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Revisiting the indicator problem: Can three epigean arthropod taxa inform about each other's biodiversity?

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Abstract

Conservation studies often investigate the biodiversity of one taxonomic group with the expectation that it reflects biodiversity of other taxa as well. However, previous studies have found that biodiversity patterns are often only weakly correlated across ecologically very different taxa. Using three arthropod taxa that share the same habitat, utilize similar resources and are sampled with identical technique, we investigate the applicability of two levels of biodiversity indication: (1) prediction of biodiversity patterns, and (2) inference of environment–biodiversity relationships. The second aspect is of high relevance to applied conservation management yet mostly neglected, at least in terrestrial systems, when discussing the indicator concept.

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... on its own contains limited biological information 6,13 , since assemblages identical in their α -diversity can have a completely different species composition, fulfil very different ecosystem functions and provide distinctly different ecosystem services. Accordingly, the congruence in turnover patterns or community similarity across taxa that can provide important insights for biodiversity conservation 11,17 has recently received increasing attention 10,18,19 . Respective studies have confirmed an apparent wide-spread, strong congruence in spatial community dissimilarity patterns across taxonomic groups 6,13,20 , but the underlying causes for these patterns are still poorly understood 17,21,22 . ...
... key environmental factors 23 , such as available energy 24 , humidity 28 or grazing regimes 34 . In contrast, other authors argue that different taxa will show highly independent specific responses to changes in environmental conditions 16,18,19,39 , which in turn is often linked to weak congruence 10,17,20 . The variations in the independent influence environmental factors exert on cross-taxon congruence of different taxon pairs in our study can be related to this divergence in viewpoints and past observations. ...
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High cross-taxon congruence in species diversity patterns is essential for the use of surrogate taxa in biodiversity conservation, but presence and strength of congruence in species turnover patterns, and the relative contributions of abiotic environmental factors and biotic interaction towards this congruence, remain poorly understood. In our study, we used variation partitioning in multiple regressions to quantify cross-taxon congruence in community dissimilarities of vascular plants, geometrid and arciinid moths and carabid beetles, subsequently investigating their respective underpinning by abiotic factors and biotic interactions. Significant cross-taxon congruence observed across all taxon pairs was linked to their similar responses towards elevation change. Changes in the vegetation composition were closely linked to carabid turnover, with vegetation structure and associated microclimatic conditions proposed causes of this link. In contrast, moth assemblages appeared to be dominated by generalist species whose turnover was weakly associated with vegetation changes. Overall, abiotic factors exerted a stronger influence on cross-taxon congruence across our study sites than biotic interactions. The weak congruence in turnover observed particularly between plants and moths highlights the importance of multi-taxon approaches based on groupings of taxa with similar turnovers, rather than the use of single surrogate taxa or environmental proxies, in biodiversity assessments.
... An implicit assumption of this approach is that the relationships between the diversity of taxa are consistent across broad environmental gradients (e.g., Sauberer et al. 2004, Larsen et al. 2012). However, this assumption has only been tested for a limited range of taxa (Schulze et al. 2004, Beck et al. 2013, Gossner et al. 2014), and has not been investigated at all for grasslands differing in their land-use intensity. Relationships between the biodiversities of different taxa can be generated by a range of underlying causes. ...
... Although correlations were strong in some cases, the diversities of most taxa were weakly positively correlated with each other. This pattern is consistent with previous studies where similarly moderate levels of correlation have been observed across a wide range of ecosystems and spatial scales (Howard et al. 1998, Schulze et al. 2004, Wolters et al. 2006, Kessler et al. 2011, Beck et al. 2013. ...
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Land-use intensification is a key driver of biodiversity change. However, little is known about how italters relationships between the diversities of different tax on omicgroups, which are often correlated due to shared environmental drivers and trophic interactions.Using data from 150 grassland sites, we examined how land-use intensification (increased fertilization, higher livestock densities, and increased mowing frequency) altered correlations between the species richness of 15 plant, invertebrate, and vertebrate taxa. We found that 54%of pairwise correlations between taxonomic groups were significant and positive among all grasslands, while only one was negative. Higher land-use intensity substantially weakened these correlations (35% decrease in rand 43% fewer significantpair wise correlations at high intensity), apattern which may emerge as a result of biodiversity declines and the breakdown of specialized relationships in these conditions. Nevertheless, some groups (Coleoptera, Heteroptera, Hymenoptera and Orthoptera) were consistently correlated with multidiversity, an aggregate measure of total biodiversity comprised of the standardized diversities of multiple taxa, at both high and lowland-use intensity. The form of intensification was also important; increased fertilization and mowing frequency typically weakened plant-plantand plant-primary consumer correlations, whereas grazingintensification didnot. This may reflect decreased habitat heterogeneity under mowing and fertilization and increased habitat heterogeneity under grazing.While these results urge caution in using certain taxonomic groups to monitor impacts of agricultural management on biodiversity, they also suggest that the diversities of some groups are reasonably robust indicators of total biodiversity across a range of conditions.
... Small-scale processes are expected to obscure patterns of community variation at more local scales (Prendergast et al., 1999). Different taxonomic groups can also show considerable differences in relation to the same variables (Beck et al., 2013). Another important factor could be a mismatch between predictor resolution and the actual processes that affect turnover patterns locally. ...
Article
Biosphere reserves (BRs) are areas of high biodiversity value that promote conservation and sustainable development. BRs consist of core, buffer, and transition zones. Buffer zones are where human and ecological activities overlap, and are key functional spaces that can have important complementarity value. We test this using ground-living arthropods in the highly biodiverse Kogelberg Biosphere Reserve in South Africa. We use generalized dissimilarity modelling to describe the compositional dissimilarity of assemblages as a function of environmental correlates between pairs of survey sites. Transformed spatial predictors were used as surrogates for biodiversity to assess complementarity. Important correlates of arthropod species turnover were related to mesoclimate, fire history, and geology. Buffer areas had important complementary value. Current habitat transformation across core and buffer zones does not change this, as results were the same when removing all transformed areas from the analyses. Important areas in buffer zones that increased local representativeness coincided with areas of increased intra-annual temperature variability. Orchards in transformed areas also influenced arthropod diversity in adjacent natural vegetation by < 1 km from orchard edges. This edge effect influenced both core and buffer sites due to the lack of a continuous buffer, indicating that the buffer zone is important for protecting the core. As fire management is an important correlate of arthropod turnover here, the complementary value of the buffer zone can have a strong temporal dimension. Given the important complementary value of the buffer zone, conservation management should not be restricted to core areas only, especially when maximising local representativeness
... Using different approaches and measurements of diversity can elucidate congruence in diversity patterns that may otherwise not be detected, especially in studies restricted to finer scales (Gioria et al. 2011). While some authors argue that different taxa will show highly independent responses to environmental gradients (Beck et al. 2013, Guareschi et al. 2015, and others link cross-taxon congruence to common responses (Axmacher et al. 2009, Jetz et al. 2009), a combination of these two extremes influencing congruence in arthropod and plant species turnover occurs. Low congruence between plant and arthropod diversity was due to the influence of habitat association of the target group, spatial scale, and differential turnover patterns along environmental variables. ...
Article
Plants often form the basis of conservation planning and management. The effectiveness of plant diversity as a surrogate for arthropod diversity was assessed in natural areas in the Kogelberg Biosphere Reserve, a floral endemism hotspot in the Cape Floristic Region (CFR), South Africa. Arthropods and plants were sampled across 30 topographically heterogeneous sites in a spatially nested design. The relationship between plants and arthropods were quantified in terms of species richness, assemblage variation, and assemblage turnover. The influence of arthropod trophic groups, habitat association, and spatial scale were also explored. Generalized dissimilarity modelling was used to investigate differential influence of explanatory groups (geology, disturbance, local site characteristics, refuge, mesoclimate, terrain) on arthropod and plant turnover. Congruence in assemblage variation was restricted to local scales, and only present between plants and those arthropods associated with the foliar component of the habitat. Weak congruence in species turnover was due to differences in the relative importance of explanatory groups, with different variables within each explanatory group being important, and similar variables predicting different turnover patterns. For both groups, variables related to geology and fire history were important for assemblage turnover. These variables are already incorporated in conservation planning and management for plant diversity across the CFR. Overall plant diversity was a weak surrogate for the arthropod groups included in this study, suggesting that as an alternative, environmental surrogates for arthropod diversity perform better. This article is protected by copyright. All rights reserved.
... To this end, we make our GIS data for this region fully available (Online Resources 2, 3). Different taxonomic groups, as well as different aspects of biodiversity or other metrics of 'conservation value', may likely indicate different priority regions (e.g., Schulze et al. 2004;Wolters et al. 2006;Grenyer et al. 2006;Beck et al. 2013). Consensus methods, or clear criteria for what is to be protected in a particular region, will then be required for objective decision making. ...
Article
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The range size of species co-occurring in local assemblages is a pivotal variable in assessments of a site’s conservation value. Assemblages featuring many small-ranged species are given more priority than assemblages consisting mainly of wide-ranging species. However, the assembly of relevant information can be challenging and local range size distributions of tropical invertebrates are rarely available for conservation planning. We present such data for sphingid moths in East Africa, a highly diverse region of high conservation value. We compare geographic range size distributions based on field samples with predictions from modelled range map data. Using this system as a case study, we provide evidence for a systematic sampling bias when inferring average local range sizes from field data. Unseen species (i.e., species present but missed in local sampling) are often those with small ranges (hence, of high conservation value). Using an elevational gradient, we illustrate how this bias can lead to false, counterintuitive assessments of environmental effects on local range size distributions. Furthermore, with particular reference to sphingid moths in the study region, we show that current protected areas appear unrelated to the spatial distribution of species richness or average geographic range sizes at a local scale. We discuss the need to treat field sampled data with caution and in concert with other data sources such as probabilistic models.
... We compared beetle assemblages among urban vacant lots, urban farms, and urban prairies within the shrinking City of Cleveland, Ohio. We collected ground beetles (Carabidae) and rove beetles (Staphylinidae) as they are considered biological indicators of habitat change (Bohac 1999, Rainio and Niemela 2003, Beck et al. 2013, their distribution patterns vary across natural and urban gradients (Deichsel 2006, Magura et al. 2013, Work et al. 2013, Vergnes et al. 2014, and some function as biological control agents (Coaker andWilliams 1963, Hatteland et al. 2010). Our research objective was to answer the following questions: (1) Does the conversion of vacant land to alternative forms of greenspace influence beetle abundance and species richness? ...
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Urbanization is a leading cause of species extinction; however, interest in urban greenspaces as sites for conservation has grown considerably in recent decades, raising questions about the ability of these habitats to support desired wildlife. Our goal was to determine how distinct forms of urban greenspace and their landscape context influenced the species composition of ground-dwelling beetle communities. We examined the taxonomic and functional composition of Carabidae and Staphylinidae in urban vacant lots, urban farms, and planted urban prairies within the City of Cleveland, Ohio. Beetles were collected using pitfall traps across 23 sites. We found that the three habitats examined varied significantly in beetle composition, with several unique species found within each type of greenspace. Carabidae abundance and richness were greater in urban prairies and urban farms relative to vacant lots. The abundance and taxonomic richness of Staphylinidae were highest within urban farms. Canonical correspondence analysis (CCA) and partial CCA revealed that both local features and landscape variables influenced beetle community assembly. Most beetle taxa were negatively associated with buildings within the surrounding 1-km landscape, whereas grass was the most important local habitat feature. Additionally, we found variation in the distribution of species traits among habitats; ecological traits such as moisture tolerance and dispersal capacity differed significantly among urban greenspaces. Most interesting from a conservation perspective was a greater abundance of brachypterous carabids found in urban prairies, which suggests that these habitats provide overwintering and breeding habitat for some beetle species. Our findings demonstrate that urban greenspaces play important roles in shaping arthropod diversity in cities, and maintaining habitats that vary in design and management is important for their conservation.
... In order to gain a more complete understanding of the biodiversity loss occurring in the Sahel and the role protected areas play in arthropod conservation, we examined general arthropod as well as beetle, spider and ant diversity and assemblage structure in western Senegal. We included multiple taxonomic groups since arthropod taxa can respond to environmental disturbances differently (Cabra-García et al., 2012;Fattorini et al., 2012;Beck et al., 2013;Leach et al., 2013) and a dry and rainy season sample to account for seasonal changes in their abundance and assemblage structure (Bourliere and Hadley, 1970). ...
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Drylands are highly vulnerable to desertification and among the most endangered ecosystems. To understand how biodiversity responds to environmental degradation in these fragile ecosystems, we examined whether arthropod, beetle, spider and ant diversity and assemblage structure differed (1) between seasons, (2) among locations (3) between protected areas of tropical dry forest and adjacent communal lands suffering from desertification, as well as (4) how vegetation impacts assemblage structures. We established 12 plots spaced homogenously throughout each protected area and the adjacent communal land at three locations: Beersheba, Bandia and Ngazobil. Within each plot, we measured canopy closure, vegetation height, percent cover of bare ground, leaf litter, grasses and forbs and collected arthropods using pitfall traps during the 2014 dry (May) and rainy (September) seasons. We collected 123,705 arthropods representing 733 morphospecies, 10,849 beetles representing 216 morphospecies, 4969 spiders representing 91 morphospecies and 59,183 ants representing 45 morphospecies. Results showed greater arthropod and beetle diversities (P = 0.002–0.040) in the rainy season, no difference in diversity among locations for any taxonomic group and a difference (P ≤ 0.001) in diversity for all taxa between protected areas and communal lands. Assemblage structures of all taxa responded (P = 0.001) to vegetation characteristics, differed (P = 0.015–0.045) between seasons and, with a few exceptions, locations and fragments. Our results illustrate the importance of a multi-taxa approach in understanding biodiversity response to anthropogenic disturbances as well as the value of protected areas in preserving biodiversity of the Sahel.
... We compared beetle assemblages among urban vacant lots, urban farms, and urban prairies within the shrinking City of Cleveland, Ohio. We collected ground beetles (Carabidae) and rove beetles (Staphylinidae) as they are considered biological indicators of habitat change (Bohac 1999, Rainio and Niemela 2003, Beck et al. 2013, their distribution patterns vary across natural and urban gradients (Deichsel 2006, Magura et al. 2013, Work et al. 2013, Vergnes et al. 2014, and some function as biological control agents (Coaker andWilliams 1963, Hatteland et al. 2010). Our research objective was to answer the following questions: (1) Does the conversion of vacant land to alternative forms of greenspace influence beetle abundance and species richness? ...
... Furthermore, in the absence of a globally coordinated research program on data management, there is a huge variety of methods (including data analysis and its reporting), systems, spatial scales, and taxa studied. Different taxa can react very differently to the same environmental variation, jeopardizing overall conclusions [112,170]. The majority of studies were not experimental but compared already existing farmer-managed systems, which further weakened conclusions on causalities. ...
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Agroforestry systems potentially deliver win–win solutions to production and biodiversity conservation in the tropics, but they need to be adapted to farmers needs. We reviewed the literature on functional roles of biodiversity and resilience in tropical agroforestry systems, and we evaluated the evidence base for the beneficial role of biodiversity on yield, and effects of farmer management practices. Most studies investigated the biodiversity of taxa assumed to have positive functions for farmers. Shaded commodities and shifting cultivation were the systems most frequently assessed. Half of studies investigated plants, while Hymenoptera and birds were other major groups. Many agroforests had lower diversity than forest, while less than half had higher diversity than agriculture. The effects of management within systems were rarely addressed, with shade level the most frequent factor. Papers on resilience, mainly from shifting cultivation systems,showed the positive influence of adjacent old-growth forest to biodiversity, and the negative effects of tillage. Better reporting of results for meta-analyses, and long-term experiments on key questions are needed to evaluate the potential of agroforestry more thoroughly.
... These two taxa were chosen because generalist arthropod predators play an important role in grassland functioning as natural enemies of pests (Symondson et al., 2002) or as food for insectivorous vertebrates (Vickery et al., 2001;Mooney et al., 2010). From a conservational perspective, generalist predators have been proven to be informative indicators of both local habitat conditions (Marc et al., 1999;Rainio and Niemelä, 2003) and the species richness in other taxa (Wolters et al., 2006;Beck et al., 2013). Numerous studies have shown that the species richness or the number of threatened species of spiders and ground beetles in grasslands decrease with the intensity (e.g., grazing) and the type (e.g., organic versus conventional farming) of management as well as with landscape homogenization (e.g., proportion of annually ...
Article
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Grasslands host large parts of Europe’s agricultural arthropod diversity. Considering the adverse effects of ongoing land use changes on many grassland taxa, there is an urgent need to establish measures that allow for optimizing the conservation of permanent grassland habitats and their climatic, environmental and ecological benefits. Here, data from 42 permanent grasslands were used to quantify the effect of individual management practices on different diversity components in spider and ground beetle communities. Intensive fertilization and frequent cutting reduced the species richness of spiders and the number of threatened spider species, but increased the average taxonomic distinctness of communities. Moreover, high grazing intensity reduced the average body size of individuals in local spider communities. Frequent cutting led to a higher abundance of predaceous and omnivorous ground beetles but a lower abundance of herbivorous species. These opposing responses of both different biodiversity components and different taxa to individual grassland management practices confirm that no single management practice maximizes the biodiversity of arthropod predators in permanent grasslands at the local scale. Rather, our study suggests that arthropod predator diversity can only be conserved by promoting a landscape-scale combination of different management practices and intensities in permanent grasslands. When considering conservation measures, conservation goals should not only be formulated in terms of local species richness, but also need to address other components of diversity such as taxonomic or functional diversity.
... This leads to the question whether spider assembly patterns at Sphagnum farming sites are indicative for invertebrate succession on the whole. There is general agreement that reliable bioindication should be based on sets of multiple taxa, preferably including different trophic levels and functional groups, to minimize the risk of biased conclusions and management decisions (McGeoch 1998;Pryke and Samways 2012;Beck et al. 2013;Gerlach et al. 2013). Spiders belong to the more vagile arthropod taxa due to their ability of using silk as a medium for passive aerial transport (''ballooning'') (Bell et al. 2005). ...
Article
Sphagnum farming is a promising approach towards sustainability in growing media production for horticulture. In this study we focus on the additional value of Sphagnum farming sites as a surrogate habitat for threatened peat bog fauna. The highly diverse arthropod groups of spiders and harvestmen were used as bioindicators to track changes in species assemblages over the first 3 years of Sphagnum farming on a site in northwestern Germany. The results were compared with simultaneously studied reference habitats of nearby bog grasslands and degraded peat bog remnants. Spider communities changed rapidly from assemblages dominated by disturbance specialists (pioneer species) in the year of artificial Sphagnum establishment to diverse assemblages with large proportions of peatland generalists in the following years. Conservation value based on rarity, Red List status, disturbance tolerance and peatland association of individual species was in the later stage of Sphagnum farming as high as in the seminatural reference sites. Species quality index as derived from rarity scores was particularly high in the first year of succession due to the occurrence of some rare disturbance specialists. Despite the fact that each succession stage has its own conservation value, we advocate long rotation cycles in Sphagnum farming to allow establishment of slowly colonizing peatland specialists. We generally recommend the establishment of Sphagnum farms on degraded peatland, as creation of this artificial habitat promotes landscape and species diversity and provides refuges for endangered species of peatland and ephemeral habitats.
... In the present review we found a number of longterm datasets (e.g. Beck et al., 2013;Sebek et al., 2012), but only one revealing changes in species richness in relation to structure (Gil-Tena et al., 2009). However, we did not primarily search for and emphasise long-term data, but rather "present data". ...
... On the other hand, no correlation between these biodiversity or conservation measures and the diversity of threatened plants was detected. It indicates that effective restoration of habitats valuable for the whole multitaxa communities should include monitoring of several unrelated groups and consider their individual requirements (Ruiz-Jaen and Aide, 2005;Tropek et al., 2008;Beck et al., 2013). Simultaneously, the fact that no correlation was found between species richness of all and threatened plants indicates that "simple numbers" of detected species could not reflect the whole conservation value of surveyed sites or techniques, and that the individual species' lifehistory, such as their red-list status, should be reflected (Tropek et al., 2008). ...
Article
It is usually not practical for invertebrates to be comprehensively included in biodiversity surveys that underpin conservation planning, and so a representative subset of taxa needs to be selected. One approach to representativeness is to select taxa whose patterns of richness and composition are most strongly correlated with those of total invertebrates (i.e. all taxa combined). However, if different groups show very different distribution patterns then ‘total diversity’ cannot be considered as representative of the diversity of invertebrate taxa, and so an alternative approach to achieving representativeness is to base selection on complementarity (i.e. representing the full range of distribution patterns shown by different taxa). We use data on 12 invertebrate families (comprising ants, beetles, flies and spiders) sampled using pitfall traps across 78 sites in a tropical savanna landscape of northern Australia to identify a subset of target taxa (families) to represent their diversity patterns. We use a simple scoring system that incorporates both survey practicality and biological representativeness to compare selection of taxa based on (1) representing ‘total diversity’ and (2) representativeness through complementarity (‘complementary diversity’). Congruence among taxa in terms of both species richness and composition was generally low (ρ < 0.5), suggesting that taxa are poorly representative of each other and thus a complementary approach is required for target taxa selection. The taxa that scored highest in representing ‘complementary diversity’ were very different to those representing ‘total diversity’. To our knowledge, this is the first time that invertebrate representativeness based on ‘total diversity’ and ‘complementary diversity’ have been directly compared. The selected target taxa are specific to our study system, but our simple method for selecting representative invertebrate taxa for conservation planning is widely applicable, including for biodiversity monitoring and environmental impact assessment.
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Community-level models (CLMs) consider multiple, co-occurring species in model fitting and are lesser known alternatives to species distribution models (SDMs) for analyzing and predicting biodiversity patterns. CLMs simultaneously model multiple species, including rare species, while reducing overfitting and implicitly considering drivers of co-occurrence. Many CLMs are direct extensions of well-known SDMs and therefore should be familiar to ecologists. However, CLMs remain underutilized, and there have been few tests of their potential benefits and no systematic reviews of their assumptions and implementations. Here we review this emerging field and provide examples in R to fit common CLMs. Our goal is to introduce CLMs to a broader audience, and discuss their attributes, benefits, and limitations relative to SDMs. 2.We review i) statistical implementations and applications of CLMs, ii) their advantages and limitations, and iii) comparative analyses of CLMs and SDMs. We also suggest directions for future research. 3.We identify seven CLM algorithms with similar data structures and predictive outputs as SDMs that should be most accessible to ecologists familiar with species-level modeling, including five methods that predict assemblage composition and individual species distributions and two methods that model compositional turnover along environmental gradients. CLMs have been applied to numerous taxa, regions, and spatial scales, and a variety of topics (e.g., studying drivers of community structure or assessing relationships between community composition and functional traits). Studies suggest that the relative benefits of CLMs and SDMs may be case specific, especially in terms of predicting species distributions and community composition. However, CLMs may offer advantages in terms of computational efficiency, modeling rare species, and projecting to no-analog climates. A major shortcoming of CLMs is their reliance on presence-absence community composition data. 4.Studies are needed to assess the relative merits of SDMs and CLMs, and different CLM algorithms, with a focus on three key areas: i) under which circumstances CLMs improve predictions for rare species, ii) how CLMs perform under different community compositions (e.g. relative abundance of rare vs. common species), including the extent to which co-occurrence patterns are structured by biotic interactions, and iii) ability to project across time/space. This article is protected by copyright. All rights reserved.
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Flowery field margins and intersowing of crops with flowers are used as management practices to promote arthropod biodiversity as well as biocontrol agents. Positive effects of enhancement (in abundance and species richness) of hymenopteran parasitoids on control of Lepidoptera pests have previously been demonstrated. However, effects on predatory arthropods, which may also serve as pest control agents, remain unclear. In an experimental study in cabbage fields we tested how sown flower strips on field margins and intersowing with cornflower affected the species richness, abundance and community composition of ground beetles and spiders. Furthermore, we investigated whether effects of flower margins are dependent on the distance from the field margins. We found that field margins generally harboured higher species richness, whereas effects on abundance were weaker. Intersown cornflower had positive effects on spider and ground beetle abundance, but affected species richness only weakly. Our results do not provide evidence for effects of distance from the flowery field margins on predator richness or abundance. Species composition was strongly affected by the habitat management actions. We conclude that habitat management practices like flower strips on field margins and intersowing with flowers, which are primarily added to attract and enhance parasitoids for pest control, also benefit biodiversity conservation in spiders and ground beetles. They also positively affect the abundance of these primarily predatory taxa, which adds to the biocontrol potential of non-crop flowering plants.
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Robert H. Whittaker defined beta diversity as the variation in species composition among sites in a geographic area. Beta diversity is a key concept for understanding the functioning of ecosystems, for the conservation of biodiversity, and for ecosystem management. This paper explains how hypotheses about the origin of beta diversity can be tested by partitioning the spatial variation of community composition data (presence-absence or abundance data) with respect to environmental variables and spatial base functions. We compare two statistical methods to accomplish that. The sum-of-squares of a community composition data table, which is one possible measure of beta diversity, is correctly partitioned by canonical ordination; hence, canonical partitioning produces correct estimates of the different portions of community composition variation. In recent years, several authors interested in the variation in community composition among sites (beta diversity) have used another method, variation partitioning on distance matrices (Mantel approach). Their results led us to compare the two partitioning approaches, using simulated data generated under hypotheses about the variation of community composition among sites. The theoretical developments and simulation results led to the following observations: (1) the variance of a community composition table is a measure of beta diversity. (2) The variance of a dissimilarity matrix among sites is not the variance of the community composition table nor a measure of beta diversity; hence, partitioning on distance matrices should not be used to study the variation in community composition among sites. (3) In all of our simulations, partitioning on distance matrices underestimated the amount of variation in community composition explained by the raw-data approach, and (4) the tests of significance had less power than the tests of canonical ordination. Hence, the proper statistical procedure for partitioning the spatial variation of community composition data among environmental and spatial components, and for testing hypotheses about the origin and maintenance of variation in community composition among sites, is canonical partitioning. The Mantel approach is appropriate for testing other hypotheses, such as the variation in beta diversity among groups of sites. Regression on distance matrices is also appropriate for fitting models to similarity decay plots.
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Spiders (Arachnida, Araneae) in winter – differences in the appearance of species in small-scale spaces as a response to daily temperature fluctuations. Pitfall traps were positioned for the investigation of the spider fauna at the northern and southern slopes of three mountain ridges (Chilchberg, Riedberg, and Buechenberg, municipalities Nunningen and Zullwil, canton Solothurn, Switzerland) within the Swiss Jura Mountains. The temperature in the upper litter was measured at three hour intervals. Independent of the weather more or less clear differences between northern and southern slopes could be observed. Maximum day temperature fluctuations of 15.8 °C were measured. There were no significant differences in spider communities based on quantitative comparison methods. However, a qualitative analysis showed major differences in species composition. More than 50% of all species per investigation area showed clear preferences for the northern or the southern slope, with more then two thirds of the individuals only found on either the north or south slopes.
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We assess the national conservation status of the amphibians and reptiles of Morocco by applying the IUCN Red List Criteria at the national level and assess its utility as a planning tool to establish regional priorities for con-servation. We rely on the accessory data accompanying regional red lists, mainly distribution range and habitats used by, and threats affecting, species of conservation concern. We also correlated some natural history traits to examine the nature and causes of the risk of extinction. With 13 species of amphibians (31% regionally threatened) and 99 species of reptiles (14% regionally threatened), Morocco is one of the Mediterranean countries with the highest diversity of herpetofauna, mainly because of the high percentage of endemism (amphibians 31%, reptiles 24%). The relative frequencies of threatened species were found to be contingent on both taxonomic group and hab-itat. The overwhelming importance of the threats of small range and number of habitats used by species is different from the threats to the same species at the global level; this demonstrates the usefulness of national or regional anal-yses of conservation status for setting conservation prior-ities. The importance of regional assessment derives from the fact that the boundaries set for conservation manage-ment are mainly political rather than biogeographical.
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The study examined the influence of sown wildflower strips on ground beetles and spiders in Grosses Moos, a part of the Berner Seeland region of Western Switzerland and a former low moor that has recently changed to an intensively cultivated agricultural area. Three wildflower strips of differing ages sown in native wild and cultivated plant species were sampled by means of pitfall (funnel) traps from May to July 1999. Also, adjacent cereal crops at distances of 15 m (field edge) and 70 to 100 m (field centre) were investigated. More than 44,000 individual ground beetles and spiders in 123 species were recorded. One hundred and ten species were found in the wildflower strips, 85 in field edges and 82 in field centres. Activity densities of ground beetles and spiders were lowest in the wildflower strips. Many stenotopic grassland species occurred exclusively or primarily in the wildflower strips. The species communities of ground beetles and spiders in the field edges were influenced positively by the wildflower strips, and accordingly exhibited greater species diversity than the field centres. Wildflower strips provide suitable habitats for many ground beetles and spiders species; they consequently contribute to increase species diversity and enhance beneficial species in the locations studied.
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Introduction to the checklists of arachnids by the AraGes (Arachnida: Araneae, Opiliones, Pseudoscorpiones, Scorpiones, Palpigradi). Ed. Arachnologische Gesellschaft (AraGes). The Internet lists provide an opportunity for everyone to easily inform themselves about the current status of the checklists of Germany, Switzerland and Austria and to get an overview of the species occurring in surrounding countries.
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Despite concern about the effects of tropical forest disturbance and clearance on biodiversity,, data on impacts, particularly on invertebrates, remain scarce. Here we report a taxonomically diverse inventory on the impacts of tropical forest modification at one locality. We examined a gradient from near-primary, through old-growth secondary and plantation forests to complete clearance, for eight animal groups (birds, butterflies, flying beetles, canopy beetles, canopy ants, leaf-litter ants, termites and soil nematodes) in the Mbalmayo Forest Reserve, south-central Cameroon. Although species richness generally declined with increasing disturbance, no one group serves as a good indicator taxon for changes in the species richness of other groups. Species replacement from site to site (turnover) along the gradient also differs between taxonomic groups. The proportion of `morphospecies' that cannot be assigned to named species and the number of `scientist-hours' required to process samples both increase dramatically for smaller-bodied taxa. Data from these eight groups indicate the huge scale of the biological effort required to provide inventories of tropical diversity, and to measure the impacts of tropical forest modification and clearance.
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The sub-project “Effects of newly established extended field margins upon ground beetles and spiders” examined the influence of extended field margins (Säume) upon epigeal arthropods, especially ground beetles and spiders. Surveys were conducted in the Klettgau area in Schaffhausen canton, Switzerland, and in Litzibuch in Aargau canton. In each of the two areas, two extended field margins were examined, as well as two sown wildflower strips (Buntbrachen) and two permanent meadow strips (Wegrandstreifen) as reference elements. The selected bioindicators – ground beetles and spiders – and, as by-catch, bugs and cicadas were surveyed by means of pitfall traps. At the 12 sites, a total of 21’000 ground beetles in 93 species, 11’000 spiders in 100 species, 1’691 bugs in 44 species and 270 cicadas in 29 species were counted. Compared to the sown wildflower strips and permanent meadow strips, extended field margins had an intermediate position. The extended field margins were found to provide habitat for both characteristic fallow species and grassland specialists. They provide a valuable complement to sown wildflower strips and meadows. They thus contribute to increasing and preserving the species diversity of ground beetles, epigeal spiders, bugs and cicadas in farmed landscapes.
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Tropical landscapes are dominated by land-use systems, but their contribution to the conservation of biodiversity is largely unknown. Since changes in biodiversity in response to human impact are known to differ widely among taxonomic groups and guilds, there is a need for multidisciplinary collaboration of plant, vertebrate, and invertebrate experts. We used inventories of trees, understory plants, birds (subdivided into endemics, insectivores, frugivores/nectar feeders), butterflies (endemics, fruit feeders), and dung bee- tles in Sulawesi (Indonesia) to characterize a gradient from near-primary to secondary forests, agroforestry systems, and annual crops. As expected, overall species richness tended to decrease within this gradient of increasing habitat modification, but, in contrast to pre- vious studies, we found the species richness between most taxonomic groups to be signif- icantly correlated (36 out of 38 pairwise comparisons). However, on average only 48% of the variance could be explained (within the five main groups), and only a few taxonomic groups/guilds turned out to be good predictors for others: for example, trees for fruit- and nectar-feeding birds (88% explanation) and fruit-feeding butterflies (83%), endemic birds for endemic butterflies (72%), and frugivorous/nectar-feeding birds for fruit-feeding but- terflies (67%). Although biodiversity of land-use systems showed taxonomic group- and guild-specific differences, most groups were affected in a similar way by habitat modifi- cation. Near-primary forest sites proved to be of principal importance for conservation; however, land-use systems such as secondary forests (for understory plants, birds, and butterflies) and agroforestry systems (for butterflies) supported relatively high numbers of species and might play a significant role for biodiversity conservation in tropical landscapes.
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Agricultural intensification poses a serious threat to biodiversity as a consequence of increased land-use intensity, decreased landscape heterogeneity and reduced habitat diversity. Although there is interest in the preservation of total species richness of an agricultural landscape (gamma diversity), the effects of intensification have been assessed primarily by species richness at a local scale (alpha diversity). This ignores species richness between local communities (beta diversity), which is an important component of total species richness. In this study, measures of land-use intensity, landscape structure and habitat diversity were related to gamma, alpha and beta diversity of wild bees (Apoidea), carabid beetles (Carabidae), hoverflies (Syrphidae), true bugs (Heteroptera) and spiders (Araneae) within 16 local communities in 24 temperate European agricultural landscapes. The total landscape species richness of all groups was most strongly affected by increased proximity of semi-natural habitat patches. Bees also decreased in landscapes with a high intensity of farmland management, demonstrating additive effects of both factors. Separating total species diversity into components, the decrease in total species richness could be attributed primarily to a decrease in species diversity between local communities. Species richness of the local communities of all investigated groups decreased with increasing land-use intensity and, in the case of spiders, decreasing proximity of the semi-natural habitat patches. The effect of increased habitat diversity appeared to be of secondary importance to total species richness but caused a shift in the relative contribution of alpha and beta diversity towards the latter. Synthesis and applications. This study demonstrates that the effects of agricultural change operate at a landscape level and that examining species diversity at a local level fails to explain the total species richness of an agricultural landscape. The coincidence of patterns of beta diversity with those of gamma diversity emphasizes that such information is of crucial importance for the implementation and evaluation of restoration programmes aiming to restore sustainable countryside diversity. As local extinction processes in highly fragmented landscapes shape biodiversity, priority should be given to the conservation of diverse agricultural landscape remnants in Europe.
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Spiders from ecological compensation areas in the Swiss cantons Aargau and Schaffhausen (Arachnida: Araneae) – with remarks on Phrurolithus nigrinus (Corinnidae). The spider fauna of open habitats adjacent to arable land was investigated in northern Switzerland. The three habitat types were (1) herbaceous edges of fields (Sa), (2) fallow land sowed with flowers (BB), and (3) grass borders of fields (GS). Four funnel pitfall traps (10 cm diameter) were used to catch spiders in three stripe-types in two geographical regions in two years over 5 weeks in May and June: in total 12 sets of data. Spider species typical for open habitats were dominant, mostly lycosids (6 of the 10 most active species). The results were analysed together with environ-mental factors using a canonical correspondence analysis (CCA) and spiders were compared with carabid beetles (Coeloptera: Carabidae). Geographical region, though not very distant, had the largest influence on both spiders and carabids. The age and type of the habitats had a stronger influence on spiders than on carabids. In spiders a larger part of the total variance was explained by the analysed factors. Finally we discuss briefly a remarkable spider species. A review of all known records of Phrurolithus nigrinus in Switzerland and Germany, together with adjacent regions in France, is given. Its phenology is indicated, its habitat discussed and the overall distribution within Europe is listed. Die hier vorgestellten Daten wurden im Rahmen des Projektes "Wirkung neu angelegter Säume auf die Laufkäfer-und Spinnenfauna" vom FiBL (Forschungsinstitut für biologischen Landbau, CH-Frick) erhoben (JACOT & BOSSHARD 2005). In zwei Regionen in der Nordschweiz wurden jeweils zwei krautige Säume und als Vergleichselemente zwei 'Buntbrachen' (Brachstreifen mit Wildblu-meneinsaat) und zwei Wegrandstreifen (Grasstrei-fen am Feldrand) untersucht. Eine Auswertung der Daten, inkl. weiterer Tiergruppen, ist bereits publiziert, allerdings ohne Artentabellen (LUKA et al. 2006). Die vorliegende Arbeit dient im Wesentli-chen dazu, die Spinnendaten faunistisch zugänglich zu machen und dabei die Spinnengemeinschaften vorzustellen sowie einige Arten, insbesondere Phru-rolithus nigrinus, kurz zu diskutieren.
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Aims We examine the relationships between the distribution of British ground beetle species and climatic and altitude variables with a view to developing models for evaluating the impact of climate change. Location Data from 1684 10-km squares in Britain were used to model species–climate/altitude relationships. A validation data set was composed of data from 326 British 10-km squares not used in the model data set. Methods The relationships between incidence and climate and altitude variables for 137 ground beetle species were investigated using logistic regression. The models produced were subjected to a validation exercise using the Kappa statistic with a second data set of 30 species. Distribution patterns for four species were predicted for Britain using the regression equations generated. Results As many as 136 ground beetle species showed significant relationships with one or more of the altitude and climatic variables but the amount of variation explained by the models was generally poor. Models explaining 20% or more of the variation in species incidence were generated for only 10 species. Mean summer temperature and mean annual temperature were the best predictors for eight and six of these 10 species respectively. Few models based on altitude, annual precipitation and mean winter temperature were good predictors of ground beetle species distribution. The results of the validation exercise were mixed, with models for four species showing good or moderate fits whilst the remainder were poor. Main conclusions Whilst there were many significant relationships between British ground beetle species distributions and altitude and climatic variables, these variables did not appear to be good predictors of ground beetle species distribution. The poor model performance appears to be related to the coarse nature of the response and predictor data sets and the absence of key predictors from the models.
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A biological community usually has a large number of species with relatively small abundances. When a random sample of individuals is selected and each individual is classified according to species identity, some rare species may not be discovered. This paper is concerned with the estimation of Shannons index of diversity when the number of species and the species abundances are unknown. The traditional estimator that ignores the missing species underestimates when there is a non-negligible number of unseen species. We provide a different approach based on unequal probability sampling theory because species have different probabilities of being discovered in the sample. No parametric forms are assumed for the species abundances. The proposed estimation procedure combines the Horvitz–Thompson (1952) adjustment for missing species and the concept of sample coverage, which is used to properly estimate the relative abundances of species discovered in the sample. Simulation results show that the proposed estimator works well under various abundance models even when a relatively large fraction of the species is missing. Three real data sets, two from biology and the other one from numismatics, are given for illustration.
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The rapid decrease of biodiversity and limited resources for surveying it have forced researchers to devise short-cuts for biodiversity surveys and conservation planning. These short-cuts include environmental surrogates, higher taxon surrogates, indicator species and indicator groups. We considered indicator groups as surrogates for wholesale biodiversity and cross-taxon congruence in biodiversity patterns in littoral macroinvertebrates of boreal lakes. Despite the fact that we considered indicator groups amongst a wide variety of taxa, such as two-winged flies, mayflies, caddisflies, beetles, bugs and molluscs, none of the proposed groups possessed all of the qualities of a good indicator taxon for biodiversity surveys and conservation planning. We found generally weak, yet typically significant, relationships between the proposed indicator groups and remaining taxa in both species richness and assemblage similarity. Low congruence was paralleled by somewhat differing relationships of the taxonomic groups to various environmental features of lakes. Furthermore, the relationships of most indicator groups to the environmental features of lakes were not particularly strong. The present findings are unfortunate, because indicator groups did not perform well in predicting the wholesale biodiversity of littoral macroinvertebrates. Thus, there appears to be no short-cut for considering all groups of macroinvertebrates in biodiversity surveys, conservation planning and characterisation of environmental relationships of lake littoral assemblages.
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Long-term societal trends which include decreasing population in structurally poorer regions and changes in agricultural policies have been leading to land abandonment in various regions of Europe. One of the consequences of this development includes spontaneous forest regeneration of formerly open-land habitats with likely significant effects on plant and animal diversity. We assess potential effects of agricultural decline in Switzerland (41,000km2) and potential impacts on the spatial distribution of seven open-land species (insects, reptile, birds) under land-use change scenarios: (1) a business-as-usual scenario that extrapolates trends observed during the last 15years into the future, (2) a liberalisation scenario with limited regulation, and (3) a lowered agricultural production scenario fostering conservation. All scenarios were developed in collaboration with socio-economists. Results show that spontaneous reforestation is potentially minor in the lowlands since combinations of socio-economic (better accessibility), topographic (less steep slopes), and climatic factors (longer growing seasons) favour agricultural use and make land abandonment less likely. Land abandonment, spontaneous reforestation, and subsequent loss of open-land, however, are potentially pronounced in mountainous areas except where tourism is a major source of income. Here, socio-economic and natural conditions for cultivation are more difficult, leading to higher abandonment and thus reforestation likelihood. Evaluations for open-land species core habitats indicate pronounced spatial segregation of expected landscape change. Habitat losses (up to 59%) are observed throughout the country, particularly at high elevation sites in the Northern Alps. Habitat gains under the lowered agricultural production scenario range between 12 and 41% and are primarily observed for the Plateau and the Northern Alps.
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Ideally, an indicator for biodiversity is a linear correlate to the entity or aspect of biodiversity under evaluation. Different motivations for assessing entities or aspects of biodiversity lead to different value systems; their indicators may not correlate at all. For biodiversity evaluation in agricultural landscapes, three indices are proposed, each consisting of a basket of concordant indicators. They represent the three value systems “conservation” (protection and enhancement of rare and threatened species), “ecology” (ecological resilience, ecosystem functioning, based on species diversity), and “biological control” (diversity of antagonists of potential pest organisms). The quality and reliability of commonly used indicators could and should be tested with a three-step approach. First, the motivations and value systems and their corresponding biodiversity aspects or entities have to be defined. In a time consuming second step, a number of habitats have to be sampled as thoroughly as possible with regard to one or several of the three value systems or motivations. The third step is to test the linear correlations of a choice of easily measurable indicators with the entities quantified in the second step. Some examples of good and bad correlations are discussed.
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Pitfall traps were positioned for the investigation of the spider fauna at the northern and southern slopes of three mountain ridges (Chilchberg, Riedberg, and Buechenberg, municipalities Nunningen and Zullwil, canton Solothurn, Switzerland) within the Swiss Jura Mountains. The temperature in the upper litter was measured at three hour intervals. Independent of the weather more or less clear differences between northern and southern slopes could be observed. Maximum day temperature fluctuations of 15.8 °C were measured. There were no significant differences in spider communities based on quantitative comparison methods. However, a qualitative analysis showed major differences in species composition. More than 50% of all species per investigation area showed clear preferences for the northern or the southern slope, with more then two thirds of the individuals only found on either the north or south slopes.
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Spatially explicit forecasting of changes in species richness is key to designing informative scenarios on the development of diversity on our planet. It might be possible to predict changes in the richness of inadequately investigated groups from that of groups for which enough information is available. Here we evaluate the reliability of this approach by reviewing 237 richness correlations extracted from the recent literature. Of the 43 taxa covered, beetles, vascular plants, butterflies, birds, ants, and mammals (in that order) were the most common ones examined. Forests and grasslands strongly dominated the ecosystem types studied. The variance explanation (R2) could be calculated for 152 cases, but only 53 of these were significant. An average correlation effect size of 0.374 (95% CI = +/- 0.0678) indicates positive but weak correlations between taxa within the very heterogeneous data set. None of the examined explanatory variables (spatial scale, taxonomic distance, trophic position, biome) could account for this heterogeneity. However, studies focusing on 10-km2 grid cells had the highest variance explanation. Moreover, within-phylum between-class comparisons had marginally significantly lower correlations than between-phylum comparisons. And finally, the explanatory power of studies conducted in the tropics was significantly higher than that of studies conducted in temperate regions. It is concluded that the potential of a correlative approach to species richness is strongly diminished by the overall low level of variance explanation. So far, no taxon has proved to be a universal or even particularly good predictor for the richness of other taxa. Some suggestions for future research are inclusion of several taxa in models aiming at regional richness predictions, improvement of knowledge on species correlations in human dominated systems, and a better understanding of mechanisms underlying richness correlations.
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Resources for biodiversity surveys and conservation planning are limited, and conservation biologists and environmental managers are thus striving to find suitable surrogates for mapping and predicting biodiversity. Among popular surrogates are indicator groups that could be used for predicting variation in the biodiversity of other taxonomic groups. Despite some success at large scales, surveys of multiple taxonomic groups across ecosystems have suggested that no single group can be used effectively to predict variation in the biodiversity of other taxonomic groups. This paper concentrates on indicator groups and cross-taxon congruence in species richness and assemblage composition patterns in inland aquatic ecosystems. As has been found in studies of terrestrial ecosystems, there is low utility for indicator groups in predicting the biodiversity of other taxa in aquatic ecosystems. Even when statistically highly significant correlations between taxonomic groups have been detected, these correlations have been too weak to provide reliable predictions of biodiversity among various taxonomic groups or biodiversity in general. Indicator groups and, more generally, cross-taxon congruence thus do not appear to be particularly relevant for conservation in the freshwater realm.
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Aim A better understanding of the processes driving local species richness and of the scales at which they operate is crucial for conserving biodiversity in cultivated landscapes. Local species richness may be controlled by ecological processes acting at larger spatial scales. Very little is known about the effect of landscape variables on soil biota. The aim of our study was to partly fill this gap by relating the local variation of surface-dwelling macroarthropod species richness to factors operating at the habitat scale (i.e. land use and habitat characteristics) and the landscape scale (i.e. composition of the surrounding matrix).
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Summary1. Surrogate species measures of biodiversity (SSB) are used worldwide in conservation prioritisations. We address the important question whether the ideas behind SSB are consistent with current knowledge on distribution patterns of species, as reflected in theories of community assembly.2. We investigated whether assumptions necessary for successful functioning of SSB (nested species assemblages, cross-taxon congruence, spatio-temporal consistency) were supported by predictions from either niche or neutral community models.3. We found a general mismatch between ideas behind SSB and ecological community theory, except that SSB based on complementarity may be consistent with niche-based theory when gradients in species composition are strong.4.  Synthesis and applications. The lack of a necessary scientific foundation may explain the disappointing results of empirical tests of SSB. We argue that site selection should be based on costs and opportunities within complementary environmental/land units, rather than expensive inventories of unfounded surrogate species.
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The vast majority of species are animals that, unlike most plants and fungi, are variably and often highly mobile. While species’ mobility affects species’ probabilities of being sampled, effects of movement on the estimation of species richness have yet to be systematically investigated. Information-rich abundance-based estimators may be able to address variably mobile species but the accuracy of these estimators has also yet to be investigated. Here, we address both issues by variably sampling simulated landscapes with up to 250 species and evaluating the performance of ten non-parametric estimators and one species accumulation curve. Our results show that some abundance-based estimators are as accurate as better known and tested incidence-based estimators. Increased movement heterogeneity between the species reduced estimator performance by reducing the sample coverage, which systematically determined which estimator was most accurate. Based on these findings, we present the first decision framework for choosing the most accurate of many available abundance-based species-richness estimators. These decisions, based on data coverage, can significantly improve investigators’ ability to estimate faunal species richness.
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Entropies such as the Shannon–Wiener and Gini–Simpson indices are not themselves diversities. Conversion of these to effective number of species is the key to a unified and intuitive interpretation of diversity. Effective numbers of species derived from standard diversity indices share a common set of intuitive mathematical properties and behave as one would expect of a diversity, while raw indices do not. Contrary to Keylock, the lack of concavity of effective numbers of species is irrelevant as long as they are used as transformations of concave alpha, beta, and gamma entropies. The practical importance of this transformation is demonstrated by applying it to a popular community similarity measure based on raw diversity indices or entropies. The standard similarity measure based on untransformed indices is shown to give misleading results, but transforming the indices or entropies to effective numbers of species produces a stable, easily interpreted, sensitive general similarity measure. General overlap measures derived from this transformed similarity measure yield the Jaccard index, Sørensen index, Horn index of overlap, and the Morisita–Horn index as special cases.
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Current approaches in terrestrial biodiversity conservation focus predominantly on plants and vertebrates. While these groups account for less than 4% of the estimated global species richness, it is commonly argued that especially the species richness in higher plants is a suitable indicator of overall biodiversity. We tested this assumption, investigating species richness and equitability patterns in three highly species-rich insect families and their links with the vegetation and other environmental factors. Vegetation surveys were combined with pitfall and light trapping to establish the α-diversity of ground beetles, geometrid moths and arctiid moths on 48 plots at varying altitudes between Beijing and the Inner Mongolian Plateau. Soil pH and nutrient status were also recorded. The α-diversity patterns in the three insect families were non-congruent, and links with phytodiversity were weak. The spatial α-diversity patterns in each of the three insect families were significantly correlated with the species density of individual plant families. These links varied between the three insect taxa and were mostly negative in moths. Furthermore, geometrid moth diversity decreased with increasing elevation and decreasing soil pH. Strongly diverging α-diversity patterns across different insect taxa illustrate that it is impossible to find a simple surrogate representing cross-taxon diversity for these highly diverse groups. Furthermore, phytodiversity and vegetation composition appear to play a limited role in governing insect diversity patterns. These results underline the significant risk that current plant-focused approaches in terrestrial biodiversity conservation are inadequate in addressing the conservation needs of the vast majority of species on earth.
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1. Measuring biodiversity quantitatively is a key component to its investigation, but many methods are known to be biased by undersampling (i.e. incomplete inventories), a common situation in ecological field studies. 2. Following a long tradition of comparing measures of alpha diversity to judge their usefulness, we used simulated data to assess bias of nine diversity measures – some of them proposed fairly recently, such as estimating true species richness depending on the completeness of inventories (Brose, U. & Martinez, N.D. Oikos (2004) 105, 292), bias-corrected Shannon diversity (Chao, A. & Shen, T.-J. Environmental and Ecological Statistics (2003) 10, 429), while others are commonly applied (e.g. Shannon’s entropy, Fisher’s α) or long known but rarely used (estimating Shannon’s entropy from Fisher’s α). 3. We conclude that the ‘effective number of species’ based on bias-corrected Shannon’s entropy is an unbiased estimator of diversity at sample completeness c. >0·5, while below that it is still less biased than, e.g., estimated species richness (Brose, U. & Martinez, N.D. Oikos (2004) 105, 292). 4. Fisher’s α cannot be tested with the same rigour because it cannot measure the diversity of completely inventoried communities, and we present simulations illustrating this effect when sample completeness approaches high values. However, we can show that Fisher’s α produces relatively stable values at low sample completeness (an effect previously shown only in empirical data), and we tentatively conclude that it may still be considered a good (possibly superior) measure of diversity if completeness is very low.
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The choice of metrics comparing pristine and disturbed habitats may not be straightforward. We examined the results of a study in Gabon including 21 arthropod focal taxa representing 16 855 individuals separated into 1534 morphospecies. Replication included the understorey of 12 sites representing four stages of land use after logging (old and young forests, savanna and gardens), surveyed for 1 year using three sampling methods. 2. For all focal taxa, we calculated a suite of 13 metrics accounting for the intensity of faunal changes between habitats, namely: abundance; observed, rarefied and estimated species richness; proportion of rare species; additive diversity partitioning; evenness of assemblages; higher taxonomic composition; species turnover; ordination scores of multivariate analyses; nestedness; proportion of site-specific species and ratios of functional guilds. 3. Most metrics showed large differences between forests and non-forest habitats, but were not equally discriminating for particular taxa. Despite higher taxonomic groups being present in most habitats, many insect species were site or habitat specific. There was little evidence that the disturbance gradient represented a series of impoverished habitats derived from older forests. Rather, entire suites of species were being replaced as habitats were modified. 4. Metrics based on species identity had a high sensitivity to disturbance, whereas measurements describing community structure were less discriminating in this regard. We recommend using metrics based on abundance, estimated species richness, species turnover estimated by multivariate analyses and guild structure, to avoid misleading interpretations that may result from comparisons of species richness alone.
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A major focus of geographical ecology and macroecology is to understand the causes of spatially structured ecological patterns. However, achieving this understanding can be complicated when using multiple regression, because the relative importance of explanatory variables, as measured by regression coefficients, can shift depending on whether spatially explicit or non-spatial modeling is used. However, the extent to which coefficients may shift and why shifts occur are unclear. Here, we analyze the relationship between environmental predictors and the geographical distribution of species richness, body size, range size and abundance in 97 multi-factorial data sets. Our goal was to compare standardized partial regression coefficients of non-spatial ordinary least squares regressions (i.e. models fitted using ordinary least squares without taking autocorrelation into account; “OLS models” hereafter) and eight spatial methods to evaluate the frequency of coefficient shifts and identify characteristics of data that might predict when shifts are likely. We generated three metrics of coefficient shifts and eight characteristics of the data sets as predictors of shifts. Typical of ecological data, spatial autocorrelation in the residuals of OLS models was found in most data sets. The spatial models varied in the extent to which they minimized residual spatial autocorrelation. Patterns of coefficient shifts also varied among methods and datasets, although the magnitudes of shifts tended to be small in all cases. We were unable to identify strong predictors of shifts, including the levels of autocorrelation in either explanatory variables or model residuals. Thus, changes in coefficients between spatial and non-spatial methods depend on the method used and are largely idiosyncratic, making it difficult to predict when or why shifts occur. We conclude that the ecological importance of regression coefficients cannot be evaluated with confidence irrespective of whether spatially explicit modelling is used or not. Researchers may have little choice but to be more explicit about the uncertainty of models and more cautious in their interpretation.
Article
We examined six groups of taxa—woody plants, aquatic and terrestrial herpetofauna, small ter-restrial birds, orchids, and Orthoptera—to determine their efficiency as biodiversity indicators in the Dadia Reserve in northern Greece. We investigated the indicator value of each group by examining the degree of congruence of its species-richness pattern with that of the other groups and the efficiency of its complementary network in conserving the other groups and biodiversity. The two techniques differed in many respects in their outputs, but they both showed woody plants as the best biodiversity indicator. There was in general low congru-ence in the species richness patterns across the different groups. Significant relationships were found between woody plants and birds, Orthoptera and terrestrial herpetofauna, and birds and aquatic herpetofauna. None of the optimal complementary networks of the groups we examined protected all species of the other groups. Nevertheless, the complementary network of woody plants adequately conserved all groups except orchids. We conclude that the principle of complementarity must be integrated into the methodology of evaluating an indicator. In an applied context, our results provide a scientific background on which to base a biomon-itoring program for the Dadia Reserve. In a wider scope, if the group of woody plants prove an adequate biodiversity indicator for other Mediterranean areas as well, this will be important because it will facilitate conservation-related decisions for the entire Mediterranean region.
Article
Aim Earth observation (EO) products are a valuable alternative to spectral vegetation indices. We discuss the availability of EO products for analysing patterns in macroecology, particularly related to vegetation, on a range of spatial and temporal scales. Location Global. Methods We discuss four groups of EO products: land cover/cover change, vegetation structure and ecosystem productivity, fire detection, and digital elevation models. We address important practical issues arising from their use, such as assumptions underlying product generation, product accuracy and product transferability between spatial scales. We investigate the potential of EO products for analysing terrestrial ecosystems. Results Land cover, productivity and fire products are generated from long-term data using standardized algorithms to improve reliability in detecting change of land surfaces. Their global coverage renders them useful for macroecology. Their spatial resolution (e.g. GLOBCOVER vegetation, 300 m; MODIS vegetation and fire, ≥ 500 m; ASTER digital elevation, 30 m) can be a limiting factor. Canopy structure and productivity products are based on physical approaches and thus are independent of biome-specific calibrations. Active fire locations are provided in near-real time, while burnt area products show actual area burnt by fire. EO products can be assimilated into ecosystem models, and their validation information can be employed to calculate uncertainties during subsequent modelling. Main conclusions Owing to their global coverage and long-term continuity, EO end products can significantly advance the field of macroecology. EO products allow analyses of spatial biodiversity, seasonal dynamics of biomass and productivity, and consequences of disturbances on regional to global scales. Remaining drawbacks include inter-operability between products from different sensors and accuracy issues due to differences between assumptions and models underlying the generation of different EO products. Our review explains the nature of EO products and how they relate to particular ecological variables across scales to encourage their wider use in ecological applications.
Article
Aim The aim of this study was to analyse whether, and how, the inclusion of habitat specialists and edge-preferring species modifies the species–area relationship predictions of the island biogeography theory for an insect group (ground beetles, Coloptera: Carabidae) living in natural fragments. Species–habitat island area relationships applied to terrestrial habitat islands can be distorted by the indiscriminate inclusion of all species occurring in the fragments. Matrices surrounding terrestrial habitat fragments can provide colonists that do not necessarily distinguish the fragment from the matrix and can survive and reproduce there. Edge-preferring species can further distort the expected relationship, as smaller fragments have larger edge:core ratios.
Article
Aim We surveyed the empirical literature to determine how well six diversity hypotheses account for spatial patterns in species richness across varying scales of grain and extent. Location Worldwide. Methods We identified 393 analyses (‘cases’) in 297 publications meeting our criteria. These criteria included the requirement that more than one diversity hypothesis was tested for its relationship with species richness. We grouped variables representing the hypotheses into the following ‘correlate types’: climate/productivity, environmental heterogeneity, edaphics/nutrients, area, biotic interactions and dispersal/history (colonization limitation or other historical or evolutionary effect). For each case we determined the ‘primary’ variable: the one most strongly correlated with taxon richness. We defined ‘primacy’ as the proportion of cases in which each correlate type was represented by the primary variable, relative to the number of times it was studied. We tested for differences in both primacy and mean coefficient of determination of the primary variable between the hypotheses and between categories of five grouping variables: grain, extent, taxon (animal vs. plant), habitat medium (land vs. water) and insularity (insular vs. connected). Results Climate/productivity had the highest overall primacy, and environmental heterogeneity and dispersal/history had the lowest. Primacy of climate/productivity was much higher in large-grain and large-extent studies than at smaller scales. It was also higher on land than in water, and much higher in connected systems than in insular ones. For other hypotheses, differences were less pronounced. Throughout, studies on plants and animals showed similar patterns. Coefficients of determination of the primary variables differed little between hypotheses and across the grouping variables, the strongest effects being low means in the smallest grain class and for edaphics/nutrients variables, and a higher mean for water than for land in connected systems but vice versa in insular systems. We highlight areas of data deficiency. Main conclusions Our results support the notion that climate and productivity play an important role in determining species richness at large scales, particularly for non-insular, terrestrial habitats. At smaller extents and grain sizes, the primacy of the different types of correlates appears to differ little from null expectation. In our analysis, dispersal/history is rarely the best correlate of species richness, but this may reflect the difficulty of incorporating historical factors into regression models, and the collinearity between past and current climates. Our findings are consistent with the view that climate determines the capacity for species richness. However, its influence is less evident at smaller spatial scales, probably because (1) studies small in extent tend to sample little climatic range, and (2) at large grains some other influences on richness tend to vary mainly within the sampling unit.
Article
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.
Article
The term beta diversity has been used to refer to a wide variety of phenomena. Although all of these encompass some kind of compositional heterogeneity between places, many are not related to each other in any predictable way. The present two-part review aims to put the different phenomena that have been called a beta component of diversity into a common conceptual framework, and to explain what each of them measures. In this first part, the focus is on defining beta diversity. This involves deciding what diversity is and how the observed total or gamma diversity () is partitioned into alpha () and beta (β) components. Several different definitions of “beta diversity” that result from these decisions have been used in the ecological literature. True beta diversity is obtained when the total effective number of species in a dataset (true gamma diversity) is multiplicatively partitioned into the effective number of species per compositionally distinct virtual sampling unit (true alpha diversityd) and the effective number of such compositional units (βMd=/d). All true diversities quantify the effective number of types of entities. Because the other variants of “beta diversity” that have been used by ecologists quantify other phenomena, an alternative nomenclature is proposed here for the seven most popular beta components: regional-to-local diversity ratio, two-way diversity ratio, absolute effective species turnover (=regional diversity excess), Whittaker's effective species turnover, proportional effective species turnover, regional entropy excess and regional variance excess. In the second part of the review, the focus will be on how to quantify these phenomena in practice. This involves deciding how the sampling units that contribute to total diversity are selected, and whether the entity that is quantified is all of “beta diversity”, a specific part of “beta diversity”, the rate of change in “beta diversity” in relation to a given external factor, or something else.
Article
The present study evaluates indicators in Swedish spruce forests. We ask whether different species groups co-vary in their occurrence and to what extent species richness and composition is predictable from habitat structures. We studied 10 boreal spruce forest stands constituting a gradient in degree of selective logging. Occurrences of vascular plants, bryophytes, epiphytic lichens and wood-inhabiting fungi as well as habitat structures was inventoried. In addition, in five of the stands, beetles were sampled with windows traps. Total species richness was correlated with several habitat factors, mainly particular substrates and degree of forestry impact. However, the richness of a set of species regularly used as indicators did not correlate with habitat factors. Correlation in species richness among different organism groups were few and scale dependent. Only lichens and vascular plants formed nested subset patterns (i.e. species composition at poorer sites is subsets of the species present at richer sites) among the study sites. The study shows that in this forest type one cannot a priori assume that richness in one group of species correlated with richness in other, and measures of single habitat features may be relevant only to particular groups of species. Instead, monitoring and inventories should be based on a set of factors reflecting important aspects for different groups of organisms and if indicator species are to be used these should be chosen from several species groups.
Article
Generalized dissimilarity modelling (GDM) is a statistical technique for analysing and predicting spatial patterns of turnover in community composition (beta diversity) across large regions. The approach is an extension of matrix regression, designed specifically to accommodate two types of nonlinearity commonly encountered in large-scaled ecological data sets: (1) the curvilinear relationship between increasing ecological distance, and observed compositional dissimilarity, between sites; and (2) the variation in the rate of compositional turnover at different positions along environmental gradients. GDM can be further adapted to accommodate special types of biological and environmental data including, for example, information on phylogenetic relationships between species and information on barriers to dispersal between geographical locations. The approach can be applied to a wide range of assessment activities including visualization of spatial patterns in community composition, constrained environmental classification, distributional modelling of species or community types, survey gap analysis, conservation assessment, and climate-change impact assessment.
Article
In order to determine the significance of field margins for the overwintering of arthropods in agricultural landscapes, different sites of an integrated and of an organically managed farm were investigated in the northwest of Switzerland. During December 1995 and January 1996, soil samples were taken with an electronic-hydraulic soil borer (depth: 25 cm, diameter: 8 cm). After hand sorting the larger arthropods, the small ones were extracted with a modified MacFadyen apparatus.The abundance of arthropods in the arable fields was significantly lower than in the adjacent semi-natural habitats. Highest abundances and species diversities were found in a sown wildflower strip, a hedge, a permanent meadow and a meadow under the cherry trees of the organic farm. With a total of 90 arthropod species in the semi-natural habitats, five times more species were found than in the arable fields. Staphylinids, carabids, spiders and chilopods were the most abundant arthropod groups. The data showed that undisturbed semi-natural habitats and extensively managed field margins play a key role as overwintering sites for many predatory arthropods.
Article
We compared the effects of different low-input farming systems on carabids and spiders. The study was performed in a 3-year field survey using a paired-farm approach in six different landscapes units in northwestern Switzerland considering also the nearby semi-natural habitats. Carabids and spiders were sampled in 24 winter cereal crops and 18 semi-natural habitats using five funnel pitfall traps per site. Considering all cereal sites, in low-input ICM fields (= no insecticides, fungicides and growth regulators; ICM: Integrated crop management) 36% less carabids and 8% less spider specimens were found. In several cases, carabid populations of organic fields were significantly richer in species and abundance than in the low-input integrated crop management farmed plots. Endangered, stenoceous carabids (e.g. xero-thermophilous) and top-predators were more abundant in the organic fields. Spider communities differed less in mean number of species and abundance between the two low-input agricultural systems. Multivariate analysis showed that farming method and weed abundance were significant factors altering the carabid fauna and weed diversity influence spider fauna. Wolfspiders such as Pardosa agrestis, P. palustris and Trochosa ruricola seem to be enhanced by organic management. Linyphiids (Erigone atra, Oedothorax apicatus) were more abundant in low-input ICM fields. Several carabid species and wolfspiders which have their main distribution in semi-natural habitats occurred more abundant in organic fields. This indicates that seminatural habitats in combination with organic farming may be an important factor for the conservation and enhancement of the species rich assemblages on agricultural land.
Article
The natural complexity of ecological communities regularly lures ecologists to collect elaborate data sets in which confounding factors are often present. Although multiple regression is commonly used in such cases to test the individual effects of many explanatory variables on a continuous response, the inherent collinearity (multicollinearity) of confounded explanatory variables encumbers analyses and threatens their statistical and inferential interpretation. Using numerical simulations, I quantified the impact of multicollinearity on ecological multiple regression and found that even low levels of collinearity bias analyses (r greater than or equal to 0.28 or r(2) greater than or equal to 0.08), causing (1) inaccurate model parameterization, (2) decreased statistical power, and (3) exclusion of significant predictor variables during model creation. Then, using real ecological data, I demonstrated the utility of various statistical techniques for enhancing the reliability and interpretation of ecolo
Article
Information theoretic approaches and model averaging are increasing in popularity, but this approach can be difficult to apply to the realistic, complex models that typify many ecological and evolutionary analyses. This is especially true for those researchers without a formal background in information theory. Here, we highlight a number of practical obstacles to model averaging complex models. Although not meant to be an exhaustive review, we identify several important issues with tentative solutions where they exist (e.g. dealing with collinearity amongst predictors; how to compute model-averaged parameters) and highlight areas for future research where solutions are not clear (e.g. when to use random intercepts or slopes; which information criteria to use when random factors are involved). We also provide a worked example of a mixed model analysis of inbreeding depression in a wild population. By providing an overview of these issues, we hope that this approach will become more accessible to those investigating any process where multiple variables impact an evolutionary or ecological response.
Article
A review of potential indicators of biodiversity in British forests is presented, with a focus on the usefulness of selected biotic parameters as surrogate measures of different aspects of biodiversity in managed forests. To be effective in this respect, indicators must satisfy a number of criteria. They must be readily quantifiable, easily assessed in the field, repeatable and subject to minimal observer bias, cost effective, and ecologically meaningful (i.e. close association with, and identification of, the conditions and responses of other species). It is suggested that a combination of structural (physiognomy of stands and associated structures) and compositional indicators (indicator species or species groups) is selected which is appropriate to the aims of management and to the particular forest type in question. A useful approach is to identify two to three key compositional indicators, shown to be functionally linked to a broad range of other species, such as the extent and species composition of the broadleaved component in conifer forests; and two to three key structural indicators, which act as surrogates for general species richness or diversity, such as the quantity and quality of deadwood.
Article
A generic framework for setting conservation priorities based on the principles of classic decision theory is provided. This framework encapsulates the key elements of any problem, including the objective, the constraints, and knowledge of the system. Within the context of this framework the broad array of approaches for setting conservation priorities are reviewed. While some approaches prioritize assets or locations for conservation investment, it is concluded here that prioritization is incomplete without consideration of the conservation actions required to conserve the assets at particular locations. The challenges associated with prioritizing investments through time in the face of threats (and also spatially and temporally heterogeneous costs) can be aided by proper problem definition. Using the authors' general framework for setting conservation priorities, multiple criteria can be rationally integrated and where, how, and when to invest conservation resources can be scheduled. Trade-offs are unavoidable in priority setting when there are multiple considerations, and budgets are almost always finite. The authors discuss how trade-offs, risks, uncertainty, feedbacks, and learning can be explicitly evaluated within their generic framework for setting conservation priorities. Finally, they suggest ways that current priority-setting approaches may be improved.
Article
Searching for indicator taxa representative of diverse assemblages, such as arthropods, is an important objective of many conservation studies. We evaluated the impacts of a wide gradient of disturbance in Gabon on a range of arthropod assemblages representing different feeding guilds. We examined 4 × 105 arthropod individuals from which 21 focal taxa were separated into 1534 morphospecies. Replication included the understory of 3 sites in each of 4 different stages of forest succession and land use (i.e., habitats) after logging (old and young forests, savanna, and gardens). We used 3 complementary sampling methods to survey sites throughout the year. Overall differences in arthropod abundance and diversity were greatest between forest and open habitats, and cleared forest invaded by savanna had the lowest abundance and diversity. The magnitude of faunal differences was much smaller between old and young forests. When considered at this local scale, anthropogenic modification of habitats did not result in a monotonous decline of diversity because many herbivore pests and their associated predators and parasitoids were abundant and diverse in gardens, where plant productivity was kept artificially high year-round through watering and crop rotation. We used a variety of response variables to measure the strength of correlations across survey locations among focal taxa. These could be ranked as follows in terms of decreasing number of significant correlations: species turnover > abundance > observed species richness > estimated species richness > percentage of site-specific species. The number of significant correlations was generally low and apparently unrelated to taxonomy or guild structure. Our results emphasize the value of reporting species turnover in conservation studies, as opposed to simply measuring species richness, and that the search for indicator taxa is elusive in the tropics. One promising alternative might be to consider “predictor sets” of a small number of taxa representative of different functional groups, as identified in our study. Resumen: La búsqueda de taxa indicadores representativos de ensambles diversos, como lo artrópodos, es un objetivo importante de muchos estudios de conservación. Evaluamos los impactos de un gradiente de perturbación amplio en Gabón sobre ensambles de artrópodos representando gremios alimentarios diferentes. Examinamos 4 × 105 individuos de artrópodos de los cuales 21 taxa focales fueron separados en 1534 morfoespecies. La replicación incluyó el sotobosque de tres sitios en cada una de cuatro etapas diferentes de la sucesión de bosques y de uso de suelo (i.e., hábitats) después de ser talados (bosques jóvenes y maduros, sabana y jardines). Utilizamos tres métodos de muestreo complementarios para estudiar los sitios a lo largo del año. Las diferencias generales en la abundancia y diversidad de artrópodos fueron mayores entre bosques y hábitats abiertos, y el bosque talado invadido por sabana tuvo la menor abundancia y diversidad. La magnitud de las diferencias fue mucho más pequeña entre los bosques maduros y viejos. Al considerarla en esta escala local, la modificación antropogénica de hábitats no resultó en una declinación monótona de la diversidad porque muchas plagas de herbívoros y sus depredadores y parasitoides asociados fueron abundantes y diversas en los jardines, donde la productividad de plantas fue mantenida artificialmente a lo largo del año mediante riego y rotación de cultivos. Utilizamos una variedad de variables de respuesta para medir la robustez de las correlaciones en los sitios de muestreo entre taxa focales. Estos pudieron ser clasificados, en términos del número decreciente de correlaciones significativas, como sigue: renovación de especies > abundancia > riqueza de especies observada > riqueza de especies estimada > porcentaje de especies específicas de sitios. El número de correlaciones significativas generalmente fue bajo y aparentemente sin relación con la taxonomía ni la estructura del gremio. Nuestros resultados enfatizan el valor de reportar la renovación de especies en los estudios de conservación, en lugar de simplemente medir la riqueza de especies, y que la búsqueda de taxa indicadores es elusiva en los trópicos. Una alternativa prometedora pudiera ser la consideración de “conjuntos pronosticadores” de números pequeños de taxa representativos de grupos funcionales diferentes, como los identificados en nuestro estudio.
Article
Conservationists are far from able to assist all species under threat, if only for lack of funding. This places a premium on priorities: how can we support the most species at the least cost? One way is to identify 'biodiversity hotspots' where exceptional concentrations of endemic species are undergoing exceptional loss of habitat. As many as 44% of all species of vascular plants and 35% of all species in four vertebrate groups are confined to 25 hotspots comprising only 1.4% of the land surface of the Earth. This opens the way for a 'silver bullet' strategy on the part of conservation planners, focusing on these hotspots in proportion to their share of the world's species at risk.
Article
Predictions of plant and animal species distributions are important for conservation and for the assessment of large-scale ecosystem change. Land cover data are becoming more widely available for use in land management and conservation. We use a logistic regression modelling approach to investigate the utility of these data for modelling. The relationship between the distribution of 137 British ground beetles species and land cover was investigated using data from 1,687 10 km national grid squares. Land cover data were simplified using ordination and the axes used as predictors in logistic regression with presence absence data for individual beetle species as response variables. Significant regression models were generated for all species with first and second axis scores. The amounts of variation explained by models were generally low, but predictions derived from models generally matched the known distributions of the species in Britain. Species with coastal preferences were poorly modelled and predicted to occur throughout lowland Britain whilst a number of species occurring in southern Britain were predicted to occur into Scotland. A validation exercise comparing model predictions with new data from a survey of 59 10 km(2) produced mixed results with the distribution of grassland species being better predicted than riverine species. Jack-knifing was used to assess the robustness of models for four species which differed in their apparent responses to the land cover variables. Methods for improving the predictive power of these models and their potential for use in assessing the impact of global climate change are discussed.