Effect of island geological age on the arthropod species richness of Azorean pastures

Species richness of six pasture arthropod assemblages (total arthropod species, total herbivore species, sucking and chewing herbivores, total predatory species and spiders) were regressed against several geographical variables (area, distance from the nearest mainland, maximum elevation and geological age of the islands) of three Azorean islands (S. Maria, Terceira and Pico). The species were sampled by the fixed-quadrat size sampling method and the results obtained are consistent with the geological age hypothesis, i.e. the species richness of the six indigenous arthropod assemblages increases with the geological age of the islands, both at local and regional scales. Higher values of indigenous and endemic species richness were consistendy found on the older island (S. Maria), and the lowest values on the most recent island (Pico). Moreover, when considering the age of Faial (an older island probably once connected with Pico) as a estimate of the age of Pico, correlations between species richness and island age were improved, thereby strengthening the relationship. The older island (S. Maria) has more specialized herbivores and a greater proportion of herbivores in relation to predatory arthropods. Ecological and biogeographical studies in the Azores should take into account the effects of the time each island has been available for colonization and evolution.     

Landscape diversity of pasture dung beetle communities in the central region of mainland Japan and implications for conservation management

We studied the diversity of dung beetle communities in Japanese pastures to identify the factors that maintain or enhance the diversity of dung beetles at a landscape scale. We surveyed dung beetles from 17 pastures located in the northeastern part of Tochigi Prefecture, which is in the center of mainland Japan. From 1999 to 2001, surveys were conducted during the 6-month grazing period (May to October) by using dung baited basket traps. We also collected information about the environmental conditions and pasture management practices. Twenty-five dung beetle species belonging to Geotrupinae, Scarabaeinae, and Aphodiinae (including 13 tunneler and 12 dweller species) were recorded. The abundance of dweller species decreased with increasing elevation, possibly because of the effect of rainfall, whereas the species richness of tunneler species was affected by cattle disturbance and soil condition. Beetle species richness significantly increased with the number of years that the pastures had been grazed. Ivermectin administration did not appear to have any adverse effect on dung beetle abundance, species richness, or species diversity. The dung beetle datasets of the current study (including specific tunneler and dweller beetle groups) supported the widely documented positive relationship between local abundance and species distribution ranges. The within pasture, within area, and between area hierarchical additive partitioning of regional total diversity indicated that landscape-scale management should be implemented to conserve the regional diversity of the dung beetle communities inhabiting Japanese pastures.     

Grazing history influences biodiversity: a case study on ground-dwelling arachnids (Arachnida: Araneae, Opiliones) in the Natural Park of Alpi Marittime (NW Italy)

Alpine pastures are typical examples of “high nature value farmlands”, representing important habitats harbouring unique biological communities. Disturbance induced by overgrazing influences significantly ecosystem processes, in which invertebrates play a major role. To develop new models of sustainable management of pastures, more knowledge is needed of the animal communities, essential to the ecological functioning of pasture ecosystems. The apparent poor ecological state of several pastures in the Natural Regional Park of Alpi Marittime (NW-Italy) lead us to evaluate the influence of grazing history on biodiversity, using spider and harvestmen assemblages as key groups. Four different pastoral types characterized by four different grazing histories were identified using the Daget-Poissonet method. Spiders and harvestmen were collected by means of pitfall traps. Arachnid assemblages were characterized in terms of composition, abundance, species richness, richness of endemic species and taxonomic relatedness. Generalized linear mixed models (GLMM) were used to test differences among assemblages occurring in each pastoral type. Furthermore, we tested differences in terms of plant communities (species richness and percentage of zoogenic species). Specificity and fidelity of every spider and harvestmen species within pastoral types were explored by the IndVal (Indicator Value) procedure. Fifty-eight species of spiders and seven species of harvestmen were collected (2,304 individuals). Pastoral types related to intensive grazing were characterized by the dominance of diurnal wanderer spiders (namely Lycosidae) while, conversely, nocturnal wanderers (mainly Gnaphosidae) were more abundant in extensive pastoral types. Results show that both species richness and spider abundance were higher in abandoned areas of extensive grazing, while endemic assemblages were richer in extensive grazed areas, which also hosted the most diverse plant community. Furthermore, most of the indicator species of spiders of this type were endemic, characterized by more demanding ecological requirements.     

The impact of overgrazing on dung beetle diversity in the Italian Maritime Alps

Dung beetles (Coleoptera: Scarabaeidae) are undoubtedly the most typical and ecologically relevant insects of grazed alpine habitats because they provide valuable ecological services such as biological pest control and soil fertilization. Despite the great ecological contribution of these insects to pasture ecosystem functioning, little is known about their direct or indirect relationships with pastoral activities. The main aim of the study was to assess whether dung beetle diversity was influenced by different intensities of cattle grazing. Dung beetle communities of two adjacent alpine valleys within the Maritime Alps Natural Park (north-western Italian Alps), representing overgrazed and ungrazed pastures, were studied by pitfall trapping. A hierarchical design (three levels: valleys, transects, and replicates) was established for additive partitioning of γ-diversity and Indicator Species Analysis. Evenness and Shannon diversity were significantly higher at the ungrazed than at the overgrazed site because abundances were much more evenly distributed at the former than at the latter site (where one species was dominant over all the others). Dung beetle abundance and species richness of the overgrazed graminaceous pasture vegetation types were in most cases significantly lower than those of the ungrazed nongraminaceous vegetation type. In the additive partitioning of γ -diversity analysis relative to the whole study area, the randomization procedure indicated that the contribution of β to γ-diversity was significantly different from that expected by chance, suggesting that one or more environmental factors has intervened to change the partition of total diversity in the system considered. The analysis of the preferences and fidelity of species (Indicator Species Analysis) showed that only one species chose overgrazed pastures; all the others positively selected the ungrazed site, or the only ungrazed pasture vegetation type (Rumicetum alpini Beger) occurring at the overgrazed site. Results conformed to evidences that overgrazing represents a serious threat to the conservation of alpine dung beetles. To conserve local dung beetle assemblages, especially in protected areas, cattle overgrazing should be avoided. This does not mean, however, that pastoral activities are incompatible with biodiversity conservation. The contemporaneous presence of wild ungulates and low intensity extensive pastoral activities may be useful to preserve both local dung beetle assemblages and alpine pasture ecosystems.     

Are local patterns of anthropoid primate diversity related to patterns of diversity at a larger scale?

Aims (1) To determine the relationship between local and regional anthropoid primate species richness. (2) To establish the spatial and temporal scale at which the ultimate processes influencing patterns of primate species coexistence operate. Location Continental landmasses of Africa, South America and Asia (India to China, and all islands as far south as New Guinea). Methods The local–regional species richness relationship for anthropoid primates is estimated by regressing local richness against regional richness (independent variable). Local richness is estimated in small, replicate local assemblages sampled in regions that vary in total species richness. A strong linear relationship is taken as evidence that local assemblages are unsaturated and local richness results from proportional sampling of the regional pool. An asymptotic curvilinear relationship is interpreted to reflect saturated communities, where strong biotic interactions limit local richness and local processes structure the species assemblage. As a further test of the assumption of local assemblage saturation, we looked for density compensation in high‐density local primate assemblages. Results The local–regional species richness relationship was linear for Africa and South America, and the slope of the relationship did not differ between the two continents. For Asia, curvilinearity best described the relationship between local and regional richness. Asian primate assemblages appear to be saturated and this is confirmed by density compensation among Asian primates. However, density compensation was also observed among African primates. The apparent assemblage saturation in Asia is not a species–area phenomenon related to the small size of the isolated islands and their forest blocks, since similar low local species richness occurs in large forests on mainland and/or peninsular Asia. Main conclusions In Africa and South America local primate assemblage composition appears to reflect the influence of biogeographic processes operating on regional spatial scales and historical time scales. In Asia the composition of primate assemblages are by‐and‐large subject to ecological constraint operating over a relatively small spatial and temporal scale. The possible local influence of the El Niño Southern Oscillations on the evolution and selection of life‐history characteristics among Asian primates, and in determining local patterns of primate species coexistence, warrants closer inspection.     

The biogeography and filtering of woody plant functional diversity in North and South America

Aim In recent years evidence has accumulated that plant species are differentially sorted from regional assemblages into local assemblages along local‐scale environmental gradients on the basis of their function and abiotic filtering. The favourability hypothesis in biogeography proposes that in climatically difficult regions abiotic filtering should produce a regional assemblage that is less functionally diverse than that expected given the species richness and the global pool of traits. Thus it seems likely that differential filtering of plant traits along local‐scale gradients may scale up to explain the distribution, diversity and filtering of plant traits in regional‐scale assemblages across continents. The present work aims to address this prediction. Location North and South America. Methods We combine a dataset comprising over 5.5 million georeferenced plant occurrence records with several large plant functional trait databases in order to: (1) quantify how several critical traits associated with plant performance and ecology vary across environmental gradients; and (2) provide the first test of whether the woody plants found within 1° and 5° map grid cells are more or less functionally diverse than expected, given their species richness, across broad gradients. Results The results show that, for many of the traits studied, the overall distribution of functional traits in tropical regions often exceeds the expectations of random sampling given the species richness. Conversely, temperate regions often had narrower functional trait distributions than their smaller species pools would suggest. Main conclusion The results show that the overall distribution of function does increase towards the equator, but the functional diversity within regional‐scale tropical assemblages is higher than that expected given their species richness. These results are consistent with the hypothesis that abiotic filtering constrains the overall distribution of function in temperate assemblages, but tropical assemblages are not as tightly constrained.     

The role of plant fidelity and land-use changes on island exotic and indigenous canopy spiders at local and regional scales

Understanding the processes that lead to successful invasions is essential for the management of exotic species. We aimed to assess the comparative relevance of habitat (both at local and at regional scale) and plant features on the species richness of local canopy spiders of both indigenous and exotic species. In an oceanic island, Azores archipelago, we collected spiders in 97 transects belonging to four habitat types according to the degree of habitat disturbance, four types of plants with different colonisation origin (indigenous vs. exotic), and four types of plants according to the complexity of the vegetation structure. Generalised linear mixed models and linear regressions were performed separately for indigenous and exotic species at the local and regional landscape scales. At the local scale, habitat and plant origin explained the variation in the species richness of indigenous spiders, whereas exotic spider richness was poorly correlated to habitat and plant structure. The surrounding landscape matrix substantially affected indigenous spiders, but did not affect exotic spiders, with the exception of the negative effect exerted by native forests on the richness of exotic species. Our results revealed that the local effect of habitat type, plant origin and plant structure explain variations in the species richness observed at a regional scale. These results shed light on the mechanistic processes behind the role of habitat types in invasions, i.e., plant fidelity and plant structure are revealed as key factors, suggesting that native forests may act as physical barriers to the colonisation of exotic spiders.     

Coexistence of Banksia species in southwestern Australia: the role of regional and local processes

Abstract. 60 of the 75 Banksia species are confined to southwestern Australia where five or six species often coexist. We explored the role of regional species richness, niche differentiation, and habitat specialization in structuring banksia assemblages. The diversity of growth forms and categories of seed production and response to fire were assessed in actual assemblages at 40 sites throughout southwestern Australia. Diversity indices at each site were compared with those from null communities assembled on the basis of the abundance and sociability of taxa in regional species pools. The relationship between local and regional species richness suggests that processes at the scale of 100-m² quadrats limit local richness and therefore coexistence. However, there was no consistent evidence that taxa are differentiated by growth form or regeneration strategy. No particular biological profile makes a banksia adept at coexisting with a wide range of other taxa. Habitat specialization is an important factor contributing to lower local richness than would be predicted from niche differentiation of taxa in regional pools. There is recent empirical evidence of several mechanisms whereby the number of coexisting banksias is increased beyond the limits suggested by simple niche theories. Variability in the fire regime also provides a mechanism for maintaining local species richness because different fires favour recruitment of different taxa.     

Phenotypic differentiation within a foundation grass species correlates with species richness in a subalpine community

The effects of species loss on ecosystems depend on the community’s functional diversity (FD). However, how FD responds to environmental changes is poorly understood. This applies particularly to higher trophic levels, which regulate many ecosystem processes and are strongly affected by human-induced environmental changes. We analyzed how functional richness (FRic), evenness (FEve), and divergence (FDiv) of important generalist predators—epigeic spiders—are affected by changes in woody plant species richness, plant phylogenetic diversity, and stand age in highly diverse subtropical forests in China. FEve and FDiv of spiders increased with plant richness and stand age. FRic remained on a constant level despite decreasing spider species richness with increasing plant species richness. Plant phylogenetic diversity had no consistent effect on spider FD. The results contrast with the negative effect of diversity on spider species richness and suggest that functional redundancy among spiders decreased with increasing plant richness through non-random species loss. Moreover, increasing functional dissimilarity within spider assemblages with increasing plant richness indicates that the abundance distribution of predators in functional trait space affects ecological functions independent of predator species richness or the available trait space. While plant diversity is generally hypothesized to positively affect predators, our results only support this hypothesis for FD—and here particularly for trait distributions within the overall functional trait space—and not for patterns in species richness. Understanding the way predator assemblages affect ecosystem functions in such highly diverse, natural ecosystems thus requires explicit consideration of FD and its relationship with species richness.     

Influence of climate changes on animal communities in space and time: the case of spider assemblages along an alpine glacier foreland

The impact of global warming in space and time is described for species assemblages of wandering spiders along the alpine glacier foreland of the Forni Valley (Northern Italy). We tested the effect of environmental variables (e.g. elevation, age of glacier retreat, vegetation cover, debris cover) on species richness and on species composition of spiders. Age of glacier retreat was the only significant variable influencing spider species assemblages in the valley. A spatially structured distribution of species and species assemblages along the chronosequence of glacier retreat was evidenced. The threshold abruptly differentiating two groups of species richness and species composition fell between sites deglaciated 100 and 155 years before the analysis. Latitudinal shifts towards the poles in species ranges at the global scale in response to climatic changes are known, and an altitudinal shift in species range should be expected for spiders at the local scale of the Forni Valley. Such a shift is present in spider species assemblages, although not as an expected gradual change in species richness and composition, but with a threshold effect after one century of glacier retreat. We discuss our results in the light of plausible future scenarios due to global warming, the consequence of further glacier retreats onto spiders, and caveats for monitoring studies.     

Linking ecological function to species composition in ecological restoration: Seed removal by ants in recreated woodland

Evaluations of ecological restoration typically focus on associating measures of structural properties of ecosystems (e.g. species diversity) with time since restoration efforts commenced. Such studies often conclude a failure to achieve restoration goals without examining functional performance of the organism assemblages in question. We compared diversity and composition of ant assemblages and the rates of seed removal by ants in pastures, 4‐ to 10‐year old revegetated areas and remnants of Cumberland Plain Woodland, and an endangered ecological community in Sydney, Australia. Ant assemblages of forest remnant sites had significantly higher species richness, significantly different species composition and a more complex functional group structure in comparison with ant assemblages of pasture and revegetated sites, which did not differ significantly. However, the rates of seed removal by ants in revegetated sites were similar to those in forest remnants, with the rates in pasture sites being significantly lower. Approximately, one‐third of all ant species were observed to remove seeds. Forest remnant sites had significantly different assemblages of seed removing ant species from those in pasture and revegetated sites. These results demonstrate that similar ant assemblages of unrestored and restored areas can function differently, depending on habitat context. Evaluation of restoration success by quantifying ecosystem structure and function offers more insights into ecosystem recovery than reliance on structural data alone.     

Spider diversity responds strongly to edge effects but weakly to vegetation structure in riparian forests of Southern Brazil

Riparian forests bordering open terrestrial environments may have three microhabitats differing in structure and conditions: a grassland/pasture-forest edge (GE), a forest interior (FI) and a river–forest edge. The influence of such edge effects and vegetation characteristics on spider diversity of riparian forests was evaluated in Southern Brazil. Four different rivers were sampled on the tree–shrub strata with a beating tray, twice per season for 2 years. There were six transects per river, two per microhabitat. We compared spider abundance, species richness and composition. Vegetation variables sampled were vertical structure and (horizontal) density, canopy height and cover. Overall 42,057 spiders were sampled, 28 spider families and 440 species. The FI had higher spider abundance than the edges. Average species richness differed among rivers. Microhabitats did not differ in average richness, although overall richness (from sample-based rarefaction) was higher for GE than FI. High abundances in FI may result from lowered stress due to abiotic conditions, while higher GE richness may result from a faunal superposition between forest species and those from the grassland/pasture. Only canopy cover returns a positive relationship with spider diversity (richness and adult abundance). This might result from more spider species preferring to build webs or hunt under low-light environments. Rivers had spider faunas differing in composition but among microhabitats species composition was the same. Vegetation structure has been hypothesized to affect spiders, but this impact might be best seen in specific subgroups or guilds within spiders, not in the whole assemblage.     

Biome transitions as centres of diversity: habitat heterogeneity and diversity patterns of West African bat assemblages across spatial scales

It is widely accepted that species diversity is contingent upon the spatial scale used to analyze patterns and processes. Recent studies using coarse sampling grains over large extents have contributed much to our understanding of factors driving global diversity patterns. This advance is largely unmatched on the level of local to landscape scales despite being critical for our understanding of functional relationships across spatial scales. In our study on West African bat assemblages we employed a spatially explicit and nested design covering local to regional scales. Specifically, we analyzed diversity patterns in two contrasting, largely undisturbed landscapes, comprising a rainforest area and a forest‐savanna mosaic in Ivory Coast, West Africa. We employed additive partitioning, rarefaction, and species richness estimation to show that bat diversity increased significantly with habitat heterogeneity on the landscape scale through the effects of beta diversity. Within the extent of our study areas, habitat type rather than geographic distance explained assemblage composition across spatial scales. Null models showed structure of functional groups to be partly filtered on local scales through the effects of vegetation density while on the landscape scale both assemblages represented random draws from regional species pools. We present a mixture model that combines the effects of habitat heterogeneity and complexity on species richness along a biome transect, predicting a unimodal rather than a monotonic relationship with environmental variables related to water. The bat assemblages of our study by far exceed previous figures of species richness in Africa, and refute the notion of low species richness of Afrotropical bat assemblages, which appears to be based largely on sampling biases. Biome transitions should receive increased attention in conservation strategies aiming at the maintenance of ecological and evolutionary processes.     

Additive partitioning of plant diversity with respect to grassland management regime,fertilisation and abiotic factors

Understanding patterns of vascular plant diversity in managed temperate grasslands and the processes that determine them requires analyses at multiple spatial scales. In this study, we applied additive partitioning to plant species richness data of two contrasting management regimes (meadow vs. pasture) collected from a nested sampling design that consisted of two hierarchical scales. At the local scale, we quantified additive diversity components in 180 vegetation plots, and at the regional scale in 60 grassland parcels. Total observed regional species richness (γ_r) was partitioned into its additive components within (α_l) and among vegetation plots (β_l) and among grassland parcels (β_r). We used the same approach in a comparison of common and infrequent plant species. Partitioning analyses revealed that the relative contributions of diversity components to total observed regional species richness changed as a function of spatial scale. We found that species richness among grassland parcels (β_r) of both meadows and pastures contributed most to total observed regional species richness (γ_r) of all and infrequent plant species (up to 81% and 96%, respectively), whereas for common species only up to 51% of γ_r were attributable to species richness among grassland parcels (β_r). To gain insight into the processes that may affect local patterns of species richness in grasslands, we analysed the observed local species diversity components with respect to management regime, nitrogen fertilisation and abiotic environmental factors (slope angle and soil quality). Our results show that grazing at a low-to-moderate stocking density promotes the β-diversity of all plant species at the local scale due to increased within-habitat heterogeneity. Low application rates of nitrogen fertilisers and abiotic environmental conditions such as steep slopes and soils with a low nutrient status generally benefited local species diversity components. We conclude that the observed patterns of plant species diversity are shaped by processes at multiple spatial scales.     

Large-scale spatial ecology of dung beetles

Recent modelling work shows that the composition of local communities can be influenced by the configuration of the surrounding landscape, but many of these models assume that all community members display the same type of extinction‐colonization dynamics. I use Aphodius dung beetles to test the hypothesis that interspecific differences in habitat selection and dispersal capacity may translate into differences in spatial population dynamics, even among closely related species coexisting on the same resource. If this is true, then groups of species with different characteristics would show different responses to landscape configuration. I first divided the area of Finland into a grid, and used collection records to describe regional variation in the Aphodius fauna of open cattle pastures. I then sampled dung beetles on 131 cattle farms, to examine whether the subset of species found on each farm was related to the density of pastures in the surrounding grid square. Finally, I used historical records to analyze changes in dung beetle communities during the last century, when there was great loss of pasture. Overall, I found no relationship between landscape characteristics and the total proportion of the regional species pool that was found on each farm. However, the distribution of species among guilds with different habitat specificity did relate to the configuration of the landscape, and the pattern was most pronounced in a specialists species with limited dispersal. Associations between community structure and landscape configuration were superimposed on two much larger and stronger patterns: a large‐scale latitudinal gradient in regional species richness, and a decelerating gain of species to local communities with an increasing regional species pool. I conclude that ecological variation among community members is a crucial factor in the analysis of local community composition, and that local species richness should always be conditioned on regional richness.     

Does natural reforestation represent a potential threat to dung beetle diversity in the Alps?

Traditional agro-pastoral practices are in decline over much of the Alps, resulting in the complete elimination of livestock grazing in some areas. Natural reforestation following pastoral abandonment may represent a significant threat to alpine biodiversity, especially that associated with open habitats. This study presents the first assessment of the potential effects of natural reforestation on dung beetles by exploring the relationships between the beetle community (abundance, diversity, species turnover and assemblage structure) and the vegetation stages of ecological succession following pastoral abandonment. A hierarchical sampling design was used in the montane belt of the Sessera Valley (north-western Italian Alps). Dung beetles were sampled across 16 sampling sites set in four habitat types corresponding to four different successional stages (pasture, shrub, pioneer forest and beech forest) at two altitudinal levels. The two habitats at the extremes of the ecological succession, i.e. pasture and beech forest, had the greatest effect on the structure of local dung beetle assemblages. Overall, dung beetle abundance was greater in beech forest, whereas species richness, Shannon diversity and taxonomic diversity were significantly higher in pasture, hence suggesting this latter habitat can be considered as a key conservation habitat. Forests and pastures shared a lower number of species than the other pairs of habitats (i.e. species turnover between these two habitats was the highest). The two intermediate seral stages, i.e. shrub and pioneer forest, showed low dung beetle abundance and diversity values. Local dung beetle assemblages were also dependent on season and altitude; early-arriving species were typical of pastures of high elevation, whereas late-arriving species were typical of beech forests. It is likely that grazing in the Alps will continue to decrease in the future leading to replacement of open habitats by forest. This study suggests therefore that, at least in the montane belt, reforestation may have potentially profound and negative effects on dung beetle diversity. Maintaining traditional pastoral activities appears to be the most promising approach to preserve open habitats and adjacent beech forests, resulting in the conservation of species of both habitats.     

Dung beetle (Coleoptera: Scarabaeinae) persistence in Amazonian forest fragments and adjacent pastures: biogeographic implications for alpha and beta diversity

The aim of this study is to analyze the effects of habitat loss and forest replacement by cattle pasture on the alpha and beta diversity, abundance, biomass and species composition of dung beetles with different dispersal ability. Dung beetles were captured in 19 forest fragments and neighbouring pastures. Forest fragment area ranged from 3.7 to 4825 ha and in this study were grouped into four categories: small, medium, large and control forest. A total of 35,048 dung beetles representing 101 species were collected. Forest fragments had the highest richness with 81 species, followed by pasture with 58 species. Replacement of forest by pasture reduced species richness; however, due to the proximity and connectivity of these areas with Cerrado patches, pastures also had high species richness, but species composition was independent of adjacent fragments. Small fragments had lower abundance and species richness than our other habitat categories, even pastures. Our results highlight that proximity and connectivity with Cerrado areas influenced the patterns of alpha and beta diversity of dung beetles in fragments and pastures. We highlight that the ability to cross the pasture matrix is a strong adaptive trait for species living in human-modified landscapes. Consequently, species with these abilities are less susceptible to the effects of forest fragmentation and local extinction. Our results reinforce the importance of considering the biogeographic location and distribution pattern of species in forest fragmentation studies.     

The importance of small-scale heterogeneity in boreal forests: variation in diversity in forest-floor invertebrates across the succession gradient

Heterogeneity in species assemblages of forest-floor arthropods — carabid beetles, ants and spiders — within and between different forest age classes was studied in the southern Finnish taiga. The importance of processes operating on the local scale (within the movement radius of the species) vs on the regional scale (among forest stands) in determining the observed variation was assessed. Four data sets with different spatial resolutions in mesic forests in the same general study area were used. The material consists of 18 283 carabids of 51 species, 48 769 spiders of 212 species, and 126 718 worker ants of 23 species. Analyses of abundance variation and species complementarity among successional stages revealed that in all the three taxa species occurring in the mature forest were prevalent in the younger successional stages as well, constituting more than half of the catch in any age class. A great majority of carabid and spider species were widely distributed across the forest age classes, whereas ants include a higher proportion of species with a narrower amplitude across the succession gradient. Comparisons of similarity between samples at increasing distance from one another on the local scale within forest stands (a few tens of meters to a few hundreds of meters) showed a quite consistent pattern in carabids and spiders: there was more variation between sampling sites in young successional forests than in the mature forest. Furthermore, only in the mature forest a slight, albeit statistically not significant, negative relationship between similarity of samples and distance between sampling sites was detected. In carabids and spiders, comparisons between samples located at a distance of 10–15 m from each other showed considerable heterogeneity, the mean percentage similarity being c. 0.6 (in ants c. 0.8). On the regional scale, systematic variation between young and mature forest stands is a major element increasing the total diversity (species turnover c. 50% in carabids and spiders; compositional similarity c. 0.3–0.4 in carabids, 0.2–0.3 in spiders), but variation within forest stands on a spatial scale of 10–15 meters is another important component in the total heterogeneity. The results suggest that regional abundance variation is a primary factor influencing the composition of local assemblages; a set of hypotheses elaborating this conclusion is formulated. The result implies that maintenance of habitat heterogeneity on a small scale (10–15 m) is needed to preserve biodiversity in managed forests.     

Local–regional species richness relationships are linear at very small to large scales in west-central Pacific corals

If local communities are saturated with species, the relationship between local and regional species richness [the local species richness (LSR)–regional species richness (RSR) relationship] is predicted to become increasingly curvilinear at more local spatial scales. This study tested whether the LSR–RSR relationship for coral species was linear or curvilinear at three local scales across the west-central Pacific Ocean, along a regional biodiversity gradient that includes the world’s most diverse coral assemblages. The local scales comprised transects 10^0–2 m apart, sites 10^3–4 m apart and islands 10^4–6 m apart. The LSR–RSR relationship was never significantly different from linear at any scale. When the Chao1 estimator was used to predict true RSR and LSR, all relationships were also strongly linear. We conclude that local assemblages are open to regional influences even when the local scale is very small relative to the regional scale, and even in extraordinarily rich regions.     

Comparing assemblages of Asteraceae and their insect herbivores under different land‐use regimens

Accelerated tropical landscape changes occurring over recent decades have produced environmental mosaics comprising remaining isolated green areas and mixed land‐use types. Our objective was to study the effects of alterations in the natural landscape on the species composition and structure of assemblages of Asteraceae and their endophagous insects through comparisons between cerrado (savanna), pastures and Eucalyptus stands. We first investigated whether similarities between assemblages of Asteraceae and their insects varied among land uses or localities. Secondly, we asked whether assemblages of Eucalyptus stands and pastures are subsets of those within the cerrado. We sampled within randomly deployed transects in 15 areas. Land use was found to be an important factor in determining plant composition similarity; however, locality did not exert any significant influence. Pastures were less similar to one another, suggesting high beta diversity. Similarities among insect assemblages were correlated with plant assemblage composition, but not with land use or locality. Species of Tephritidae were distributed along localities independently of land use. High beta diversity in Asteraceae assemblages among cerrados and pastures was supported by nestedness analysis. Plant assemblages in Eucalyptus stands were subsets of cerrado, but pasture assemblages were only partial subsets. A higher degree of nestedness in insect assemblages than in plant assemblages indicated lower beta diversity within these herbivores. Our data indicate that many herbivores are specialized on widely distributed plant genera. Conservation of Asteraceae species and their flower head insects depends not only on maintenance of landscape fragments but also on the correct matching of management form and land use. Such management may contribute to reducing isolation of plant and insect species by increasing the connectivity of remaining cerrado tracts, allowing population maintenance even at low abundances.