The latitudinal diversity gradient (LDG) is a prevalent feature of modern ecosystems across diverse clades. Recognized for well over a century, the causal mechanisms for LDGs remain disputed, in part because numerous putative drivers simultaneously covary with latitude. The past provides the opportunity to disentangle LDG mechanisms because the relationships among biodiversity, latitude and possible causal factors have varied over time. Here we quantify the emergence of the LDG in planktonic foraminifera at high spatiotemporal resolution over the past 40 million years, finding that a modern-style gradient arose only 15 million years ago. Spatial and temporal models suggest that LDGs for planktonic foraminifera may be controlled by the physical structure of the water column. Steepening of the latitudinal temperature gradient over 15 million years ago, associated with an increased vertical temperature gradient at low latitudes, may have enhanced niche partitioning and provided more opportunities for speciation at low latitudes. Supporting this hypothesis, we find that higher rates of low-latitude speciation steepened the diversity gradient, consistent with spatiotemporal patterns of depth partitioning by planktonic foraminifera. Extirpation of species from high latitudes also strengthened the LDG, but this effect tended to be weaker than speciation. Our results provide a step change in understanding the evolution of marine LDGs over long timescales.
AbstractLarge-scale temporal and spatial biodiversity patterns have traditionally been explained by multitudinous particular factors and a few theories. However, these theories lack sufficient generality and do not address fundamental interrelationships and coupled dynamics among resource availability, community abundance, and species richness. We propose the equilibrium theory of biodiversity dynamics (ETBD) to address these linkages.
Plant species diversity has long been a focal point in ecological studies. In order to study the changes in species diversity at different spatial scales (α, β, and γ diversities) in the restoration process of grassland vegetation in fragile desert steps, this study took desert steppe of Inner Mongolia as the research object and employed a two-factor experimental design that combined exclosure years (the years when an area was isolated to prevent grazing and other disturbances) with years of monitoring (the years when data were collected). It analyzed the plant groups (dominant species, common species, and rare species) and species diversity, and obtained the preliminary conclusions as follows: The optimal exclosure duration for promoting species diversity balance in desert steppe management is between 16 and 18 years.
Natural wetlands and paddy fields support a rich diversity of life forms. The study objective includes assessing the macrophyte community in relation to environmental variables and providing information on floristic compositions. The research is significant for determining the extent of disturbance and potential remedies from the standpoint of the health of the wetland ecosystem.
Department of Environmental Science and Engineering, School of Environmental and Chemical Engineering, Shanghai University, 150#, 99 Shangda Road, Shanghai, 200444, China.
Freshwater ecosystem is a significant natural source of CH emission in the atmosphere. To fully understand the dynamics of methane emissions in reservoirs, it is essential to grasp the temporal and vertical distribution patterns, as well as the factors that influence the methanogenic bacterial communities within the sediments. This study investigates the methane dynamics, carbon isotope fractionation (δCH), and abundance of functional microorganisms along the geochemical gradient in the in situ sedimentary column of Hongfeng Reservoir (China).
Faculty of Engineering, Department of Chemical Engineering and Biotechnological Engineering, 3D Dynamic Cell Culture Systems Laboratory, Université de Sherbrooke, Sherbrooke, QC, Canada.
Glioblastoma multiforme (GBM) is the most prevalent malignant brain tumor, with an average survival time of 14 to 20 months. Its capacity to invade brain parenchyma leads to the failure of conventional treatments and subsequent tumor recurrence. Recent studies have explored new therapeutic strategies using a chemoattracting gradient to attract GBM cells into a soft hydrogel trap where they can be exposed to higher doses of radiation or chemotherapy.
