Small-scale spatial patterns determine ecological relationships: an experimental example using nectar production rates

The structuring of populations at small scales has important consequences for ecological relationships and may contribute to the maintenance of genetic diversity within populations. As an example we tested the effects of variation in nectar production rates (NPR) on pollinator visitation in experimental populations of Echium vulgare with different spatial arrangements. Bumblebees discriminate between groups of plants with different NPRs only when these groups are separated by distances larger than 6 m. Within groups, plants with high and low NPR receive similar numbers of approaches. Plants with high NPR increase the average number of approaches to all plants in the group; therefore, plants with low NPR benefit from nectar-rich plants nearby. These results demonstrate that the effects of NPR on pollinator service depend on the spatial structuring of the population. We suggest that this may help to explain the large genetic differences in NPR that we find for E. vulgare at our study site.     

A climate for speciation: rapid spatial diversification within the Sorex cinereus complex of shrews

The cyclic climate regime of the late Quaternary caused dramatic environmental change at high latitudes. Although these events may have been brief in periodicity from an evolutionary standpoint, multiple episodes of allopatry and divergence have been implicated in rapid radiations of a number of organisms. Shrews of the Sorex cinereus complex have long challenged taxonomists due to similar morphology and parapatric geographic ranges. Here, multi-locus phylogenetic and demographic assessments using a coalescent framework were combined to investigate spatiotemporal evolution of 13 nominal species with a widespread distribution throughout North America and across Beringia into Siberia. For these species, we first test a hypothesis of recent differentiation in response to Pleistocene climate versus more ancient divergence that would coincide with pre-Pleistocene perturbations. We then investigate the processes driving diversification over multiple continents. Our genetic analyses highlight novel diversity within these morphologically conserved mammals and clarify relationships between geographic distribution and evolutionary history. Demography within and among species indicates both regional stability and rapid expansion. Ancestral ecological differentiation coincident with early cladogenesis within the complex enabled alternating and repeated episodes of allopatry and expansion where successive glacial and interglacial phases each promoted divergence. The Sorex cinereus complex constitutes a valuable model for future comparative assessments of evolution in response to cyclic environmental change.     

Individual personality and the spatial distribution of groups of grazing animals: An example with sheep

Impacts of individual personality on group distribution were investigated using sheep (Ovis aries) as a model. In an indoor exploration test, individuals who visited <4 (out of 6) objects in a novel environment were classified as ‘shy’ (n = 10), and those who visited 5 or 6 objects were classified as ‘bold’ (n = 10). Nine weeks later, using a series of groups (n = 40) of either 5 shy or 5 bold sheep, we measured distribution at pasture and responses to disturbance and the approach of a human handler. When grazing undisturbed, the mean nearest neighbour distance and spread (minimum convex hull area) of shy groups were less than those of bold groups, with shy individuals moving towards one another more often. Shy groups explored a smaller area than bold groups. When disturbed, shy sheep were more likely to stop grazing and move closer together. Shy sheep kept further away from the handler and moved faster when driven. The results demonstrate a link between personality and group distribution, suggesting that our ‘shy’ and ‘bold’ individuals may occupy different positions on the shy-bold continuum documented for other species. We discuss implications for diet composition and impacts on vegetation grazed by animals with different personalities.     

Unravelling the chemical basis of competitive scent marking in house mice

Major urinary proteins (MUPs) in the urine of male house mice, Mus domesticus, bind the male signalling volatiles 2- sec -butyl-4,5-dihydrothiazole (thiazole) and 3,4-dehydro- exo -brevicomin (brevicomin) and slowly release these volatiles from urinary scent marks. To examine the role of urinary proteins and volatiles, either attached or unattached to the proteins, in competitive scent marking, we fractionated urine from isolated male BALB/c laboratory mice, Mus musculus, by size-exclusion chromatography into three pools. Pool I contained all of the urinary proteins and their bound ligands while pools II and III contained lower molecular weight components including unbound signalling volatiles. In experiment 1, pools I-III were streaked out on to absorbent paper (Benchkote) and introduced into enclosures housing single wild-caught male mice, together with a clean control surface. Each male was tested with fresh stimuli and with aged stimuli deposited 24 h previously. Only pool I stimulated significantly more countermarking and investigation than the control, attracting mice to investigate from a distance even when the rate of ligand release was considerably reduced after 24 h. Experiment 2 examined responses to pool I when this was fresh, aged by 7 days, or had been mixed with menadione to displace ligands from the proteins. Although all three protein stimuli were investigated and countermarked more than a clean control, the aged and menadione-treated pool I stimulated the strongest responses, despite containing the lowest levels of thiazole and brevicomin. Thus competitive countermarking is stimulated by proteins or by nonvolatile protein-ligand complexes in male urine, while release of volatile ligands attracts attention to a competitor's scent marks. Copyright 1999 The Association for the Study of Animal Behaviour.     

Analysis of spatial point patterns in nuclear biology

There is considerable interest in cell biology in determining whether, and to what extent, the spatial arrangement of nuclear objects affects nuclear function. A common approach to address this issue involves analyzing a collection of images produced using some form of fluorescence microscopy. We assume that these images have been successfully pre-processed and a spatial point pattern representation of the objects of interest within the nuclear boundary is available. Typically in these scenarios, the number of objects per nucleus is low, which has consequences on the ability of standard analysis procedures to demonstrate the existence of spatial preference in the pattern. There are broadly two common approaches to look for structure in these spatial point patterns. First a spatial point pattern for each image is analyzed individually, or second a simple normalization is performed and the patterns are aggregated. In this paper we demonstrate using synthetic spatial point patterns drawn from predefined point processes how difficult it is to distinguish a pattern from complete spatial randomness using these techniques and hence how easy it is to miss interesting spatial preferences in the arrangement of nuclear objects. The impact of this problem is also illustrated on data related to the configuration of PML nuclear bodies in mammalian fibroblast cells.     

基于植物-地形关系的物种丰富度空间格局预测——GAMs途径的一种应用

将基于样本调查数据的群落-生境因子回归分析与GIS支持下的植物属性空间格局预测结合起来,是国际上植被-环境关系定量研究的新途径。通用可加性模型（GAM）的非参数属性使之具有对不同数据类型的广泛适应性,成为这种“回归分析＋空间预测”途经的有效手段;不同程度上依赖于数字高程模型的环境空间数据集是实现空间预测的必要条件。介绍了这一新的研究途径,并应用于案例研究区域植物多样性指标空间格局的预测和分析。野外调查的一组样方地形特征指标和植物多样性指标（包括样方物种丰富度及乔木、灌木、草本、常绿木本、珍稀种类的丰富度）,分别作为预测变量和响应变量,建立GAM模型。结合研究区域10m分辨率的数字高程模型,对该区域植物物种丰富度的空间格局进行空间预测,并对预测模型和结果进行统计分析和检验。结果表明：（1）不同的多样性指标具有不同的模型结构和模拟效果,重复模拟的结果稳定性也不同,反映了所受地形因子影响的差异;（2）影响各多样性指标空间格局的地形变量主要是坡位和坡度等小尺度特征,大尺度海拔因素的影响并不显著;（3）模拟结果与独立检验数据的相关分析表明,对乔木种、草本种、珍稀种的模拟全部有效;对常绿种和样方物种总数的模拟部分有效;而对灌木种丰富度的预测基本失败。（4）模型预测变量有效性和全面性决定了模型对数据的解释能力,样本大小对模型的稳定性和可靠性也有显著影响。就地形因子对生境条件的代表性、模拟误差的来源及GAMs模型的优缺点和应用前景进行了讨论。     

Optimizing the mass marking of fish with alizarin red S: an example with glass eels

Fish marking is an essential tool for fisheries management, especially for evaluating the stocking of endangered fish species to support conservation and sustainable use of fish stocks. Batch marking of young European eels Anguilla anguilla (L.) prior to stocking is recommended as the benefits of stocking for the spawning stock can be evaluated by recapturing marked fish over time, therefore mass marking of young eels with substances such as alizarin red S (ARS) is becoming increasingly important. To improve the marking method and reduce marking costs when immersing glass eels in an ARS solution, eight laboratory experiments under varying conditions (e.g., temperature, ARS concentration, immersion time, osmotic induction, fish density) and with ARS from different suppliers were carried out. The results show that optimal marking of glass eels can be carried out in the field or during transport by putting approximately 50 g of glass eels per liter in 150 mg L⁻¹ ARS solution for 3 h at 10–15°C. Lower concentrations did not result in reliable marking. Water temperatures of 5°C and below can have a stunning effect on the eels and increase mortality significantly, regardless of the concentration of ARS. Glass eel densities below 50 g L⁻¹ in the marking bath increase marking costs unnecessarily, while a higher density of 100 g L⁻¹ resulted in significantly higher mortality and lower marking success. A somewhat more difficult but less expensive alternative is to bathe the fish in a saline solution of 1% (10 PSU) of 80 mg L⁻¹ ARS for 3 h at 10°C. Costs can also be significantly reduced by choice of supplier for ARS, but care should be taken as the quality of the powder appears to vary (mean percentage of sufficiently marked eels ranged from 59% to 91% among suppliers in the present study) and can lead to marking failure. The optimal marking conditions can help ensure that stocked glass eels can be reliably identified in future studies to assess stocking benefits while reducing costs.     

An analysis on the spatial distribution patterns of basidiocarps of Agaricales in aCastanopsis-dominated forest in Kyoto

Spatial distribution patterns of basidiocarps of Agaricales were studied in aCastanopsis-dominated forest in Kyoto. Sixty-seven species were recorded, of which 45 species and 99% of total dry weight were ectomycorrhizal fungi belonging to Amanitaceae, Cortinariaceae, Russulaceae, Boletaceae and Strobilomycetaceae. The data were analyzed statistically by using the m-m regression method. Three distribution patterns were recognized: aggregated, random and uniform. Although total basidiocarps were distributed randomly, basidiocarps of most species showed aggregated distributions, suggesting mycelium of ectomycorrhizal and saprotrophic fungi extend in a limited area in the soil. The degree of aggregation was different among species and this difference was suggested to reflect the difference of niche among the species.     

Foraging efficiency and the fitness consequences of spatial marking by ladybeetle larvae

Marking and avoiding poor‐quality resources can be an important mechanism by which animals lacking a spatial memory can maximize their foraging efficiency. Here, we investigate the behaviour of larval Harmonia axyridis ladybeetles that leave chemical tracks as they forage. We built a model of an individual larva foraging for aphids, parameterized it using experimental data, and used the model to predict the effect of larval track production and detection on foraging efficiency, an important component of fitness. The model predicted that there is an optimal sensitivity of larvae to tracks which maximizes foraging efficiency; if the larva is too sensitive to tracks, it will avoid areas that might still contain resources, whereas if it is too insensitive, it will forage in areas that have depleted resources. Furthermore, the increased efficiency conferred by detecting tracks depends on the spatial arrangement of resources, with more aggregated resource distributions allowing greater benefits of detecting tracks. We tested the predictions of the model experimentally by measuring predation on aggregated versus dispersed soybean aphids by H. axyridis larvae whose ability to produce tracks was experimentally manipulated. The experiments corroborated the results of the model: larvae that could produce tracks consumed more aphids than those that could not, and this difference was greatest when aphids were aggregated among plants. Our results suggest that larval tracks play an important role in foraging efficiency, and we discuss implications for the evolution of larval track production and detection in ladybeetles.     

An evaluation of the analysis system of video transects used to sample subtidal epibiota

Two popular methods of benthic cover estimation (the point intercept technique with two sets of position points, and digital interactive color segmentation) were compared with an alternative method of digital cover estimation using Bezier curves as a tool for outlining the objects on an images and AutoCAD® software for the final evaluation of abundance. The comparison was done using still video images obtained from two 10-m transects on subtidal rocks off the Rimsky-Korsakov islands in the Sea of Japan (Russia). Ten rectangular sectors (1×0.4 m each) selected randomly within both video transects were analyzed. One-way ANOVA for repeated measurements was used to test the differences between methods. The point intercept technique differed significantly from both methods of digital estimation and had an essential positive bias. The Tukey multiple comparison test revealed the differences among digital estimation methods in the species, which have the complicated color with many contrast spots. The proposed approach using Bezier curves has an advantage over the interactive color segmentation if the objects under selection are lit at different levels or have a contrast coloration or are hidden by canopy organisms. Besides, estimation of cover in the field of AutoCAD® software is more precise and takes less time than that obtained using a scaled grid, available for automatically segmented species. The results showed that digital cover estimation using Bezier curves and AutoCAD® software is a convenient method for analyzing benthic samples at large spatial scales.     

Adaptive intraspecific divergence: an example using the animal cytochrome b gene

The topologies of phylogenetic trees characterized by a high level of intraspecific divergence between the phylogenetic DNA groups (clades) are often explained in terms of the theory of Pleistocene refugia. To elucidate the issue of the adaptive role of intraspecific divergence, the changes in the physicochemical properties of amino acids in the course ofcladogenesis (MM01 model of the TreeSAAP 3.2 package) were analyzed in this work using as an example the nucleotide sequences of the cytochrome b gene in some species of northern animals (lemmings, redbacked voles, chipmunks, flying squirrels, ermines). It was shown that the process of intraspecific divergence was rarely accompanied by radical amino acid substitutions in cytochrome b caused by adaptation (directional selection). In connection with this, the hypothesis is discussed according to which the adaptive variants formed in the species at the peak of cold were lost with climatic warming due to the drift or selection against individuals adapted to cold.     

A computational perspective on the neural basis of multisensory spatial representations

We argue that current theories of multisensory representations are inconsistent with the existence of a large proportion of multimodal neurons with gain fields and partially shifting receptive fields. Moreover, these theories do not fully resolve the recoding and statistical issues involved in multisensory integration. An alternative theory, which we have recently developed and review here, has important implications for the idea of 'frame of reference' in neural spatial representations. This theory is based on a neural architecture that combines basis functions and attractor dynamics. Basis function units are used to solve the recoding problem, whereas attractor dynamics are used for optimal statistical inferences. This architecture accounts for gain fields and partially shifting receptive fields, which emerge naturally as a result of the network connectivity and dynamics.     

中国壳斗科植物空间多样性格局研究

采用地理信息系统技术,制作空间分布图、从空间上计算多样性格局指数,研究中国壳斗科植物属、种的空间多样性分布格局。结果显示,云南南部、广西北部和广东北部的属、种数量均较多,是中国壳斗科植物多样性的重要分布地区,甘肃南部、陕西南部、河南西部及南部是壳斗科植物向南、向北扩散的重要通道;从多样性指数来看,种的多样性指数值均比属的值高,但均匀度指数却是属的值高;当属或种的数量为1时,其所占面积、占景观的比例、斑块数量、最大斑块指数、景观形状指数均最大,随着属或种的数量逐渐增加,其多样性明显提高,但其各项指标基本呈依次降低的趋势。通过对壳斗科植物空间多样性格局进行量化研究,获取了中国壳斗科植物空间多样性分布规律及多样性格局数量特点,利用地理信息系统技术可以使多样性研究体现出空间性和定量化的特征。     

An investigation of the population ecology of syntopic shrews inhabiting water-cress beds

The population ecology of the shrews Neomys fodiens, Sorex araneus and S. minutus living syntopically in an area of commercial water-cress beds was investigated by live-trapping over a two-year period. The shrew population comprised 52% 5. araneus , 31% N. fodiens and 17% S. minutus. Sorex araneus was the most numerous species in all seasons. Peak numbers of shrews occurred in summer with low numbers in the ensuing winter. Input of new individuals was high, especially of N. fodiens which exceeded 60% in most months. Survival in the study area never exceeded 8 months in N. fodiens and 11 months in S. araneus. Both species suffered approximately 50% mortality and emigration in the first two months of life. Apart from a few, more nomadic, shrews, N. fodiens and S. araneus seemed quite sedentary during trapping periods, moving a mean distance of 13.7 m and 17.2 m between successive captures, respectively. The relatively low numbers of recaptures of N. fodiens at successive trapping periods indicated nomadic behaviour. Both species were more active during darkness than during daylight, and were more active in spring and summer than in winter. High turnover of the shrew population was attributed to mortality and emigration. Emigration was possibly encouraged by competition for space, particularly for nesting sites.     

Not so divided: the common basis of plant and animal cell division

Plant cells do not have centrioles and their mitosis is frequently likened to the chromosome-based mechanism seen in acentriolar animal cells. However, this is a false analogy. Although plants can use this mechanism, they generally divide by a method that uses bipolar mitotic caps, which is more similar to the canonical centrosome-based method of animals.     

Geographic patterns of diversification: an example with ectoparasitic insects

On any spatial scale, the species composition of a taxonomic group often departs from a phylogenetically random subset drawn from the pool of species available on a higher scale. Analysis of the uneven representation of related lineages in different assemblages can reveal the action of various forces shaping their diversification. For any assemblage, unequal diversification among lineages can be estimated using diversity skewness, an index of the balance of a phylogenetic tree whose values increase with increasing differences in diversification rates among tree branches. We tested for geographical patterns in the diversity skewness of flea assemblages parasitic on small mammals in 26 distinct geographic localities from the Palaearctic and 15 from the Nearctic. Overall, diversity skewness of the Nearctic flea assemblage was unexpectedly high compared to that of the global flea fauna, whereas that of the Palaearctic did not depart from the expectations of a null model. On a smaller scale, the diversity skewness of local flea assemblages was sometimes lower, sometimes higher, but, in most of the 41 localities, it did not differ significantly from that of random subsets taken from the species pool available on the larger spatial scale (either the world fauna or that of the biogeographical realm, i.e. Palaearctic or Nearctic). More importantly, among Palaearctic assemblages, diversity skewness increased with increasing latitude and/or decreasing mean air temperatures. The different patterns observed in the Palaearctic and Nearctic may be in part due the fact that flea diversification appears to have been more intense in the former than the latter, and to differences between them in relief and glacial history. Temperature‐driven speciation rates may well explain the latitudinal gradient in diversity skewness in the Palaearctic. The results illustrate the action of various biogeographical processes in shaping the uneven differentiation of flea lineages on different spatial scales. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 807–814.     

川西丘陵区景观空间格局分析

采用分形维数、平均斑块面积、形状指数和伸张度分析了川西不同丘陵地貌区灌溉水田、一般旱地、果园、有林地和农村居民点斑块的空间格局特征,并用分形维数、平均斑块面积和Shannon-Weiner指数3种方法研究了浅丘、中丘和高丘的综合景观特征。结果表明,不同景观斑块在同一丘陵区内的格局特征不同,同一景观斑块在3种丘陵区的格局也有差异。浅丘、中丘和高丘的综合景观格局特点是随着地势起伏的增加、人类活动和土地利用强度的减弱,分形维数增加,从1.1865到1.3123;斑块平均面积则依次变小,从2.2204hm^2减少到1.2403hm^2。3种丘陵区的景观多样性指数分别为1.7199、1.9802和2.0898。