes were observed for the fungal phyla. This suggests that the karst bacterial communities can be influenced by the addition of water during the wet season likely linked to changes in soil K and Na contents. These findings implied that increased rainfall might alter the elemental compositions of karst soils, and bacterial communities are likely to be more sensitive to variations in soil moisture in contrast to their fungal counterparts.

Two new species of Paraboea (Gesneriaceae) in Caryota obtusa forests in Southwest China, with compound and simple dichasia, respectively.

Two new species of Gesneriaceae, Paraboea myriantha sp. nov. and P. brevipedunculata sp. nov. are described and illustrated with photos. They grow in the Caryota obtusa forests from Yunnan Province of China. P. myriantha is closely related to P. glutinosa (Hand.-Mazz.) K.Y.Pan, but differs mainly in corolla outside glandular-puberulent, adaxial corolla lobes semicordate, corolla tube obliquely campanulate, and filaments glandular-puberulent. P. brevipedunculata is closely related to P. crassifolia (Hemsley) B. L. Burtt, but different mainly in simple dichasia with 1 and 2 flowers, peduncles 0.5-2 cm long and capsules slightly twisted. The geographical relationship between the two new species and their similar species has been discussed.

Habitat Selection and Genetic Structure of the Endangered Frog Species Odorrana wuchuanensis (Anura: Ranidae).

Understanding the habitat selection and population genetic structure of an endangered species can play important roles in its protection. The Wuchuan odorous frog (Odorrana wuchuanensis) is endemic to the karst regions of southwest China. This frog is currently listed as "Critically Endangered" by the IUCN, but little is known about its habitat selection and population genetics. In this study, we conducted analyses of habitat selection with occurrence/absence sites and environmental data, and assessed the genetic structure between north and south populations in Guizhou provinces in China using three mitochondrial markers. The results revealed that the probability of this frog occupying cave habitats increased with higher average humidity in July and higher lowest temperature in January, but was negatively related to precipitation in January. Analyses of F statistics combined with analyses of median-joining haplotype networks and the phylogenetic tree showed low genetic differentiation between the two populations of O. wuchuanensis. Considering the small population size and geographic isolation because of the complex karst terrains, we suggest careful management practices are needed to protect this species.

Molecular systematics of the Labeonini inhabiting the karst regions in southwest China (Teleostei, Cypriniformes).

The major phylogenetic pattern of the cyprinid tribe Labeonini has been revealed by previous molecular studies; however, the relationships within a clade that mainly inhabits the karst regions, which we refer to as the "karst group", in southwest China remain unresolved due to the low taxon sampling. This group includes more than 50% of the genera and species of Labeonini in China. Moreover, more than 90% of the genera of this group are endemic to China. In addition, some new genera and species of Labeonini have been discovered from these karst regions, but their taxonomic validity and phylogenetic position have not been examined. In this contribution, partial sequences of four nuclear (exon 3 of recombination activating protein 1, rhodopsin, early growth response protein 2B gene and interphotoreceptor retinoid binding protein gene) and three mitochondrial genes (cytochrome b, cytochrome oxidase subunit I and 16S ribosomal RNA) from 36 ingroup taxa and 25 outgroup taxa were analyzed to provide a hypothesis of the phylogenetic relationships within the labeonins of the karst regions in China. We propose that the monophyly of Parasinilabeo, Ptychidio, Rectoris and Semilabeo are supported. A new genus, Prolixicheilus, is erected for Pseudogyrinocheilus longisulcus. Cophecheilus bamen is the sister to Prolixicheilus longisulcus. Ptychidio, Pseudocrossocheilus, Semilabeo, Rectoris and Stenorynchoacrum are closely related with high support values. Sinocrossocheilus, Pseudogyrinocheilus, Paraqianlabeo, Hongshuia, Discogobio and Discocheilus form a clade together with high support. Considering molecular results and morphological differences, Parasinilabeo longicorpus and Ptychidio macrops might be the synonyms of Parasinilabeo assimilis and Ptychidio jordani respectively. Comprehensive taxonomic revisions of the two genera Parasinilabeo and Ptychidio may be necessary.