Species In Southwestern China Research Articles

An unprotected vulnerable relict subtropical conifer— Keteleeria evelyniana: its forests, populations, growth and endangerment by invasive alien plant species in China

Relict subtropical coniferous forests in China face severe fragmentation, resulting in declining populations, and some are under significant threat from invasive alien species. Despite the crucial importance of understanding forest dynamics, knowledge gaps persist, particularly regarding the impact of invasive plants on vulnerable natives like Keteleeria evelyniana. In this study, we investigated the impact of invasive plants on the regeneration of forests dominated by K. evelyniana, a subtropical relict species in southwestern China. For this purpose, we characterized forest dynamics of 160 forest plots featuring K. evelyniana as the primary dominant species and determined whether the presence of invasive plants was correlated with regeneration of K. evelyniana. We identified four distinct forest types in which K. evelyniana was dominant. We found that radial growth of K. evelyniana trees is faster in younger age-classes today than it was for older trees at the same age. The population structure of K. evelyniana in each forest type exhibited a multimodal age-class distribution. However, three forest types lacked established saplings younger than 10 years old, a situation attributed to the dense coverage of the invasive alien Ageratina adenophora. This invasive species resulted in a reduction of understory species diversity. Additionally, our analysis uncovered a significant negative correlation in phylogenetic relatedness (net relatedness index) between native and invasive alien plant species in eastern Yunnan. This suggests closely related invasive species face heightened competition, hindering successful invasion. Taken together, our findings indicate that successful establishment and habitat restoration of K. evelyniana seedling/saplings require effective measures to control invasive plants.

Chromosome-level genome assembly of the largefin longbarbel catfish (Hemibagrus macropterus).

The largefin longbarbel catfish, Hemibagrus macropterus, is an economically important fish species in southwestern China, with males growing faster than females. This study presents a high-quality chromosome-level genome assembly of the largefin longbarbel catfish, generated by integrating Illumina short reads, PacBio HiFi long reads, and Hi-C data. The assembled genome size was 858.5Mb, with a contig and scaffold N50 of 5.8Mb and 28.4Mb, respectively. A total of 656 contigs were successfully anchored to 30 pseudochromosomes with a BUSCO score of 97.7%, consistent with the number of chromosomes analyzed by karyotype. The genome contained 29.5% repeat sequences, and a predicted total of 26,613 protein-coding genes, of which 25,769 (96.8%) were functionally annotated in different databases. Evolutionary analysis showed that H. macropterus was most closely related to H. wyckioides, with a divergence time of approximately 16.3 million years. Chromosomal syntenic relationships among H. macropterus, H. wyckioides, and Pelteobagrus fulvidraco revealed a one-to-one relationship for most chromosomes, except for break, fission, and inversion of some chromosomes. The first high-quality reference genome will not only provide a valuable genetic resource for the study of sex determination mechanisms and genetic breeding of largefin longbarbel catfish, but also contribute to comparative analyses of genome and chromosome evolution within Siluriformes.

Comprehensive transcripts analysis based on single-molecule real-time sequencing and Illumina sequencing provides insights into the mining of Toll-like receptor family in Schizothorax lissolabiatus.

Schizothorax lissolabiatus is an economically important cold-water fish species in southwestern China. Because of water pollution and habitat destruction, the number of wild populations has dramatically decreased. In this study, we used PacBio single-molecule real-time (SMRT) sequencing and Illumina sequencing to generate the first full-length transcriptome and transcriptome, respectively. A total of 19310 polished consensus reads (PC) were obtained, with an average length of 1379 bp and an N50 length of 1485 bp. Meanwhile, 12253 transcripts were successfully annotated as known homologous genes. The pathway annotation indicated that the enrichment and expression of most genes were mainly related to membrane, signal transduction and binding, and immune response. Furthermore, we identified 16 Toll-like receptors (TLRs) by mining the data from the transcripts. Phylogeny analysis showed that S. lissolabiatus TLR genes (slTLRs) supported the classification of TLRs into six families as in other vertebrates. Selection pressure analyses showed that 16 slTLRs revealed purification selection at the overall evolutionary selection. Further, positive selection signals were still detected in eight slTLRs, and most of the positive selection sites were located in the leucine-rich repeat region (LRR domain) associated with the recognition of pathogenic microorganisms, indicating that the function of these slTLR genes may be affected. Tissue specific expression analysis showed all slTLRs are present in kidney, spleen and liver but the relative expression varied among tissues. In conclusion, this study not only provided a valuable resource of transcripts for further research on S. lissolabiatus, but also contributed to improve the current understanding of the evolutionary history of immune-related genes and the TLR gene family in S. lissolabiatus.

Identity of the holotype and type locality of Rhabdophis leonardi (Wall, 1923) (Colubridae: Natricinae), with notes on the morphology and natural history of the species in southwestern China.

The original description of Natrix leonardi (currently Rhabdophis leonardi) by Frank Wall in 1923, based on a specimen from the "Upper Burma Hills," lacked important morphological details that have complicated the assignment of recently collected material. Furthermore, although the holotype was never lost, its location has been misreported in one important taxonomic reference, leading to further confusion. We report the correct repository of the holotype (Natural History Museum, London), together with its current catalog number. We also describe key features of that specimen that were omitted from the original description, and provide new details on the morphology of the species, including sexual dichromatism unusual for the genus, based upon specimens from southern Sichuan, China. Rhabdophis leonardi is distinguished from its congeners by the following characters: 15 or 17 DSR at midbody and 6 supralabials; distinct annulus around the neck, broad and red in males, and narrow and orange with a black border in females; dorsal ground color light green or olive; some lateral and dorsal scales possessing black edges, the frequency of black edges gradually increasing from anterior to posterior, forming irregular and ill-defined transverse black bands; eye with prominent green iris; black ventral spots with a red edge, most numerous at midbody but extending halfway down the length of the tail. In southwestern China, this species is frequently found at 1730-2230 m elevation. It has been documented to prey upon anuran amphibians, including toads. A recently published phylogenetic analysis showed this species to be deeply nested with the genus Rhabdophis, as a member of the R. nuchalis Group. That analysis also revealed the existence of two closely related but geographically distinct subclades in the molecular analysis, one of which may represent an unnamed taxon.

Global Transcriptomic Analyses Provide New Insight into the Molecular Mechanisms of Endocarp Formation and Development in Iron Walnut (Juglans sigillata Dode)

Iron walnut (Juglans sigillata Dode) is a native species in southwestern China that exhibits variation in both fruit morphology and shell thickness. However, the underlying molecular processes controlling hardened endocarp development in walnut has not yet been reported. Here, we generated transcriptional profiles of iron walnut endocarp at three developmental stages using "Dapao", the most common commercial variety. Using pairwise comparisons between these three stages, a total of 8555 non-redundant differentially expressed genes (DEGs) were identified, and more than one-half of the total DEGs exhibited significant differential expression in stage I as compared with stage II or stage III, suggesting that the first stage may ultimately determine the final characteristics of the mature walnut shell. Furthermore, in the clustering analysis of the above DEGs, 3682, 2349, and 2388 genes exhibited the highest expression in stages I, II, and III, respectively. GO enrichment analysis demonstrated that the major transcriptional variation among the three developmental stages was caused by differences in cell growth, plant hormones, metabolic process, and phenylpropanoid metabolism. Namely, using the tissue-specific expression analysis and a gene co-expression network, we identified MADS-box transcription factor JsiFBP2 and bHLH transcription factor JsibHLH94 as candidate regulators of endocarp formation in the early stage, and JsiNAC56 and JsiMYB78 might play key roles in regulating the lignification process of endocarp in the late stage. This study provides useful information for further research to dissect the molecular mechanisms governing the shell formation and development of iron walnut.

Comparative Analyses of Rhizosphere Bacteria Along an Elevational Gradient of Thuja sutchuenensis.

Thuja sutchuenensis Franch. is an endangered species in southwestern China, primarily distributed in 800–2,100 m of inaccessible mountainous areas. Rhizosphere soil physicochemical properties and bacterial communities play an essential role in managing plant growth and survival. Nonetheless, the study investigating rhizosphere soil properties and bacterial communities of T. sutchuenensis is limited. The present study investigated soil properties, including soil pH, organic matter, water content, nitrogen, phosphorus, and potassium contents, and bacterial communities in nearly all extant T. sutchuenensis populations at five elevational gradients. Our results demonstrated that the increase in elevation decreased rhizosphere and bulk soil phosphorus content but increased potassium content. In addition, the elevational gradient was the dominant driver for the community composition differentiation of soil bacterial community. Proteobacteria and Acidobacteria were the dominant bacterial phyla distributed in the rhizosphere and bulk soils. Co-occurrence network analysis identified key genera, including Bradyrhizobium, Acidicapsa, Catenulispora, and Singulisphaera, that displayed densely connected interactions with many genera in the rhizosphere soil. The dominant KEGG functional pathways of the rhizosphere bacteria included ABC transporters, butanoate metabolism, and methane metabolism. Further correlation analysis found that soil phosphorus and potassium were the dominant drivers for the diversity of soil bacteria, which were distinctively contributed to the phylum of Planctomycetes and the genera of Blastopirellula, Planctomycetes, and Singulisphaera. Collectively, this comprehensive study generated multi-dimensional perspectives for understanding the soil bacterial community structures of T. sutchuenensis, and provided valuable findings for species conservation at large-scale views.

Bauhinia (Leguminosae) Fossils from the Paleogene of Southwestern China and Its Species Accumulation in Asia

Extant Bauhinia (Leguminosae) is a genus of 300 species of trees, shrubs, and lianas, widely distributed in pantropical areas, but its diversification history in southeastern Asia, one of its centers of highest diversity, remains unclear. We report new fossils of three Bauhinia species with cuticular preservation from the Paleogene of Puyang Basin, southwestern China. Our finding likely extends the emergence of Bauhinia in Asia to the late Eocene. Together with previously reported fossil records, we show that the diversification of Bauhina in Asia and the phenomenon of a small region harboring multiple Bauhinia species in southwestern China could be traced back to the Paleogene.

The complete chloroplast genome of Aconitum piepunense (Ranunculaceae) and its phylogenetic analysis

Aconitum piepunense belonging to the family Ranunculaceae is an endangered herb species in southwestern China. In this study, the complete chloroplast genome of A. piepunense was sequenced, and the results revealed a typical quadripartite structure with a length of 155,836 bp, including a large single-copy region (LSC, 86,433 bp), a small single-copy region (SSC, 16,945 bp), and a pair of inverted repeat (IR) regions (IRa and IRb, 26,229 bp, respectively). A total of 130 genes were identified in the A. piepunense chloroplast genome, containing 85 protein-coding genes, 37 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. Phylogenetic analysis based on the maximum likelihood method indicated that A. piepunense formed a monophyletic group, which was sister to A. contortum and A. vilmorinianum.

Distinct Genetic Structure Reflects Ploidy Level Differentiation in Newly Discovered, Extremely Small Populations of Xanthocyparis vietnamensis from Southwestern China

Population genetic assessment is crucial for the conservation and management of threatened species. Xanthocyparis vietnamensis is an endangered species that is currently restricted to karst mountains in southwestern China and Vietnam. This rare conifer was first recorded in 2002 from northern Vietnam and then in 2013 from Guangxi, China, yet nothing is known about its genetic diversity nor ploidy level variation, although previous cytological study suggest that Vietnamese populations are tetraploids. There have been about 45 individuals found to date in Guangxi, China. Here, we genotyped 33 X. vietnamensis individuals using 20 newly developed, polymorphic microsatellite loci, to assess the genetic variability of its extremely small populations. The genetic diversity of X. vietnamensis (H E = 0.511) was lower than that of two other heliophile species, Calocedrus macrolepis and Fokienia hodginsii, which have similar distribution ranges. This is consistent with the signature of a genetic bottleneck detected in X. vietnamensis. Although the population genetic differentiation coefficient across loci is moderate (F ST = 0.125), STRUCTURE analysis revealed two distinct genetic clusters, namely the northern and southern population groups; DAPC analysis grouped the southern populations together in one cluster separate from the northern populations; AMOVA analysis detected a significant genetic differentiation between the two population groups (F RT = 0.089, p < 0.05), and BARRIER analysis detected a genetic barrier between them. Moreover, we detected differentiation in ploidy level between northern and southern populations, sampled individuals from the former and the later are all diploid and tetraploid cytotypes with mean genome sizes of 26.08 and 48.02 pg/2C, respectively. We deduced that heterogeneous geomorphology and historical events (e.g., human deforestation, Quaternary climate oscillations) may have contributed to population fragmentation and small population size in X. vietnamensis. Considering both genetic and ploidy level differentiation, we propose that two different management units (northern and southern) should be considered and a combination of in situ and ex situ conservation measures should be employed to preserve populations of this endangered species in southwestern China in the light of our findings.

New Insights into the Taxonomy of the Genus Cantharellus in China: Epityfication of C. yunnanensis W.F. Chiu and the First Record of C. cibarius Fr.

Yellow chanterelles are one of the most common edible mushrooms found in Yunnan Province, China. Previous studies identified the species of these mushrooms as Cantharellus cibarius Fr. based on morphology alone. However, the diversity of yellow chanterelles comprises many species within the C. cibarius complex, including C. yunnanensis W.F. Chiu. We hypothesized that the latter species is widely marketed in Yunnan Province and does not actually belong to C. cibarius. Hence, to confirm the species identity, taxonomic re-evaluation using integrated taxonomic approaches is required. Herein, samples collected from different markets and from near the type locality were subjected to morphological and molecular analyses. We generated tef-1α sequences and analyzed them using the maximum likelihood and Bayesian inference methods. The study revealed that the specimens previously identified as C. cibarius with a wide distribution in southwestern China are indeed C. yunnanensis. Our morphological assessment was markedly influenced by the revision of the type specimen (C. yunnanensis) and its original description, as some characteristics of the specimen did not match the description (e.g., the size and shape of the spores). Similarly, our single-locus phylogenetic analysis strongly supported the identification of the marketed species in Southwestern China (Guizhou and Yunnan Provinces) as C. yunnanensis instead of C. cibarius. Following our findings, we epitypified C. yunnanensis. Additionally, we collected, identified, and confirmed the presence of C. cibarius in northeastern China.

Distribution and host selection of the chigger mite vector of scrub typhus, Leptotrombidium deliense, in southwest China

ABSTRACT Leptotrombidium deliense (Walch) is believed to be the most important vector of scrub typhus in China. From 2001–2019, a long-term investigation was made in 82 counties of southwestern China, covering five provincial divisions: Yunnan, Guizhou, Sichuan, Tibet and Chongqing. The results showed that L. deliense was not the most dominant chigger species in southwestern China. A total of 8,385 L. deliense were collected from 13 counties, which accounted for only 5.42% of all the identified chiggers (299 species with 154,665 individuals). Leptotrombidium deliense was mainly distributed in the low latitude (21–22°N: 48.16%), low elevation (<1000 m: 81.75%), flat landscape (70.14%) and outdoor habitat (90.66%). Although 73.98% of L. deliense were collected from the Asian house rat (Rattus tanezumi), the mite had low host specificity, being collected from 22 species of rodents and other small mammals across different species, genera, families and orders. Leptotrombidium deliense was of an aggregated distribution among its animal hosts.

Characterization of the complete chloroplast genome of Polyspora tiantangensis (Theaceae), an endemic and endangered species in southwestern China

Polyspora tiantangensis (Theaceae) is an endangered woody plant in southwestern China. In this study, we assembled complete chloroplast (cp) genome of P. tiantangensis based on the Illumina reads. The cp genome of P. tiantangensis is 157,057 bp in length, including a large single-copy (LSC) region of 86,593 bp and a small single-copy (SSC) region of 18,284 bp, separated by two inverted repeat (IR) regions of 26,090 bp each. The cp genome encoded 132 genes including 87 protein-coding genes, 37 tRNA genes, and eight rRNA genes. The GC content of cp genome of P. tiantangensis is 37.3%. A total of 68 SSRs were discovered. Phylogenetic analysis of cp genomes from 26 species of Theaceae revealed that all species of Polyspora formed one monophyletic clade and P. tiantangensis was closely related with its congeneric species P. longicarpa with 100% bootstrap value.

Morphological and molecular identification of Diaporthe species in south-western China, with description of eight new species.

Diaporthe species have often been reported as plant pathogens, endophytes and saprophytes, commonly isolated from a wide range of infected plant hosts. In the present study, twenty strains obtained from leaf spots of twelve host plants in Yunnan Province of China were isolated. Based on a combination of morphology, culture characteristics and multilocus sequence analysis of the rDNA internal transcribed spacer region (ITS), translation elongation factor 1-α (TEF), β-tubulin (TUB), calmodulin (CAL), and histone (HIS) genes, these strains were identified as eight new species: Diaporthe camelliae-sinensis, D. grandiflori, D. heliconiae, D. heterostemmatis, D. litchii, D. lutescens, D. melastomatis, D. pungensis and two previously described species, D. subclavata and D. tectonendophytica. This study showed high species diversity of Diaporthe in tropical rain forests and its hosts in south-western China.

Low genetic diversity and population differentiation in Thuja sutchuenensis Franch., an extremely endangered rediscovered conifer species in southwestern China

Thuja sutchuenensis Franch. is an extremely endangered conifer (Cupressaceae) species that is endemic to southwestern China. It was once considered extinct in the wild and was rediscovered after 100 years later in October 1999. Due to the habitat destruction from nature and humans, the population has decreased sharply and the distribution range is narrow. Thus there is an urgent need to evaluate genetic variation within this species in order to establish a feasible conservation strategy. In this study, we used six single-copy nuclear loci (4CL, LEAFY, NEEDLY, CC1147, GAPC and RABGGTB) to investigate the genetic diversity, population structure and dynamics of T. sutchuenensis based on a sampling of 109 individuals from 6 natural populations across the known extant geographical range. Our results indicated that the genetic diversity of T. sutchuenensis was relatively lower (πt = 0.00219, θwt = 0.00240) than that of other Cupressaceae species. Extensive gene flow (Nm ≥ 11.07) and low genetic differentiation among populations were detected. Extended Bayesian skyline plots revealed that the population size of T. sutchuenensis has remained constant through time. The low genetic diversity was believed to result primarily from genetic drift caused by habitat fragmentation and population dynamics caused by climate fluctuations. The low genetic differentiation among populations was largely attributed to high levels of gene flow and small geographic distribution. Based on the above analyses, we should first conserve all extant populations and their habitats to maintain its current genetic diversity. Besides these, artificial propagation efforts such as seed propagation, cuttage breeding or tissue culture methods should be made to rescue this rare and endangered tree species.

Characteristics of fungal community structure during the decomposition of mixed foliage litter from Pinus massoniana and broadleaved tree species in southwestern China

Abstract Aims The conifer litter is fairly recalcitrant and nutrient poor, and broadleaved litter promotes coniferous litter decomposition by increasing degradable nutrients and promoting microbial metabolism. Mixing Pinus massoniana litter and three broadleaved litters may increase the diversity and abundance of fungal decomposers compared with those in P. massoniana litter and vary depending on the number and proportion of broadleaved species included. Methods We analysed the composition and diversity of fungal communities during mixed litter decomposition in southwestern China with 35 treatments (P. massoniana, Toona sinensis, Cinnamomum camphora and Sassafras tzumu litter) using Illumina high-throughput sequencing. Important Findings The mixed litters increased fungal diversity and richness compared with those in the single-species litter, except in the following treatments: P. massoniana litter accounting for 70%–80% in the P. massoniana + T. sinensis, P. massoniana + S. tzumu + T. sinensis and P. massoniana + S. tzumu + C. camphora combinations, and P. massoniana + S. tzumu + C. camphora + T. sinensis combination with small proportion of T. sinensis litter. The diversity and richness of the 7:1:2 combination of P. massoniana + C. camphora + T. sinensis were significantly higher than those in the other treatments. Ascomycota and Basidiomycota were the dominant phyla, and Aspergillus was the most abundant genus. The decomposition of litters from one needleleaf and one broadleaved species (6:4) and one needleleaf species and two broadleaved species (broadleaved litter accounting for 30%–40%) exhibited synergistic interactions throughout the decomposition process, and the relative abundance of fungi that decompose refractory substances increased. The P. massoniana + C. camphora + T. sinensis combination and a 30%–40% broadleaf litter proportion increased fungal diversity and accelerated the decomposition of recalcitrant coniferous litter. Therefore, C. camphora and T. sinensis are a potential candidate species for mixed planting with P. massoniana.

Development of 32 novel microsatellite loci in Juglans sigillata using genomic data.

PremiseA novel set of microsatellite markers was developed for Juglans sigillata (Juglandaceae), an endemic walnut species in southwestern China, to facilitate cultivar identification and future investigations into the genetic structure and domestication history of this species and its close relatives.Methods and ResultsWe developed 32 microsatellite loci for J. sigillata using genomic data and used them to examine 60 individuals from three natural populations. A high level of polymorphism was detected by these primers, with up to eight alleles observed per locus, and an average of four alleles across populations. The levels of observed and expected heterozygosity ranged from 0.000–1.000 and 0.000–0.785, respectively. All but two of the loci were also successfully amplified in three closely related Eurasian Juglans species (J. regia, J. cathayensis, and J. mandshurica).ConclusionsThe microsatellite loci identified here provide a powerful resource for examining the genetic structure and domestication history of Juglans, as well as identification of its cultivars.

Ophiostomatales (Ascomycota) associated with Tomicus species in southwestern China with an emphasis on Ophiostoma canum

Ophiostomatalean fungi may facilitate bark beetle colonization and reproduction. In the present study of the fungal community associated with bark beetle species belonging to Tomicus in Yunnan, China, six ophiostomatalean fungi (Ophiostoma canum, O. ips, O. tingens, Leptographium yunnanense, Leptographium sp. 1 and Leptographium sp. 2) were isolated from the beetles or their galleries; O. canum was the most common fungal species. The distribution of O. canum was associated with stands heavily damaged by Tomicus species and a higher percentage of valid galleries of Tomicus yunnanensis and T. minor in Yunnan pine (Pinus yunnanensis). After inoculation of Yunnan pine with the fungus, a phloem reaction zone formed and monoterpenes accumulated in the phloem. These results suggested that O. canum was pathogenic to Yunnan pine and that the wide distribution of the fungus might be beneficial to reproduction of pine shoot beetles in Yunnan pine. However, because the reaction zone and monoterpene accumulation were mild, fungal damage of Yunnan pine might be limited. A more integrated study considering all the fungal species should be done to better understand the interactions among bark beetles, blue-stain fungi, and the tree hosts in the region.

On the identity of the genus Flavoperla (Plecoptera: Perlidae), with description of a new species in southwestern China.

Flavoperla basomarginata sp. nov. is described and illustrated as a new species of the genus Flavoperla Chu, 1929 from Sichuan Province of southwestern China. The new species is characterized by the male having an unpigmented head, a "butterfly-shaped" epiproct sclerite, a boot-shaped hammer in lateral view, and the basolaterally sclerotized paraprocts. Morphology of the new species is compared with similar taxa. A provisional key is provided for known Flavoperla males. Relevant taxonomic information and a distribution map for described Flavoperla species are discussed.

The complete chloroplast genome of Acer catalpifolium (Sapindaceae), a rare and endangered plant in Southwest China

Acer catalpifolium is a rare and endangered species in southwestern China. In this study, the complete chloroplast genome sequence of A. catalpifolium was characterized by de novo assembly using high-throughput sequencing. The length of the whole chloroplast genome was 156,225 bp, containing a large single copy region (LSC) of 85,976 bp and a small single copy region (SSC) of 18,066 bp, which were separated by a pair of 26,092 bp inverted repeat regions (IRs). The sequence contained 135 unique genes, including 40 tRNA, eight rRNA, and 87 protein-coding genes. The overall GC content of the chloroplast genome is 37.9% and those in the LSC, SSC, and IR regions are 36.1%, 32.2%, and 42.9%, respectively. The phylogenetic analysis based on reported chloroplast sequences of Sapindaceae showed that A. catalpifolium is sister to A. miaotaiense, and the genera of Acer and Dipteronia are closely related to Aesculus.

Do karst woody plants control xylem tension to avoid substantial xylem cavitation in the wet season?

BackgroundPlants have been hypothesized to maintain strong control over xylem tension by closing stomata and to operate at a water potential above or near the critical potential at which cavitation commences. An alternative hypothesis holds that cavitation temporarily relieves water stress and stomatal closure is insufficient to prevent short term “run-away” cavitation.MethodsThe objectives of this study were to investigate the leaf conductivity loss at noon (Loss) of 13 woody species differing in leaf phenology at two sites on karst topography in the wet season in southwestern China; the hydraulic architecture of woody species has rarely been reported previously. Loss was predicted from minimum field leaf water potentials (Ψmin) and laboratory-generated vulnerability curves. We also measured the maximum quantum efficiency of photosystem II using chlorophyll a fluorescence (Fv/Fm) and other associated leaf traits.ResultsLoss in the field varied substantially, from 1.39% in evergreen Itea chinensis to 90.07% in deciduous Sapium sebiferum. However, the Loss did not significantly decrease the efficiency of photosystem II. The water potential at which a 50% loss in leaf conductivity occurred (Ψ50) was not correlated to Ψmin. The co-occurring evergreen and deciduous species differed significantly in some stem hydraulic and associated leaf traits. Deciduous species had higher hydraulic conductance, photosynthetic rate, stomatal conductance, lower cavitation-resistance and minimum water potential than co-occurring evergreen species.ConclusionsThere was no sign that karst woody species in southwestern China could control xylem tension above the threshold to avoid substantial xylem cavitation in the wet season. There was no association between Loss and Fv/Fm among the studied species. This “isohydric” regulation behaviour, as well as abundant rainfall in the wet season, may explain why large variations of Loss existed across karst woody species in southwestern China.