停止人为去除植物功能群后的高寒草甸多样性恢复过程与群落构建

已有大量研究利用功能性状或系统发育来推断群落构建机制, 然而不同过程可能会导致相似的格局。本文基于对甘南高寒草甸植物功能群去除处理后群落恢复过程的跟踪调查, 对比了物种多样性、功能多样性和系统发育多样性的动态变化, 并分析了物种定殖与消失过程对功能多样性和系统发育多样性变化的影响。结果表明: 去除不同数量功能群的群落中: (1)包括物种丰富度(SR)、Shannon-Wiener指数(H°)和Simpson指数(D)在内的传统物种多样性均随时间快速上升并与自然群落趋同, 不同群落的均匀度指数(J)随时间呈增加趋势并趋于相似; 功能多样性(FD)与系统发育多样性(PD)呈现出与物种多样性相似的动态变化趋势, 而平均配对距离(MPD/MPD_a、MFD/MFD_a)则向中等程度聚集。(2)不同群落的功能群和物种组成在短期内均恢复到与自然群落非常相似的程度。(3)物种定殖与消失过程的功能格局是群落恢复过程中趋同效应的主要驱动力。本研究揭示了高寒草甸植物功能群去除停止后群落短期内快速恢复的过程, 说明在小尺度且周边具有大范围未退化草甸的情况下, 无论物种多样性、功能多样性还是系统发育多样性都具有较快的恢复能力, 同时说明了利用群落系统发育多样性格局来推断群落构建机制的局限性。     

Scale-specific correlations between habitat heterogeneity and soil fauna diversity along a landscape structure gradient

Habitat heterogeneity contributes to the maintenance of diversity, but the extent that landscape-scale rather than local-scale heterogeneity influences the diversity of soil invertebrates—species with small range sizes—is less clear. Using a Scottish habitat heterogeneity gradient we correlated Collembola and lumbricid worm species richness and abundance with different elements (forest cover, habitat richness and patchiness) and qualities (plant species richness, soil variables) of habitat heterogeneity, at landscape (1 km²) and local (up to 200 m²) scales. Soil fauna assemblages showed considerable turnover in species composition along this habitat heterogeneity gradient. Soil fauna species richness and turnover was greatest in landscapes that were a mosaic of habitats. Soil fauna diversity was hump-shaped along a gradient of forest cover, peaking where there was a mixture of forest and open habitats in the landscape. Landscape-scale habitat richness was positively correlated with lumbricid diversity, while Collembola and lumbricid abundances were negatively and positively related to landscape spatial patchiness. Furthermore, soil fauna diversity was positively correlated with plant diversity, which in turn peaked in the sites that were a mosaic of forest and open habitat patches. There was less evidence that local-scale habitat variables (habitat richness, tree cover, plant species richness, litter cover, soil pH, depth of organic horizon) affected soil fauna diversity: Collembola diversity was independent of all these measures, while lumbricid diversity positively and negatively correlated with vascular plant species richness and tree canopy density. Landscape-scale habitat heterogeneity affects soil diversity regardless of taxon, while the influence of habitat heterogeneity at local scales is dependent on taxon identity, and hence ecological traits, e.g. body size. Landscape-scale habitat heterogeneity by providing different niches and refuges, together with passive dispersal and population patch dynamics, positively contributes to soil faunal diversity. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Seasonal Change of Species Diversity Patterns of Non‐volant Small Mammals along Three Subtropical Elevational Gradients

Our understanding of geographic patterns of species diversity and the underlying mechanisms is increasing rapidly, whereas the temporal variation in these patterns remains poorly understood. We examined the seasonal species richness and species turnover patterns of non‐volant small mammals along three subtropical elevational gradients in southwest China. Small mammal diversity was surveyed in two seasons (early wet season and late wet season) using a standardized sampling protocol. The comparison of species richness patterns between two seasons indicated a temporal component in magnitude and shape, with species richness at high elevations clearly increased during the late wet season. Species richness demonstrated weak correlations with modelled temperature and precipitation. The elevational pattern of species turnover measured by Chao‐Sørenson similarity index also changed seasonally, even though the temporal pattern varied with scale. Species turnover between neighboring elevations at high elevations was slower in the late wet season. Meanwhile, there was an acceleration of species turnover along the whole range of the gradient. The seasonal change in species diversity patterns may be due to population‐level increases in abundance and elevational migration, whereas seasonal variation in factors other than temperature and precipitation may play a greater role in driving seasonal diversity patterns. Our study strongly supports the seasonality in elevational patterns of small mammal diversity in subtropical montane forests. Thus it is recommended that subsequent field surveys consider temporal sampling replicate for elevational diversity studies.     

Spatiotemporal changes of beetle communities across a tree diversity gradient

Aim Plant and arthropod diversity are often related, but data on the role of mature tree diversity on canopy insect communities are fragmentary. We compare species richness of canopy beetles across a tree diversity gradient ranging from mono‐dominant beech to mixed stands within a deciduous forest, and analyse community composition changes across space and time. Location Germany’s largest exclusively deciduous forest, the Hainich National Park (Thuringia). Methods We used flight interception traps to assess the beetle fauna of various tree species, and applied additive partitioning to examine spatiotemporal patterns of diversity. Results Species richness of beetle communities increased across the tree diversity gradient from 99 to 181 species per forest stand. Intra‐ and interspecific spatial turnover among trees contributed more than temporal turnover among months to the total γ‐beetle diversity of the sampled stands. However, due to parallel increases in the number of habitat generalists and the number of species in each feeding guild (herbivores, predators and fungivores), no proportional changes in community composition could be observed. If only beech trees were analysed across the gradient, patterns were similar but temporal (monthly) species turnover was higher compared to spatial turnover among trees and not related to tree diversity. Main conclusions The changes in species richness and community composition across the gradient can be explained by habitat heterogeneity, which increased with the mix of tree species. We conclude that understanding temporal and spatial species turnover is the key to understanding biodiversity patterns. Mono‐dominant beech stands are insufficient to conserve fully the regional species richness of the remaining semi‐natural deciduous forest habitats in Central Europe, and analysing beech alone would have resulted in the misleading conclusion that temporal (monthly) turnover contributes more to beetle diversity than spatial turnover among different tree species or tree individuals.     

Environmental drivers of ant species richness and composition across the Argentine Pampas grassland

Understanding the underlying mechanisms causing diversity patterns is a fundamental objective in ecology and science‐based conservation biology. Energy and environmental‐heterogeneity hypotheses have been suggested to explain spatial changes in ant diversity. However, the relative roles of each one in determining alpha and beta diversity patterns remain elusive. We investigated the main factors driving spatial changes in ant (Hymenoptera, Formicidae) species richness and composition (including turnover and nestedness components) along a 500 km longitudinal gradient in the Pampean region of Argentina. Ants were sampled using pitfall traps in 12 sample sites during the summer. We performed a model selection approach to analyse responses of ant richness and composition dissimilarity to environmental factors. Then, we computed a dissimilarity partitioning of the contributions of spatial turnover and nestedness to total composition dissimilarity. Temporal habitat heterogeneity and temperature were the primary factors explaining spatial patterns of epigean ant species richness across the Pampas. The distance decay in species composition similarity was best accounted by temperature dissimilarity, and turnover had the greatest contribution to the observed beta diversity pattern. Our findings suggest that both energy and environmental‐heterogeneity‐related variables are key factors shaping richness patterns of ants and niche‐based processes instead of neutral processes appear to be regulating species composition of ant assemblages. The major contribution of turnover to the beta diversity pattern indicated that lands for potential reconversion to grassland should represent the complete environmental gradient of the Pampean region, instead of prioritizing a single site with high species richness.     

Species turnover in lake littorals: spatial and temporal variation of benthic macroinvertebrate diversity and community composition

Aims Despite wide consensus that ecological patterns and processes should be studied at multiple spatial scales, the temporal component of diversity variation has remained poorly examined. Specifically, rare species may exhibit patterns of diversity variation profoundly different from those of dominant taxa. Location Southern Finland. Methods We used multiplicative partitioning of true diversities (species richness, Shannon diversity) to identify the most important scale(s) of variation of benthic macroinvertebrate communities across several hierarchical scales, from individual samples to multiple littorals, lakes and years. We also assessed the among‐scale variability of benthic macroinvertebrate community composition by using measures of between‐ and within‐group distances at hierarchical scales. Results On average, a single benthic sample contained 23% of the total regional macroinvertebrate species pool. For both species richness and Shannon diversity, beta‐diversity was clearly the major component of regional diversity, with within‐littoral beta‐diversity (β₁) being the largest component of gamma‐diversity. The interannual component of total diversity was small, being almost negligible for Shannon index. Among‐sample (within‐littoral) diversity was related to variation of substratum heterogeneity at the same scale. By contrast, only a small proportion of rare taxa was found in an average benthic sample. Thus, dominant species among lakes and years were about the same, whereas rare species were mostly detected in a few benthic samples in one lake (or year). For rare species, the temporal component of diversity was more important than spatial turnover at most scales. Main conclusions While individual species occurrences and abundances, particularly those of rare taxa, may vary strongly through space and time, patterns of dominance in lake littoral benthic communities are highly predictable. Consequently, many rare species will be missed in temporally restricted samples of lake littorals. In comprehensive biodiversity surveys, interannual sampling of littoral macroinvertebrate communities is therefore needed.     

Mountain summer farms in Røldal,western Norway –; vegetation classification and patterns in species turnover and richness

This paper discusses vegetation types and diversity patterns in relation to environment and land-use at summer farms, a characteristic cultural landscape in the Norwegian mountains. Floristic data (189 taxa) were collected in 130 4-m² sample plots within 12 summer farms in Røldal, western Norway. The study was designed to sample as fully as possible the range of floristic, environmental, and land-use conditions. Vegetation types delimited by two-way indicator species analysis were consistent with results from earlier phytosociological studies. Detrended correspondence analysis and canonical correspondence analysis show that rather than being distinct vegetation types, the major floristic variation is structured along a spatial gradient from summer farm to the surrounding heathland vegetation. Species richness (alpha diversity) was modelled against environmental variables by generalized linear modelling and compositional turnover (beta diversity) by canonical correspondence analysis. Most environmental factors made significant contributions, but the spatial distance-to-farm gradient was the best predictor of both species richness and turnover. While summer farms reduce mean species richness at the plot scale, the compositional heterogeneity of the upland landscapes is increased, thereby creating ‘ecological room’ for additional vegetation types and species. Within an overall similarity across scales, soil variables (pH, base saturation, LOI, phosphate and nitrogen) differed considerably in their explanatory power for richness and turnover. A difference between ‘productivity limiting’ factors and ‘environmental sieves’ is proposed as an explanation. Species turnover with altitude is relatively low in grasslands as compared to heaths.     

陕南秦巴山区药用植物群落物种多样性研究

采用样方法对陕南秦巴山区药用植物群落物种多样性进行了研究。结果显示,该地区药用植物共计105科268属361种,其中药用裸子植物5科6属7种,药用被子植物92科254属344种,药用蕨类植物7科8属10种;含1属的科、含2~5属的科和含1种的属的药用植物数量较多,所占比例较高;该地区各植被类型的物种多样性变化各具特点,其中,物种丰富度指数(S)、Shannon-Wiener多样性指数(H)及Simpson多样性指数(D)表现为:乔木层最小、灌木层较大、草本层最大,但Pielou物种均匀度指数(J)的变化较为复杂;药用植物群落总的物种丰富度、乔木层物种丰富度和草本层物种丰富度均随海拔的升高表现出先升高后下降的趋势,且物种丰富度最大值出现在海拔1000~1200 m的山地常绿落叶阔叶林和温性针阔混交林的过渡区域,但灌木层物种丰富度与海拔之间无相关关系。本研究结果为阐明山地物种多样性的分布格局提供了基础资料,也为该区域药用植物的保护和管理提供参考。     

黄土高原马栏林区基于不同植被组织尺度的群落物种多样性

物种多样性格局随着时空尺度的变化而变化, 同时也与植被组织尺度的变化密切相关, 基于多组织尺度的研究能更好地揭示一个地区的物种多样性规律。在应用数量分类(TWINSPAN)和主成分分析法(PCA)确定黄土高原马栏林区不同组织尺度的群落类型及其相互关系的基础上, 采用加性分配法分析该区域物种多样性与植被型、群系和群丛3种植被组织尺度之间的关系, 结果表明: (1) 区域物种多样性(γ)可加性分配分为群丛内(α₁)、群丛间(β₁)、群系间(β₂)和植被型间(β₃) 4个多样性成分, 无论用物种丰富度指数还是Shannon-Wiener多样性或Simpson多样性指数, 乔木、灌木和草本植物的最大物种多样性都存在于群丛内(草本层的物种丰富度除外), 说明群丛尺度是度量该区物种多样性的最佳尺度。(2)植被型、群系和群丛3种组织尺度的Shannon-Wiener多样性百分比均大于Simpson多样性百分比, 说明稀有种的分布对马栏林区各植被组织尺度的物种多样性格局起主要作用。(3)各尺度间的β多样性大小顺序在乔木、灌木、草本植物3层以不同多样性指数表示时各不相同, 这与乔木、灌木、草本植物3层的物种组成和分布, 以及主导不同植被组织尺度的物种多样性的因素差异有密切联系。     

合肥市小微湿地鸟类多样性的时空格局及其影响因素

小微湿地是城市生态系统的重要组成部分, 也是生物多样性的重要庇护场所。鸟类作为城市小微湿地生态系统的指示类群, 其多样性时空格局受多种环境因子影响。本研究于2020年8月至2021年7月采用样点法对合肥市45个小微湿地鸟类的种类、数量分布和生境因子进行了调查, 并获取湿地面积、湿地形状、建筑面积比例、植被面积比例、环境噪声、人为干扰和城市化指数等生境变量。通过α多样性和β多样性分析, 研究城市小微湿地鸟类多样性的时空特征及其决定因素。采用信息论模型选择和模型平均法以及基于距离矩阵的多重回归模型进行计算, 确定影响鸟类群落α多样性和β多样性及其组分的主要环境因子。结果显示, 研究区域共有鸟类13目39科102种, 其中水鸟31种, 国家二级重点保护鸟类2种, 安徽省重点保护鸟类17种, IUCN濒危物种红色名录中的易危(VU)物种1种。湿地面积和城市化指数对小微湿地陆地鸟类和水鸟的α多样性、β多样性及其组分均具有显著影响, 其中陆地鸟类物种丰富度在中度和低度城市化之间的小微湿地中达到最高值, 面积超过4 ha的小微湿地能维持较多的水鸟物种。植被面积比例对陆地鸟类多样性具有重要的影响, 而建筑面积比例对水鸟多样性具有显著影响。此外, 总体β多样性及其组分计算结果显示物种周转组分占明显优势, 表明城市小微湿地群作为城市复合生态系统的重要组成部分, 加强整体保护更为必要。研究结果对于加强城市鸟类保护和提高城市生态环境质量具有指导意义。     

浙江仙居俞坑森林群落物种多样性研究

分别采用物种丰富度、物种多样性指数和群落均匀度指标对浙江省仙居县俞坑森林群落的物种多样性进行测定和分析。结果表明：本木植物的物种多样性以生境优越的常绿阔叶林为高,木本植物的物种丰富度、物种多样性指数明显大于草本植物。在群落垂直结构中,木本植物等2层的物种丰富度、物种多样性指数均显著大于第1层。物种丰富度以木本第3层最大,草本层最小;而物种多样性指数、群落均匀度则以木本第2层最大、草本层最小。木本植物各层次、草本层的物种多样性各项指标在群落各样地间均有一定的差异。     

Climate and plant structure determine the spatiotemporal butterfly distribution on a tropical mountain

Mountains are among the most powerful natural gradients for testing ecological and evolutionary responses of biota to environmental influences because differences in climate and plant structure occur over short spatial scales. We describe the spatiotemporal distribution patterns and drives of fruit‐feeding butterfly diversity in the mountainous region of Serra do Cipó, Minas Gerais, Brazil. Seven elevations from 822 to 1,388 m a.s.l. were selected for evaluating the effects of abiotic factors and vegetation characteristics on butterfly diversity. A total of 44 fruit‐feeding butterfly species were recorded in a two‐year study. Species richness (local and regional) of fruit‐feeding butterflies decreased with increasing elevation. The interaction between temperature or humidity and precipitation influenced the abundance and β‐diversity of butterflies in the elevation gradient, whereas β‐diversity decreased with increasing plant richness. Butterfly richness (local and regional) and β‐diversity varied with the sampling period, with fewer species in July (2012 and 2013), the dry period, as expected for Neotropical insects. β‐Diversity in space and time was due to species replacement (turnover), indicating that butterfly composition differs throughout the mountain and over time. In summary, climate and plant richness largely influence butterfly diversity in the elevational gradient. Climatic changes in conjunction with increasing anthropic impacts on mountainous regions of southeast Brazil will likely influence the community of mountaintop butterflies in the Espinhaço Mountain Range. Abstract in Portuguese is available with online material.     

北京东灵山辽东栎林植物物种多样性的多尺度分析

多尺度分析物种多样性格局能够为有效保护生物多样性提供重要信息.利用物种多样性的加法分配法则分析了样方-坡位-坡面等级尺度系统辽东栎林植物物种多样性(gamma多样性)的alpha多样性和beta多样性在各尺度上的分配关系.结果表明以物种丰富度为指标的区域物种多样性的最大贡献来自坡面尺度,表明坡面尺度是维持辽东栎林物种多样性的有效尺度;而对Simpson多样性和Shannon多样性的最大贡献则来自样方内,这决定于群落物种优势度和稀有度格局;各尺度间beta多样性组分随尺度的增大而增大可能是环境异质性和扩散作用的综合结果.各尺度间Shannon多样性对总体多样性的贡献大于Simpson多样性的贡献是偶见种在各尺度间分配的结果.物种多样性分配的加法法则为物种多样性格局的多尺度分析提供了理论框架,是检验物种多样性格局形成机制的有效方法.     

Scale-dependent spatial patterns of species diversity in the tropical montane rain forest in Jianfengling,Hainan Island,China

Aims Spatial distribution patterns and formation mechanisms of species diversity are fundamental issues in community ecology. The objectives of this study are to assess the species diversity patterns at the different spatial scales in Jianfengling, Hainan Island, China.
Methods Based on the dataset from the 60 hm² plot in the tropical montane rain forest in Jianfengling, Hainan Island, the spatial distribution patterns of species richness, species abundance, Shannon-Wiener, Simpson and Pielou’s evenness indices were analyzed at six spatial scales, including 5 m × 5 m, 10 m × 10 m, 20 m × 20 m, 40 m × 40 m, 100 m × 100 m, and 200 m × 200 m, respectively.Important findings
Results showed that spatial distribution patterns of species richness, species abundance and Shannon-Wiener index were much more obviously changed with the spatial scales than Simpson and Pielou’s evenness indices. Change of variance of the species richness with the increase of spatial scales was unimodal, which had the maximum value at the 20 m × 20 m scale. Variance of the species abundance showed a linear relationship with the increase of spatial scales. The positive relationship between species richness and abundance gradually decreased and even disappeared with the increase of sampling scales, which may be correlated with the increase of habitat heterogeneity. The effects of spatial scales on Shannon-Wiener, Simpson, and Pielou’s evenness indices may be also correlated with the composition of rare species in the plot.     

It's a long way to the top: Plant species diversity in the transition from managed to old‐growth forests

Questions

Do vascular plant species richness and beta‐diversity differ between managed and structurally complex unmanaged stands? To what extent do species richness and beta‐diversity relate to forest structural attributes and heterogeneity?

Location

Five national parks in central and southern Italy.

Methods

We sampled vascular plant species composition and forest structural attributes in eight unmanaged temperate mesic forest stands dominated or co‐dominated by beech, and in eight comparison stands managed as high forests with similar environmental features. We compared plant species richness, composition and beta‐diversity across pairs of stands (unmanaged vs managed) using GLMM s. Beta‐diversity was quantified both at the scale of each pair of stands using plot‐to‐plot dissimilarity matrices (species turnover), and across the whole data set, considering the distance in the multivariate species space of individual plots from their centroid within the same stand (compositional heterogeneity). We modelled the relationship between species diversity (richness and beta‐diversity) and forest structural heterogeneity and individual structural variables using GLMM s and multiple regression on distance matrices.

Results

Species composition differed significantly between managed and unmanaged stands, but not richness and beta‐diversity. We found weak evidence that plant species richness increased with increasing levels of structural heterogeneity and canopy diversification. At the scale of individual stands, species turnover was explained by different variables in distinct stands, with variables related to deadwood quantity and quality being selected most often. We did not find support for the hypothesis that compositional heterogeneity varies as a function of forest structural characteristics at the scale of the whole data set.

Conclusions

Structurally complex unmanaged stands have a distinct herb layer species composition from that of mature stands in similar environmental conditions. Nevertheless, we did not find significantly higher levels of vascular plant species richness and beta‐diversity in unmanaged stands. Beta‐diversity was related to patterns of deadwood accumulation, while for species richness the evidence that it increases with increasing levels of canopy diversification was weak. These results suggest that emulating natural disturbance, and favouring deadwood accumulation and canopy diversification may benefit some, but not all, facets of plant species diversity in Apennine beech forests.

     

海南尖峰岭热带山地雨林物种多样性空间分布格局的尺度效应

物种多样性的空间分布格局和维持机制是群落生态学的基本问题。为了探讨海南尖峰岭地区物种多样性空间分布格局的尺度效应, 以海南尖峰岭热带山地雨林60 hm²样地为研究对象, 分析了物种丰富度、物种多度、Shannon-Wiener指数、Simpson指数以及Pielou均匀度指数随6个空间取样尺度(5 m × 5 m、10 m × 10 m、20 m × 20 m、40 m × 40 m、100 m ×100 m、200 m × 200 m)的变化。结果表明: 相比Simpson指数和Pielou均匀度指数, 物种丰富度、多度以及Shannon-Wiener指数具有更为明显的空间尺度效应; 物种丰富度的方差随取样尺度增加呈现单峰分布特征, 并且在20 m × 20 m尺度上达到最大值, 而物种多度的方差随取样尺度的增加而增大; 物种丰富度和多度的正相关性随着取样尺度的增加逐渐减小甚至消失, 这可能与随取样尺度增加生境异质性增加有关; 取样尺度对3个物种多样性指数空间分布的影响可能与研究区域内稀有种的组成有关。     

太白红杉群落物种多样性与环境因子的关系

定量研究了太白红杉群落物种多样性与环境因子的关系,结果表明:(1)海拔与物种丰富度和种间相遇机率呈极显著的负相关;与Shannon指数、Simpson指数和Pielou指数表现为"中间高度膨胀"的规律,即中等海拔高度上多样性高而低海拔和高海拔多样性较低。(2)岩石裸露度与物种丰富度呈显著的负相关。(3)土壤含水量与物种丰富度呈极显著的正相关;与种间相遇机率呈先降后升的趋势。(4)环境因子与物种多样性逐步回归结果是:海拔和岩石裸露度与物种丰富度关系密切,其回归方程为:S=90.62-0.02E-14.14B(r=0.769,P<0.05)。     

古田山中亚热带常绿阔叶林群落物种多样性的空间变异特征

古田山常绿阔叶林的群落组成、结构及其维持机制已有许多研究, 但该地区亚热带常绿阔叶林生物多样性空间变异特征还缺乏认识。本文以古田山24 ha大样地(划分为24个1 ha小样地)为基础, 具体分析了α多样性和β多样性在1 ha尺度上的空间变异特征。结果表明: (1)群落第一、二优势物种在各小样地之间变化不大, 但第三优势种变化较大; (2) α多样性变化中, 样地间木本植物个体数量变异最大, 物种丰富度其次, Pielou均匀度指数变异性最小; (3)物种丰富度与植株个体数量、Pielou均匀度指数没有显著的相关性, 与Shannon-Wiener指数呈显著正相关; Shannon-Wiener指数与Pielou均匀度指数呈显著正相关; (4)相邻样地间物种替代速率空间变异较大, 与物种丰富度的空间变化格局有明显差异。这些结果说明尺度对认识群落结构、探讨群落维持机制有重要作用; 由于森林群落是多尺度生态过程作用的结果, 大尺度样地可能有利于更好地揭示森林群落维持机制。     

Determinants of avian species richness at different spatial scales

ABSTRACT. Studies of factors influencing avian biodiversity yield very different results depending on the spatial scale at which species richness is calculated. Ecological studies at small spatial scales (plot size 0.0025–0.4 km²) emphasize the importance of habitat diversity, whereas biogeographical studies at large spatial scales (quadrat size 400–50,000 km²) emphasize variables related to available energy such as temperature. In order to bridge the gap between those two approaches the bird atlas data set of Lake Constance was used to study factors determining avian species diversity at the intermediate spatial scales of landscapes (quadrat size 4–36 km²). At these spatial scales bird species richness was influenced by habitat diversity and not by variables related to available energy probably because, at the landscape scale, variation in available energy is small. Changing quadrat size between 4 and 36 km², but keeping the geographical extension of the study constant resulted in profound changes in the degree to which the amount of different habitat types was correlated with species richness. This suggests that high species diversity is achieved by different management regimes depending on the spatial scale at which species richness is calculated. However, generally, avian species diversity seems to be determined by spatial heterogeneity at the corresponding spatial scale. Thus, protecting the diversity of landscapes and ecosystems appears to ensure also high levels of species diversity.     

Spatial variability of hosts,parasitoids and their interactions across a homogeneous landscape

Species assemblages and their interactions vary through space, generating diversity patterns at different spatial scales. Here, we study the local‐scale spatial variation of a cavity‐nesting bee and wasp community (hosts), their nest associates (parasitoids), and the resulting antagonistic network over a continuous and homogeneous habitat. To obtain bee/wasp nests, we placed trap‐nests at 25 sites over a 32 km² area. We obtained 1,541 nests (4,954 cells) belonging to 40 host species and containing 27 parasitoid species. The most abundant host species tended to have higher parasitism rate. Community composition dissimilarity was relatively high for both hosts and parasitoids, and the main component of this variability was species turnover, with a very minor contribution of ordered species loss (nestedness). That is, local species richness tended to be similar across the study area and community composition tended to differ between sites. Interestingly, the spatial matching between host and parasitoid composition was low. Host β‐diversity was weakly (positively) but significantly related to geographic distance. On the other hand, parasitoid and host‐parasitoid interaction β‐diversities were not significantly related to geographic distance. Interaction β‐diversity was even higher than host and parasitoid β‐diversity, and mostly due to species turnover. Interaction rewiring between plots and between local webs and the regional metaweb was very low. In sum, species composition was rather idiosyncratic to each site causing a relevant mismatch between hosts and parasitoid composition. However, pairs of host and parasitoid species tended to interact similarly wherever they co‐occurred. Our results additionally show that interaction β‐diversity is better explained by parasitoid than by host β‐diversity. We discuss the importance of identifying the sources of variation to understand the drivers of the observed heterogeneity.