The influence of spatial scale on cross-taxon congruence patterns and prediction accuracy of species richness

A comparison of species richness patterns of butterflies and birds was made using data from two grids of squares (small squares 137.5 km on a side and large squares 275 km on a side) covering western North America. Using geostatistical procedures, we found that the spatial patterns of species richness of these two taxa were related. The influence of grain size on the strength of this relationship was investigated by analysing the two data sets. For both data sets, the number of butterfly species in a square was a statistically significant predictor of the corresponding number of bird species. However, cross-validation techniques showed that the marginal improvement in prediction accuracy due to including butterflies as a predictor was greater in the large-square data. We explored the effect of areal extent on cross-taxon congruencies by investigating species richness patterns in four subsets of the small-square data. In regions with smaller areal extent, the cross-taxon congruence patterns were not substantially different from the pattern found in the full data set. Finally, using data-splitting techniques, we explored the relationships between prediction accuracy of species richness, sample size, areal extent of the sample, and grain size.     

黄淮海湿地生态系统服务与生物多样性保护格局的耦合性

研究生物多样性格局与生态系统服务格局之间的空间耦合效应,探讨以生物多样性保育为核心目标的自然保护体系同时能多大程度满足对生态系统服务功能的维护和支撑,已成为自然保护领域新的热点关注问题。目前研究多限于陆域生态系统,其方法难以适用于湿地生态系统。以黄淮海湿地——这一高强度人类活动的区域为研究区,基于湿地生态系统的横向连接度、纵向连接度(2D)以及结合地下水的垂向连接度(3D),对黄淮海地区湿地具有的生态系统服务功能进行了空间评估和分析,识别出具有重要意义的生态系统服务功能区域,结合现有保护区分布情况进行空间分析,评价现有保护区对生态系统服务功能的支持程度,即生物多样性保护与生态系统服务功能重点区域的空间耦合性。研究结果表明:目前湿地保护区并未有效覆盖湿地生态系统关键区域,湿地生态系统服务关键格局也存在大量明显的保护空缺。同时,随着2D到3D延伸,保护区对生态系统服务功能的支持程度也稍有提高,这与系统保护规划中选择不同保护目标后保护规划格局发生变化的情况类似,而生态系统服务功能的"热点地区"(重要区域)与保护生物学中所指的物种保护的热点地区类似,这表明生态系统服务功能的规划和保护也可以借鉴保护生物学中系统保护规划的理论和方法,为后续研究提供参照。     

Monitoring marine macroalgae: the influence of spatial scale on the usefulness of biodiversity surrogates

Aim To examine the influence of spatial scale on the usefulness of commonly employed biodiversity surrogates in subtidal macroalgae assemblages. Location South‐west Australia. Methods The relationship between biodiversity surrogates and univariate and multivariate species‐level patterns was tested at multiple spatial scales, ranging from metres (between quadrats) to hundreds of kilometres (between regions), using samples collected from almost 2000 km of temperate coastline that represented almost 300 species. Biodiversity surrogates included commonly used cost‐effective alternatives to species‐level sampling, such as those derived from functional groups and from taxonomic aggregation. Results Overall, surrogates derived from taxonomic aggregation to genus or family level correlated strongly with species‐level patterns, although the family‐level surrogate was a less effective predictor of species richness at large spatial scales. Surrogates derived from aggregation to coarser taxonomic levels and functional groups performed poorly, while the effectiveness of a surrogate measure derived from canopy‐forming species improved with increasing spatial scale. Main conclusions A critical, but rarely examined, assumption of biodiversity surrogates is that the relationship between surrogate and species‐level patterns is consistent in both space and time, and across a range of spatial and temporal scales. As the performance of all surrogates was, to some degree, scale‐dependent, this work empirically demonstrated the need to consider the spatial extent and design of any biodiversity monitoring programme when choosing cost‐effective alternatives to species‐level data collection.     

Spatial congruence of ecological transition at the regional scale in South Africa

Aim To determine whether patterns of avian species turnover reflect either biome or climate transitions at a regional scale, and whether anthropogenic landscape transformation affects those patterns. Location South Africa and Lesotho. Methods Biome and land transformation data were used to identify sets of transition areas, and avian species occurrence data were used to measure species turnover rates (β‐diversity). Spatial congruence between areas of biome transition, areas of high vegetation heterogeneity, high climatic heterogeneity, and high β‐diversity was assessed using random draw techniques. Spatial overlap in anthropogenically transformed areas, areas of high climatic heterogeneity and high β‐diversity areas was also assessed. Results Biome transition areas had greater vegetation heterogeneity, climatic heterogeneity, and β‐diversity than expected by chance. For the land transformation transition areas, this was only true for land transformation heterogeneity values and for one of the β‐diversity measures. Avian presence/absence data clearly separated the biome types but not the land transformation types. Main conclusions Biome edges have elevated climatic and vegetation heterogeneity. More importantly, elevated β‐diversity in the avifauna is clearly reflected in the heterogeneous biome transition areas. Thus, there is spatial congruence in biome transition areas (identified on vegetation and climatic grounds) and avian turnover patterns. However, there is no congruence between avian turnover and land transformation transition areas. This suggests that biogeographical patterns can be recovered using modern data despite landscape transformation.     

玉米根系形态性状和空间分布对水分利用效率的调控

玉米根系形态性状(总根长、根系表面积和根系干物质重)与植物整体水分利用效率间具有显著或极显著的相关性,回归曲线趋势基本相同,均呈二次曲线关系,只是相关系数不同。说明从提高水分利用效率来说,根系需要维持适宜的大小。其中根长对水分利用效率的贡献是第一位的,而根系干物质重的贡献最小,根系表面积介于二者之间。从空间分布来说,玉米每层节根数、节根长度和直径在父母本和杂交种间也具有显著或极显著的差异。与中下层根量相比,母本与不抗旱的父本处于上层干土中的根系数量明显较多,且根系直径大,吸水困难。而杂交种在干旱条件下上层根重和数量维持不变,或略高于不抗旱品种,但中层和下层根系数量和长度明显高于不抗旱品种,且根系直径小于不抗旱品种,这样从多的有效根系数量和低的吸水阻力两方面保证了水分的吸收,从而使其产量和水分利用效率均最高,说明通过根系形态特性和空间分布的优化能够调节作物整体的水分利用效率。     

The influence of spatial scale on the genetic structure of a widespread tropical wetland tree, Pterocarpus officinalis (Fabaceae)

Identifying factors that cause genetic differentiation in plant populations and the spatial scale at which genetic structuring can be detected will help to understand plant population dynamics and identify conservation units. In this study, we determined the genetic structure and diversity of Pterocarpus officinalis, a widespread tropical wetland tree, at three spatial scales: (1) drainage basin “watershed” (<10 km), (2) within Puerto Rico (<100 km), and (3) Caribbean-wide (>1000 km) using AFLP. At all three spatial scales, most of the genetic variation occurred within populations, but as the spatial scale increased from the watershed to the Caribbean region, there was an increase in the among population variation (Φ_ST=0.19 to Φ_ST=0.53). At the watershed scale, there was no significant differentiation (P=0.77) among populations in the different watersheds, although there was some evidence that montane and coastal populations differed (P<0.01). At the island scale, there was significant differentiation (P<0.001) among four populations in Puerto Rico. At the regional scale (>1000 km), we found significant differentiation (P<0.001) between island and continental populations in the Caribbean region, which we attributed to factors associated with the colonization history of P. officinalis in the Neotropics. Given that genetic structure can occur from local to regional spatial scales, it is critical that conservation recommendations be based on genetic information collected at the appropriate spatial scale.     

景观生态学中的尺度分析方法

多尺度空间分析法是发现和识别景观特征尺度的主要方法.当前这类方法很多,缺乏归类和对比分析评价.基于空间类型变量和数值变量,对多尺度空间分析方法进行了重新梳理.同时对当前常用的尺度分析方法:半方差分析、尺度方差分析、小波分析和孔隙度指数分析,以中国三北防护林为例,对比了各种尺度分析方法的特点和优劣.结果表明,在特征尺度的识别上:小波方差方法清晰明了;半方差分析法灵活简捷,结果明显;尺度方差分析法和孔隙度指数法在本研究中的判识结果不甚明显.在计算速度上:半方差分析法计算量最大、耗时最长,尺度方差次之,小波方差速度最快,孔隙度指数法计算速度快于前两种,慢于小波方差分析方法.半方差分析方法简单灵活,而且相关理论方法成熟,但缺乏对大尺度格局的整体把握,而小波分析恰恰能很好的弥补这一不足.最后提出,半方差分析和小波变换相结合将会是最优的尺度分析方法.     

Intra- and interspecific aggregation of north temperate dung beetles on standardised and natural dung pads: the influence of spatial scale

Abstract.  1. The spatial distribution of north temperate dung beetles ( Aphodius , Sphaeridium , and Margarinotus ) was investigated at three spatial scales (scale  a between all pads – large spatial scale, small patch size; scale  b between block – large spatial scale, large patch size; scale  c within block – small spatial scale, small patch size) in the field using standardised and naturally dropped dung pads that varied in size and volume.
2. Results indicated that all the major colonising species of dung beetle expressed strong intraspecific aggregation, while interspecific aggregation, though present, was of a lesser magnitude.
3. In both controlled and natural dung treatments, intra- and interspecific aggregation decreased with increasing patch size (from pad to block) and also decreased with decreasing spatial scale (from whole plot to within-block scale).
4. The data also suggested that intraspecific aggregation was more important than interspecific aggregation in the distribution of adult dung beetles in natural and standardised dung pads and hence has the potential to facilitate coexistence.
5. Intra- and interspecific aggregation was greater in the natural dung compared with that of the standardised dung, and the effect of pad size partly explains this phenomenon.
6. The within-patch spatial distribution of dung beetles observed in the natural and standardised dung was possibly mediated through within-patch differences between the two treatments. Six confounding factors could explain this difference and these factors are discussed in relation to resource utilisation by north temperate dung beetles.     

The contribution of geographically common and rare species to the spatial distribution of biodiversity

Motivation and aim

Mapping the spatial distribution of biodiversity is critical for understanding its fundamental drivers (e.g. speciation, environmental filtering) as well as for conservation assessment. An important dimension of this topic is how the distributions of subsets of species contribute to the overall distribution of biodiversity. Although studies have previously investigated the role of geographically common and rare species in determining these patterns, their respective contributions appear to vary between studies. Knowing which species contribute disproportionately to the spatial distribution of biodiversity enables the identification of key indicator species for biodiversity assessments across large areas and is important for prioritising areas for conservation actions. An extensive review of the literature was carried out to synthesise research on how geographic rarity contributes to spatial patterns of biodiversity. We identify potential explanations for the discrepancies in findings between studies and identify opportunities for further research.

Results

Many studies on the contribution of geographic commonness and rarity to the spatial distribution of biodiversity focus on species richness. A prevalent view is that common (widespread) species contribute disproportionately, although this is not ubiquitous across studies due to factors such as the geographic extent from which relative rarity is quantified. We identify research pathways that will further improve our knowledge of how geographically common and rare species shape the spatial distribution of biodiversity including the impact of spatial scale on species contributions and the incorporation of biodiversity components beyond taxonomic alpha diversity, that is functional and phylogenetic diversity.

Main conclusions

Future research should incorporate multiple biodiversity components and model scale dependency. This will further our knowledge on the underlying processes that shape the spatial variation of biodiversity across the planet and help inform biological surveys and conservation activities.     

The effect of spatial scale on interactions between two weevils and their parasitoid

1. The effect of spatial scale on the interactions between three hymenopteran parasitoids and their weevil hosts was investigated. The parasitoid Mesopolobus incultus (Walker) parasitised Gymnetron pascuorum Gyll.; the parasitoids Entodon sparetus (Walker) and Bracon sp. parasitised Mecinus pyraster Herbst. Both of these weevils develop inside the seedhead of Plantago lanceolata L. but occupy different niches. Seedheads were sampled annually from 162 plants at each of two experimental sites consisting of a series of habitat patches of two distinct sizes. Data were analysed from three site‐years. 2. Parasitoid densities at each site‐year were closely related to the abundance of their respective weevil hosts. The overall proportion of hosts parasitised was more variable for M. incultus than for E. sparetus and Bracon sp. 3. Changes in spatial scale affected the variability of parasitoid densities. For M. incultus, there was generally a greater degree of additional heterogeneity for all increases of scale; for E. sparetus, this was true only at the largest scales; for Bracon sp., all components of variance were negative. 4. The rate of parasitism was related to host density in different ways at different spatial scales. Mesopolobus incultus exhibited inverse density dependence at the finest (seedhead) scale, direct density dependence at the intermediate (plant) scale, and density independence at the large (habitat area 729 m²) scale. Entodon sparetus showed no response to variation in host density at any spatial scale. Bracon sp. showed direct density dependence only at the intermediate and largest scales. 5. Parasitoids E. sparetus and Bracon sp. seemed able to detect more than one M. pyraster individual in seedheads with multiple host occupancy; a greater incidence of conspecific parasitoids than expected emerged from such seedheads.     

土壤侵蚀定量评价的空间尺度效应

土壤侵蚀的空间尺度效应使得小尺度上观测到的大量数据无法得到有效的利用,给多空间尺度土壤侵蚀定量评价带来了困难和问题。对土壤侵蚀定量评价研究中的空间尺度效应及其机理和空间尺度转换方法进行了综述。分离、搬运和堆积子系统之间的协同效应与大尺度土壤侵蚀背景条件之间的协同效应是土壤侵蚀空间尺度效应产生的根本原因。在土壤侵蚀定量评价中,基本侵蚀单元地表参数的定量描述是建立土壤侵蚀空间尺度转换模型的基础。     

Patterns of variability in early-life traits of fishes depend on spatial scale of analysis

Estimates of early-life traits of fishes (e.g. pelagic larval duration (PLD) and spawning date) are essential for investigating and assessing patterns of population connectivity. Such estimates are available for a large number of both tropical and temperate fish species, but few studies have assessed their variability in space, especially across multiple scales. The present study, where a Mediterranean fish (i.e. the white seabream Diplodus sargus sargus) was used as a model, shows that spawning date and PLD are spatially more variable at a scale of kilometres than at a scale of tens to hundreds of kilometres. This study indicates the importance of considering spatial variability of early-life traits of fishes in order to properly delineate connectivity patterns at larval stages (e.g. by means of Lagrangian simulations), thus providing strategically useful information on connectivity and relevant management goals (e.g. the creation of networks of marine reserves).     

Micro‐spatial separation and associated morphological adaptations in the original case of avian character displacement

Divergent evolution between Western Rock Nuthatch Sitta neumayer and Eastern Rock Nuthatch Sitta tephronota is widely recognized as the original case study of character displacement. However, in their contact zone in the Zagros Mountains, Iran, the morphological differences important for niche segregation between the two species remain unknown. We investigated microhabitat use and morphological adaptations of the two species, predicting that morphological adaptations to different habitats in these two nuthatches have led to spatial segregation. Seventy‐seven birds were captured and measured in the contact zone and allopatric zone in Iran. Twenty‐two primary variables related to flight apparatus, functional foot apparatus and feeding apparatus were measured and 11 ratios of primary variables were calculated as secondary variables due to their importance in habitat use. We also measured environmental variables related to geological features, mineral substrates and vegetation cover at a random sample of 100 of the locations where a nuthatch was observed. Results of morphometric and habitat analyses indicated that, in addition to trophic niche segregation, the two nuthatch species also differ in their microhabitat use and show differences in morphological features accordingly. In many case studies of character displacement, much more interest has been focused on the morphological differences in feeding apparatus than on those relating to habitat use. We suggest that future studies of character displacement should pay more attention to spatial niche segregation between sympatric species rather than trophic niche segregation.     

The role of spatial scale and the perception of large-scale species-richness patterns

Despite two centuries of exploration, our understanding of factors determining the distribution of life on Earth is in many ways still in its infancy. Much of the disagreement about governing processes of variation in species richness may be the result of differences in our perception of species‐richness patterns. Until recently, most studies of large‐scale species‐richness patterns assumed implicitly that patterns and mechanisms were scale invariant. Illustrated with examples and a quantitative analysis of published data on altitudinal gradients of species richness (n = 204), this review discusses how scale effects (extent and grain size) can influence our perception of patterns and processes. For example, a hump‐shaped altitudinal species‐richness pattern is the most typical (c. 50%), with a monotonic decreasing pattern (c. 25%) also frequently reported, but the relative distribution of patterns changes readily with spatial grain and extent. If we are to attribute relative impact to various factors influencing species richness and distribution and to decide at which point along a spatial and temporal continuum they act, we should not ask only how results vary as a function of scale but also search for consistent patterns in these scale effects. The review concludes with suggestions of potential routes for future analytical exploration of species‐richness patterns.     

The mathematical influence on global patterns of biodiversity

Although we understand how species evolve, we do not appreciate how this process has filled an empty world to create current patterns of biodiversity. Here, we conduct a numerical experiment to determine why biodiversity varies spatially on our planet. We show that spatial patterns of biodiversity are mathematically constrained and arise from the interaction between the species’ ecological niches and environmental variability that propagates to the community level. Our results allow us to explain key biological observations such as (a) latitudinal biodiversity gradients (LBGs) and especially why oceanic LBGs primarily peak at midlatitudes while terrestrial LBGs generally exhibit a maximum at the equator, (b) the greater biodiversity on land even though life first evolved in the sea, (c) the greater species richness at the seabed than at the sea surface, and (d) the higher neritic (i.e., species occurring in areas with a bathymetry lower than 200 m) than oceanic (i.e., species occurring in areas with a bathymetry higher than 200 m) biodiversity. Our results suggest that a mathematical constraint originating from a fundamental ecological interaction, that is, the niche–environment interaction, fixes the number of species that can establish regionally by speciation or migration.     

Comparative influence of spatial scale on beta diversity within regional assemblages of birds and butterflies

Aim We examined whether variation in species composition of breeding birds and resident butterflies in the Great Basin of North America depended on sampling grain (the smallest resolvable unit of study) and on the relative proximity of sampling units across the landscape. We also compared patterns between the two taxonomic groups with reference to their life‐history characteristics. Location Data for our analyses were collected from 1996 to 2003 in three adjacent mountain ranges in the central Great Basin (Lander and Nye counties, Nevada, USA): the Shoshone Mountains, Toiyabe Range and Toquima Range. Methods Data on species composition for both taxonomic groups were collecting using standard inventory methods for birds and butterflies in temperate regions. Data were compiled at three sampling grains, sites (average 12 ha), canyons (average 74 ha) and mountain ranges. For each sampling grain in turn, we calculated similarity of species composition using the Jaccard index. First, we investigated whether mean similarity of species composition among the three ranges differed as a function of the grain size at which data were compiled. Secondly, we explored whether mean similarity of species composition was greater for canyons within the same mountain range than for canyons within different mountain ranges. Thirdly, we examined whether mean similarity of species composition at the site level was different for sites within the same canyon, sites within different canyons in the same mountain range, and sites within canyons in different mountain ranges. We used a Bayesian model to analyse these comparisons. Results For both taxonomic groups, mean similarity of species composition increased as the sampling grain increased. The effect of spatial grain was somewhat greater for birds than for butterflies, especially when the intermediate sampling grain was compared with the smallest sampling grain. Similarity of species composition of butterflies at each sampling grain was greater than similarity of species composition of birds at the same grain. Mean similarity of species composition of both birds and butterflies at the canyon level and site level was affected by relative proximity of sampling locations; beta diversity increased as the relative isolation of sampling locations increased. Main conclusions The sensitivity of beta diversity to sampling grain likely reflects the effect of local environmental heterogeneity: as sampling grain increases, biotic assemblages appear more homogeneous. Although breeding birds in our study system have larger home ranges than resident butterflies, birds may have more specialized resource requirements related to vegetation structure and composition, especially at small sampling scales. The degree of variation in species composition of both taxonomic groups suggests that spatially extensive sampling will be more effective for drawing inferences about regional patterns of species diversity than intensive sampling at relatively few, smaller sites.     

The influence of spatial scale on quantifying insect dispersal: an analysis of butterfly data

Abstract. 1. A linear relationship between mean movement distances recorded and the size of the study area was found in a comparison of five mark–release–recapture studies of the meadow brown butterfly.
2. The scale impact on mean butterfly movement distances was also apparent when comparing the results for different butterfly species reported in 21 mark–release–recapture studies.     

The effect of spatial scale on evenness

Abstract. The effect of spatial scale on species evenness has not previously been investigated. As the area of each sample of vegetation (i.e. the spatial grain) increases, evenness could in theory increase, decrease, or stay the same, though the simplest model predicts an increase. We use biomass data from four dune slack sites and two semi-arid grasslands, sampled to allow calculation of evenness at a range of spatial grains. In all six sites, evenness decreases as grain size increases, almost monotonically. It is hypothesized that such a pattern is a result of a general feature of plant species abundance distributions and of vegetation response to environmental microheterogeneity.