Plant size and spatial pattern in a natural population of Myosotis micrantha

Abstract. We examined spatial distributions and plant sizes along a transect through a natural population of a winter annual, Myosotis micrantha. A size hierarchy existed, as indicated by high values of Gini coefficients of inequality for plant mass and correlated measures. Plants with no immediate conspecific neighbors were larger than plants with one or more near neighbors, suggesting that competition from near neighbors depressed plant size. However, there was strong positive spatial autocorrelation in plant size: large plants were associated with large neighbors and small ones with small neighbors. Plant size was also positively correlated with the combined biomass of near neighbors. The population formed a two-phase mosaic of patches of relatively large plants alternating with patches of smaller plants. The data suggest that individual plants compete with conspecifics, but the effects of competition are symmetrical. The most likely explanations for this spatially structured size hierarchy are variation in plant density, patchy distribution of resources, or a combination of the two.     

Increasing phosphorus concentration in seed of annual pasture legume species increases herbage and seed yields

In glasshouse experiments with low levels of soil applied phosphorus (P), yields of four annual pasture legumes (Medicago polymorpha, Trifolium subterraneum, T. balansae, Ornithopus compressus) increased with increasing P concentration in the seed. In a further experiment, M. polymorpha cv. Serena was grown at the same plant density from seed of two P concentrations and two seed sizes when two levels of finely ground superphosphate were applied to the soil. Higher P concentrations in the seed increased yields of dried tops by about 30% for the first harvest (21 days), 20% for the second harvest (52 days), and 9% at maturity (103 days), and seed yields by 11%. Larger seeds increased yields of dried tops by between 6–46% for the first two harvests but at maturity yields of dried tops and seed were unaffected by seed size. None of the interactions were statistically significant (P>0.05), except for the first harvest when two interactions (P concentration in the seed × seed size (i.e. P content in seed), and P applied to the soil × P concentration in the seed × seed size) were significant at P<0.05 level. In a field experiment, Trifolium subterraneum clover seed (two cultivars) of the same size but with two different P concentrations was sown at the same plant density and two levels of granulated (0.2–5 mm) superphosphate were applied to the soil surface. The higher level of superphosphate increased dried herbage yields of the dense clover swards by three- to four-fold 90 and 120 days after sowing. The higher P concentration in the seed increased yields of dried herbage by between 50 to 25%, depending on the level of P applied to the soil and the harvest date.     

The effect of diversity and spatial arrangement on biomass of agricultural cultivars and native plant species

Various spatial arrangements can be found within natural grassland plant populations and communities. In contrast, spatial arrangement diversity is typically not observed in agroecosystems. Little is known about the influence of spatial arrangement on the productivity and success of agricultural or native plants. Such information is of interest to farmers who want to increase yield and restorationists working with native ecosystems. Agricultural and native plants were planted in two-way mixtures that included combinations of cultivars, species, genera, or functional groups. Each combination was arranged as a random mixture within rows, alternating rows of the different genotypes or species, and as alternating pairs of rows. Aboveground biomass was determined for each mixture component and compared to monoculture controls. Though plot composition had the most consistent influence on aboveground biomass, spatial arrangement appeared to have some influence among agricultural cultivars. Whether native or agricultural, biomass was greater for mixtures containing both a grass and a legume.     

Effects of spatial heterogeneity on butterfly species richness in Rocky Mountain National Park, CO, USA

We investigated butterfly responses to plot-level characteristics (plant species richness, vegetation height, and range in NDVI [normalized difference vegetation index]) and spatial heterogeneity in topography and landscape patterns (composition and configuration) at multiple spatial scales. Stratified random sampling was used to collect data on butterfly species richness from seventy-six 20 × 50 m plots. The plant species richness and average vegetation height data were collected from 76 modified-Whittaker plots overlaid on 76 butterfly plots. Spatial heterogeneity around sample plots was quantified by measuring topographic variables and landscape metrics at eight spatial extents (radii of 300, 600 to 2,400 m). The number of butterfly species recorded was strongly positively correlated with plant species richness, proportion of shrubland and mean patch size of shrubland. Patterns in butterfly species richness were negatively correlated with other variables including mean patch size, average vegetation height, elevation, and range in NDVI. The best predictive model selected using Akaike’s Information Criterion corrected for small sample size (AIC_c), explained 62% of the variation in butterfly species richness at the 2,100 m spatial extent. Average vegetation height and mean patch size were among the best predictors of butterfly species richness. The models that included plot-level information and topographic variables explained relatively less variation in butterfly species richness, and were improved significantly after including landscape metrics. Our results suggest that spatial heterogeneity greatly influences patterns in butterfly species richness, and that it should be explicitly considered in conservation and management actions.     

On the scaling patterns of species spatial distribution and association

Understanding how species distribution (occupancy and spatial autocorrelation) and association (that is, multi-species co-distribution) change across scales is fundamental to unlocking the pattern formation in population ecology and macroecology. Based on the Bayesian rule and join-count statistics, I present here a mathematical model that can demonstrate the effect of spatial scale on the observation of species distribution and association. Results showed that the intensity of spatial autocorrelation and species association declines when the grain in the spatial analysis increases, although the category of species distribution (aggregated or segregated) and association (positive or negative) remains the same. Random distribution and species independence were proved to be scale-free. Regardless of the possible patterns of species distribution and association, species tend to be randomly distributed and independent from each other when scaling-up (an increasing grain), reflecting a percolation process. This model, thus, grasps the statistical essence of species scaling pattern and presents a step forward for unveiling mechanisms behind species distributional and macroecological patterns.     

Threatened species in a vanishing habitat: plants and invertebrates in calcareous grasslands in the Swiss Jura mountains

We examined the diversity of vascular plants, butterflies, grasshoppers, gastropods and carabid beetles in three calcareous grasslands in the northwestern Swiss Jura mountains, a habitat type that has decreased dramatically during the recent decades. As many as 58 species (ca 22%) of the 266 collected are listed as threatened in northern Switzerland. The number of threatened species ranged from 27 to 49 per site, and 26 species occurred in only one of the three grasslands. The species richness of butterflies and vascular plants correlated positively among the grasslands, while the species richness of other groups did not covary. An index of complementarity indicated that the species compositions (including non-threatened species, and spiders and oribatid mites) of the groups varied greatly among the grasslands. In addition, herbivorous groups were more widely distributed than predators among the three grasslands. Due to this variation in species composition none of the three sites c an substitute for the others, if the biodiversity of these grasslands is to be maintained. Furthermore, the taxonomic groups studied are poor indicators of each others' diversity. Consequently, we support the shopping basket approach to conservation evaluation, i.e. measuring species richness, species composition and complementarity of several groups instead of just one.     

People, energy and avian species richness

Aim To investigate the inter‐relationships between energy availability, species richness and human population density, particularly whether human population density influences the manner in which species richness responds to energy availability. Location British 10‐km grid cells. Methods Using regressions, we investigate how human population density varies with energy availability and the nature of relationships between the numbers of species, classified by abundance and threat categories, and human population density. We then assess whether the relationships between these species richness measures and energy availability are altered when accounting for human population density. We conduct analyses using both independent error models and ones that control for spatial autocorrelation. Results Human population density was strongly and positively correlated with energy availability. Total species richness, and that of unthreatened, threatened, common and moderately common species, increases in a positive decelerating manner with human density. When human population density was taken into account, these species groups exhibited similar species–energy relationships, but the slopes of these relationships were significantly reduced in independent error models and, in the case of total richness, in spatial models. Main conclusions Positive correlations between human density and species richness probably arise as both increase with energy availability. Our data are compatible with the suggestion that high human population densities reduce the rate at which species richness increases with energy availability, but additional research is required before causality can be confirmed.     

Positive effects of shrubs on herbaceous species richness across several spatial scales: evidence from the semiarid Andean subtropics

Question: What is the effect of shrubs on herbaceous species richness at three spatial scales: quadrat, site, and region? Location: Prepuna, subtropical semi‐arid Andes. Methods: At eight sites, we recorded the presence of herbaceous species in spaces beneath shrubs/small trees and in open areas. At the quadrat scale, the average species number per quadrat was calculated and compared between the two microhabitats (shrubs/open). At the local (site) scale, all quadrats of each site were pooled according to microhabitat, and all sites were then combined for the regional analysis. Results and conclusions: We found greater herbaceous species richness below shrubs at all three spatial scales considered. Several species were found exclusively associated with the shrub undercanopy. This effect seems to depend more on greater inventory diversity at the different scales than on greater differentiation diversity in the herbaceous communities associated with shrubs. Facilitation seems to be responsible for the increase of species richness beneath shrubs, but further experimental study is needed to obtain insight into the underlying mechanisms.     

IgG abzymes with peroxidase and oxidoreductase activities from the sera of healthy humans

We present the evidence showing that small fractions of electrophoretically homogeneous immunoglobulin G (IgGs) from the sera of healthy humans and their Fab and F(ab)₂ fragments oxidize 3,3′‐diaminobenzidine through a peroxidase activity in the presence of H₂O₂ and through an oxidoreductase activity in the absence of H₂O₂. During purification on protein G‐Sepharose and gel filtration, the polyclonal IgGs partially lose the Me²⁺ ions. After extensive dialysis of purified Abs against agents chelating metal ions, the relative peroxidase activity decreased dependently of IgG analyzed from 100 to ~10–85%, while oxidoreductase activity from 100 to 14–83%. Addition of external metal ions to dialyzed and non‐dialyzed IgGs leads to a significant increase in their activity. Chromatography of the IgGs on Chelex non‐charged with Cu²⁺ ions results in the adsorption of a small IgG fraction bound with metal ions (~5%), while Chelex charged with Cu²⁺ ions bind additionally ~38% of the total IgGs. Separation of Abs on both sorbents results in IgG separation to many different subfractions demonstrating various affinities to the chelating resin and different levels of the specific oxidoreductase and peroxidase activities. In the presence of external Cu²⁺ ions, the specific peroxidase activity of several IgG subfractions achieves 20–27 % as compared with horseradish peroxidase (HRP, taken for 100%). The oxidoreductase activity of these fractions is ~4–6‐fold higher than that for HRP. Antioxidant enzymes such as superoxide dismutases, catalases, and glutathione peroxidases are known to represent critical defence mechanisms for preventing oxidative modifications of DNA, proteins, and lipids. Peroxidase and oxidoreductase activities of human IgGs could also play an important role in the protection of organisms from oxidative stress and toxic compounds. Copyright © 2015 John Wiley & Sons, Ltd.     

Stability of spatial pattern of fish species diversity in the Strait of Sicily (central Mediterranean)

In this paper, species diversity of demersal fish communities was analysed over an area covering about 45,000 km² of the Italian side of the Strait of Sicily (central Mediterranean). Fish abundance data come from a 10-year series (1994–2003) of experimental bottom trawl surveys carried out within the framework of the international program MEDITS. A simple GIS-based method was proposed to identify areas supporting high or low values of diversity and evaluate their temporal stability. A well-defined spatio-temporal pattern in diversity emerged from the analysis, with some areas of great ecological relevance being identified. Importantly, the greatest diversity within the fish communities was consistently seen at the offshore bank on the western part of the south Sicilian shelf (Adventure Bank). The site also supports high total biomass of demersal resources and shows the presence of species of great concern to fisheries. Results suggest that Adventure Bank represents a priority site for investigating the possibility of innovative management of marine ecosystems and demersal fisheries in offshore zones.     

陆生高等植物碳含量及其特点

精确评估植被碳贮量是阐明植被恢复对全球陆地生态系统碳平衡影响的核心。碳贮量一般根据碳含量系数与生物量来估计。本文收集了植物碳含量实测数据,分析了不同生长型植物、植物构件和不同区域植物的碳含量状况及其特点,结果表明:植物碳含量在24.95%~55.44%,平均为(43.63±0.14)%;不同生长类型植物平均碳含量是乔木(46.22%)>灌木(45.93%)>苔藓(41.64%)>草本(37.13%);不同的构件的碳含量是花(48.52%)>果(47.19%)>枝(45.42%)>干(44.48%)>叶(43.36%)>根(42.88%);不同地带的碳含量是高纬度地区(50.30%)>低纬度地区(45.30%)>中纬度地区(39.68%),且不同气候型之间均有显著差异。因此,用固定的碳含量系数来估计碳贮量存在较大误差。     

The origin of modern humans: A cytogenetic model

A new model of the origin of man is proposed on the basis of recent studies on cytogenetics of chromosomal Q-heterochromatin regions (Q-HRs) in man and other higher primates. This model is based on the following facts: a) chromosomal Q-HRs were found in the genome of only three higher primates (man, the chimpanzee and the gorilla); b) chromosomal Q-HRs in the human genome, unlike those in apes, exhibit considerable quantitative variability; c) the number of human chromosomal Q-HRs in the genome has a selective value in the adaptation of human populations to various environmental conditions. According to this model, the three major morphofunctional distinctions of man—great physiological flexibility, characteristic morphological structure, and conceptual thinking—arose as a result of the capacity of our remote ancestors to broadly change their genome mass owing to features of chromosomal Q-HRs that are only intrinsic to man. We feel that genome-mass variability through chromosomal Q-HRs allowed man to adapt himself to various environments over such a short period of time.     

Growth strategies differentiate the spatial patterns of 11 dipterocarp species coexisting in a Malaysian tropical rain forest

We examined relationships between mortality rate, relative growth rate (RGR), and spatial patterns of three growth stages (small, medium, and large trees) for 11 dipterocarp species in the Pasoh 50-ha plot. Mortality rates for these species tended to be positively correlated with RGRs, although the correlation was significant only at the small-tree stage. Seven species with high growth and mortality rates exhibited peaks in spatial aggregation at small distances (<100 m) in small trees, but this aggregation disappeared in medium and large trees. In contrast, the other four species with low growth and mortality rates aggregated at large distances (>200 m) throughout the three growth stages in all but one species. Negative associations between different growth stages were observed only for the high-mortality species, suggesting density-dependent mortality. The high-mortality species showed habitat associations with topography, soil type, and the forest regeneration phase after gap formation, whereas the three low-mortality species only had associations with the forest regeneration phase. A randomization procedure revealed that these habitat associations explained little of their spatial aggregation. Our results suggest that the growth strategy has a large effect on the structuring of the spatial distribution of tree species through mortality processes.     

The scale of analysis determines the spatial pattern of woody species diversity in the Mediterranean environment

We examine the spatial pattern of woody species diversity at different scales, in two sites of Mt. Holomontas in northern Greece, which falls within the transitional zone between temperate forests and Mediterranean-type ecosystems. We investigate how diversity is distributed in space and whether the perceived pattern changes with the scale of observation. We use two different metrics of diversity: species richness and species turnover. Our main finding is that the spatial pattern of diversity changes with the scale of observation or analysis. For a given scale, the pattern of species richness (alpha diversity) is negatively correlated with the pattern of species turnover (beta diversity). Species-rich areas have more species in common with their neighbors than species-poor areas. The between-scale disparity of the spatial pattern of diversity may be a general feature of ecological systems. For this to be validated, studies with different groups of species in different biomes and in different biogeographical areas are required; our study contributes to this direction providing evidence that this holds true for woody species in Mediterranean communities. Finally, we discuss how these findings might affect important issues in theoretical and applied ecology, such as identifying the environmental factors driving biodiversity.     

Predicting spatial patterns of plant species richness: a comparison of direct macroecological and species stacking modelling approaches

Aim This study compares the direct, macroecological approach (MEM) for modelling species richness (SR) with the more recent approach of stacking predictions from individual species distributions (S‐SDM). We implemented both approaches on the same dataset and discuss their respective theoretical assumptions, strengths and drawbacks. We also tested how both approaches performed in reproducing observed patterns of SR along an elevational gradient. Location Two study areas in the Alps of Switzerland. Methods We implemented MEM by relating the species counts to environmental predictors with statistical models, assuming a Poisson distribution. S‐SDM was implemented by modelling each species distribution individually and then stacking the obtained prediction maps in three different ways – summing binary predictions, summing random draws of binomial trials and summing predicted probabilities – to obtain a final species count. Results The direct MEM approach yields nearly unbiased predictions centred around the observed mean values, but with a lower correlation between predictions and observations, than that achieved by the S‐SDM approaches. This method also cannot provide any information on species identity and, thus, community composition. It does, however, accurately reproduce the hump‐shaped pattern of SR observed along the elevational gradient. The S‐SDM approach summing binary maps can predict individual species and thus communities, but tends to overpredict SR. The two other S‐SDM approaches – the summed binomial trials based on predicted probabilities and summed predicted probabilities – do not overpredict richness, but they predict many competing end points of assembly or they lose the individual species predictions, respectively. Furthermore, all S‐SDM approaches fail to appropriately reproduce the observed hump‐shaped patterns of SR along the elevational gradient. Main conclusions Macroecological approach and S‐SDM have complementary strengths. We suggest that both could be used in combination to obtain better SR predictions by following the suggestion of constraining S‐SDM by MEM predictions.     

Ontogenetic migration of the mental foramen in Neandertals and modern humans

Since the nineteenth century, researchers have noted that Neandertal and modern human adults differ in mental foramen position, although the ontogenetic changes in the position of this feature have only recently come under the scrutiny of paleoanthropologists. Research on mental foramen position has focused on whether this feature is inferior to a particular tooth. However, tooth position may not be a reliable indicator of mental foramen position because of variability in tooth size within and between taxa and during eruption events. As opposed to observing the mental foramen with respect to the postcanine teeth, we examined linear distances from the mental foramen to other mandibular landmarks. Modern human adults may appear truncated, or paedomorphic, in mental foramen position with respect to Neandertal adults. However, infants of the two taxa differ substantially in anterior mandibular form. The initial differences in the shape of the mental region may be related to the embryological position of the mental foramen in modern humans and its role in the development of the mental trigone. The shape changes that accrue thereafter, possibly from faster mandibular growth rates in Neandertals, further distinguish the adults from one another. Although mandibular shape differences exist from early infancy onwards, adults of the two taxa are broadly similar in bi-mental foramen breadth with respect to mandibular size. For this reason, qualitative assessments of mental foramen position may provide less taxonomic information than previously thought.     

大气CO2浓度升高和N沉降对南亚热带主要乡土树种叶片元素含量的影响

大气CO₂浓度升高和N沉降以及二者之间的耦合作用对陆地森林生态系统的影响是当前国际生态学界关注的热点之一。该实验运用大型开顶箱(open-top chamber, OTC)研究: 1)高CO₂浓度(700 μmol×mol^-1) +高N沉降(100 kg N×hm^-2×a^-1) (CN); 2)高CO₂浓度(700 μmol×mol^-1)和背景N沉降(CC); 3)高N沉降(100 kg N×hm^-2×a^-1)和背景CO₂浓度(NN); 4)背景CO₂和背景N沉降(CK) 4种处理对南亚热带主要乡土树种木荷(Schima superba)、红锥(Castanopsis hystrix)、肖蒲桃(Acmena acuminatissima)、红鳞蒲桃(Syzygium hancei)、海南红豆(Ormosia pinnata)叶片元素含量的影响。研究结果表明, 大气CO₂浓度升高对5种乡土树种叶片元素含量有较大的影响, 除海南红豆叶片的Ca含量外, 其他树种的叶片元素含量在高CO₂浓度处理下都显著升高(p < 0.05); 而在N沉降处理下, 5个树种的叶片K和Ca含量都降低。大气CO₂浓度升高与N沉降处理对5种乡土树种植物叶片元素含量影响的交互作用不是很明显, 仅仅木荷和红鳞蒲桃的叶片Ca和Mn以及海南红豆的叶片Mn含量在大气CO₂浓度上升和N沉降交互处理下显著下降, 而肖蒲桃的叶片P含量在大气CO₂浓度上升和N沉降交互处理下显著上升。