Aims: The tropical niche conservatism (TNC) hypothesis and the out of the tropics (OTT) hypothesis propose mechanisms generating patterns of species diversity across warm‐to‐cold thermal gradients at large spatial scales. These two hypotheses both integrate ecological and biogeography‐related evolutionary factors, but they predict opposite patterns for phylogenetic structure. Mount Namjagbarwa possesses one of the longest elevational gradients for flowering plant diversity in the world. We aim to analyse the elevational patterns of the phylogenetic structure of flowering plants in this mountain, and investigate underlying causes for the emergence of the patterns.Location: Mt. Namjagbarwa located at the eastern edge of the Himalaya.Methods: Species distribution data of Mt. Namjagbarwa were extracted from specimen records in online sources, literature, herbarium and our fieldwork. Bioclimatic data were extracted from the CHELSA database. Mt. Namjagbarwa was divided into 100‐m elevational belts, which were grouped into three elevation segments (100–2000 m, 2000–4000 m and 4000–5200 m) for data analysis. We calculated phylogenetic metrics for each belt. The relationships of phylogenetic metrics with elevation and climatic factors were analysed using generalized additive models and structural equation models.Results: A typical hump‐shaped pattern of species richness was observed along the elevational gradient of Mt. Namjagbarwa. However, the phylogenetic structure showed a zig‐zag pattern with the three elevation segments, each of which has different formation mechanisms. Temperature tolerance played important roles throughout the entire elevational gradient in species richness and phylogenetic structure.Main conclusions: Neither TNC nor OTT alone can fully explain the patterns of floristic assembly of the entire elevational gradient of Mt. Namjagbarwa. OTT and TNC are better explanation for the patterns of low and middle elevations respectively. Potential mechanisms for species assembly of different elevation segments in Mt. Namjagbarwa region alternate between niche convergence and niche conservatism. The patterns observed in this study are likely to be common across the entire Himalaya. This is important for preserving the evolutionary potential of mountain biodiversity. However, more studies are needed to determine the underlying mechanisms generating the zig‐zag pattern of the phylogenetic structure in the Himalaya.

Oxyria (Polygonaceae) is a small genus only comprising two species, Oxyria digyna and O. sinensis. Both species have well-documented usage in Chinese herbal medicine. We sequenced and assembled the complete mitogenomes of these two species and conducted a comparative analysis of the mitogenomes within Polygonaceae. Both O. digyna and O. sinensis displayed distinctive multi-branched conformations, consisting of one linear and one circular molecule. These two species shared similar gene compositions and exhibited distinct codon preferences, with mononucleotides as the most abundant type of simple sequence repeats. In the mitogenome of O. sinensis, a pair of long forward repeat sequences can mediate the division of molecule 1 into two sub-genomic circular molecules. Homologous sequence analysis revealed the occurrence of gene transfer between the chloroplast and mitochondrial genomes within Oxyria species. Additionally, a substantial number of homologous collinear blocks with varied arrangements were observed across different Polygonaceae species. Phylogenetic analysis suggested that mitogenome genes can serve as reliable markers for constructing phylogenetic relationships within Polygonaceae. Comparative analysis of eight species revealed Polygonaceae mitogenomes exhibited variability in gene presence, and most protein-coding genes (PCGs) have undergone negative selection. Overall, our study provided a comprehensive overview of the structural, functional, and evolutionary characteristics of the Polygonaceae mitogenomes.

Cover crop in orchards is recognized as a sustainable practice that enhances multiple ecosystem services, yet systematic evaluations of different cover crop management models in citrus orchards remain limited. This study investigated the effects of cover crop management models (natural cover crop: T1, Lolium perenne L.: T2, Trifolium repens L.: T3, Vicia villosa Roth: T4, and mixed cover crops: T5) on soil properties, soil CO₂ flux, leaf physiological traits, fruit quality, and yield in a citrus orchard, using clean tillage as a control. Results showed that cover crop management models significantly influenced soil water content, available nitrogen (AN), available phosphorus (AP), and available potassium (AK). The V. villosa model (T4) reduced AN and AP but enhanced leaf chlorophyll (Cl) and nitrogen (N) content. Soil CO₂ flux was significantly higher under T4, and it showed the lowest soil moisture. The results of mantel tests revealed that AP and soil moisture were key drivers of leaf traits, though no significant treatment effects on fruit quality or yield were detected within the two-year experimental period. These findings indicate that cover crop management models rapidly alter soil properties and CO₂ emissions, but longer-term observations are needed to evaluate cascading effects on fruit. This study offers evidence-based soil management solutions and a framework for enhancing multiple ecosystem services in orchards worldwide.

Oxyria (Polygonaceae) is a small genus only comprising two species, Oxyria digyna and O. sinensis. Both species are well-known Chinese herbal medicines with a long history of use. We sequenced and assembled the complete mitogenomes of these two species and conducted a comparative analysis of the mitogenomes within Polygonaceae. Both O. digyna and O. sinensis displayed distinctive multi-branched conformations, consisting of one linear and one circular molecule. These two species shared similar gene compositions and exhibited distinct codon preferences, with mononucleotides as the most abundant type of simple sequence repeats. In the mitogenome of O. sinensis, a pair of long forward repeat sequences can mediate the division of molecule 1 into two sub-genomic circular molecules. Homologous sequence analysis revealed the occurrence of gene transfer between the chloroplast and mitochondrial genomes within Oxyria species. Additionally, a substantial number of homologous collinear blocks with varied arrangements were observed across different Polygonaceae species. Phylogenetic analysis suggested that mitogenome genes can serve as reliable markers for constructing phylogenetic relationships within Polygonaceae. Comparative analysis of eight species revealed Polygonaceae mitogenomes exhibited variability in gene presence, and most protein-coding genes (PCGs) have undergone negative selection. Overall, our study provided a comprehensive overview of the structural, functional, and evolutionary characteristics of the Polygonaceae mitogenomes.