Variation in the diversity of ducks along a gradient of environmental variability

Tramer (1969) proposed that communities regulated by competition in benign, predictable environments were characterized by (i) damped variation in evenness relative to variation in richness over time, and (ii) high evenness relative to communities regulated by variation in the abundance and diversity of resources in rigorous, unpredictable environments. To test whether patterns of variation in diversity could reflect the mechanisms proposed to regulate community structure, temporal and spatial changes in the diversity, richness and evenness of breeding duck communities were examined along a gradient of variability in wetland conditions using thirty-three years of duck census and climate data from the Canadian prairie and boreal forest regions. Temporal variation in evenness was independent of wetland habitat variability. Changes in richness were more parsimoniously explained by the appearance of ducks displaced (by drought) from rigorous, variable, wetland habitats into relatively benign ones, than by competition in benign areas. Evenness was not significantly higher for duck guilds in more constant wetland habitats, as predicted. Variation in richness, evenness and diversity, predicted by Tramer, do not provide a basis for distinguishing the factors that regulate duck community structure.     

新型鸭呼肠孤病毒的分离与鉴定

本研究从临床表现为出血性坏死性肝炎的病死鸭肝脾中分离到病毒。病原特性鉴定显示,分离毒能致死番鸭胚和鸡胚;人工感染1日龄雏番鸭、雏半番鸭均能复制出与临床自然发病鸭相同的临床症状和病理变化,并能回收到病毒。分离毒能在MDEF等多种细胞中增殖并产生细胞病变。电镜下病毒在细胞浆中呈大量散在、成堆和晶格状排列,病毒粒子呈球形、无囊膜、双层衣壳、直径70nm左右。在SDS-PAGE中具有禽呼肠孤病毒10个RNA片段的特征,但M1-3和S1-4片段的迁移率明显不同于番鸭呼肠孤病毒(MDRV)。分离毒S3基因全序列与禽呼肠孤病毒(ARV)、火鸡呼肠孤病毒(TRV)和MDRV的核苷酸同源性分别为60%～60.2%,61.9%,62.3%～62.7%,氨基酸同源性分别为68.2%～69%,68.2%,69.3%～70.1%;S3基因编码的σB蛋白属于单独的进化分支,提示分离毒S3基因具有不同于ARV和MDRV的特征。结果表明鸭出血性坏死性肝炎的病原是一种属于呼肠孤病毒科正呼肠孤病毒属新型鸭呼肠孤病毒。     

Climate-forced patterns in midge feeding guilds

Feeding behavior of macroinvertebrates is significant in determining aquatic ecosystem functioning. However, there is a lack of knowledge on the distribution of feeding guilds, and in particular on the influence of climate on the feeding functions at large spatial and long temporal scales. In this study, lakes at different climatic zones are examined for modern abundances of midge (Diptera) feeding guilds to establish the relationships between the feeding functions and climate. In addition, 11,000-year and 700-year sediment core records are investigated for their midge feeding guilds to establish their long-term relationships with climate changes. The results indicated that feeding guilds had a significant relationship with air temperature in the modern dataset and similar climate-related patterns in trait abundances had also occurred during the important climatic intervals of the past. In addition, the long-term records agreed with the modern spatial dataset in that feeding guild diversity was decreased under warm and cold climate compared to intermediate climate conditions. The results of this study are significant in demonstrating the influence of climate on the functioning of aquatic ecosystems and in providing valuable information on long-term variability in feeding functions that is needed to better understand future changes under the ongoing climate change.     

中国人身体质量指数的地理性分布

2009-2013年测量了中国11个汉语方言族群26954例汉族人的身高、体重值,计算了身体质量指数(I_(bm)),将汉族人的I_(bm)与经度、纬度进行相关分析。研究结果表明:总的说来,随年龄增长,11个方言族群I_(bm)值均呈线性增大,并且年龄组间差异均具有统计学意义。11个族群中,北方话族群I_(bm)值明显大于南方各族群。乡村男性(r=0.671; p0.05)、城市女性(r=0.043; p=0.820>0.05)I_(bm)与经度无相关。按照I_(bm)均数大于24.0、I_(bm)均数在23.1～24.0之间、I_(bm)均数小于23.0,可以将中国方言族群分成3个层次,中国北方话族群均分布在第1、2层次,南方族群主要分布在第2、3层次,也就是说11个族群大致按照纬度高低顺序依次分布在第1、2、3层次。遗传、环境、饮食、劳作强度等因素都不同程度影响身高、体重,也影响中国人的I_(bm)值。     

Circumtropical patterns in butterflyfish communities

Synopsis Butterflyfish species richness increases along a longitudinal circumtropical gradient from lows of 3–5 species in the tropical Atlantic and Eastern Pacific to highs of 40 or more in the Indo-Pacific region. Biomass of the fishes increases as species richness increases, and single-site (alpha) diversity increases as does between-site (beta) diversity. There is no evidence of density compensation in richer communities, but at the level of islands and regions, habitat breadth diminishes as species richness increases. Morphologically, species are added to communities both at the boundaries and in the middle of morphospace.     

Low persistence of the induced mutant phenotype in Chinese hamster cells

We have analysed the recovery of individual CHO-derived mutants during the generations immediately following their induction. This characteristic, which we call persistence, was measured by propagating mutagenized cultures in non-selective medium after subdivision into many very small populations, each containing either zero or one mutant. The recovery of most hypoxanthine phosphoribosyltransferase (hprt)-deficient mutants induced by ethyl methanesulphonate was low, and we have previously shown that this was usually due to an apparent rapid loss of the mutant phenotype with continued culture in non-selective medium (Bradley, 1980). A minority of about 15% manifest high persistence. We now show that most adenine phosphoribosyltransferase (aprt)-deficient mutants and some ouabain-resistant mutants had low persistence. Mutants induced by UV irradiation also generally exhibited low persistence but those induced by X-irradiation had significantly higher persistence than what was seen among EMS-induced mutants. Among various sublines of CHO cells which were tested for persistence of induced mutants, only one group consistently yielded mutants of high persistence. These were lines which carried glucose-6-phosphate dehydrogenase mutations which themselves had been originally induced by EMS.     

Geographical and typological changes in fish guilds of South African estuaries

A comparative analysis of fish estuary association guilds was undertaken on some 190 South African estuaries. This pioneering study spanned three zoogeographic regions and included three broad estuarine types. The guild compositions of the estuaries were compared based on an importance value, incorporating taxonomic composition, numerical abundance and relative biomass. Multivariate analyses included both inter‐regional (zoogeographic) and intra‐regional (estuarine typology) comparisons. The major estuary‐associated guilds (estuarine species and marine migrant species) were important in all estuary types within all biogeographic regions. Significant differences both between regions and between estuary types within regions, however, were recorded. Cool–temperate estuaries were generally dominated by migratory species (estuarine migrants and marine migrant opportunists) while the importance of species dependent on estuaries (estuarine residents and estuarine‐dependent marine migrants) was higher in warm–temperate and subtropical regions. The significance of estuarine nursery areas, particularly in regions where estuaries are few in number, is highlighted. In terms of typology, migratory species assumed a greater importance in predominantly open systems, while freshwater and estuarine‐resident species were more important in predominantly closed systems. Predominantly closed estuaries, however, were also important for marine migrant species, which further highlights the significance of these systems as nursery areas for fishes.     

嵊泗海岛不同底质潮间带春秋季大型底栖动物的群落格局

于2006年9月(秋季)和2007年4月(春季)对嵊泗海岛的不同底质潮间带断面设立的8个取样站采集的调查资料,采用ABC曲线方法和大型多元统计分析软件PRIMER5对嵊泗海岛大型底栖动物进行Bray-Curtis相似性聚类分析和非度量MDS标序,研究群落结构格局以及用物种多样性指数、物种均匀度和物种丰富度指数分析潮间带大型底栖动物物种多样性和群落种类组成,并对大型底栖动物的群落结构进行了初步研究。调查获得嵊泗海岛的不同底质潮间带大型底栖动物130种,其中多毛类31种,软体动物57种,节肢动物32种,棘皮动物4种,其它类6种。春、秋季嵊泗潮间带大型底栖动物多样性指数(H′)(F1,13=0.10,P=0.75)、物种丰富度(D)(F1,13=0.66,P=0.43)和均匀度指数(J)(F1,13=0.33,P=0.58)均无显著差异;不同底质嵊泗潮间带大型底栖动物多样性指数(H′)(F1,13=14.28,P<0.01)、物种丰富度(D)(F1,13=14.07,P<0.01)存在显著差异,而均匀度指数(J)(F1,13=1.62,P=0.23)无显著差异。群落结构聚类分析和MDS标序表明,8个取样站的群落可分为3组(Ⅰ、Ⅱ和Ⅲ组)。根据所调查嵊泗海岛潮间带的丰度和生物量资料做的ABC曲线分析表明,底栖动物群落受到了中等程度的污染或者扰动。     

Geographical gradients in seed mass in relation to climate

Aim To determine whether latitudinal and longitudinal gradients in seed mass are related to variation in climatic features including temperature, solar radiation and rainfall. Location Australia. Methods Seed mass was estimated from over 1600 provenances covering the latitudinal and longitudinal extents of 34 perennial Glycine taxa in Australia. Climatic data were obtained from ANUCLIM 5.1 for collection locations based on long‐term meteorological records across Australia. These climatic data were subject to principal components analysis to extract three components as climatic indices. Generalized linear models were used in three separate sets of analyses to evaluate whether seed mass–latitude and seed mass–longitude relationships persisted after taking climatic variation into account. First, relationships were examined across species in analyses that did not explicitly consider phylogenetic relationships. Secondly, phylogenetic regressions were performed to examine patterns of correlated evolutionary change throughout the Glycine phylogeny. Within‐species analysis was also performed to examine consistency across different taxonomic levels. Results Geographical variation in seed mass among species was related primarily to temperature and solar radiation, while rainfall was much less influential upon seed mass. Partialing out the influence of temperature and solar radiation in models resulted in the disappearance of significant seed mass–latitude and seed mass–longitude relationships. Patterns within species were generally consistent with patterns among species. However, in several species, factors additional to these climatic variables may contribute to the origin and maintenance of geographical gradients in seed mass, as significant seed mass–latitude and seed mass–longitude relationships remained after controlling for the influence of climatic variables. Main conclusions Our empirical results support the hypotheses that (1) seed mass is larger at low latitudes and in the interior of the Australian continent due to increased metabolic costs at high temperatures, and that (2) higher levels of solar radiation result in an increase in the availability of photosynthate, which in turn leads to an increase in biomass for the production of large seeds. In effect, our findings show that greater energy is available precisely where needed, that is, where high temperatures require large seed mass on the basis of metabolic requirements.     

土壤中乙草胺的微生物降解及其对防除稗草持效性的影响

采用气相色谱法和生物测定法,研究了土壤中乙草胺的微生物降解及其对防除稗草持效性的影响.结果表明,在同样的湿度和温度条件下,当添加到土壤中的乙草胺浓度为125、25和5.0 mg·kg^-1时,相同浓度的乙草胺在非灭菌土壤中的半衰期显著短于灭菌土壤,说明土壤微生物对乙草胺有明显的降解作用.三大主要菌群分离培养物降解实验与上述结果一致.生物测定结果表明,乙草胺在非灭菌土壤中防除稗草的持效期显著短于灭菌土壤,微生物的存在缩短了乙草胺在土壤中的滞留时间,从而降低了乙草胺防除稗草的持效性.     

Factors affecting species number and density of dabbling duck guilds in North Europe

We addressed how species number and pair density in guilds of co-existing species is related to habitat structure, and to the abundance and diversity of food resources using the assemblage of seven species of dabbling ducks (genus Anas ) breeding in 60 lakes distributed over six regions in temperate north Europe
Partial correlation and multiple regression revealed that species richness was best predicted by habitat structural diversity as indexed by a principal component analysis based on 18 vegetation and lake characteristics, and by the abundance of aquatic and emergent prey We found no effect of lake size or prey size diversity on species richness Pair density was correlated with the percentage of shoreline with horsetails ( Equisetum ), by habitat structural diversity and by the abundance of emergent invertebrate prey Neither prey size diversity nor abundance of aquatic prey correlated with pair density Species richness and pair density in North European duck guilds vary both with habitat structure and prey availability     

The effects of fire on communities,guilds and species of breeding birds in burnt and control pinewoods in central Italy

Breeding bird communities in burnt and unburnt residual pinewoods were studied over 3 years by line-transect method, following a catastrophic fire event in Castelfusano (Rome, Central Italy; July 2000). We applied bootstrap procedures to evaluate whether the observed data were true or just produced by chance, and then examined the emerging patterns at three levels: community, guild and species levels. At the community level, fire acted on breeding bird communities by altering especially the total abundance patterns: the species abundance decreased in the burnt pinewood compared to the residual one, but other parameters were not significantly affected by fire. As a consequence of fire, the destruction and structural simplification of the canopy and shrubby component, as well as the increase of edge habitat and patchiness at landscape scale, induced a turnover in species between pinewoods. Species turnover was higher at the burnt than at the residual pinewoods, during all the 3 years of study. At the guild level, the forest species decreased strongly in terms of richness and abundance in the burnt pinewoods, contrary to the edge and open habitat species which increased in terms of richness, abundance and evenness. Edge species showed the highest turnover in burnt pinewood during the whole period of study. At species level, after an a priori subdivision (based on bibliographic search) of the various species in two ecological guilds (forest versus edge species), it was found that an a posteriori statistical analysis confirmed the expected trend, i.e. that the species which decreased significantly in burnt pinewood were essentially the forest species, whereas the species which increased were essentially the edge/open habitat ones. Overall, in order to investigate the effects of fire catastrophes on birds, the guild approach seems more exhaustive than the taxonomic community approach, where intrinsic confounding trends are present.     

Periphytic diatom ecological guilds in floodplain: Ten years after dam

Periphytic diatoms are a key primary producer in floodplain systems. In this study, we assessed the species and functional traits in the periphytic diatom community in three lentic environments directly connected to the Paraná River shortly after damming and a decade later. Samples were collected in 2001–2002 and 2010–2011 during high waters phase. Periphytic samples were obtained from Eichhornia azurea Kunth, found in the shore zone of these environments. We recorded a total of 90 diatom species. 47 taxa were exclusive during the period shortly after damming and 18 taxa were only found in 2010–2011. The analysis of the similarity, diversity, beta diversity and non-metric multidimensional scaling (NMDS) suggested that there were differences in the species and functional traits of the periphytic diatom community between the two study periods. Variations in water transparency and nutrient (including nitrogen and phosphorus forms) were the most important variables shaping diatom communities diatoms during the study periods. High and motile profiles were characteristic shortly after damming and taxa of high and low profiles predominated a decade later. High transparency, high water and nitrogen levels favored the development of high and low profile, such as Gomphonema augur var. augur, Synedra goulardii and Amphora sp., whereas taxa belonging to high-profile and motile algae (e.g., Eunotia indica, Nitzschia amphibia) were found in the opposite conditions. Species turnover was an important diversity component that was greatly influenced by limnologic differences over time, represented by environmental and temporal dissimilarities between the years. These changes reinforce the modifications that have occurred in the environmental component of the Upper Paraná River floodplain downstream of the dam from the start of its operation.     

中国汉族乡村成年人的身高与体质量的地理性分布

目前尚未见大样本的中国乡村汉族人随纬度、经度增长,身高、体质量值的变化规律的报道。为此,2009～2013年测量了16501例汉族人(共36个调查地区)乡村成人的身高、体质量等13项指标值,并计算了3项指数。研究不同纬度、经度地区汉族乡村成人的身高、体质量值变化规律以及这种规律形成的原因。研究发现,汉族人的身高、体质量与纬度、经度均呈正相关。随纬度增加,男性和女性的躯干、下肢的高度值均增大是身高与纬度呈正相关的原因。随纬度增加,男性身高的增加、躯干的增粗共同促进体质量与纬度呈正相关,女性身高、躯干围度、四肢围度、背部皮下脂肪厚度值的增大是体质量与纬度呈正相关的原因。男性随经度增加,身高增大,躯干部的增粗是导致体质量与经度相关的原因。而四肢和躯干的皮下脂肪、四肢的围度并不随经度的增加而线性增大。随经度增加,女性的身高、臀围呈线性增大,这是导致女性体质量与经度相关的主要原因。遗传、环境、经济发展水平的差异是导致身高、体质量与纬度、经度呈正相关的因素。     

Geographical distribution of myxomycetes living on Cryptomeria japonica bark in Japan

There is little available data on the biogeography of myxomycetes at the regional scale within any given climate zone. To investigate the geographical distribution of these protozoans, we focused on corticolous myxomycetes associated with the bark of Cryptomeria japonica trees, which we sampled extensively throughout Japan. Myxomycete sporophores developed in 73% of 2244 moist-chamber cultures of 188 bark samples from 24 regions, including 31 species. The most abundant species were Paradiacheopsis rigida and Cribraria confusa, which accounted for over 20% of all myxomycetes sampled. Non-metric multidimensional scaling was used to analyze the distribution of myxomycetes in relation to geographical variables and bark pH. The distribution of myxomycetes was influenced by altitude, temperature and bark pH. Temperature gradients and relative abundance of species were negatively correlated in P. rigida and Comatricha laxa and positively correlated in C. confusa, Macbrideora cornea, and Diderma chondrioderma. Bark pH was also positively correlated with the relative abundance of C. confusa, D. chondrioderma, and Physarum nutans and negatively correlated with that of P. rigida, P. cribrata, Enerthnema papillatum, and E. melanospermum. Geographical distribution of corticolous myxomycete communities was determined based on temperature and bark pH, which acted as local barriers in our study area.     

Bird communities in habitats along a successional gradient: Divergent patterns of species richness,specialization and threat

The long history of human influence on northern temperate landscapes has created a mosaic of successional stages, from closed forest to open grassland. Various species thus adapted to different habitats and it is interesting to explore how these differences in species composition among particular successional stages translate into differences at the community level. For this purpose, we surveyed breeding birds in 233 patches of five different habitats covering a gradient from bare ground to forest in 29 abandoned military training sites scattered throughout the Czech Republic. Linear mixed effects modelling revealed that late-successional habitats (dense scrubland and forest) were the most species-rich, whereas early-successional stages hosted bird communities with the highest habitat specialization and threat level. These results suggest that the habitats of late-successional stages are important for the maintenance of high bird species richness, but that early-successional habitats are essential for highly specialized and threatened bird species. Given the highly adverse impacts of agricultural intensification and land abandonment on open habitats, it is necessary to promote factors creating initial successional stages suitable for specialized and threatened species.     

Mycobacterium tuberculosis persistence in various adipose depots of infected mice and the effect of anti-tubercular therapy

The adipocytes are one of the non-professional phagocytes postulated to be a haven for Mycobacterium tuberculosis during persistence in the human host. The adipocyte – M. tuberculosis interaction data available to date are ex vivo. The present study was primarily aimed to investigate M. tuberculosis infection of adipocytes in course of infection of mouse model. Using primary murine adipocytes, the study first confirmed the infection and immunomodulation of natural adipocytes by M. tuberculosis. The bacilli could be isolated form visceral, subcutaneous, peri renal and mesenteric adipose depots of immunocompetent mice infected with M. tuberculosis intravenously. The bacilli could be isolated from adipocytes and the stromal vascular fraction, even though the numbers were significantly higher in the latter. The bacterial burden in the adipose depots was comparable to those in lungs in the early phase of infection. But with time, the burden in the adipose depots was either decreased or kept under control, despite the increasing burden in the lungs. Infected mice treated with standard anti tubercular drugs, despite effective elimination of bacterial loads in the lungs, continued to harbour M. tuberculosis in adipose depots at loads similar to untreated mice in the late infection phase.     

Top predator persistence in differential equation models of food chains: The effects of omnivory and external forcing of lower trophic levels

Persistence criteria are given for the highest trophic level predator in ordinary differential equation models of food chains exhibiting arbitrary omnivory and external supplementation of food source or an intermediate predator. The results are expressed in terms of inequalities involving the bounds on the intrinsic growth and interaction rates. Whether omnivory or external forcing enhances persistence is discussed, particularly for the examples of three-, four-, and five-link Lotka-Volterra food chains.     

The effect of temporal variability on persistence conditions in rivers

There has been great interest in the invasion and persistence of algal and insect populations in rivers. Recent modeling approaches assume that the flow speed of the river is constant. In reality, however, flow speeds in rivers change significantly on various temporal scales due to seasonality, weather conditions, or many human activities such as hydroelectric dams. In this paper, we study persistence conditions by deriving the upstream invasion speed in simple reaction-advection-diffusion equations with coefficients chosen to be periodic step functions. The key methodological idea to determine the spreading speed is to use the exponential transform in order to obtain a moment generating function. In a temporally periodic environment, the averages of each coefficient function determine the minimal upstream and downstream propagation speeds for a single-compartment model. For a two-compartment model, the temporal variation can enhance population persistence.