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.     

Ecological drivers of plant diversity patterns in remnants coastal sand dune ecosystems along the northern Adriatic coastline

Coastal sand dunes represent one of the most fragile ecosystems in the Mediterranean basin. These habitats naturally suffer the action of several limiting factors such as sand burial, marine aerosol and low soil fertility; on the other hand, they often host species of high conservation value. Over the last decades, they have also experienced a high level of biological invasion. In this study, we sampled psammophilous vegetation in two sites in the northern Adriatic coast belonging to the Natura 2000 network to describe diversity patterns and to identify the main ecological drivers of species diversity. Plant species richness and their abundance were assessed in each plot. Differences in species composition for native and alien species were compared via PERMANOVA analysis. Species complementarity was explored by partitioning beta diversity in its spatial components (richness and replacement). A Generalized Linear Model was also computed to assess the main environmental factors that may promote invasiveness in these ecosystems. For the investigated area, our results highlight the strong differentiation in community composition both in alien and native species: in particular alien species showed on average a lower complementarity among habitats compared to native species. Specifically, communities seem to be more diversified when larger spatial scales were considered. Beta diversity in both groups appears to be more dominated by the richness component with respect to the replacement component. Furthermore, in these habitats, the occurrence of alien species was shown to be related to geomorphological predictors more than climatic variables.     

Priority areas for the conservation of subtropical indigenous forest in southern Africa: a case study from KwaZulu-Natal

Southern Africa's subtropical forest biome, though small and highly fragmented, supports much of the region's biodiversity. With limited resources available for conservation and the exploitative use of forest escalating, identifying a network of priority forest reserves is important. We examine the distribution of forest birds, butterflies and mammals in KwaZulu-Natal, South Africa. Using an iterative algorithm we explore the efficiency of existing protected areas, species richness and rarity hotspots, prime forest sites (selected by forest area) and complementary networks as alternative approaches to priority reserve selection, as well as the potential use of indicator taxa. Existing protected areas represent 98% of species but are relatively inefficient in terms of area. Alternative selection criteria represent a high proportion of species (86–92%) and provide efficient bases for developing fully representative reserve networks. All species are represented within a network of 22 complementary quarter degree cells. This network includes several larger forests and existing protected areas and is recommended for priority conservation. Complementary networks identified separately for birds, butterflies and mammals overlap little, but each represents a high proportion of the remaining taxa, supporting their potential as representative 'indicator' taxa. The evolutionary history of the three main forest types in KwaZulu-Natal explains observed spatial patterns of alternative reserve networks. Priority areas are concentrated in scarp and coastal forest belts, regions of comparatively recent evolutionary activity with high species richness. Afromontane forest is older and less diverse, but its inclusion in any reserve network is necessary for the full representation of forest diversity.     

Strengthening the Natural and National Park system of Iberia to conserve vascular plants

The diversity of the Iberian vascular flora has been investigated using WORLDMAP versions 3.08 and 3.18. Two data sets scoring plant distributions as presences within the Iberian Peninsula were compiled; one for 2133 species at 50 × 50 km grid and the other for 801 species at 10 × 10 km map grids. Patterns of biodiversity were determined using the diversity measures of species richness, range-size rarity and character richness diversity. Using the diversity measures, combined with an area selection method, maps of priority areas were calculated using iterative procedures. Near minimum sets (NMSs) for both scales were calculated. Comparison of the NMS for the 10 × 10 km grid with the near minimum set for existing reserves (NMSER) showed that at least 2% more of the land surface would be required above and beyond the existing protected area network, currently comprising 6% of the area, to ensure representation of all species at least once as listed within the present data-base. It is demonstrated that reserve systems selected on a variety of different criteria are suboptimal when compared to particular groups of target organisms with a definite goal of representation for conservation. Calculating efficiency of existing reserve systems and accounting for all taxa identifies precisely the extra required areas for the protected area system to satisfy particular goals of representation.     

Additive partitioning of rarefaction curves and species-area relationships: unifying alpha-, beta- and gamma-diversity with sample size and habitat area

Additive partitioning of species diversity is widely applicable to different kinds of sampling regimes at multiple spatial and temporal scales. In additive partitioning, the diversity within and among samples ( α and β ) is expressed in the same units of species richness, thus allowing direct comparison of α and β . Despite its broad applicability, there are few demonstrated linkages between additive partitioning and other approaches to analysing diversity. Here, we establish several connections between diversity partitions and patterns of habitat occupancy, rarefaction, and species–area relationships. We show that observed partitions of species richness are equivalent to sample-based rarefaction curves, and expected partitions from randomization tests are approximately equivalent to individual-based rarefaction. Additive partitions can also be applied to species–area relationships to determine the relative contributions of factors influencing the β -diversity among habitat fragments.     

Biodiversity surrogate groups and conservation priority areas: birds of the Brazilian Cerrado

The choice of surrogates of biodiversity is an important aspect in conservation biology. The quantification of the coincidence in the spatial patterns of species richness and rarity between different groups and the vulnerability of groups are different approaches frequently considered to accomplish this task. However, a more appropriate approach is to verify the efficiency of priority networks selected using information from one group of organisms to capture the biodiversity of other groups. Using a deconstructive approach, the main purposes of this study were to evaluate the performance of some orders and families of birds in the Cerrado biome (a savanna-like biome) as surrogates of other bird groups, in a pairwise analysis, and to investigate the characteristics of these groups that predict the efficiency in representation of other groups. We used biogeographical data on bird orders or families with more than 10 species that occur in the Brazilian Cerrado. The best surrogate group was the Thamnophilidae. Moreover, this group is not the most specious, favouring further survey efforts that are necessary to verify the conservation value of areas at suitable scales. The majority of the species from this family are dependent on forest habitats, one of the characteristics that most influenced representativeness level, probably due to the spatial distribution of these habitats throughout the Brazilian Cerrado. Beta diversity patterns of the different groups also affected representativeness, and our analyses showed that the networks selected by a surrogate group will be more effective in the representation of other groups of species if their patterns of beta diversity (not richness) are correlated.     

Capturing biodiversity: selecting priority areas for conservation using different criteria

International treaties call for the protection of biodiversity in all its manifestations, including ecosystem and species diversities. The selection of most priority area networks focuses, however, primarily on species richness and occurrence. The effectiveness of this approach in capturing higher order manifestations of biodiversity, that is ecosystem and environmental diversity patterns, remains poorly understood. Using a case study of birds and environmental data from South Africa and Lesotho, we test how complementary networks that maximise species diversity perform with regard to their representation of ecosystem and environmental diversity, and vice versa. We compare these results to the performance of the existing reserve network. We conclude that focusing on any single biodiversity component alone is insufficient to protect other components. We offer explanations for this in terms of the autocorrelation of species diversity in environmental space.     

Biodiversity surrogate effectiveness in two habitat types of contrasting gradient complexity

Enormous and increasing loss of biodiversity requires evaluation of surrogate taxa as a tool for conservation biology and new reserve selection, in spite of the fact that this approach has become questionable. The aim of this study was to assess the effect of gradient complexity on species richness and community composition among three taxonomic groups. We compared efficiency of vascular plants to indicate diversity of cryptogams (bryophytes, lichens) and snails in two contrasting habitat types (treeless fens and forests) within the same geographic region. We examined correlation of their species richness (Spearman rank correlation), community composition (Bray–Curtis similarity, Mantel test) and their responses to environmental variables (detrended and canonical correspondence analysis). We also focused on Red List species. We found that spatial congruence among studied taxa was affected by habitat type, however vascular plants were good indicator of snail biodiversity in both habitats. Nevertheless, all significant positive correlations of species richness were associated with the congruence in main environmental gradients. Although there was a consistency in significantly positive cross-taxon correlation in community similarity, the congruence was insufficient for conservation purposes. Furthermore we confirmed the necessity of integration of at-risk species in conservation planning as Red List species were poor indicators for total species richness and vice versa. We suggest the complementation of existing reserve network with small-scale protected areas focused on conservation of at-risk ecosystems, communities or species. In this study vascular plants were not found as a sufficient indicator for fine-filter conservation of other taxa.     

Distribution of Vascular Plant Species Richness Along an Elevational Gradient in the Dongling Mountains, Beijing, China

Quantifying spatial patterns of species richness and determining the processes that give rise to these patterns are core problems In blodlveralty theory. The aim of the present paper was to more accurately detect patterns of vascular species richness at different scales along altitudinal gradients in order to further our understanding of biodlverslty patterns and to facilitate studies on relationships between biodiversity and environmental factors. Species richness patterns of total vascular plants species, including trees, shrubs, and herbs, were measured along an altitudinal gradient on one transect on a shady slope in the Dongling Mountains, near Beijing,China. Direct gradient analysis, regression analysis, and geostatistics were applied to describe the spatial patterns of species richness. We found that total vascular species richness did not exhibit a linear pattern of change with altitude, although species groups with different ecological features showed strong elevational patterns different from total species richness. In addition to total vascular plants, analysis of trees, shrubs, and herbs demonstrated remarkable hierarchical structures of species richness with altitude (i.e. patchy structures at small scales and gradients at large scales). Species richness for trees and shrubs had similar spatial characteristics at different scales, but differed from herbs. These results indicated that species groups with similar ecological features exhibit similar biodlveraity patterns with altitude, and studies of biodiversity based on species groups with similar ecological properties or life forms would advance our understanding of variations in species diversity. Furthermore, the gradients or trends appeared to be due mainly to local variations in species richness means with altitude. We also found that the range of spatial scale dependencies of species richness for total vascular plants, trees, shrubs, and herbs was relatively large. Thus, to detect the relationships betweenspecies richness with environmental factors along altitudinal gradients, it was necessary to quantify the scale dependencies of environmental factors in the sampling design or when establishing non-linear models.     

Assessing and conserving groundwater biodiversity: synthesis and perspectives

1. This paper is a synthesis of a special issue on groundwater biodiversity with a focus on obligate subterranean species, the stygobionts. The series of papers constitutes a great leap forward in assessing and understanding biodiversity patterns because of the use of large quantitative data sets obtained over a broad geographic scale. They also represent a conceptual shift, away from a purely taxonomic and phylogenetic focus to the analysis of whole groundwater assemblages.
2. The general patterns emerging for groundwater fauna are: very high levels of endemism, low local diversity relative to regional diversity, a limited number of lineages, occurrence of many relicts, and truncated food webs with very few predators.
3. β-Diversity is at least as important as α-diversity in determining total richness at different scales (aquifer, basin and region) and overall taxa richness increases across spatial scales.
4. Advances in understanding groundwater biodiversity patterns further include identification of several important factors related to geology and hydrology that determine the composition of European stygobiotic assemblages.
5. Important challenges for future research include improving sampling strategies, filling gaps in sampling coverage, intensifying research on theoretical and statistical models, and including functional and genetic diversity components in biodiversity assessments.
6. Strategies are proposed for protecting groundwater biodiversity and an argument is made to integrate biodiversity in groundwater management. Applying principles such as complementarity and flexibility for groundwater biodiversity conservation is a major step toward delineating a reserve network that maximise species representation at the European scale.     

Multiple facets of stream macroinvertebrate alpha diversity are driven by different ecological factors across an extensive altitudinal gradient

Environmental filtering and spatial structuring are important ecological processes for the generation and maintenance of biodiversity. However, the relative importance of these ecological drivers for multiple facets of diversity is still poorly understood in highland streams. Here, we examined the responses of three facets of stream macroinvertebrate alpha diversity to local environmental, landscape‐climate and spatial factors in a near‐pristine highland riverine ecosystem. Taxonomic (species richness, Shannon diversity, and evenness), functional (functional richness, evenness, divergence, and Rao's Quadratic entropy), and a proxy of phylogenetic alpha diversity (taxonomic distinctness and variation in taxonomic distinctness) were calculated for macroinvertebrate assemblages in 55 stream sites. Then Pearson correlation coefficient was used to explore congruence of indices within and across the three diversity facets. Finally, multiple linear regression models and variation partitioning were employed to identify the relative importance of different ecological drivers of biodiversity. We found most correlations between the diversity indices within the same facet, and between functional richness and species richness were relatively strong. The two phylogenetic diversity indices were quite independent from taxonomic diversity but correlated with functional diversity indices to some extent. Taxonomic and functional diversity were more strongly determined by environmental variables, while phylogenetic diversity was better explained by spatial factors. In terms of environmental variables, habitat‐scale variables describing habitat complexity and water physical features played the primary role in determining the diversity patterns of all three facets, whereas landscape factors appeared less influential. Our findings indicated that both environmental and spatial factors are important ecological drivers for biodiversity patterns of macroinvertebrates in Tibetan streams, although their relative importance was contingent on different facets of diversity. Such findings verified the complementary roles of taxonomic, functional and phylogenetic diversity, and highlighted the importance of comprehensively considering multiple ecological drivers for different facets of diversity in biodiversity assessment.     

Selecting networks of nature reserves: methods do affect the long-term outcome

Data on vascular plants of boreal lakes in Finland were used to compare the efficiency of reserve selection methods in representing four aspects of biodiversity over a 63 year period. These aspects included species richness, phylogenetic diversity, restricted range diversity and threatened species. Our results show that the efficiency of reserve selection methods depends on the selection criteria used and on the aspect of biodiversity under consideration. Heuristic methods and optimizing algorithms were nearly equally efficient in selecting lake networks over a small geographical range. In addition, a scoring procedure was observed to be efficient in maintaining different aspects of biodiversity over time. However, the random selection of lakes seems to be the most inefficient option for a reserve network. In general, reserve selection methods seem to favour lakes that maximize one aspect of diversity at the time of selection, but the network may not be the best option for maintaining the maximum diversity over time. The reserve selection methods do affect the long-term outcome but it is impossible to recommend one method over the others unequivocally.     

贡嘎山东坡植被垂直带谱的物种多样性格局分析

为了探讨贡嘎山东坡海拔梯度上植物多样性的结构物征及格局变化,基于植被垂直带谱的样带和样方调查,分析了物种丰度与种－面积关系的垂直变化,物种多样性生态和地理成分的海拔梯度格局,去势对应分析（DCA）和典范对应分析（CCA）被用于分析17种环境因子之间的相关性,和环境因子对27个多样性结构成分和67个样方空间格局的影响,并定量分离不同尺度的环境变量对多样性格局分异的贡献。结果表明：1）贡嘎山东坡的植物物种多样性总体上表现了自下而上降低的梯度,但从河谷干旱灌草丛带到常绿阔叶林带和高山灌丛带到草甸带显示了相反的梯度变化;2）10种分布区类型的物种有各不相同的垂直丰度格局,9种生活型的物种多样性垂直格局则反映了草本与木本类型的明显差异;3）从河谷干旱草丛到山地针阔混交林的生物多样性结构变化主要反映水分梯度的影响;而从山地针阔混交林到高山草甸,多样性结构变化的主导因子是气温;4）气候的垂直梯度和生境的局部异质性是物种多样性格局两组不同作用尺度和性质的影响因子,总体上76．83％的多样性变异得到了解释,其中寒冷指数的作用最为突出,分析结果支持了关于生物多样性格局机理的不同假说,同时表明,贡嘎山东坡植物地理的垂直变化不仅受到现代环境因子的控制,区域环境变迁和区系发育历史的影响也是不可忽略的。     

村落文化林与非文化林多尺度物种多样性加性分配

文化林是指村民按照文化传统、风俗习惯或宗教信仰自觉保护和管理的森林,具有一定社会文化功能。目前国内外对文化林物种多样性研究主要为定性描述,缺乏对文化林和非文化林生物多样性的定量比较及差异来源分析。利用物种多样性加性分配方法,将总的Gamma 多样性分成样格内的Alpha多样性以及样格间、样方间和林型间Beta多样性,对中国亚热带地区3个村落文化林的乔木层、灌木层、草本层和藤本层进行物种多样性的多尺度分析。调查发现:(1)文化林共有维管束植物296种,以苦槠,樟和米槠为优势种,非文化林共有维管束植物189种,以杉木、马尾松和毛竹为优势种。文化林乔木层和灌木层物种数显著高于非文化林,草本层和藤本层物种数差异不显著。(2)Beta多样性随尺度增大而增加,林型间Beta多样性最高,占区域总Gamma多样性的41.9%-62.8%,其次是样方间Beta多样性(18.6%-31.9%),对区域多样性贡献最小为样格内Alpha和样格间Beta多样性。(3)林型间的多样性对区域物种多样性的贡献中,文化林占主导作用,乔木层占54.4%-81.0%,灌木层占51.2%-60.2%,草本层占42.9%-64.1%,藤本层占49.9%-62.2%。(4) 物种累积-面积曲线表明,在各个尺度上,文化林物种多样性始终高于非文化林,从而在相同面积下保护了更多的物种。加性分配模型在多个空间尺度上阐明了Alpha和Beta多样性的变化,突出了文化林对区域物种多样性的贡献,对保护对象和保护范围的决策以及生物多样性的保护与恢复具有重要意义。     

宏生态尺度上景观破碎化对物种丰富度的影响

生物多样性的地理格局及其形成机制是宏生态学与生物地理学的研究热点。大量研究表明,景观尺度上的生境破碎化对物种多样性的分布格局具有重要作用,但目前尚不清楚这种作用是否足以在宏生态尺度上对生物多样性地理格局产生显著影响。利用中国大陆鸟类和哺乳动物的物种分布数据,在100 km×100 km网格的基础上生成了这两个类群生物的物种丰富度地理格局,进一步利用普通最小二乘法模型和空间自回归模型研究了物种丰富度与气候、生境异质性、景观破碎化的相关关系。结果表明,景观破碎化因子与鸟类和哺乳动物的物种丰富度都具有显著的关联关系,其方差贡献率可达约30%—50%(非空间模型)和60%—80%(空间模型),略低于或接近于气候和生境异质性因子。方差分解结果显示,景观破碎化因子与气候和生境异质性因子的方差贡献率的重叠部分达20%—40%。相对鸟类而言,景观破碎化对哺乳动物物种丰富度的地理格局具有更高的解释率。     

Inclusion of explicit measures of geodiversity improve biodiversity models in a boreal landscape

Measures of geodiversity may provide a potentially useful surrogate for biodiversity patterns in insufficiently surveyed areas. However, their reliability in modelling the spatial variation in species richness is inadequately understood. We investigated whether the explanatory and predictive power of species richness models can be improved by considering explicit measures of geodiversity (variability of earth surface materials, forms and processes) in addition to climate and topography variables. Vascular plant species richness was modelled in two study areas in Northern Europe, Finland at the resolution of 500 or 1000?m, and as a function of three geodiversity (geological, geomorphological and hydrological diversity) variables, and six climate and topography variables. Variation partitioning was used to identify the independent and shared contributions of the geodiversity, climate and topography variable groups in explaining the spatial patterns of species richness. Generalized additive models were used to explore the ability of the different explanatory variables in predicting plant species richness within and between the study areas. In both the study areas, the inclusion of measures of geodiversity improved the explanatory power, predictive ability and robustness of the plant species richness models. In conclusion, the explicit measures of geodiversity appear to be promising surrogates of biodiversity, which reflect important abiotic resource factors, and may thus provide an equally, or even more reliable basis for transferring biodiversity models to new areas than models based on climate and topography variables.     

Ant diversity partitioning across spatial scales: Ecological processes and implications for conserving Tropical Dry Forests

Several ecological and evolutionary processes can drive changes in diversity at different spatial scales. To determine the scale at which these processes are most influential, we hypothesized that (i) broad‐scale differences between ecoregions had greater influence on ant species richness and species turnover than local differences among fragments within ecoregions; and (ii) the degree of dissimilarity in ant species composition is larger between Tropical Dry Forest fragments and the surrounding vegetations than among Tropical Dry Forests located in different ecoregions, indicating that extant Tropical Dry Forests are relicts of a broader distribution of this vegetation. To examine ant diversity patterns, we built a nested hierarchical design on three spatial scales, ranging from fragments (local scale), Tropical Dry Forest + surroundings vegetation (landscape scale) and Brazilian ecoregions (regional scale). We used 450 sampling units (45 sampling units × two fragments × five ecoregions = 450). A null model based on the sample was used to identify variations in the random distribution across spatial scales. Spatial partitioning of ant diversity showed that observed β₁ diversity (between fragments) and β₂ diversity (among ecoregions) were higher than expected by chance. When the partitioning was analysed separately for each region, the observed β₁ diversity (Tropical Dry Forest and surrounding vegetation) was higher than expected by the null hypothesis in all ecoregions of Brazil. Based on species composition and diversity patterns, we stress the importance of creating more protected areas throughout the coverage area of Tropical Dry Forests, favouring a more efficient conservation process.     

Cross-taxon congruence in tree,bird and bat species distributions at a moderate spatial scale across four tropical forest types in the Philippines

Indicator species groups are often used as surrogates for overall biodiversity in conservation planning because inventories of multiple taxa are rare, especially in the tropics where most biodiversity is found. At coarse spatial scales most studies show congruence in the distribution of species richness and of endemic and threatened species of different species groups. At finer spatial scale levels however, cross-taxon congruence patterns are much more ambiguous. In this study we investigated cross-taxon patterns in the distribution of species richness of trees, birds and bats across four tropical forest types in a ca. 100 × 35 km area in the Northern Sierra Madre region of Luzon Island, Philippines. A non-parametric species richness estimator (Chao1) was used to compensate for differential sample sizes, sample strategies and completeness of species richness assessments. We found positive but weak congruence in the distribution of all and endemic tree and bird and tree and bat species richness across the four forest types; strong positive congruence in the distribution of all and endemic bat and bird species richness and low or negative congruence in the distribution of globally threatened species between trees, birds and bats. We also found weak cross-taxon congruence in the complementarity of pairs of forest types in species richness between trees and birds and birds and bats but strong congruence in complementarity of forest pairs between trees and bats. This study provides further evidence that congruence in the distribution of different species groups is often ambiguous at fine to moderate spatial scales. Low or ambiguous cross-taxon congruence complicates the use of indicator species and species groups as a surrogate for biodiversity in general for local systematic conservation planning.