Caryodaphnopsis, a group of tropical trees (ca. 20 spp.) in the family Lauraceae, has an amphi-Pacific disjunct distribution: ten species are distributed in Southeast Asia, while eight species are ...restricted to tropical rainforests in South America. Previously, phylogenetic analyses using two nuclear markers resolved the relationships among the five species from Latin America. However, the phylogenetic relationships between the species in Asia remain poorly known. Here, we first determined the complete mitochondrial genome (mitogenome), plastome, and the nuclear ribosomal cistron (nrDNA) sequences of C. henryi with lengths of 1,168,029 bp, 154,938 bp, and 6495 bp, respectively. We found 2233 repeats and 368 potential SSRs in the mitogenome of C. henryi and 50 homologous DNA fragments between its mitogenome and plastome. Gene synteny analysis revealed a mass of rearrangements in the mitogenomes of Magnolia biondii, Hernandia nymphaeifolia, and C. henryi and only six conserved clustered genes among them. In order to reconstruct relationships for the ten Caryodaphnopsis species in Asia, we created three datasets: one for the mitogenome (coding genes and ten intergenic regions), another for the plastome (whole genome), and the other for the nuclear ribosomal cistron. All of the 22 Caryodaphnopsis individuals were divided into four, five, and six different clades in the phylogenies based on mitogenome, plastome, and nrDNA datasets, respectively. The study showed phylogenetic conflicts within and between nuclear and organellar genome data of Caryodaphnopsis species. The sympatric Caryodaphnopsis species in Hekou and Malipo SW China may be related to the incomplete lineage sorting, chloroplast capture, and/or hybridization, which mixed the species as a complex in their evolutionary history.
Both deterministic and stochastic processes have been linked to forest community assembly; however, their contribution to beta diversity has not been properly explored, and no studies to date have ...investigated their impacts on sparse depleted soils in forests that contain widespread exposed limestone karst. We found that the pairwise differences in species composition between quadrates was determined by a balanced variation in abundance, whereby the individuals of some species at one site were substituted by an equivalent number of individuals of different species at another site. Both the total beta diversity and its balanced variation in abundance declined with increasing sampling grain size. Our research indicated that environmental differences exert a strong influence on beta diversity, particularly total beta diversity and its balanced abundance variation in larger grain sizes. It was evident that deterministic and stochastic processes worked together, and that deterministic processes were more important than stochastic processes in the regulation of beta diversity in this heterogeneous tropical karst seasonal rainforest of Southern China. However, in future research a functional trait based approach will be required to tease out the relative degree of deterministic and stochastic processes toward an assessment of the temporal changes in species composition.
Lianas are a crucial component of karst seasonal rainforests, yet research on them has predominantly focused on non-karst regions. Consequently, their abundance and species richness remain relatively ...understudied within karst ecosystems. We aimed to document the abundance and species richness of lianas and investigate their relationships with abiotic and biotic factors, based on data from a fully mapped 15 ha plot in a karst seasonal rainforest of Nonggang (SW China). Structural equation models (SEMs) were employed to estimate the path coefficients and variation of dependent variables, enabling a comprehensive analysis of the factors affecting the abundance and species richness of liana. Within the 15 ha plot, a total of 23,819 lianas were identified, encompassing 113 species from 34 families. These lianas constituted 24.16% of the total woody plant density and 33.44% of the species present, but only 4.32% of the total woody plant basal area. Lianas are primarily influenced by abiotic factors, especially elevation and phosphorus (P), with less impact from biotic factors. Our findings reveal that lianas, despite constituting a relatively small percentage of the total woody plant basal area, significantly contribute to the density and diversity of the forest. Notably, abiotic factors such as elevation and phosphorus availability predominantly shape the distribution and richness of lianas, highlighting the importance of these environmental variables. The findings offer valuable insights for future liana studies and the preservation of karst forests’ biodiversity.
•There were only 58 individuals of Camellia longzhouensis in three sub-populations.•The population structure of C. longzhouensis is spindle-shaped.•Its abundance was related with soil fertility and ...light intensity.•It was reassessed as Critically Endangered C2a(i,ii).•Integrated conservation approach of rare plants is needed in karst poor areas.
Camellia longzhouensis (Theaceae) is an endemic evergreen shrub or small tree with a distribution restricted to South China. It is listed as Grade-II in the National Key Protected Wild Plants List. In this study, we surveyed its distribution, examined its population structure, identified factors affecting its survival, and reassessed its extinction risk. We found that C. longzhouensis was only distributed in the Nonggang National Nature Reserve and the surrounding area. Its individuals only grew under the secondary forest canopy in the karst mountain. A total of 58 individuals of C. longzhouensis in three sub-populations were found. Soil fertility and understory light availability were the main habitat factors influencing the survival of C. longzhouensis. Anthropogenic disturbances and reproductive obstacles have caused a low seed-setting rate, poor seedling survival, and a lack of adult plants of C. longzhouensis in the natural habitat. The population structure of C. longzhouensis is spindle-shaped, indicating poor natural regeneration and inhibited seedling recruitment. Cleistanthus petelotii had a significant positive interspecific interaction with C. longzhouensis in the community. Based on the information obtained here and IUCN criterion C2ai, we recommend that C. longzhouensis be categorized in the International Union for Conservation of Nature (IUCN) Red List as Critically Endangered. We also developed a comprehensive protection strategy, consisting of in situ conservation, ex situ conservation, reintroduction, and commercial utilization. This strategy can be readily applied to protect other endangered plants with economic value in karst poor regions.
Rural agricultural activity generates cropland, secondary vegetation and straggling primary forest and can modify the soil seed bank (SSB), potentially impacting the restoration of preferred species. ...The interaction between vegetation and seed banks during the recovery process is dependent on management practices and recovery pathways. This study was carried out in Guilin of southwest China to assess the variation in plant diversity and species composition of both aboveground and soil seed banks across three typical vegetation types with different human interventions: orchard, bamboo shrub and primary forest. The results show that there were significant differences in the species composition and diversity of aboveground vegetation and SSB, as well as in soil properties among three typical vegetation types. The primary forest had the highest aboveground species diversity, while the orchard had the highest species diversity and seed density of SSB. In addition, principal component analysis (PCA) and canonical correspondence analyses (CCAs) showed that the species composition and plant life forms of the three typical vegetation types were significantly influenced by soil properties. Based on these findings, the characteristics of aboveground vegetation and the soil seed bank and their correlations with soil properties are expected to drastically change with human intervention. These results imply that unsustainable land use has greatly impacted soil properties, and consequently, the aboveground vegetation and SSB. Nevertheless, vegetation will recover quickly after farming is abandoned. The successful restoration of fragmented ecosystems requires the addition of seeds and seedlings of target species, especially perennial woody plants from the relevant natural ecosystems, to accelerate succession from bamboo shrub to forest.
In an era of global environmental change, understanding how disturbance affects the dynamics of ecological communities is crucial. However, few studies have theoretically explored the potential ...influence of disturbance including both intensity and frequency on compositional change over time in communities with stage structure. A spatially explicit, individual‐based model was constructed incorporating the various demographic responses to disturbance of plants at two different growth stages: seedlings and adults. In the model, we assumed that individuals within each stage were demographically equivalent (neutral) but differed between stages. We simulated a common phenomenon that seedlings suffered more from disturbance such as grazing and fire than adults. We showed how stage‐structured communities of seedlings and adults responded to disturbance with various levels of disturbance frequency and intensity. In “undisturbed” simulations, the relationship between average species abundance (defined here as the total number of individuals divided by species richness) and community composition turnover (measured by the Bray–Curtis similarity index) was asymptotic. However, in strongly “disturbed” simulations with the between‐disturbance intervals greater than one, this relationship became unimodal. Stage‐dependent response to disturbance underlay the above discrepancy between undisturbed and disturbed communities.
Through a spatially explicit, individual‐based model (IBM), we found divergent temporal turnover patterns observed from undisturbed and strongly disturbed communities, which was explained by the stage‐dependent response to disturbance.
Spatial patterns can reveal many ecological processes in forest communities; thus, understanding the spatial patterns of trees and their interactions is key to exploring forest dynamics. However, few ...studies have explored the spatial patterns and interactions between adults and recruits over longer time spans in tropical karst forests. A forest dynamics census was conducted (2011–2021) in a 15-ha karst seasonal rainforest plot at the Nonggang National Nature Reserve, in Guangxi, China. The tree community structure, which included a total of 20 tree species (≥ 50 individuals) at various states of recruitment, survival, and mortality, were selected and investigated via detailed analyses. First, univariate pair correlation functions and bivariate mark correlation functions were utilized to analyze the spatial patterns of dead recruits, surviving recruits, and adults. Aggregation was the dominant intraspecific distribution pattern in the plot that decreased at larger scales, which indicated that dispersal was limited. The segregation of bivariate patterns in most species suggested that there was scramble competition between the surviving and dead recruits, which translated to their not clustering around adults. Second, it was revealed through testing that density dependence was not prevalent. However, negative density dependence was more common in species that exhibited density dependence, as various species respond differently to changes in population density. Third, most recruits had a low probability of survival, which for several dominant species was influenced by neighborhood effects. This study did not support the Janzen-Connell hypothesis, as the survival probability of most recruits was not enhanced with the distance from adults. This meant that the effects of distance from adults on the growth of recruits in Nonggang forests were negligible. These results suggested that dispersal limitations and habitat heterogeneity played more significant roles in the regulation of tree spatial patterns and seedling growth (or mortality) in tropical karst seasonal rain forests. This work will contribute to the restoration and conservation of fragile forest communities in Karst regions, while providing a theoretical basis for biodiversity research, forest management planning, and ecosystem services.
•Habitat heterogeneity plays a key role in the survival of recruits.•Most recruits do not aggregate around adults.•Density dependence is not universal.•Negative density dependence is more prominent than positive density dependence.•Only a few species are affected by neighborhood effects and distance dependence.
•Tree size has consistent and the strongest negative effect on tree mortality.•Interspecific and conspecific neighbors usually had a facilitative effect on lowering the mortality.•Abiotic factors, ...such as topographic wetness index have negative effect on tree mortality.
Tree mortality plays a vital role in forest dynamics and contributes to species coexistence and community assembly. However, the mechanisms that control tree mortality are poorly understood, particularly in species-rich tropical forests. Size-dependent abiotic constraints and biotic interactions act simultaneously to cause tree mortality in natural forests. However, these drivers are often studied independently, which can limit our understanding of how they interact to affect tree mortality in natural forests. We employed a hierarchical Bayesian logistic regression modeling approach to quantify the simultaneous effects of tree size, topography, neighborhoods, and their interactions on tree mortality in a 15-ha fully mapped tropical karst seasonal rainforest in Southern China. Of the variables tested, tree size exhibited the most consistent and strongest negative effect on tree mortality, while topography and neighborhood competition were of secondary importance. Neighbors, particularly heterospecific neighbors, had a facilitative effect on lowering mortality, while only several species showed conspecific negative density dependent on mortality. The topographical wetness index had a significant positive effect on tree mortality. Size-dependent and neighborhood competition-induced tree mortality was stronger for shade-intolerant than for shade-tolerant species, and the size-dependent mortality was the strongest for shrub species among the three growth forms. Our results indicated that the size-dependent effect was the dominant cause of tree mortality; however, neighbors, particularly heterospecific neighbors, had a facilitative effect on lowering tree mortality. Furthermore, the relative importance of these mechanisms for tree mortality differed within life-history strategies guilds. Our study highlighted the value of simultaneously considering the individual and interactive effects of multiple mechanisms toward understanding the dynamics and coexistence of highly diverse metacommunities in harsh environments.
Persistent infection with Helicobacter pylori may contribute to the carcinogenesis of gastric cancer through modulating local prostaglandin E2 (PGE2) levels. Cyclooxygenase-2 (COX-2) and 15-hydroxy ...prostaglandin dehydrogenase (15-PGDH) are two key enzymes that regulate PGE2 synthesis and inactivation, respectively. The present study was designed to investigate the expression of COX-2 and 15-PGDH in gastric cancer specimens (n=66) in comparison to that of control specimens (n=70) and, furthermore, to semi-quantitatively assess the level of COX-2 and 15-PGDH mRNA and protein in tissues with or without H. pylori infection by reverse transcription-polymerase chain reaction and immunohistochemistry, respectively. It was revealed that COX-2 was expressed in almost all gastric cancer specimens infected with H. pylori (32 out of 33 specimens), but it was also expressed in 2/3 gastric cancers without H. pylori infection (22 out of 33 specimens). By contrast, COX-2 was expressed in <1/6 control subjects regardless of H. pylori infection. Furthermore, 15-PGDH was expressed in control samples but significantly downregulated in gastric cancer specimens. H. pylori infection resulted in slight inhibition of 15-PGDH in control subjects, but significant inhibition of 15-PGDH mRNA expression and protein synthesis in the gastric cancer specimens. These findings indicated that COX-2 and 15-PGDH, the two enzymes that regulate PGE2 levels, were significantly altered in gastric cancer, and that H. pylori may contribute to gastric carcinogenesis through modulating COX-2 and 15-PGDH mRNA expression and protein synthesis.
Climate is widely recognised as an important determinant of the latitudinal diversity gradient. However, most existing studies make no distinction between direct and indirect effects of climate, ...which substantially hinders our understanding of how climate constrains biodiversity globally. Using data from 35 large forest plots, we test hypothesised relationships amongst climate, topography, forest structural attributes (stem abundance, tree size variation and stand basal area) and tree species richness to better understand drivers of latitudinal tree diversity patterns. Climate influences tree richness both directly, with more species in warm, moist, aseasonal climates and indirectly, with more species at higher stem abundance. These results imply direct limitation of species diversity by climatic stress and more rapid (co‐)evolution and narrower niche partitioning in warm climates. They also support the idea that increased numbers of individuals associated with high primary productivity are partitioned to support a greater number of species.
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