An evaluation of environmental factors affecting species distributions

Many different models can be built to explain the distributions of species. Often there is no single model that is clearly better than the alternatives, and this leads to uncertainty over which environmental factors are limiting species’ distributions. We investigated the support for different environmental factors by determining the drop in model performance when selected predictors were excluded from the model building process. We used a paired t-test over 37 plant species so that an environmental factor was only deemed significant if it consistently improved the results for multiple species. Geology and winter minimum temperatures were found to be the environmental factors with the most support, with a significant drop in model performance when either of these factors was excluded. However, there was less support for summer maximum temperature, as other environmental factors could combine to produce similar model performance. Our method of evaluating environmental factors using multiple species will not be capable of detecting predictors that are only important for one or two species, but it is difficult to distinguish these from spurious correlations. The strength of the method is that it increases inference for factors that consistently affect the distributions of many species. We discourage the assessment of models against predefined benchmarks, such as an area under the curve (AUC) of more than 0.7, as many alternative models for the same species produce similar results. Therefore, the benchmarks do not provide any indication of how the performance of the selected model compares to alternative models, and they provide weak inference to accept any selected model.     

Ecological niche similarities of Peponapis bees and non-domesticated Cucurbita species

Peponapis bees are considered specialized pollinators of Cucurbita flowers, a genus that presents several species of economic value (squashes and pumpkins). Both genera originated in the Americas, and their diversity dispersion center is in Mexico. Ten species of Peponapis and ten species of Cucurbita (only non-domesticated species) were analyzed considering the similarity of their ecological niche characteristics with respect to climatic conditions of their occurrence areas (abiotic variables) and interactions between species (biotic variables). The similarity of climatic conditions (temperature and precipitation) was estimated through cluster analyses. The areas of potential occurrence of the most similar species were obtained through ecological niche modeling and summed with geographic information system tools. Three main clusters were obtained: one with species that shared potential occurrence areas mainly in deserts (P. pruinosa, P. timberlakei, C. digitata, C. palmata, C. foetidissima), another in moist forests (P. limitaris, P. atrata, C. lundelliana, C. o. martinezii) and a third mainly in dry forests (C. a. sororia, C. radicans, C. pedatifolia, P. azteca, P. smithi, P. crassidentata, P. utahensis). Some species with similar ecological niche presented potential shared areas that are also similar to their geographical distribution, like those occurring predominantly on deserts. However, some clustered species presented larger geographical areas, such as P. pruinosa and C. foetidissima suggesting other drivers than climatic conditions to shape their distributions. The domestication of Cucurbita and also the natural history of both genera were considered also as important factors.     

三峡库区城镇化与移民对农村社会经济的影响——以万州区五桥河流域为例

城镇化与移民对三峡库区农村社会经济环境有重要影响 ,通过运用生态学的物种多样性和生态位理论和方法对五桥河流域作实例研究发现 :区域人口增长方式转为机械增长为主 ,农村农业劳动力向非农产业转移趋势显著。农村产业多样性与农民人均总收入存在非线性关系 ,城镇化与移民使农村产业多样性演替速度加快 ,使农业、工业经济生态位持续下降 ,商业服务业和交通运输业经济生态位持续上升 ,尽管能促进区域绝对经济生态位提高 ,但能否使区域形成与其区位相适应的优势产业体系是相对经济生态位提升的关键     

Predicted Climate‐Driven Bird Distribution Changes and Forecasted Conservation Conflicts in a Neotropical Savanna

Abstract: Climate‐change scenarios project significant temperature changes for most of South America. We studied the potential impacts of predicted climate‐driven change on the distribution and conservation of 26 broad‐range birds from South America Cerrado biome (a savanna that also encompass tracts of grasslands and forests). We used 12 temperature or precipitation‐related bioclimatic variables, nine niche modeling techniques, three general circulation models, and two climate scenarios (for 2030, 2065, 2099) for each species to model distribution ranges. To reach a consensus scenario, we used an ensemble‐forecasting approach to obtain an average distribution for each species at each time interval. We estimated the range extent and shift of each species. Changes in range size varied across species and according to habitat dependency; future predicted range extent was negatively correlated with current predicted range extent in all scenarios. Evolution of range size under full or null dispersal scenarios varied among species from a 5% increase to an 80% decrease. The mean expected range shifts under null and full‐dispersal scenarios were 175 and 200 km, respectively (range 15–399 km), and the shift was usually toward southeastern Brazil. We predicted larger range contractions and longer range shifts for forest‐ and grassland‐dependent species than for savanna‐dependent birds. A negative correlation between current range extent and predicted range loss revealed that geographically restricted species may face stronger threat and become even rarer. The predicted southeasterly direction of range changes is cause for concern because ranges are predicted to shift to the most developed and populated region of Brazil. Also, southeastern Brazil is the least likely region to contain significant dispersal corridors, to allow expansion of Cerrado vegetation types, or to accommodate creation of new reserves.     

生态经济系统边缘效应的实证分析

在理论层面,从生态经济系统的生态位角度探讨省域行政边界地区的生态经济系统边缘效应的优势和特性;在实践层面,以广西玉林为例,通过探讨省域生态经济系统边缘效应的形成过程和动力机制,剖析省域生态经济系统的边缘地区玉林今后发展的优势、劣势、机遇和挑战.针对生态经济系统边缘效应的发挥提出相应对策和建议,以期为经济转型升级过程中省域生态经济系统边缘地区经济的发展和腾飞提供理论参照.     

Ecological‐Niche Modeling and Prioritization of Conservation‐Area Networks for Mexican Herpetofauna

Abstract: One of the most important tools in conservation biology is information on the geographic distribution of species and the variables determining those patterns. We used maximum‐entropy niche modeling to run distribution models for 222 amphibian and 371 reptile species (49% endemics and 27% threatened) for which we had 34,619 single geographic records. The planning region is in southeastern Mexico, is 20% of the country's area, includes 80% of the country's herpetofauna, and lacks an adequate protected‐area system. We used probabilistic data to build distribution models of herpetofauna for use in prioritizing conservation areas for three target groups (all species and threatened and endemic species). The accuracy of species‐distribution models was better for endemic and threatened species than it was for all species. Forty‐seven percent of the region has been deforested and additional conservation areas with 13.7% to 88.6% more native vegetation (76% to 96% of the areas are outside the current protected‐area system) are needed. There was overlap in 26 of the main selected areas in the conservation‐area network prioritized to preserve the target groups, and for all three target groups the proportion of vegetation types needed for their conservation was constant: 30% pine and oak forests, 22% tropical evergreen forest, 17% low deciduous forest, and 8% montane cloud forests. The fact that different groups of species require the same proportion of habitat types suggests that the pine and oak forests support the highest proportion of endemic and threatened species and should therefore be given priority over other types of vegetation for inclusion in the protected areas of southeastern Mexico.     

Temperature niche of the Altai Zokor Myospalax myospalax Laxmann (1773)

With consideration of the data on soil temperature within the range of the Altai zokor Myospalax myospalax Laxmann (1773) published in the Handbook on the Climate of the Soviet Union, it has been shown that the actual temperature niche of this species is relatively narrow. Seasonal movements over the vertical profile of the burrow allow zokors to avoid exposure to subzero temperatures.     

基于生态安全格局的山地丘陵区自然资源空间精准识别与管制方法

自然资源空间管制是平衡生态保护和经济发展关系的基本工具,严守生态安全格局的底线思维对于重建系统完备、生态盈余的自然资源空间管制新格局具有重要指导意义。以胶东半岛典型山地丘陵区——栖霞市为例,应用数据密集型知识挖掘,集成地理信息方法与模型,基于栅格从生态服务功能重要性和生态环境敏感性两方面精准识别生态源地,利用地形位指数修正基本阻力面,并运用最小累积阻力模型提取生态廊道,从而构建生态安全格局,实现自然资源分区管制。结果表明：栖霞市生态源地面积为627.80 km²,占全市总面积的31.14%,集中分布在中东、中南和西北部,且超过一半源地为林地;关键、优化生态廊道各237.19 km、83.90 km,大多由林地组成,主要分布在中东、西北和西南部,形成完整的生态网络;划定禁止建设区、限制建设区、条件建设区和优先建设区,为自然资源空间精准管制提供方法保障。     

包头南海湖浮游植物优势种生态位及种间联结性季节分析

为了解寒旱区浮游植物群落年内结构变化和演替规律及其优势种的联结性,于2017年12月~2018年11月对包头市南海湖的浮游植物群落进行了调查分析.共鉴定出浮游植物7门66属151种,其中浮游植物优势种有4门15属15种,其种类和丰度随季节而变化.运用改进的Levins公式和Petraitis指数测定浮游植物优势种的生态位量度,发现不同季节各优势种的生态位宽度和生态位重叠不尽相同,各优势种对环境因子的适应能力也存在较大差异,在年内各种生境条件下,微小平裂藻生态位变化幅度最显著,依此认为微小平裂藻可作为南海湖水体污染状态指示种,且有可靠的生态学依据.生态位重叠值中ΔSO_ij值表示物种发展趋势,可第一时间反映南海湖水质是否受到外来因素干扰.群落物种相关性、种间联结性检验结果显示,南海湖浮游植物种间联结性总体上呈正关联关系,128对优势种对中仅有10对显现显著联结性,可见南海湖群落种间联结不紧密,群落结构不稳定,处于演替的初、中期阶段.     

土地利用的经济生态位分析和耕地保护机制研究

土地利用变化包括土地利用结构和土地利用强度两个方面,是土地利用类型从低生态位层次向高生态位转变的自组织行为。对不同层次的土地利用生态位进行控制与协调,才能实现一定耕地保有量下土地利用资源场的均衡。而这种均衡正是耕地总量动态平衡得以实现的前提。在生态位势理论与系统边界理论的基础上,论文构建了土地利用经济生态位的模型,并以江苏省锡山市为例定量分析了不同土地利用类型相互作用的强度。研究显示,经济发达区非农用地与农用地生态位差较大,城市化进程加快,使耕地更易损失。从资源流动的场论分析角度,探讨了建立耕地保护机制的途径和方法。在目前的水平上,把土地利用生态位作为土地利用/覆被研究中的一种新方法论更有意义。