Biology subjects

Stevens, C. J.

Publications and source records attributed to Stevens, C. J..

7 recordsLinked to original sources

bioRxiv2026

Chronic trazodone treatment consolidates sleep, improves memory, and reduces amyloid pathology in a mouse model of Alzheimer's disease

Sleep disturbance in Alzheimers disease (AD), particularly the reduction of slow wave sleep (SWS), has been proposed as a novel therapeutic target, with disease-modifying potential. Trazodone, an antidepressant with robust SWS-promoting properties, is currently the most prescribed sleep-promoting medication in the United States. Here, we demonstrate that chronic trazodone administration consolidates sleep in the APPNL-F knock-in mouse model of AD, increasing NREM sleep duration and slow wave power during the rest phase while promoting wake during the active phase. These sleep consolidating effects were accompanied by lower regional glial activation and amyloid burden, particularly in male mice. Most notably, hippocampal amyloid plaque burden was 45% lower in mice treated from 14 to 16 months of age than in vehicle-treated controls. Chronic trazodone treatment was also associated with better short-term and long-term recognition memory. Together, these findings support the potential of repurposing trazodone as a well-tolerated, disease-modifying therapeutic for AD, capable of enhancing sleep quality, improving cognition, and lowering AD-relevant neuropathology.

neuroscience↗

bioRxiv2023

Multidimensional responses of ecological stability to eutrophication in grasslands

Eutrophication usually impacts biodiversity, species composition, and functioning of grassland communities. Whether such effects propagate to influence the stability of these community aspects is unknown. Using standardized experiments across 55 global grasslands, we quantified the effects of nutrient addition on five stability facets (i.e., temporal invariability and resistance during and recovery after dry and wet growing seasons) for three community aspects (i.e., aboveground biomass, community composition, and species richness). Nutrient addition reduced the temporal invariability and resistance of species richness and community composition, but not biomass, during dry and wet growing seasons. Temporal invariability and resistance during, but not recovery after, dry and wet growing seasons were strongly positively correlated in both ambient and eutrophic conditions. This indicates that maintaining and restoring the stability of plant communities requires increasing resistance rather than recovery. Harnessing the complexity of ecological stability provides new insights for grassland ecosystem sustainability in a changing world.

ecology↗

bioRxiv2022

Bayesian analyses of radiocarbon dates on rice reveal geographic variations in the rate of agricultural dispersal in prehistoric Japan

The adoption of rice farming during the 1st millennium BC was a turning point in Japanese prehistory, defining the subsequent cultural, linguistic, genetic variation in the archipelago. Here we employ a suite of novel Bayesian techniques to estimate the regional rates of dispersal and arrival time of rice farming using radiocarbon dates on charred rice remains. Our results indicate substantial variations in the pace of agricultural adoption within the Japanese islands, hinting at the presence of a mixture of demic and cultural diffusion, geographic variations in the suitability of rice cultivation, as well as the possible role of existing social networks in facilitating or hindering the adoption of the new subsistence economy. TeaserThe adoption of rice farming in prehistoric Japan was characterised by regional episodes of slowdowns and accelerations.

plant biology↗

bioRxiv2021

The Evolutionary History of Wild, Domesticated, and Feral Brassica oleracea (Brassicaceae)

Understanding the evolutionary history of crops, including identifying wild relatives, helps to provide insight for designing new approaches in crop breeding efforts. Cultivated Brassica oleracea has intrigued researchers for centuries due to its wide diversity in forms, which include cabbage, broccoli, cauliflower, kale, kohlrabi, and Brussels sprouts. Yet, the evolutionary history of this species remains understudied. With such different vegetables produced from a single species, B. oleracea is a model organism for understanding the power of artificial selection. Persistent challenges in the study of B. oleracea include conflicting hypotheses regarding domestication and the identity of the closest living wild relative. Using a diversity panel of 224 accessions, which represents 14 different B. oleracea crop types and nine potential wild progenitor species, we integrate phylogenetic and population genetic techniques with ecological niche modeling, archaeological, and literary evidence to examine relationships among cultivars and wild relatives to clarify the origin of this horticulturally important species. Our analyses point to the Aegean endemic B. cretica as the closest living relative of cultivated B. oleracea, supporting an origin of cultivation in the Eastern Mediterranean region. Additionally, we identify several feral lineages, suggesting that cultivated plants of this species are able to revert to a wild-like state with relative ease. By expanding our understanding of the evolutionary history in B. oleracea, these results contribute to a growing body of knowledge on crop domestication that will facilitate continued breeding efforts including adaptation to changing environmental conditions.

evolutionary biology↗

bioRxiv2021

Multiple resource limitations explain biomass-precipitation relationships in grasslands

Interannual variability in grassland primary production is strongly driven by precipitation, nutrient availability and herbivory, but there is no general consensus on the mechanisms linking these variables. If grassland biomass is limited by the single most limiting resource at a given time, then we expect that nutrient addition will not affect biomass production at arid sites. We conducted a distributed experiment manipulating nutrients and herbivores at 44 grassland sites in 8 regions around the world, spanning a broad range in aridity. We estimated the effects of 5-11 years of nutrient addition and herbivore exclusion treatments on precipitation sensitivity of biomass (proportional change in biomass relative to proportional change in rainfall among years), and the biomass in the driest year (to measure treatment effects when water was most limiting) at each site. Grazer exclusion did not interact with nutrients to influence driest year biomass or sensitivity. Nutrient addition increased driest year biomass by 74% and sensitivity by 0.12 (proportional units), and that effect did not change across the range of aridity spanned by our sites. Grazer exclusion did not interact with nutrients to influence sensitivity or driest year biomass. At almost half of our sites, the previous year's rainfall explained as much variation in biomass as current year precipitation. Overall, our distributed fertilization experiment detected co-limitation between nutrients and water governing grasslands, with biomass sensitivity to precipitation being limited by nutrient availability irrespective of site aridity and herbivory. Our findings refute the classical ideas that grassland plant performance is limited by the single most limiting resource at a site. This suggests that nutrient eutrophication will destabilize grassland ecosystems through increased sensitivity to precipitation variation.

ecology↗

bioRxiv2020

A novel cost framework reveals evidence for competitive selection in the evolution of complex traits during plant domestication

Most models of selection incorporate some notion of environmental degradation where the majority of the population becomes less fit with respect to a character resulting in pressure to adapt. Such models have been variously associated with an adaptation cost, the substitution load. Conversely, adaptative mutations that represent an improvement in fitness in the absence of environmental change have generally been assumed to be associated with negligible cost. However, such adaptations could represent a competitive advantage that diminishes resource availability for others and so induces a cost. This type of adaptation in the form of seedling competition has been suggested as a mechanism for increases in seed size during domestication, a trait associated with the standard stabilizing selection model. We present a novel cost framework for competitive selection that demonstrates significant differences in behaviour to environmental based selection in intensity, intensity over time and directly contrasts to the expectations of the standard model. Grain metrics of nine archaeological crops fit a mixed model in which episodes of competitive selection often emerge from shifting optimum episodes of stabilizing selection, highlighting the potential prevalence of the mechanism outlined here and providing a fundamental insight into the factors driving domestication.

evolutionary biology↗

bioRxiv2020

Comment on Pescott & Jitlal 2020: Failure to account for measurement error undermines their conclusion of a weak impact of nitrogen deposition on plant species richness

Estimation of the impacts of atmospheric nitrogen (N) deposition on ecosystems and biodiversity is a research imperative. Analyses of large-scale spatial gradients, where an observed response is correlated with measured or modelled deposition, have been an important source of evidence. A number of problems beset this approach. For example, if responses are spatially aggregated then treating each location as statistically independent can lead to biased confidence intervals and a greater probably of false positive results. Using sophisticated methods that account for residual spatial autocorrelation Pescott & Jitlal (2020) re-analysed two large-scale spatial gradient datasets from Britain where modelled N deposition at 5x5km resolution had been previously correlated with species richness in small quadrats. They found that N deposition effects were weaker than previously demonstrated leading them to conclude that "..previous estimates of Ndep impacts on richness from space-for-time substitution studies are likely to have been over-estimated". We use a simple simulation study to show that their conclusion is flawed. They failed to recognise that an influential fraction of the residual spatially structured variation could itself be attributable to N deposition. This arises because the covariate used was modelled N deposition at 5x5km resolution leaving open the possibility that measured or modelled N deposition at finer resolutions could explain more variance in the response. Explicitly treating this as spatially auto-correlated error ignores this possibility and leads directly to their unreliable conclusion. We further demonstrate the plausibility of this scenario by showing that significant variation in N deposition at the 1km square resolution is indeed averaged at 5x5km resolution. Further analyses are required to explore whether estimation of the size of the N deposition effect on plant species richness and other measures of biodiversity is indeed dependent on the accuracy and hence measurement error of the N deposition covariate. Until then the conclusions of Pescott & Jitlal (2020) should be considered premature and not proven.

ecology↗