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Aim To develop an approach for assessing the spatial scale of centres of endemism among species level data.
Location Australia.
Methods Endemism is inherently scale dependent. Therefore, the Corrected Weighted Endemism (CWE) index used by Crisp et al. [ J. Biogeogr. (2001)28:183] is extended to account for species samples in local neighbourhoods as a Spatial CWE index. This then allows an analysis of how the degree of endemism of a location (cell) changes with spatial scale. The quality of the Spatial CWE index results are assessed using three spatial randomizations at the species level with and without preserving species richness and distributional patterns. We show that CWE is equivalent to beta diversity and predict that it should show high rates of change around centres of endemism.
Results Similar patterns to those found by Crisp et al. using a data set of vascular flora from Australia are retrieved, but the extent to which they are scale dependent is more easily identified. For example, the Central Australian centre discounted by Crisp et al. is identified when a three-cell radius neighbourhood is used. However, the level of endemism in this centre is no greater than in the margins of many of the coastal centres of endemism. Most of the identified centres of endemism are better than random at all scales and are increasingly so as the spatial scale increases. As predicted, the highest rate of change in Spatial CWE (beta diversity) is most often between zero- and one-cell radius neighbours in most centres of endemism.
Main conclusions The explicit incorporation of geographical space in analyses allows for a greater understanding of the scale-dependence of phenomena, in this case endemism and beta diversity. 相似文献
Location Australia.
Methods Endemism is inherently scale dependent. Therefore, the Corrected Weighted Endemism (CWE) index used by Crisp et al. [ J. Biogeogr. (2001)28:183] is extended to account for species samples in local neighbourhoods as a Spatial CWE index. This then allows an analysis of how the degree of endemism of a location (cell) changes with spatial scale. The quality of the Spatial CWE index results are assessed using three spatial randomizations at the species level with and without preserving species richness and distributional patterns. We show that CWE is equivalent to beta diversity and predict that it should show high rates of change around centres of endemism.
Results Similar patterns to those found by Crisp et al. using a data set of vascular flora from Australia are retrieved, but the extent to which they are scale dependent is more easily identified. For example, the Central Australian centre discounted by Crisp et al. is identified when a three-cell radius neighbourhood is used. However, the level of endemism in this centre is no greater than in the margins of many of the coastal centres of endemism. Most of the identified centres of endemism are better than random at all scales and are increasingly so as the spatial scale increases. As predicted, the highest rate of change in Spatial CWE (beta diversity) is most often between zero- and one-cell radius neighbours in most centres of endemism.
Main conclusions The explicit incorporation of geographical space in analyses allows for a greater understanding of the scale-dependence of phenomena, in this case endemism and beta diversity. 相似文献
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Gabriela Franzoi Dri;Nilton Carlos Cáceres;Franchesco Della-Flora;Cristian Sales Dambros; 《Oikos》2022,2022(8):e09115
Many animal species participate in interspecific groups which can provide benefits such as better detection of predator presence, but may also lead to costs such as interspecific competition. In interspecific groups, species with particular functional traits should be aggregated in a way that maximizes the benefits and minimizes the costs of these interactions. Further, the balance between costs and benefits depends on the resource availability and the spatial scale in which species interact. We aim to determine how species traits are distributed within and among interspecific groups and how intrinsic (group size) and extrinsic (environmental conditions) factors relate to aggregation patterns. We surveyed 192 bird species distributed in 355 mixed-species bird flocks along an environmental gradient in southwest Brazil and analyzed data at both scales of individual flocks (n = 355) and sites (n = 29). We used mixed-effect and multiple regression models to test if the functional richness of coexisting species changes with increasing group size and in response to environmental covariates that may influence the selection of specific traits. Using a null model approach, we inferred the differences between observed and simulated associations (random expectations). We found that groups with more than 20 species have greater diet variation (i.e. more omnivores) and are more similar in body mass than expected randomly. Indeed, larger groups consume more resources, increasing competitive dynamics and decreasing facilitation among species. Thus such groups should take advantage of a more profitable trait variation among co-occurring species. Our results suggest that the distribution of species in close associations is determined mostly by ecological processes occurring at local scales (i.e. not dependent on regional spatial context). Additionally, larger groups maximize foraging trait variation (diet diversity) and minimize predator scape variation (similar body mass) potentially increasing the benefits of the aggregation. 相似文献
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Switzerland's governmental ‘Biodiversity Monitoring’ program is designed to produce factual information on the dynamics of biodiversity within the country for governmental agencies, politicians, and the general public. Monitoring a complex issue like biodiversity in order to give relevant and accurate messages to the general public and politicians within a politically relevant timescale and at moderate cost means focusing on few elements. Because relevant human impacts on biodiversity operate differently at different spatial scales, we need at least three different indicators to observe changes over time in local (‘within‐habitat’), landscape (‘habitat‐mosaic’), and macro‐scale (‘regional’) diversity. To keep things as simple as possible, we use species richness as an indicator for all three levels of diversity, just defining three different spatial scales (10 m2, 1 km2, regions, respectively). Each indicator is based on a number of taxonomic groups which have been selected mainly on the basis of costs and the availability of appropriate methods. 相似文献
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以物种组成较为复杂的青藏高原东部地区典革高寒草甸植物群落为背景,从不同的时间和空间尺度水平研究了植物群落中物种丰富度与生产力（地上部生物量）关系的基本模式。结果表明：1）总体而言,高寒草甸植物群落中物种丰富度与生产力的关系呈对数线性增加关系,这实际上是空间和时间尺度放大时在时间和空间尺度的相互作用下高寒草甸植物群落中物种丰富度与生产力关系的一种总体模式;2）随着研究的时间和空间尺度的改变,物种丰富度与生产力的关系会发生一些相应的变化,但空间尺度比时间尺度对物种丰富度与生产力的关系造成的影响更为显著,这可能 相似文献
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高寒草甸不同草地群落物种多样性与生产力关系研究 总被引：30，自引：3，他引：30
生态系统的结构和功能、生物多样性与生产力的关系问题是近年来群落生态学中研究的中心问题,其中,生态系统生产力水平是其功能的重要表现形式,用4种不同草地类型探讨自然群落的物种多样性与生产力关系.结果表明,矮嵩草草甸、小嵩草草甸和金露梅灌丛群落中物种多样性与生产力的关系呈线性增加关系,藏嵩草沼泽化草甸群落中线性增加关系不显著,这表明群落生产力除受物种多样性的影响外,也受物种本身特征和环境资源的影响.不同的环境资源和环境异质性是形成群落结构特征、物种多样性分布格局差异的主要原因之一. 相似文献
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Guillermo Salgado‐Maldonado Juan Manuel Caspeta‐Mandujano Edgar F. Mendoza‐Franco Miguel Rubio‐Godoy Adriana García‐Vsquez Norman Mercado‐Silva Ismael Guzmn‐Valdivieso Wilfredo A. Matamoros 《Ecology and evolution》2020,10(17):9115-9131
- The role of interspecific interactions in structuring low‐diversity helminth communities is a controversial topic in parasite ecology research. Most parasitic communities of fish are species‐poor; thus, interspecific interactions are believed to be unimportant in structuring these communities.
- We explored the factors that might contribute to the richness and coexistence of helminth parasites of a poeciliid fish in a neotropical river.
- Repeatability of community structure was examined in parasitic communities among 11 populations of twospot livebearer Pseudoxiphophorus bimaculatus in the La Antigua River basin, Veracruz, Mexico. We examined the species saturation of parasitic communities and explored the patterns of species co‐occurrence. We also quantified the associations between parasitic species pairs and analyzed the correlations between helminth species abundance to look for repeated patterns among the study populations.
- Our results suggest that interspecific competition could occur in species‐poor communities, aggregation plays a role in determining local richness, and intraspecific aggregation allows the coexistence of species by reducing the overall intensity of interspecific competition.
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通过设定不同尺度的样方面积,根据2×2联列表,运用方差分析、联结系数AC、2统计量度量、 Ochiai指数系列技术,测定天宝岩国家级自然保护区长苞铁杉群落乔木层10个优势种群间的总体联结关系、 种对间联结显著性和关联系数。结果表明:长苞铁杉群落乔木层10个优势种群的总体种间关联性均呈正关 联,反映该群落处于稳定的顶极阶段;10个优势种群的种间联结关系中,有26个种对在不同尺度样方设计中 均未达到一般显著水平,种对间的相互独立性较强;样方设计为100 m2时,各项指标上规律性比较明显,它的 研究结果与实际情况相吻合。群落虽处于比较稳定的顶极阶段,但应适当调整群落结构,为长苞铁杉的生长 更新提供良好的生态环境。 相似文献
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为研究广西北部湾茅尾海自然保护区海岛红树林群落的空间点格局和演替规律,在典型红树林海岛设置调查样地,以样地内的桐花树(Aegiceras corniculatum)、秋茄(Kandelia obovata)、白骨壤(Avicennia marina)等红树植物为研究对象,构建单变量函数的完全空间随机模型、异质泊松模型与双变量函数的环形转变模型,分析3种红树林种群的结构特征、空间格局及种内种间关联性。结果发现：(1)桐花树种群的小树和中树的个体数目较多,种群年龄结构呈金字塔型,种群处于增长状态;秋茄种群的中树个体数目较多,种群结构呈钟型,种群数量处于稳定状态;白骨壤个体数相对较少,且幼树较少老树较多,种群更新受阻,种群结构呈纺锤型,属于衰退型种群。(2)红树林群落整体上呈现出空间集聚的分布特征,从不同种群的集聚程度来看：桐花树>白骨壤>秋茄。(3)随着空间尺度的增大,红树林群落在空间分布上依次表现出聚集、随机和均匀3种特征。(4)桐花树与秋茄、白骨壤的种间关系随着尺度增加均表现为空间无关联性-空间负关联性-空间无关联性的演变特征,秋茄与白骨壤的种间关系则为全尺度的空间无关联性。(5)桐花树种内不同龄级之间存在空间正关联性、空间无关联性和空间负关联性,秋茄种内不同龄级之间均表现出空间无联性,白骨壤种群则在不同龄级之间均出现空间正关联性。(6)红树植物种群的空间格局受到自身繁殖特性、生境异质性、种内和种间竞争、病虫害等多种因素的影响。红树林人工种植和恢复需要结合沿海地区的自然生态条件,按照红树林种群的适应形态学特点、群落类型和自然演替规律,种植乡土红树植物,适当引进外来物种,研制出近似天然的人工红树林林分结构,提高群落的生物多样性和群落稳定性,发挥红树林湿地生态系统的生态环境效应。 相似文献
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中国北方典型草地物种丰富度与生产力的关系 总被引：13，自引：0，他引：13
利用2002–2004年内蒙古和甘肃南部几种典型草地的实测资料,研究了不同尺度物种丰富度与生产力的关系,并初步探讨了其形成机制。结果显示,温带草地的物种丰富度随生产力的增加而增加,但受空间尺度影响。在群落尺度(同一群落),在7种样方数大于15的群落中,仅沙生针茅(Stipaglareosa)群落物种丰富度与生产力呈现单峰型关系,其余均呈现线性正相关关系;在植被类型尺度,物种丰富度–生产力之间表现为显著的正相关关系;在研究区尺度,物种丰富度随生产力的增加而显著增加。研究还表明,研究区群落生产力的变化范围为13–368g·m–2·yr–1,物种丰富度为4–35种;生产力从高到低的顺序为:高寒草甸>草甸草原>典型草原>荒漠草原。 相似文献
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Relationships between spatial patterns of bird and mammal species richness in north‐eastern Mexico were analysed in relation to the location of three biosphere reserves (El Abra‐Tanchipa, El Cielo, and Sierra Gorda) and 13 priority areas recently identified for conservation. Ecological niches were modelled and potential distributions delimited for 285 bird and 114 mammal species using a genetic algorithm based on locality information from museum specimens and 15 selected environmental attributes. Potential distributions were transformed into hypothesized current distributions based on species–habitat associations as reflected in a recent land‐use map. Although species richness was lower when distributions were reduced from potential to current, spatial patterns of potential and current richness were similar. Heuristic, complementarity‐based prioritization procedures were used to identify combinations of areas and sites with maximal species representation: the biosphere reserves included 79% of birds and 74% of mammal species; eight priority areas provided an additional 11% of birds and 13% of mammals; the remaining 10% of birds and 13% of mammals were concentrated in new sites across the study area. 相似文献
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The mid‐domain effect (MDE) aims to explain spatial patterns in species richness invoking only stochasticity and geometrical constraints. In this paper, we used simulations to show that its main qualitative prediction, a hump‐shaped pattern in species richness, converges to the expectation of a spatially bounded neutral model when communities are linked by short‐distance migration. As these two models can be linked under specific situations, neutral theory may provide a mechanistic population level basis for MDE. This link also allows establishing in which situations MDE patterns are more likely to be found. Also, in this situation, MDE models could be used as a first approximation to understand the role of both stochastic (ecological drift and migration) and deterministic (adaptation to environmental conditions) processes driving the spatial structure of species richness. 相似文献
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Abstract. 1. Recent reviews of experimental studies provide compelling evidence that competition should be retained as a potential factor influencing the success of phytophagous insects. In this context, the objective of the study was to determine the role of interspecific and intraspecific competition, both contemporaneous and plant mediated (feeding‐induced resistance), in limiting the population density of a consistently rare insect in a guild of abundant potential competitors. 2. Competitive interactions were assessed experimentally between two phloem‐feeding planthoppers, the abundant Prokelisia dolus and the rare Delphacodes penedetecta (Hemiptera: Delphacidae). Both species are monophagous on the cordgrass Spartina alterniflora and overlap broadly in their use of habitats in the intertidal salt marshes along the Atlantic coast of North America. 3. The two planthoppers partition their cordgrass host plant, with D. penedetecta feeding more on the basal stems (particularly females) and P. dolus occurring most often on the canopy leaves. Notably, there was no evidence for niche shifting in D. penedetecta because its distribution on the plant did not change in the presence or absence of P. dolus. 4. Interspecific interactions with P. dolus had very little effect on the performance (development time and body size) and survival of D. penedetecta, a result demonstrated in both the laboratory and field. This result occurred both in contemporaneous interactions and on plants fed on previously by P. dolus. Only the males of D. penedetecta experienced weak competitive effects from P. dolus, as evidenced by reduced body size and slightly protracted development. 5. By contrast, there were strong adverse effects of intraspecific crowding (both from contemporaneous interactions and on plants fed on previously by conspecifics), whereby the survival, development time, and body size of D. penedetecta were affected very adversely. 6. These results suggest that interspecific competition is a weak force influencing the abundance of D. penedetecta in the field. Rather, strong intraspecific competition, a high requirement for plant nitrogen, and intrinsically low lifetime fecundity combine to explain the rarity of D. penedetecta. 相似文献
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通过与前人工作的比较,研究鼎湖山地带性植被气候顶极群落种间联结22a来的变化。研究结果表明,经过了22a,其种类结构尤其优势种类组成没有明显变化,这反映了厚壳桂群落处于演替的顶极阶段,其物种组成上具有相对的稳定性。现群落中的种间联结强度比1984年趋于缓和,高联结值的种对减少,完全正或负联结的种对,1984年为15,而2006年为5;一般联结的种对大为增加,联结值40以下的1984年为约1,2,而2006年为约3／5弱,表明群落的种群更趋向于独立分布而不是联结分布。生物竞争特性对种间关系有一定1的影响。主要原因是与物种对群落的选择和群落对生存物种的选择和淘汰有密切的关系。特别虫灾事件使该群落的群落结构有了较大的波动,但是群落的性质没有改变。反映了厚壳桂群落作为地带性气候顶级群落具有稳定性与较强的自我调节、自我恢复能力。整个群落的种群随时间进程趋向于独立分布,但这种分布趋势有其相对性,其中强独立分布（完全没有种间联结）的种群分布格局变弱,弱独立分布（只有微弱种间联结）的种群格局变强。 相似文献
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海南岛吊罗山热带山地雨林两个演替阶段的种间联结性 总被引：16，自引：0，他引：16
种间联结一直是群落演替理论研究的焦点之一, 关于物种间相互作用与群落演替之间的动态关系仍然存在争议。本文中, 作者通过出现-不出现数据的方差比例、基于2×2列联表的种间联结分析和 2检验, 对海南岛吊罗山热带山地雨林演替前期和演替后期群落的种间联结性进行了研究, 以揭示种间联结与群落演替的相互作用。结果表明: (1)在演替前期, 群落内所有树种间总体呈正联结, 但不显著; 发展至演替后期达到显著正联结。群落内所有物种间正、负联结种对数占总种对数的比例随演替进程呈现下降趋势, 而无联结种对数的比例则大幅上升; 优势种和伴生种间呈现相同的趋势。这表明群落演替正朝着有利于物种稳定共存的方向发展。(2)演替前期建群种和后期侵入种间正联结与无联结种对数的比例(分别为37.8%与41.5%)远大于负联结的比例(20.7%), 但正联结均不显著; 前期定居树种和后期侵入种通过分割资源而共存, 而且也趋于独立存在。(3)后期侵入种间不存在负联结, 所有正联结(占总对数的33.3%)均达显著水平, 显示它们对生境有相似的适应和相互重叠的生态位。 相似文献