Spatial Variation In Biodiversity Research Articles

Processes regulating local community assembly of plants and spiders in high latitude mountains

AbstractAimMountains are often used to study how environmental factors influence biodiversity. However, we have limited understanding of the processes causing biodiversity variation in mountains and whether such processes vary across trophic levels and spatial scales. The aim of this study was to evaluate (i) whether community assembly processes varied along elevational gradients, (ii) whether there were differences in such variation between primary producers (vascular plants) and secondary consumers (spiders) and (iii) whether there were scale dependencies in any elevational variation in community assembly.LocationFennoscandia, Northern Sweden.TaxonVascular plants, spiders.MethodsWe used phenotypic and phylogenetic dispersion to quantify how elevation influenced community assembly of vascular plants and spiders and whether there were any scale dependencies in such influences. Our original data of plant and spider communities came from our own field surveys, phenotypic dispersion was calculated based on matrices of ecological traits, and phylogenetic dispersion was calculated from phylogenetic trees for each organism group. Trait matrices were based on a combination of literature values and our own measurements. The phylogeny for vascular plants was based on a published plant super‐tree, whereas the phylogeny for spiders was created by ourselves based on the DNA sequences at the mitochondrial cytochrome c oxidase subunit 1 (COI).ResultsPlants were environmentally filtered throughout all elevations and scales, but the importance of convergent evolution increased with elevation. For spiders, the importance of environmental filtering as well as niche conservatism increased with elevation. For both groups, communities at smaller scales were more influenced by biotic regulation and niche conservatism than at larger scales.Main ConclusionsOur study highlights both taxonomic differences and scale dependencies in how elevation influences community assembly. We argue that these results can have broad ramifications for our understanding of how spatial variation in biodiversity is generated and maintained. This may have particular relevance for our ability to predict the ecological consequences of climate change. Our results further highlight that high elevation specialists may suffer increased risks of climate driven extinctions due to a combination of increased competition and increased fragmentation of suitable habitats. Particularly for spiders, which had high elevation specialists clustered along specific lineages, such extinctions could lead to significant loss of phylogenetic variation.

Wetland biodiversity in Aotearoa New Zealand: an eDNA perspective on exotic and non-exotic species

ABSTRACT Invasive species threaten biodiversity in Aotearoa New Zealand. In wetlands − significant sites that provide an array of ecosystem and cultural services but represent <10% of their original extent − invasive species can affect hydrological function, nutrient regimes and overall ecological functionality. Environmental DNA (eDNA) has emerged as a valuable biomonitoring technique for cataloguing biodiversity and detecting biological incursions, but little is known about how biodiversity varies in wetlands over fine and broad spatial scales. Here, we examined the publicly available eDNA database of Wilderlab New Zealand, retrieving data from 26 sites across the country to characterise taxonomic diversity patterns, including the extent of exotic and non-exotic (native and endemic) species. We found significant spatial variation in biodiversity – even among neighbouring sites – and a pattern whereby all sites had ≥50% exotic species in their total species tally. Our results provide new information on the current state of wetland biodiversity in Aotearoa New Zealand and highlight the value of eDNA databases for generating new insights from publicly shared data. They also emphasise an urgent need for greater resource allocation to conservation and restoration initiatives in Aotearoa New Zealand that will ensure the persistence of treasured native and endemic wetland species.

Patterns and drivers of phylogenetic diversity of seed plants along an elevational gradient in the central Himalayas

The how and why of the spatial variation in biodiversity is one of the fundamental topics in biogeography research, but accurate insights require the incorporation of phylogenetic information. Here, to provide a better understanding of the origin and mechanism of biodiversity in montane ecosystems and thus support conservation planning, we explored the elevational patterns of phylogenetic diversity and structure of seed plants in the Gyirong Valley, the longest valley in China’s central Himalayas. The observed patterns were related to climatic, historical, geographical, and disturbance-related factors, and the relative contributions of these factors in explaining them were assessed. Our results showed that phylogenetic diversity of seed plants in the central Himalayas were described by a strongly hump-shaped pattern, peaking at 2700 m around. The phylogenetic structure of the plants was characterized by overdispersion at lower elevations and clustering at higher elevations, reflecting the cooperation between interspecies competition and environmental filtering in community assembly. Among the examined environmental factors, climatic factors showed the highest explanatory power, suggesting environmental filtering was largely driven by climatic rather than other factors. In summary, our finding indicating that mild climate at lower elevations presumably encourage phylogenetic differentiation by promoting interspecies competition, whereas increasingly harsh climatic condition with elevation may lead to closer phylogenetic relatedness through environmental filtering. Overall, our findings improve our knowledge about the elevational gradient of biodiversity in the Himalayas, and highlight the need for intensified conservation efforts at middle elevations as well as greater scientific concern regarding the impact of climate change on the biodiversity.

High compositional dissimilarity among small communities is decoupled from environmental variation

Communities composed of small populations are predicted to be strongly influenced by stochastic demographic events and, thus, less affected by environmental selection than those composed of large populations. However, this prediction has only been tested with computer simulations, simplified controlled experiments, and limited observational data. Here, using multiple datasets on fish abundance in 541 streams we tested 1) if communities composed of small populations are more spatially variable and 2) less related to the environment variation than communities composed of large populations. We used process‐based simulations to identify β‐diversity metrics and community–environment measures that were appropriate to investigate the role of assembly processes along a gradient of community size. We show that variation in species composition among small communities is higher than among large communities and that the strength of community–environment relationships is weaker in small communities. Our results indicate that community size affects the strength of ecological drift and environmental selection in metacommunities. We thus suggest that further declines in the size of populations and ecosystems can make spatial variation in biodiversity more unpredictable.

Global beta-diversity of angiosperm trees is shaped by Quaternary climate change.

As Earth's climate has varied strongly through geological time, studying the impacts of past climate change on biodiversity helps to understand the risks from future climate change. However, it remains unclear how paleoclimate shapes spatial variation in biodiversity. Here, we assessed the influence of Quaternary climate change on spatial dissimilarity in taxonomic, phylogenetic, and functional composition among neighboring 200-kilometer cells (beta-diversity) for angiosperm trees worldwide. We found that larger glacial-interglacial temperature change was strongly associated with lower spatial turnover (species replacements) and higher nestedness (richness changes) components of beta-diversity across all three biodiversity facets. Moreover, phylogenetic and functional turnover was lower and nestedness higher than random expectations based on taxonomic beta-diversity in regions that experienced large temperature change, reflecting phylogenetically and functionally selective processes in species replacement, extinction, and colonization during glacial-interglacial oscillations. Our results suggest that future human-driven climate change could cause local homogenization and reduction in taxonomic, phylogenetic, and functional diversity of angiosperm trees worldwide.

Biodiversity transformations in the global ocean: A climate change and conservation management perspective.

Understanding the biological diversity of different communities and evaluating the risks to biological sustainability in a time of rapid environmental change is a key challenge for providing an adapting management approach for biodiversity transformations in the ocean linked to human well-being. (Photo credit: Andrea Belgrano).

Temperature drives local contributions to beta diversity in mountain streams: Stochastic and deterministic processes

AbstractAimCommunity variation (i.e. beta diversity) along geographical gradients is of substantial interest in ecology and biodiversity reserves in the face of global changes. However, the generality in beta diversity patterns and underlying processes remains less studied across trophic levels and geographical regions. We documented beta diversity patterns and underlying ecological processes of stream bacteria, diatoms and macroinvertebrates along six elevational gradients.LocationsAsia and Europe.MethodsWe examined stream communities using molecular and morphological methods. We characterised community uniqueness with local contributions to beta diversity (LCBD), and investigated the drivers of its geographic patterns using Mid‐Domain Effect (MDE), coenocline simulation, Raup‐Crick null model approach, and through comparisons to environmental factors. MDE is a stochastic model by considering species elevational range, while coenocline simulation is a deterministic model by considering species niche optima and tolerance. The null model provides possible underlying mechanisms of community assembly with the degree to which deterministic processes create communities deviating from those of null expectations.ResultsAcross all taxa, we revealed a general U‐shaped LCBD‐elevation relationship, suggesting higher uniqueness of community composition at both elevational ends. This pattern was confirmed and could be explained by both stochastic and deterministic models, that is, MDE and coenocline simulation, respectively, and was supported by the dominance of species replacement. Temperature was the main environmental factor underlying elevational patterns in LCBD. The generalists with broad niche breadths were key in maintaining community uniqueness, and the higher relative importance of deterministic processes resulted in stronger U‐shaped patterns regardless of taxonomic group.ConclusionsOur synthesis across both mountains and taxonomic groups clearly shows that there are consistent elevational patterns in LCBD among taxonomic groups, and that these patterns are explained by similar ecological mechanisms, producing a more complete picture for understanding and bridging the spatial variation in biodiversity under changing climate.

A systematic survey of regional multi-taxon biodiversity: evaluating strategies and coverage

BackgroundIn light of the biodiversity crisis and our limited ability to explain variation in biodiversity, tools to quantify spatial and temporal variation in biodiversity and its underlying drivers are critically needed. Inspired by the recently published ecospace framework, we developed and tested a sampling design for environmental and biotic mapping. We selected 130 study sites (40 × 40 m) across Denmark using stratified random sampling along the major environmental gradients underlying biotic variation. Using standardized methods, we collected site species data on vascular plants, bryophytes, macrofungi, lichens, gastropods and arthropods. To evaluate sampling efficiency, we calculated regional coverage (relative to the known species number per taxonomic group), and site scale coverage (i.e., sample completeness per taxonomic group at each site). To extend taxonomic coverage to organisms that are difficult to sample by classical inventories (e.g., nematodes and non-fruiting fungi), we collected soil for metabarcoding. Finally, to assess site conditions, we mapped abiotic conditions, biotic resources and habitat continuity.ResultsDespite the 130 study sites only covering a minute fraction (0.0005%) of the total Danish terrestrial area, we found 1774 species of macrofungi (54% of the Danish fungal species pool), 663 vascular plant species (42%), 254 bryophyte species (41%) and 200 lichen species (19%). For arthropods, we observed 330 spider species (58%), 123 carabid beetle species (37%) and 99 hoverfly species (33%). Overall, sample coverage was remarkably high across taxonomic groups and sufficient to capture substantial spatial variation in biodiversity across Denmark. This inventory is nationally unprecedented in detail and resulted in the discovery of 143 species with no previous record for Denmark. Comparison between plant OTUs detected in soil DNA and observed plant species confirmed the usefulness of carefully curated environmental DNA-data. Correlations among species richness for taxonomic groups were predominantly positive, but did not correlate well among all taxa suggesting differential and complex biotic responses to environmental variation.ConclusionsWe successfully and adequately sampled a wide range of diverse taxa along key environmental gradients across Denmark using an approach that includes multi-taxon biodiversity assessment and ecospace mapping. Our approach is applicable to assessments of biodiversity in other regions and biomes where species are structured along environmental gradient.

Using GIS-linked Bayesian Belief Networks as a tool for modelling urban biodiversity

The ability to predict spatial variation in biodiversity is a long-standing but elusive objective of landscape ecology. It depends on a detailed understanding of relationships between landscape and patch structure and taxonomic richness, and accurate spatial modelling. Complex heterogeneous environments such as cities pose particular challenges, as well as heightened relevance, given the increasing rate of urbanisation globally. Here we use a GIS-linked Bayesian Belief Network approach to test whether landscape and patch structural characteristics (including vegetation height, green-space patch size and their connectivity) drive measured taxonomic richness of numerous invertebrate, plant, and avian groups. We find that modelled richness is typically higher in larger and better-connected green-spaces with taller vegetation, indicative of more complex vegetation structure and consistent with the principle of ‘bigger, better, and more joined up’. Assessing the relative importance of these variables indicates that vegetation height is the most influential in determining richness for a majority of taxa. There is variation, however, between taxonomic groups in the relationships between richness and landscape structural characteristics, and the sensitivity of these relationships to particular predictors. Consequently, despite some broad commonalities, there will be trade-offs between different taxonomic groups when designing urban landscapes to maximise biodiversity. This research demonstrates the feasibility of using a GIS-coupled Bayesian Belief Network approach to model biodiversity at fine spatial scales in complex landscapes where current data and appropriate modelling approaches are lacking, and our findings have important implications for ecologists, conservationists and planners.

The same but different: equally megadiverse but taxonomically variant spider communities along an elevational gradient

Spatial variation in biodiversity is one of the key pieces of information for the delimitation and prioritisation of protected areas. This information is especially important when the protected area includes different climatic and habitat conditions and communities, such as those along elevational gradients. Here we test whether the megadiverse communities of spiders along an elevational gradient change according to two diversity models – a monotonic decrease or a hump-shaped pattern in species richness. We also measure compositional variation along and within elevations, and test the role of the preference of microhabitat (vegetation strata) and the functional (guild) structure of species in the changes. We sampled multiple spider communities using standardised and optimised sampling in three forest types, each at a different elevation along a climatic gradient. The elevational transects were at increasing horizontal distances (between 0.1 and 175 km) in the Udzungwa Mountains, Eastern Arc Mountains, Tanzania. The number of species was similar between plots and forest types, and therefore the pattern did not match either diversity model. However, species composition changed significantly with a gradual change along elevations. Although the number of species per microhabitat and guild also remained similar across elevations, the number of individuals varied, e.g. at higher elevations low canopy vegetation was inhabited by more spiders, and the spiders belonging to guilds that typically use this microhabitat were more abundant. Our findings reflex the complex effects of habitat-microhabitat interactions on spider communities at the individual, species and guild levels. If we aim to understand and conserve some of the most diverse communities in the world, researchers and managers may need to place more attention to small scale and microhabitat characteristics upon which communities depend.

Microphytobenthos as an indicator of environmental quality status in intertidal flats: Case study of coastal ecosystem in Pertuis Charentais, France

Microphytobenthos communities of different sediment types were investigated in intertidal flats of the coastal area around La Rochelle (Pertuis Charentais, France) in July 2014 and January 2015. Biotic variables of biomass, abundance and species composition of microphytobenthos were evaluated together with environmental variables, including irradiance, sediment temperature, grains size, pore water salinity, pH, nutrients, organic matter, water content and heavy metal concentrations in the sediment. The relationships between biotic and environmental parameters showed that: (1) the microphytobenthos biomass and community structures showed significant differences among different sediment types; (2) variation in the microphytobenthos communities were significantly correlated with environmental variables, especially with the heavy metals, grain size, irradiance, pore water salinity, organic matter and concentration of PO43+ and Si(OH)4; (3) the species number and richness were both significantly correlated with organic matter, and (4) the species Entomoneis corrugate, Navicula aitchelbee and Gyrosigma cf.limosum were positively correlated to heavy metals, and so were N. phylleptosoma, Surirella brebissonii to Si(OH)4 and NH4+ concentrations, and G. acuminatum and S. brebissonii to PO43+ and NH4+. It is suggested that the spatial variation in biodiversity of microphytobenthos may reflect environmental quality status in coastal intertidal ecosystems.

基于综合指数法的白龙江流域生物多样性空间分异特征研究

基于综合指数法的白龙江流域生物多样性空间分异特征研究

Historical Biogeography Using Species Geographical Ranges.

Spatial variation in biodiversity is the result of complex interactions between evolutionary history and ecological factors. Methods in historical biogeography combine phylogenetic information with current species locations to infer the evolutionary history of a clade through space and time. A major limitation of most methods for historical biogeographic inference is the requirement of single locations for terminal lineages, reducing contemporary species geographical ranges to a point in two-dimensional space. In reality, geographic ranges usually show complex geographic patterns, irregular shapes, or discontinuities. In this article, we describe a method for phylogeographic analysis using polygonal species geographic ranges of arbitrary complexity. By integrating the geographic diversification process across species ranges, we provide a method to infer the geographic location of ancestors in a Bayesian framework. By modeling migration conditioned on a phylogenetic tree, this approach permits reconstructing the geographic location of ancestors through time. We apply this new method to the diversification of two neotropical bird genera, Trumpeters (Psophia) and Cinclodes ovenbirds. We demonstrate the usefulness of our method (called rase) in phylogeographic reconstruction of species ancestral locations and contrast our results with previous methods that compel researchers to reduce the distribution of species to one point in space. We discuss model extensions to enable a more general, spatially explicit framework for historical biogeographic analysis.

Do riparian reserves support dung beetle biodiversity and ecosystem services in oil palm-dominated tropical landscapes?

Agricultural expansion and intensification are major threats to global biodiversity, ecological functions, and ecosystem services. The rapid expansion of oil palm in forested tropical landscapes is of particular concern given their high biodiversity. Identifying management approaches that maintain native species and associated ecological processes within oil palm plantations is therefore a priority. Riparian reserves are strips of forest retained alongside rivers in cultivated areas, primarily for their positive hydrological impact. However, they can also support a range of forest-dependent species or ecosystem services. We surveyed communities of dung beetles and measured dung removal activity in an oil palm-dominated landscape in Sabah, Malaysian Borneo. The species richness, diversity, and functional group richness of dung beetles in riparian reserves were significantly higher than in oil palm, but lower than in adjacent logged forests. The community composition of the riparian reserves was more similar to logged forest than oil palm. Despite the pronounced differences in biodiversity, we did not find significant differences in dung removal rates among land uses. We also found no evidence that riparian reserves enhance dung removal rates within surrounding oil palm. These results contrast previous studies showing positive relationships between dung beetle species richness and dung removal in tropical forests. We found weak but significant positive relationships between riparian reserve width and dung beetle diversity, and between reserve vegetation complexity and dung beetle abundance, suggesting that these features may increase the conservation value of riparian reserves. Synthesis and applications: The similarity between riparian reserves and logged forest demonstrates that retaining riparian reserves increases biodiversity within oil palm landscapes. However, the lack of correlation between dung beetle community characteristics and dung removal highlights the need for further research into spatial variation in biodiversity–ecosystem function relationships and how the results of such studies are affected by methodological choices.

Effectiveness of habitat classes as surrogates for biodiversity in marine reserve planning

AbstractSurrogates are used in marine conservation planning when there is limited information on the distribution of biodiversity, and representation of species and assemblage diversity are conservation goals. With prior confirmation of their relationship to spatial variation in biodiversity, habitat classification schemes are a potentially useful surrogate.Polychaetes can comprise over one‐third of species of benthic infaunal assemblages, they are the most frequent and abundant marine metazoans in benthic environments, and they are a reliable surrogate for other macrobenthic taxa.It was tested whether polychaete biodiversity differed among six estuarine habitat classes defined for conservation planning in the Port Stephens–Great Lakes Marine Park, New South Wales, Australia: subtidal sand, mud, muddy sand, and seagrass beds comprisingPosidonia australis,Zostera capricorniand mixedPosidonia/Zostera. Polychaetes were sampled from replicate sites in each habitat and differences among habitat classes in species richness, abundance, and assemblage structure were examined. Several environmental variables, known to be important determinants of polychaete distribution, were also quantified at each site.Ninety‐five species of polychaetes (belonging to 35 families) were identified. Species richness and abundance did not differ among the habitat classes. Polychaete assemblages of subtidal sand differed from assemblages in both mud and muddy sand, however, assemblages in all other habitats were not different. A combination of some of the measured environmental variables (distance to the estuary entrance, depth, sediment grain size) was a more important determinant of assemblage variation than the habitat classes.Using these predictors, an alternative habitat classification scheme to the scheme currently utilized in marine park planning is proposed.This study demonstrates the critical importance of testing assumptions about surrogacy and an approach for refining surrogates.Copyright © 2013 John Wiley &amp; Sons, Ltd.

中国大陆鸟类和兽类物种多样性的空间变异

Macroecology is concerned with changes in biodiversity as well as the causes of these changes on large scales.Biodiversity can show changes over time and over space.Species diversity,as the determinant of biodiversity,shows spatial heterogeneity. China has high biodiversity.An increasing number of scientists are interested in the large-scale spatial variation in biodiversity within China.The natural environments in China have clear boundaries,which have influence the distributions of animals and ecosystems.According to climate type,China can be divided into three natural regions: the eastern monsoon region,the northwest arid region and the Qinghai-Tibetan Plateau region.Study of the spatial pattern of the biodiversity found in China may contribute to the understanding of large-scale patterns in biodiversity. The fauna information database(FID),founded by the Wildlife and Behavioral Ecology Research Group,Institute of Zoology,Chinese Academy of Sciences,contains information on the distribution of amphibians,reptiles,birds and mammals in China.The FID was compiled with data on species checklists of amphibians,reptiles,birds and mammals from 205 nature reserves across mainland China.They covered most parts of the country except Jiangsu Province,Taiwan,Hong Kong and Macau. In this study,we explored the spatial variation in the G-F indices of birds and mammals with geostatistical techniques.As a measure of species diversity,we computed the G-F index using data on birds and mammals in the FID.The G-F index,based on the Shannon-Wiener index,provides a standardized measure of the diversity of species of common origin and similar environmental requirements.We treated the G-F index as a regional variable and obtained semivariance models and parameters of birds and mammals individually for each of the three natural regions.Semivariograms were produced using semivariance analysis methods of GS-plus software.Using the semivariograms and model parameters,we analyzed the characteristics of the spatial variation in bird and mammal diversity in each natural region. The semivariance of the G-F index of birds was fitted with a linear model in the eastern monsoon region and the northwest arid region of China.The parameters demonstrated that species diversity of birds had a weak spatial dependence in the eastern monsoon region and the northwest arid region of China.There was no spatial correlation with pure nugget effects on the Qinghai-Tibetan Plateau,indicating that the spatial variation in bird species diversity was caused by random factors.This may be due to the high dispersal abilities of birds. The semivariance of the G-F index of mammals showed no relationship in the eastern monsoon region and had pure nugget effects in the northwest arid region.However,data of the Qinghai-Tibetan Plateau was best explained by a spherical model.The parameters revealed that spatial pattern of mammalian species diversity was random in the eastern monsoon region and in the northwest arid region but had a strong spatial dependence with a correlation spatial range of 71492—1020000 m on the Qinghai-Tibetan Plateau.This spatial pattern of avian and mammalian species diversity is likely attributable to the interaction between the particular physical environment and life history of birds and mammals.The macroscale spatial pattern of species diversity should be taken into account in the formation of conservation action plans.

Elevational gradients in phylogenetic structure of ant communities reveal the interplay of biotic and abiotic constraints on diversity

A central focus of ecology and biogeography is to determine the factors that govern spatial variation in biodiversity. Here, we examined patterns of ant diversity along climatic gradients in three temperate montane systems: Great Smoky Mountains National Park (USA), Chiricahua Mountains (USA), and Vorarlberg (Austria). To identify the factors which potentially shape these elevational diversity gradients, we analyzed patterns of community phylogenetic structure (i.e. the evolutionary relationships among species coexisting in local communities). We found that species at low-elevation sites tended to be evenly dispersed across phylogeny, suggesting that these communities are structured by interspecific competition. In contrast, species occurring at high-elevation sites tended to be more closely related than expected by chance, implying that these communities are structured primarily by environmental filtering caused by low temperatures. Taken together, the results of our study highlight the potential role of niche constraints, environmental temperature, and competition in shaping broad-scale diversity gradients. We conclude that phylogenetic structure indeed accounts for some variation in species density, yet it does not entirely explain why temperature and species density are correlated.

Spatial variation in biodiversity and trophic structure of soil nematode communities in a subtropical savanna parkland: Responses to woody plant encroachment

Woody plant encroachment into grasslands generally increases spatial heterogeneity of soil properties and processes and creates “islands of fertility” beneath woody canopies. However, little is known regarding the potential for these changes to influence spatial variation in soil fauna. We quantified population sizes, biodiversity, and trophic structure of soil nematode communities in a savanna parkland where woody plant clusters developed in grassland during the past century. Total nematode density was constant across transects from centers of woody clusters into grasslands. Family richness and Simpson's Dominance Index indicated nematode communities in grasslands and grassland/cluster edges were significantly more diverse than positions within the woody clusters. Relative densities of all nematode trophic groups changed significantly along the transect. Bacterivores nearly doubled in relative density from grassland (35%) to cluster centers (60%), apparently in response to higher concentrations of soil microbial biomass in wooded areas. Relative densities of plant parasitic nematodes decreased along transects from grasslands (35%) to centers of woody clusters (10%), implying decreased nematode herbivory in woody clusters despite much higher root biomass there. The structure index indicated nematode communities within woody clusters were more simplified than those in grassland and edge communities due to reductions in densities of omnivores and predators. Although nematode densities were lower at 10–20 than 0–10 cm, nematode community characteristics were generally similar between soil depths. Changes in nematode community and trophic structure described here could influence biogeochemical processes, species interactions, and successional processes in regions where woody plants are encroaching into grasslands.

Links between the Environment, Abundance and Diversity of Andean Moths

Ideas on the spatial variation of biodiversity often imply a causal link between the abundance and species richness of organisms. We investigated this ‘more individuals hypothesis’ using light-trapping data of three unrelated groups of moths (Arctiidae, Geometridae and Pyraloidea) from the Ecuadorian Andes. We analyzed environmental correlates of specimen densities found in different habitats, finding effects of temperature, moonlight, forest succession, elevation and season. We corrected abundance data for light-trapping artefacts, and we measured species diversity with various metrics known to be unbiased by undersampling. We found significant positive correlations between abundance and species diversity for all three taxonomic groups. We discuss implications for a general evaluation of species-energy theory as well as for a better understanding of ecological processes in montane habitats of the Andes.

Spatial variation in biodiversity, soil degradation and productivity in agricultural landscapes in the highlands of Tigray, northern Ethiopia

There is a growing concern about food security and sustainability of agricultural production in developing countries. However, there are limited attempts to quantify agro-biodiversity losses and relate these losses to soil degradation and crop productivity, particularly in Tigray, Ethiopia. In this study, spatial variation in agro-biodiversity and soil degradation was assessed in 2000 and 2005 at 151 farms in relation to farm, productivity, wealth, social, developmental and topographic characteristics in Tigray, northern Ethiopia. A significant decrease in agro-biodiversity was documented between 2000 and 2005, mainly associated with inorganic fertilizer use, number of credit sources and proximity to towns and major roads. Agro-biodiversity was higher at farms with higher soil fertility (available P and total N) and higher productivity (total caloric crop yield). Low soil organic matter, few crop selection criteria and steep slopes contributed to soil erosion. Sparsely and intensively cultivated land use types, as determined from satellite images, were associated with high and low agro-biodiversity classes, respectively, as determined during on-farm surveys in 2005. This study gives insight into the recent changes in and current status of agro-biodiversity and soil degradation at different spatial scales, which can help to improve food security through the maintenance of agro-biodiversity resources.