Environmental response strategies for the spatial distribution of seed plants in Gansu

The interplay between plant diversity and environmental response strategies is crucial for ecosystem adaptability and stability. A central focus in modern ecology is elucidating how environmental factors shape plant diversity patterns and regulate species distributions across heterogeneous landscapes. This study employed Joint Species Distribution Model (JSDM) to quantitatively analyze the influence of environmental variables on plant spatial distributions in Gansu Province, China, while examining interspecies interactions under varying conditions. Results demonstrated that environmental factors explained 95.4% of the variance, highlighting their predominant role in determining plant distributions. Habitat type accounted for the largest share of variance (33.5%), followed by elevation (22.1%), mean annual temperature (20.3%), mean annual precipitation (15.1%), and solar radiation (4.4%). Species' responses to environmental covariates were predominantly independent, with weak phylogenetic correlation (posterior mean: 0.17), reflecting limited ecological niche conservatism at the family level. Geographically, regions such as the northern Qilian foothills, Lanzhou-Baiyin wilderness, Loess Plateau, and Gannan Plateau exhibited negative correlations with most plant families, functioning as critical limiting or driving factors in spatial variability. Additionally, 33.7% of seed plant families showed negative correlations with light intensity, underscoring its role as a major limiting factor. Provincially, competition does not primarily constrain seed plant coexistence in Gansu. Regionally, however, pronounced differences in environmental responses were observed. In the northwest, solar radiation (37%) and precipitation (25%) were dominant drivers of plant distribution, while in the southeast, solar radiation (36.3%) and elevation (34.7%) were predominant. These findings underscore that species co-occurrence patterns are scale-dependent and influenced by regional resource availability. In resource-abundant southeastern areas, plant families displayed positive co-occurrence patterns indicative of mutualistic or symbiotic interactions, whereas resource-scarce northwestern areas experienced intensified negative co-occurrences due to heightened interspecific competition. This study highlights the critical role of environmental gradients in structuring seed plant distributions in Gansu, providing insights into the interaction of ecological adaptation and evolutionary history in shaping plant diversity. By identifying the drivers of plant distribution across heterogeneous environments, this research offers significant implications for biodiversity conservation and plant resource management strategies in Gansu Province, while contributing to a broader understanding of plant-environment dynamics in complex ecosystems.

Assembly structures of coastal woody species of eastern South America: Patterns and drivers

Tropical regions have provided new insights into how ecological communities are assembled. In dry coastal communities, water stress has been hypothesized to determine plant assembly structure by favoring preadapted lineages from neighboring ecosystems, consistent with functional clustering. However, it is unclear whether this hypothesis is sufficient to explain how coastal communities in tropical ecosystems are assembled. Here, we test whether water stress or other factors drive community assembly in woody plant communities across the coastal zone of Brazil, a tropical ecosystem. We characterized functional and phylogenetic structures of these communities and determined the underlying environmental factors (e.g., water stress, historical climate stability, edaphic constraints, and habitat heterogeneity) that drive their community assembly. Assemblages of coastal woody species show geographically varied patterns, including stochastic arrangements, clustering, and overdispersion of species relative to their traits and phylogenetic relatedness. Topographic complexity, water vapor pressure, and soil nutrient availability best explained the gradient in the functional structure. Water deficit, water vapor pressure, and soil organic carbon were the best predictors of variation in phylogenetic structure. Our results support the water-stress conservatism hypothesis on functional and phylogenetic structure, as well as the effect of habitat heterogeneity on functional structure and edaphic constraints on functional and phylogenetic structure. These effects are associated with increased phenotypic and phylogenetic divergence of woody plant assemblages, which is likely mediated by abiotic filtering and niche opportunities, suggesting a complex pattern of ecological assembly.

Relative contributions of taxonomic and functional diversity to the assembly of plant communities hosting endemic Dianthus species in a mountain steppe

Plant community assembly is the outcome of long-term evolutionary events (evident as taxonomic diversity; TD) and immediate adaptive fitness (functional diversity; FD); a balance expected to shift in favour of FD in 'harsh' habitats under intense selection pressures. We compared TD and FD responses along climatic and edaphic gradients for communities of two species (Dianthus pseudocrinitus and D. polylepis) endemic to the montane steppes of the Khorassan-Kopet Dagh floristic province, NE Iran. 75 plots at 15 sites were used to relate TD and FD to environmental gradients. In general, greater TD was associated with variation in soil factors (potassium, lime, organic matter contents), whereas FD was constrained by aridity (drought adaptation). Crucially, even plant communities hosting different subspecies of D. polylepis responded differently to aridity: D. polylepis subsp. binaludensis communities included a variety of broadly stress-tolerant taxa with no clear environmental response, but TD of D. polylepis subsp. polylepis communities was directly related to precipitation, with consistently low FD reflecting a few highly specialized stress-tolerators. Integrating taxonomic and functional diversity metrics is essential to understand the communities hosting even extremely closely related taxa, which respond idiosyncratically to climate and soil gradients.

Diversification of freshwater crabs on the sky islands in the Hengduan Mountains Region, China

The numerous naturally-fragmented sky islands (SIs) in the Hengduan Mountains Region (HMR) of southwestern China constitute discontinuous landscapes where montane habitats are isolated by dry-hot valleys which have fostered exceptional species diversification and endemicity. However, studies documenting the crucial role of SI on the speciation dynamics of native freshwater organisms are scarce. Here we used a novel set of comprehensive genetic markers (24 nuclear DNA sequences and complete mitogenomes), morphological characters, and biogeographical information to reveal the evolutionary history and speciation mechanisms of a group of small-bodied montane potamids in the genus Tenuipotamon. Our results provide a robustly supported phylogeny, and suggest that the vicariance events of these montane crabs correlate well with the emergence of SIs due to the uplift of the HMR during the Late Oligocene. Furthermore, ancestrally, mountain ridges provided corridors for the dispersal of these montane crabs that led to the colonization of moist montane-specific habitats, aided by past climatic conditions that were the crucial determinants of their evolutionary history. The present results illustrated that the mechanisms isolating SIs are reinforced by the harsh-dry isolating climatic features of dry-hot valleys separating SIs and continue to affect local diversification. This offers insights into the causes of the high biodiversity and endemism shown by the freshwater crabs of the HMR-SIs in southwestern China.