Population dynamical consequences of gregariousness in a size-structured consumer-resource interaction

Many animal species live in groups. Group living may increase exploitation competition within the group, and variation among groups in intra-group competition intensity could induce life-history variability among groups. Models of physiologically structured populations generally predict single generation cycles, driven by exploitation competition within and between generations. We expect that life-history variability and habitat heterogeneity induced by group living may affect such competition-driven population dynamics. In this study, we vary the gregariousness (the tendency to aggregate in groups) of a size-structured consumer population in a spatially explicit environment. The consumer has limited mobility, and moves according to a probabilistic movement process. We study the effects on the population dynamics, as mediated through the resource and the life-history of the consumer. We find that high gregariousness leads to large spatial resource variation, and highly variable individual life-history, resulting in highly stochastic population dynamics. At reduced gregariousness, life-history of consumers synchronizes, habitat heterogeneity is reduced, and single generation cycles appear. We expect this pattern to occur for any group living organism with limited mobility. Our results indicate that constraints set by population dynamical feedback may be an important aspect in understanding group living in nature.     

How do antiporters exchange substrates across the cell membrane? An atomic-level description of the complete exchange cycle in NarK

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Integrating multiple data sources for assessing blue whale abundance and distribution in Chilean Northern Patagonia

Aim

Species distribution models are useful tools for depicting important habitat, assessing abundance and orienting conservation efforts. For small populations in poorly studied ecosystems, available data are often scarce and patchy. To overcome this limitation, we aim to evaluate the use of different data types within a hierarchical Bayesian framework with the goal of modelling the abundance and distribution of a small and highly migratory population of blue whale (BW, Balaenoptera musculus) summering in Chilean Northern Patagonian (CNP).

Location

CNP, Eastern South Pacific (ESP).

Methods

We constructed a Bayesian hierarchical species distribution Model (HSDM), combining a binomial N‐mixture model used to model BW groups counts in line‐transect data (2009, 2012 and 2014) with a logistic regression for modelling presence‐availability data (2009–2016), allowing both models to share covariate parameters for borrowing strength in estimations.

Results

Distance to areas of high chlorophyll‐a concentration during spring before summering season (AHCC‐s) was the most important and consistent explanatory variable for assessing BW abundance and distribution in CNP. Incorporating accessorial presence‐only data reduced uncertainty in parameters estimation when comparing with a model using only line‐transect data, although other covariates of secondary importance failed to be retained in this model.

Main conclusions

Our results remark the capability of HSDM for integrating different data types providing a potential powerful tool when data are limited and heterogeneous. Results indicate that AHCC‐s, and possibly thermal fronts, could modulate BW abundance and distribution patterns in CNP. Preliminary model‐based delimitations of possible priority conservation areas for BW in CNP overlap with highly used vessel navigation routes and areas destined to aquaculture.

     

闽北地区四代三化螟发生动态Fuzzy预测模型研究

根据Fuzzy数学原理和三化螟生物学特性,组建了四代三化螟发生动态综合预测模型经对福建省将乐县16年四代三化螟发生期、发生量回报及1995年的预报,拟合率及正确率均达100％。     

Propolis Enhances 5-Fluorouracil Mediated Antitumor Efficacy and Reduces Side Effects in Colorectal Cancer: An in Vitro and in Vivo Study

In this study, we investigated the combined treatment of 5-fluorouracil (5-FU) and Anatolian propolis extract (PE) on colorectal cancer (CRC)using in vitro and in vivo studies. We exposed luciferase-transfected (Lovo-Luc CRC) cells and healthy colon cells (CCD-18Co) to varying concentrations of 5-FU and PE to assess their genotoxic, apoptotic, and cytotoxic effects, as well as their intracellular reactive oxygen species (iROS) levels. We also developed a xenograft model in nude mice and evaluated the anti-tumor effects of PE and 5-FU using various methods. Our findings showed that the combination of PE and 5-FU had selectivity against cancer cells, particularly at higher doses, and enhanced the anti-tumor effectiveness of 5-FU against colon CRC. The results suggest that PE can reduce side effects and increase the effectiveness of 5-FU through iROS generation in a dose-dependent manner.     

Complex systems, evolution, and animal models

In this paper, we respond to arguments made concerning our position regarding animal models (Shelley, 2010) by briefly examining the fact that animals (human and nonhuman) are complex systems that have different evolutionary trajectories. This historical fact has implications for using animals as predictive models for human response to drugs and disease.     

基于稳定氧同位素确定植物水分来源不同方法的比较

利用稳定同位素技术确定植物水分来源,对提高生态水文过程的认识和对干旱半干旱区的生态管理至关重要。目前基于稳定同位素技术确定植物水分来源的方法众多,但不同方法之间对比的研究较少。本研究基于原位样品采集,室内实验测试,利用直接对比法、多元线性混合模型(IsoSource)、贝叶斯混合模型(MixSIR、MixSIAR)和吸水深度模型分析植物水分来源,并对比各方法的优缺点。结果表明:相对于多元线性混合模型(IsoSource)而言,贝叶斯混合模型(MixSIR、MixSIAR)具有更好的水源区分性能,但对数据要求较高,且植物木质部水和潜在水源同位素组成的标准差越小,模型运行结果的可信度更高。本研究中贝叶斯混合模型(MixSIR)为最优解。在利用稳定氢氧同位素技术确定植物水分来源时,可先通过直接对比法定性判断植物可能利用的潜在水源,然后再用多元线性混合模型(IsoSource)、贝叶斯混合模型(MixSIR、MixSIAR)计算出各潜在水源对植物的贡献率和贡献范围,必要时可评估模型性能,选择出最优模型,定量分析植物的水分来源。若植物主要吸收利用不同土层深度的土壤水,可结合吸水深度模型计算出植物...     

Plant community composition and species richness in the High Arctic tundra: From the present to the future

Arctic plant communities are altered by climate changes. The magnitude of these alterations depends on whether species distributions are determined by macroclimatic conditions, by factors related to local topography, or by biotic interactions. Our current understanding of the relative importance of these conditions is limited due to the scarcity of studies, especially in the High Arctic. We investigated variations in vascular plant community composition and species richness based on 288 plots distributed on three sites along a coast‐inland gradient in Northeast Greenland using a stratified random design. We used an information theoretic approach to determine whether variations in species richness were best explained by macroclimate, by factors related to local topography (including soil water) or by plant‐plant interactions. Latent variable models were used to explain patterns in plant community composition. Species richness was mainly determined by variations in soil water content, which explained 35% of the variation, and to a minor degree by other variables related to topography. Species richness was not directly related to macroclimate. Latent variable models showed that 23.0% of the variation in community composition was explained by variables related to topography, while distance to the inland ice explained an additional 6.4 %. This indicates that some species are associated with environmental conditions found in only some parts of the coast–inland gradient. Inclusion of macroclimatic variation increased the model's explanatory power by 4.2%. Our results suggest that the main impact of climate changes in the High Arctic will be mediated by their influence on local soil water conditions. Increasing temperatures are likely to cause higher evaporation rates and alter the distribution of late‐melting snow patches. This will have little impact on landscape‐scale diversity if plants are able to redistribute locally to remain in areas with sufficient soil water.     

放牧到禁牧对草地土壤有机碳累积及其主控因子的影响

放牧是草地生态系统最为重要的人为影响因子,禁牧则是修复退化草原最有效的措施之一,不同管理模式势必会影响土壤理化指标和土壤有机碳(Soil Organic Carbon, SOC)及其累积量(SCS)的时空分布。为了明确从放牧到禁牧草地SCS变化过程及其影响因子,对锡林郭勒盟额里图牧场2019—2021年从放牧到禁牧SOC及土壤容重、水分、pH和生物量等进行分析。结果表明,禁牧区SCS逐年呈递增趋势,尤其是60cm土层SCS从2.54kg/m²增加到4.61kg/m²,增加了81.5%。放牧区则呈递减趋势,从5.27kg/m²下降到4.05g/m²,降低了23.15%。放牧既破坏了土壤结构又影响了草原植被,使草原生物量和土壤水分减少,土壤容重增加,同时Mantel-test分析和结构方程表明,土壤容重、全氮、温度、水分、地下生物量对SCS不同程度的影响比较明显,本研究可为草地生态研究及管理模式优化提供参考。