Environmental Effects on Vertebrate Species Richness: Testing the Energy, Environmental Stability and Habitat Heterogeneity Hypotheses

Background: Explaining species richness patterns is a central issue in biogeography and macroecology. Several hypotheses have been proposed to explain the mechanisms driving biodiversity patterns, but the causes of species richness gradients remain unclear. In this study, we aimed to explain the impacts of energy, environmental stability, and habitat heterogeneity factors on variation of vertebrate species richness (VSR), based on the VSR pattern in China, so as to test the energy hypothesis, the environmental stability hypothesis, and the habitat heterogeneity hypothesis. Methodology/Principal Findings: A dataset was compiled containing the distributions of 2,665 vertebrate species and eleven ecogeographic predictive variables in China. We grouped these variables into categories of energy, environmental stability, and habitat heterogeneity and transformed the data into 1006100 km quadrat systems. To test the three hypotheses, AIC-based model selection was carried out between VSR and the variables in each group and correlation analyses were conducted. There was a decreasing VSR gradient from the southeast to the northwest of China. Our results showed that energy explained 67.6 % of the VSR variation, with the annual mean temperature as the main factor, which was followed by annual precipitation and NDVI. Environmental stability factors explained 69.1 % of the VSR variation and both temperature annual range and precipitation seasonality had important contributions. By contrast, habitat heterogeneity variables explained only 26.3 % of the VSR variation. Significantly positive correlations were detected among VSR, annua

A brighter shade of future climate on Himalayan musk deer Moschus leucogaster

Abstract Himalayan musk deer (Moschus leucogaster) is classified as an endangered species by IUCN with a historically misunderstood distribution due to misidentification with other species of musk deer, Moschus spp. Taking advantage of recent genetic analyses confirming the species of various populations in Nepal and China, we produced an accurate estimate of the species’ current and future distribution under multiple climate change scenarios. We collected high-quality occurrence data using systematic surveys of various protected areas of Nepal to train species distribution models. The most influential determinants of the distribution of Himalayan musk deer were precipitation of the driest quarter, temperature seasonality, and annual mean temperature. These variables, and precipitation in particular, determine the vegetation type and structure in the Himalaya, which is strongly correlated with the distribution of Himalayan musk deer. We predicted suitable habitats between the Annapurna and Kanchenjunga region of Nepal Himalaya as well as the adjacent Himalaya in China. Under multiple climate change scenarios, the vast majority (85–89%) of current suitable sites are likely to remain suitable and many new areas of suitable habitat may emerge to the west and north of the current species range in Nepal and China. Two-thirds of current and one-third of future suitable habitats are protected by the extensive network of protected areas in Nepal. The projected large gains in suitable sites may lead to population expansion and conservation gains, only when the threat of overexploitation and population decline is under control

Patterns and drivers of phylogenetic diversity of seed plants along an elevational gradient in the central Himalayas

The how and why of the spatial variation in biodiversity is one of the fundamental topics in biogeography research, but accurate insights require the incorporation of phylogenetic information. Here, to provide a better understanding of the origin and mechanism of biodiversity in montane ecosystems and thus support conservation planning, we explored the elevational patterns of phylogenetic diversity and structure of seed plants in the Gyirong Valley, the longest valley in China’s central Himalayas. The observed patterns were related to climatic, historical, geographical, and disturbance-related factors, and the relative contributions of these factors in explaining them were assessed. Our results showed that phylogenetic diversity of seed plants in the central Himalayas were described by a strongly hump-shaped pattern, peaking at 2700 m around. The phylogenetic structure of the plants was characterized by overdispersion at lower elevations and clustering at higher elevations, reflecting the cooperation between interspecies competition and environmental filtering in community assembly. Among the examined environmental factors, climatic factors showed the highest explanatory power, suggesting environmental filtering was largely driven by climatic rather than other factors. In summary, our finding indicating that mild climate at lower elevations presumably encourage phylogenetic differentiation by promoting interspecies competition, whereas increasingly harsh climatic condition with elevation may lead to closer phylogenetic relatedness through environmental filtering. Overall, our findings improve our knowledge about the elevational gradient of biodiversity in the Himalayas, and highlight the need for intensified conservation efforts at middle elevations as well as greater scientific concern regarding the impact of climate change on the biodiversity

Deterministic processes drive turnover-dominated beta diversity of breeding birds along the central Himalayan elevation gradient

Beta diversity, the variation of community composition among sites, bridges alpha and gamma diversity and can reveal the mechanisms of community assembly through applying distance-decay models and/or partitioning beta diversity into turnover and nestedness components from functional and phylogenetic perspectives. Mountains as the most natural experiment system provide good opportunities for exploring beta diversity patterns and the underlying ecological processes. Here, we simultaneously consider distance-decay models and multiple dimensions of beta diversity to examine spatial variations of bird communities, and to evaluate the relative importance of niche-based and neutral community assembly mechanisms along a 3600-m elevational gradient in the central Himalayas, China. Our results showed that species turnover dominates taxonomic, functional, and phylogenetic beta diversity. We observed strongest evidence of spatial distance decays in taxonomic similarities of birds, followed by its phylogenetic and functional analogues. Turnover component was highest in taxonomic beta diversity, while nestedness component was highest in functional beta diversity. Further, all correlations of assemblage similarity with climatic distance were higher than that with spatial distances. Standardized values of overall taxonomic, functional, and phylogenetic beta diversity and their turnover components increase with increasing elevational distance, while the standardized values of taxonomic and phylogenetic nestedness decreased with increasing elevational distance. Our results highlighted the niche-based deterministic processes in shaping elevational bird diversity patterns that were determined by the relative roles of decreasing trend of environmental filtering and increasing trend of limiting similarity along elevation distances

Multiple vegetation layers interactively enhance habitat values of endangered Kashmir Musk Deer

The Kashmir musk deer (Moschus cupreus) is a globally endangered species hunted for its musk pod. Despite its endangered status, it remains one of the least studied species of musk deer. In 2019, the genetic discovery of Kashmir musk deer in Mustang district of Nepal – outside of its historically known range in Kashmir, India – opened up new avenues for research on this elusive species. Communication among individuals of musk deer is primarily based on latrine sites, which serve various purposes such as territorial marking and reproductive signaling. Hence, this study aims to investigate the association between microhabitat and latrine sites of Kashmir musk deer in the Mustang, Nepal. A systematic survey was conducted to identify latrine presence and absence sites at an elevational gradient. Data on biophysical parameters, including altitude, slope, aspect, tree height, shrub height, and regeneration height were recorded for both latrine presence and absence plots. Significant differences in tree height and regeneration height, crown cover, and trail width were observed between the presence and absence plots. Latrine presence and absence data fitted with the generalized linear model using logistic function, revealed that the interaction between tree height and regeneration height plays a pivotal role in determining the suitability of a particular site within the habitat for establishing a latrine site. This significant positive interaction indicated that the probability of discovering latrines significantly increases when the areas have taller trees and taller regeneration. This finding affects microclimate factors, such as sunlight exposure, wind speed, soil moisture, and temperature, influencing their role in sustaining scent retention in the latrine sites. Incorporating knowledge about the association between microhabitats and latrine sites can aid in preserving suitable habitats that are critical for establishing communication among individual musk deer. This information can inform various conservation efforts, including captive breeding programs, anti-poaching operations, and reintroduction initiatives

Elevational pattern of bird species richness and its causes along a central Himalaya gradient, China

This study examines the relative importance of six variables: area, the mid-domain effect, temperature, precipitation, productivity, and habitat heterogeneity on elevational patterns of species richness for breeding birds along a central Himalaya gradient in the Gyirong Valley, the longest of five canyons in the Mount Qomolangma National Nature Reserve. We conducted field surveys in each of twelve elevational bands of 300 m between 1,800 and 5,400 m asl four times throughout the entire wet season. A total of 169 breeding bird species were recorded and most of the species (74%) were small-ranged. The species richness patterns of overall, large-ranged and small-ranged birds were all hump-shaped, but with peaks at different elevations. Large-ranged species and small-ranged species contributed equally to the overall richness pattern. Based on the bivariate and multiple regression analyses, area and precipitation were not crucial factors in determining the species richness along this gradient. The mid-domain effect played an important role in shaping the richness pattern of large-ranged species. Temperature was negatively correlated with overall and large-ranged species but positively correlated with small-ranged species. Productivity was a strong explanatory factor among all the bird groups, and habitat heterogeneity played an important role in shaping the elevational richness patterns of overall and small-ranged species. Our results highlight the need to conserve primary forest and intact habitat in this area. Furthermore, we need to increase conservation efforts in this montane biodiversity hotspot in light of increasing anthropogenic activities and land use pressure

A redox homeostasis disruptor based on a biodegradable nanoplatform for ultrasound (US) imaging-guided high-performance ferroptosis therapy of tumors

ABSTRACTThe synergistic disruption of intracellular redox homeostasis through the combination of ferroptosis/gas therapy shows promise in enhancing the antitumor efficacy. However, the development of an optimal delivery system encounters significant challenges, including effective storage, precise delivery, and controlled release of therapeutic gas. In this study, we propose the utilization of a redox homeostasis disruptor that is selectively activated by the tumor microenvironment (TME), in conjunction with our newly developed nanoplatforms (MC@HMOS@Au@RGD), for highly efficient ferroptosis therapy of tumors. The TME-triggered degradation of HMOS initiates the release of MC and AuNPs from the MC@HMOS@Au@RGD nanoplatform. The released MC subsequently reacts with endogenous hydrogen peroxide (H2O2) and H+ to enable the on-demand release of CO gas, leading to mitochondrial damage. Simultaneously, the released AuNPs exhibit GOx-like activity, catalyzing glucose to generate gluconic acid and H2O2. This process not only promotes the decomposition of MnCO to enhance CO production but also enhances the Fenton-like reaction between Mn2+ and H2O2, generating ROS through the modulation of the H+ and H2O2-enriched TME. Moreover, the generation of CO bubbles enables the monitoring of the ferroptosis treatment process through ultrasound (US) imaging. The efficacy of our prepared MC@HMOS@Au@RGD disruptors in ferroptosis therapy is validated through both in vitro and in vivo experiments