Bat and bird diversity along independent gradients of latitude and tree composition in European forests

Species assemblages are shaped by local and continental-scale processes that are seldom investigated together, due to the lack of surveys along independent gradients of latitude and habitat types. Our study investigated changes in the effects of forest composition and structure on bat and bird diversity across Europe. We compared the taxonomic and functional diversity of bat and bird assemblages in 209 mature forest plots spread along gradients of forest composition and vertical structure, replicated in 6 regions spanning from the Mediterranean to the boreal biomes. Species richness and functional evenness of both bat and bird communities were affected by the interactions between latitude and forest composition and structure. Bat and bird species richness increased with broadleaved tree cover in temperate and especially in boreal regions but not in the Mediterranean where they increased with conifer abundance. Bat species richness was lower in forests with smaller trees and denser understorey only in northern regions. Bird species richness was not affected by forest structure. Bird functional evenness increased in younger and denser forests. Bat functional evenness was also influenced by interactions between latitude and understorey structure, increasing in temperate forests but decreasing in the Mediterranean. Covariation between bat and bird abundances also shifted across Europe, from negative in southern forests to positive in northern forests. Our results suggest that community assembly processes in bats and birds of European forests are predominantly driven by abundance and accessibility of feeding resources, i.e., insect prey, and their changes across both forest types and latitudes.     

180,000 Years of Climate Change in Europe: Avifaunal Responses and Vegetation Implications

Providing an underutilized source of information for paleoenvironmental reconstructions, birds are rarely used to infer paleoenvironments despite their well-known ecology and extensive Quaternary fossil record. Here, we use the avian fossil record to investigate how Western Palearctic bird assemblages and species ranges have changed across the latter part of the Pleistocene, with focus on the links to climate and the implications for vegetation structure. As a key issue we address the full-glacial presence of trees in Europe north of the Mediterranean region, a widely debated issue with evidence for and against emerging from several research fields and data sources. We compiled and analyzed a database of bird fossil occurrences from archaeological sites throughout the Western Palearctic and spanning the Saalian-Eemian-Weichselian stages, i.e. 190,000–10,000 years BP. In general, cold and dry-adapted species dominated these late Middle Pleistocene and Late Pleistocene fossil assemblages, with clear shifts of northern species southwards during glacials, as well as northwards and westwards shifts of open-vegetation species from the south and east, respectively and downwards shifts of alpine species. A direct link to climate was clear in Northwestern Europe. However, in general, bird assemblages more strongly reflected vegetation changes, underscoring their usefulness for inferring the vegetation structure of past landscapes. Forest-adapted birds were found in continuous high proportions throughout the study period, providing support for the presence of trees north of the Alps, even during full-glacial stages. Furthermore, the results suggest forest-dominated but partially open Eemian landscapes in the Western Palearctic, including the Northwestern European subregion.     

Calcareous forest seepages acting as biodiversity hotspots and refugia for woodland snail faunas

Land-snail species richness has repeatedly been found to increase with the increasing site calcium content and humidity. These two factors, reported as the main drivers of land-snail assemblage diversity, are also among the main habitat characteristics of calcareous seepages. Here we explore local species richness and compositional variation of forest spring-fed patches (i.e. seepages), to test the hypothesis that these habitats might act as biodiversity hotspots and refugia of regional snail faunas. In contrast to treeless spring fens, only little is known about land snail faunas inhabiting forest seepages. Studying 25 isolated calcareous forest seepages, evenly distributed across the White Carpathians Protected Landscape Area (SE Czech Republic), we found that these sites, albeit spatially very limited, can harbour up to 66% of the shelled land-snail species known to occur in this well-explored protected area (in total 83 species). By comparing land snail assemblages of the studied seepages with those occurring in the woodland surroundings of each site as well as those previously sampled in 28 preserved forest sites within the study area, we found the seepages to be among the most species rich sites. Although the numbers of species did not statistically differ among these three systems, we found highly significant differences in species composition. Seepage faunas were composed of many species significantly associated with spring sites, in contrast to the assemblages of both surrounding and preserved forest sites. Our results highly support the hypothesis that calcareous forest seepages might serve as refugia and biodiversity hotspots of regional land snail faunas. Protection of these unique habitats challenges both conservation plans and forest management guidelines as they might act as sources for the recolonization and restoration of forest snail assemblages particularly in areas impoverished by harvesting and clearcutting.     

Refugial ecosystems in central Asia as indicators of biodiversity change during the Pleistocene–Holocene transition

Site-scale species richness (alpha diversity) patterns are well described for many present-day ecosystems, but they are difficult to reconstruct from the fossil record. Very little is thus known about these patterns in Pleistocene full-glacial landscapes and their changes following Holocene climatic amelioration. However, present-day central Asian ecosystems with climatic features and biota similar to those of the full-glacial periods may serve as proxies of alpha diversity variation through both space and time during these periods. We measured alpha diversity of vascular plants, bryophytes, macrolichens and land snails, as well as environmental variables, in 100-m² plots located in forests and open habitats in the Russian Altai Mountains and their northern foothills. This region contains adjacent areas that possess climatic and biotic features similar to mid-latitude Europe for both the Last Glacial Maximum and contemporaneous Holocene ecosystems. We related alpha diversity to environmental variables using generalized linear models and mapped it from the best-fit models. Climate was identified as the strongest predictor of alpha diversity across all taxa, with temperature being positively correlated to number of species of vascular plants and land snails and negatively correlated to that of bryophytes and macrolichens. Factors important for only some taxa included precipitation, soil pH, percentage cover of tree layer and proportion of grassland areas in the landscape around plots. These results, combined with the high degree of similarity between the current Altai biota and dry-cold Pleistocene ecosystems of Europe and northern Asia, suggest that vascular plant and land snail alpha diversity was low during cold phases of the Pleistocene with a general increase following the Holocene climatic amelioration. The opposite trend probably existed for terricolous bryophytes and macrolichens.     

Forest snail faunas from Crimea (Ukraine), an isolated and incomplete Pleistocene refugium

The land snail faunas of 26 forest sites and two open rocky sites in the Crimean Mountains were sampled in 2011. Of the 40 species found within the forests (about half the known fauna of Crimea as a whole), 28 were species with wide western Palaearctic distributions, and only eight were endemic to Crimea. While there were significant differences in the faunas of different sampling areas, these seemed to be a consequence of ecological differences among them rather than a product of geographical isolation and differentiation. Endemic species were large, and not entirely restricted to forest; known endemics not found in these forests are mainly typical of more open habitats. There is no local radiation of small species living in damp forest litter, as with Leiostyla species in the Transcaucasian forest refugium, and families such as the Clausiliidae with many endemic forest species in both Transcaucasia and the Carpathians are sparsely represented. The one endemic clausiliid genus, Mentissa, occurs in open as well as in wooded habitats. The present faunas are rather poor considering the soil conditions and climate, and the forests hold widespread species often associated with open habitats elsewhere. While there is evidence that these mountains provided a refuge for many animals and plants during glacial episodes further north, the forest snail fauna suggests that full forest cover did not survive throughout the Pleistocene. Rather, the present fauna contains endemics that survived in other habitats and widespread species with good powers of passive dispersal. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 424–433.     

What Factors Affect Diversity and Species Composition of Endangered Tumbesian Dry Forests in Southern Ecuador?

This paper reports a study on species richness and composition of Tumbesian dry forest communities. We tested two alternative hypotheses about species assemblage processes in tropical dry forests: (1) species assemblage is determined by the filtering effect of environmental conditions and (2) species assemblage is determined by facilitative processes along the gradient of water availability, and thus, species richness and evenness increase as water becomes limited. In addition, we also explored the effect of climate and soil conditions on species composition in tropical dry forests. Species composition was sampled in 109 plots in terms of cover and tree diameter at breast height. Climatic, edaphic, topographic and anthropogenic degradation variables were obtained for each plot. We used generalized linear models and canonical correspondence analyses to evaluate the effect of environmental variables on species composition, richness and evenness. Water availability negatively affected richness and significantly determined the species assemblage. Species richness increased from ridges to valleys and evenness increased at higher altitudes. Soil characteristics showed no effect on richness and evenness but soil moisture, nitrogen concentration and soil temperature explained significant fractions of species composition. Although timber extraction and livestock in our study area were of low intensity, it negatively affected richness but had only a minor effect on species composition. Our results suggest that species composition in these endangered tropical dry forests may be at least partially explained by the stress‐gradient hypothesis, with higher species richness at drier conditions probably induced by facilitation processes.     

Diversity of forest vegetation across a strong gradient of climatic continentality: Western Sayan Mountains, southern Siberia

Southern Siberian mountain ranges encompass strong climatic contrasts from the relatively oceanic northern foothills to strongly continental intermountain basins in the south. Landscape-scale climatic differences create vegetation patterns, which are analogous to the broad-scale vegetation zonation over large areas of northern Eurasia. In their southern, continental areas, these mountains harbour forest types which potentially resemble the full-glacial forests recently reconstructed for Central Europe. To identify forest vegetation–environment relationships in the southern Siberian mountain ranges, forest vegetation of the Western Sayan Mountains was sampled on a 280 km transect running from the northern foothills with oceanic climatic features to the continental Central Tuvinian Basin in the south. Based on the species composition, vegetation was classified into hemiboreal forests, occurring at drier and summer-warm sites with high-pH soil, and taiga, occurring at wetter, summer-cool sites with acidic soil. Hemiboreal forests included Betula pendula-Pinus sylvestris mesic forest, Larix sibirica dry forest and Pinus sylvestris dry forest. Taiga included Abies sibirica-Betula pendula wet forest, Abies sibirica-Pinus sibirica mesic forest and Pinus sibirica-Picea obovata continental forest. Hemiboreal forests were richer in vascular plant species, while taiga was richer in ground-dwelling cryptogams. Vegetation–environment relationships were analysed by indirect and direct ordination. Winter and summer temperatures and precipitation exerted a dominant influence on species composition. Soil pH was also an important correlate of species composition, but this factor itself was probably controlled by precipitation. At a more local scale, the main source of variation in species composition was topography, producing landscape patterns of contrasting plant communities on slopes of different aspects and valley bottoms. The response of tree species to major environmental factors was expressed with Huisman–Olff–Fresco models. Larix sibirica appeared to be most resistant to drought and winter frosts, Pinus sibirica was adapted to low temperatures both in winter and summer, and Picea obovata had an intermediate response to climate. Betula pendula, Pinus sylvestris and Populus tremula were associated with the warmest sites with intermediate precipitation, while Abies sibirica was the most moisture-demanding species, sensitive to deep winter frosts.     

Effects of forest fragmentation on European birds: implications of regional differences in species richness

Aim In this paper, we adopted a large‐scale approach to evaluate the effect of regional richness of forest birds on the number of bird species retained by forest fragments in several localities across Europe. Location We studied bird assemblages in fourteen forest archipelagos embedded in agricultural matrices from southern Norway to central Spain. Tree composition varied from oak and beech forests of the northern localities to oak and pine xerophitic woodlands of the southern ones. The number of fragments in each forest archipelago ranged from eighteen to 211. Methods We used the Gleason equation (s = a + z log A; where s and A are, respectively, the species richness and size of forest fragments and z the rate of species loss) to estimate the species richness for 1‐ and 15‐ha fragments in each archipelago. The regional richness of forest birds was estimated by modelling the geographical distribution of species richness in the European atlas of breeding birds. Results The latitudinal distribution of regional richness displayed a convex form, with the highest values being in central Europe. Along this gradient, the number of species retained by fragments and the rate of species loss was positively related to regional richness. In addition, the percentage of the regional pool of species sampled by fragments decreased in the southern localities. Main conclusions Relationships between regional richness of forest birds and richness in fragments seem to explain why fragments in central Europe shelter more species than their southern counterparts. The decreased ability of southern forest fragments to sample the regional richness of forest birds, could be explained as an effect of the low abundance of many species in the Mediterranean, which could depress their ability to prevent extinction in fragments by a rescue effect. Alternatively, high beta diversity in the Mediterranean could produce undersampling by fragments of the regional pool of species. These regional differences in the response of bird assemblages to forest fragmentation are used to discuss the usefulness of large‐scale, biogeographical approaches in the design of conservation guidelines.     

Diversity of plant assemblages in isolated depressional wetlands from Central-Western Europe

A closed depression is defined as a geomorphologic element where a sediment depository is encircled by hillslopes. Despite the fact that closed depressions are often the only stagnant water points in many European landscapes, few ecological researches on their plant assemblages have been done. The main goal of this study was to give first results of the environmental factors responsible for the vegetation composition, richness and rarity in the closed depressions of the Lorraine biogeographical district (Belgium, France and grand-duché de Luxembourg). We surveyed for plant presence 85 forest and 77 grassland closed depressions. For each site, wetland area, local environmental factors and regional connectivities registered. For each species, the Ellenberg values were compiled. To investigate the main source of variation in species composition and in species richness (including richness in rare species), Non-metric Multidimensional Scaling analyses and Generalized Linear Models were respectively used. Species pools in forest (forest and preforest species) and in grassland (bog plants, pioneers, helophytes) were quite different. In both landscapes, a gradient from plants typical of basic high-productive soils to plants typical of acid low-productive soils reflects a shared successional gradient. The accumulation of organic matter allowed the establishment of Sphagnum spp., which slowly acidified the soil and thus acted as ecosystem engineers for the arrival of bog plants. Moreover, the species composition was additionally driven by the plant light tolerance in forests and by the plant water requirements in grasslands. Mechanisms of species accumulation (increase in species richness) were different in forests and in grasslands: respectively related to the plant light tolerance and to the wetland area. At the regional level, the averaged soil productivity was negatively related to the richness in rare species. Indeed, perennial highly-competitive plants such as Glyceria spp., Iris pseudacorus or Urtica dioica impeded the establishment of smaller and rarer species. At the habitat level, isolated closed depressions (due to either low connectivity or low grazing pressure) have more habitat rare species, giving evidences of dispersal limitation in plant assemblages of closed depressions.     

Does urbanization decrease diversity in ground beetle (Carabidae) assemblages?

Aim We wanted to test whether urbanization has similar effects on biodiversity in different locations, comparing the responses of ground beetle (Coleoptera, Carabidae) assemblages with an urbanization gradient. We also wanted to see if urbanization had a homogenizing effect on ground beetle assemblages. Locations Nine forested temperate locations in Europe, Canada and Japan. Methods Published results of the Globenet Project were used. At all locations, three stages were identified: (1) a forested (rural) area, (2) a suburban area where the original forest was fragmented and isolated, and (3) remnants of the original forest in urban parks. These habitats formed an urbanization series. Study arrangements (number and operation of traps) and methods (pitfall trapping) were identical, conforming to the Globenet protocol. Assemblage composition and diversity patterns were evaluated. Diversity relationships were analysed by the Rényi diversity ordering method considering all ground beetles and – separately – the forest specialist species. Taxonomic homogenization was examined by multivariate methods using assemblage similarities. Results Overall biodiversity (compared by species richness and diversity ordering) showed inconsistent trends by either urbanization intensity or by geographic position. However, when only forest species were compared, diversity was higher in the original rural (forested) areas than in urban forest fragments. Within‐country similarities of carabid assemblages were always higher than within‐urbanization stage similarities. Main conclusions Urbanization does not appear to cause a decrease in ground beetle diversity per se. Forest species decline as urbanization intensifies but this trend is masked by an influx of non‐forest species. The rural faunas were more similar to the urban ones within the same location than similar urbanization stages were to each other, indicating that urbanization did not homogenize the taxonomic composition of ground beetle faunas across the studied locations.     

Environment heterogeneity and seasonal effects in ground-dwelling ant (Hymenoptera: Formicidae) assemblages in the Parque Estadual do Rio Doce, MG, Brazil

This work aimed to explore the response of ant species assemblage to contrasting types of forests in a semideciduous stationary rainforest, in the Parque Estadual do Rio Doce, South Eastern Brazil. We compared antropomorphic borders of this park and natural ecotones, such as lake margins continuous with forests, as well as preserved forests far from ecotones. We investigated whether ground-dwelling ant species richness, abundance and composition would change according to forest types and ecotones. We expected greater species richness in interior tall forest, compared with low forest or ecotone habitats. In addition, we tested the effect of climate seasonality on ant assemblages found in each studied vegetation type. Each forest type was surveyed based on a minimum transect sampling unit of 150 m long summing up 30 pit-falls per unit. Two sampling events, one in dry season (September of 2001) and another in the rainy season (January of 2002) were performed. For both seasons, tall forest presented greater total number of ant species, however lower mean ant species and abundance per trap than other forest types, thus corroborating the prediction that ecotones might present high alpha diversity. Mean species richness and abundance did not differ between interior low forest and lake edge, or between these habitats and reserve border. In general, species composition were not clearly defined by forest types. Results here found suggest that species loss or community dominance by generalist species, eventually due to deforestation, is probably a much greater problem than previously thought. However, to understand patterns of insect species diversity and distribution in tropical ecosystem should be taken in account much more comprehensive, spatially explicit sampling designs.     

Relationships between land snail assemblage patterns and soil properties in temperate-humid forest ecosystems

Aim The objectives were to (1) analyse the combined effects of soil pH, Ca content and soil moisture on total density and species richness of land snails in forest ecosystems, (2) explore relationships between the quantitative composition of snail assemblages and habitat characteristics, (3) investigate the relationships between soil pH and density of some of the most frequent species, and (4) compare the data with those from studies conducted in other temperate‐humid regions of Europe. Location Study sites were selected from 15 landscape types including different lithologies within the area of Baden‐Württemberg (35,000 km²), SW Germany. Methods Snails were recorded quantitatively from 83 study sites, with four plots representing a total of 0.25 m² per site. Topsoil samples from each site were analysed for pH, exchangeable Ca, and Ca content of carbonates. Three categories of soil moisture (dry, intermediate and wet) were established and defined according to the (climatic) water balance. Numbers of individuals and species were brought in relation to soil moisture and soil pH. Cluster analyses were conducted to identify groups of quantitatively similar snail species assemblages. Results Topsoil pH (2.7–7.5) and soil Ca contents were closely correlated. On dry soils, total snail density and species richness are generally low and do not change with pH, but clearly increase with increasing pH on intermediate moisture soils and on wet soils. On the latter, numbers of individuals and species are generally much higher compared with intermediate moisture sites at the same value of soil pH. Changes of density in relation to soil pH vary between species. Depending on the species, density increases only in the lower or only in the higher range of pH, is not related to pH, or decreases with increasing pH. Furthermore, these patterns vary within the same species depending on the region. This became evident from comparisons with other studies, particularly between sites in SW Germany and southern Scandinavia. From cluster analyses, subgroups of snail assemblages of high quantitative similarity were identified. Group formation is explained by soil pH to some extent, and one subgroup showed a connection with coniferous woodland sites on acidic soils. No further environmental factors available from our data could explain the clustering of snail assemblages more detailed. Main conclusions Soil moisture is the strongest determinant of snail density and species richness at undisturbed woodland sites, but effects of soil moisture and soil pH on these patterns are closely interrelated on intermediate moisture soils and wet soils. However, the quantitative species composition of the land snail assemblages is related to soil properties to a lower degree than snail density and species richness, and other habitat characteristics such as vegetation or litter quality, can be important for species dominance in addition.     

Markedly Divergent Tree Assemblage Responses to Tropical Forest Loss and Fragmentation across a Strong Seasonality Gradient

We examine the effects of forest fragmentation on the structure and composition of tree assemblages within three seasonal and aseasonal forest types of southern Brazil, including evergreen, Araucaria, and deciduous forests. We sampled three southernmost Atlantic Forest landscapes, including the largest continuous forest protected areas within each forest type. Tree assemblages in each forest type were sampled within 10 plots of 0.1 ha in both continuous forests and 10 adjacent forest fragments. All trees within each plot were assigned to trait categories describing their regeneration strategy, vertical stratification, seed-dispersal mode, seed size, and wood density. We detected differences among both forest types and landscape contexts in terms of overall tree species richness, and the density and species richness of different functional groups in terms of regeneration strategy, seed dispersal mode and woody density. Overall, evergreen forest fragments exhibited the largest deviations from continuous forest plots in assemblage structure. Evergreen, Araucaria and deciduous forests diverge in the functional composition of tree floras, particularly in relation to regeneration strategy and stress tolerance. By supporting a more diversified light-demanding and stress-tolerant flora with reduced richness and abundance of shade-tolerant, old-growth species, both deciduous and Araucaria forest tree assemblages are more intrinsically resilient to contemporary human-disturbances, including fragmentation-induced edge effects, in terms of species erosion and functional shifts. We suggest that these intrinsic differences in the direction and magnitude of responses to changes in landscape structure between forest types should guide a wide range of conservation strategies in restoring fragmented tropical forest landscapes worldwide.     

Fungal disease incidence along tree diversity gradients depends on latitude in European forests

European forests host a diversity of tree species that are increasingly threatened by fungal pathogens, which may have cascading consequences for forest ecosystems and their functioning. Previous experimental studies suggest that foliar and root pathogen abundance and disease severity decrease with increasing tree species diversity, but evidences from natural forests are rare. Here, we tested whether foliar fungal disease incidence was negatively affected by tree species diversity in different forest types across Europe. We measured the foliar fungal disease incidence on 16 different tree species in 209 plots in six European countries, representing a forest‐type gradient from the Mediterranean to boreal forests. Forest plots of single species (monoculture plots) and those with different combinations of two to five tree species (mixed species plots) were compared. Specifically, we analyzed the influence of tree species richness, functional type (conifer vs. broadleaved) and phylogenetic diversity on overall fungal disease incidence. The effect of tree species richness on disease incidence varied with latitude and functional type. Disease incidence tended to increase with tree diversity, in particular in northern latitudes. Disease incidence decreased with tree species richness in conifers, but not in broadleaved trees. However, for specific damage symptoms, no tree species richness effects were observed. Although the patterns were weak, susceptibility of forests to disease appears to depend on the forest site and tree type.     

Revisitation of sites surveyed 19 years ago reveals impoverishment of longhorned beetles in natural and planted forests

As planted forests expand in area, they are beginning to dominate landscapes as a matrix and cause the fragmentation of remaining natural forests. To understand and predict the responses of biological assemblages to maturing planted landscapes, examining the effects of forest type (natural vs planted) and forest age on such assemblages is particularly important. Therefore, to document the effects of forest type and age on longhorned beetle assemblages, in 2008 we collected beetles in broad‐leaved natural and cedar planted forests where beetles had also been collected in 1989. Beetle species composition differed greatly between the two forest types in 1989, whereas this difference was less pronounced in 2008. Species richness and total abundance were higher in natural forests than in planted forests in 1989. In 2008, species richness had decreased in both forest types, but the difference between the two forest types had been maintained. Total abundance was also markedly lower in 2008, and the difference between forest types was much smaller. Although larval host plants were not associated with the responses of species to year (forest age or maturation), beetle species whose larvae fed on either broad‐leaved or coniferous trees (or both) exhibited slight preferences for natural forests. These results suggest that longhorned beetle assemblages become impoverished in planted landscapes as the planted matrix matures. Changes in species composition with forest maturation may be difficult to predict based on larval host plants. However, consideration of larval host plants may enable the prediction of changes in species composition caused by the replacement of natural forests by planted forests.     

Short-Term Medieval Settlement Activities Irreversibly Changed Forest Soils and Vegetation in Central Europe

In Europe, many contemporary forests are not continuous, but were established on former agricultural land in territories of deserted villages. We aimed to explore whether medieval settlement activities of only 60 years irreversibly changed soil properties and whether these changes were reflected by contemporary forest vegetation. The research was performed in the deserted village of K?í, which existed from 1357 to ca 1420 AD in a current oak forest on sandy soils in the Czech Republic. We identified four former land-use types (building sites, courtyards, the village square, and gardens), where we analyzed soil properties and plant species composition of the forest understory. Higher concentrations of plant-available P, K, Ca, and Mg as well as the total concentrations of organic C and trace elements (As, Cd, Cu, and Zn) were recorded at former building sites with neutral soils, compared to the other former land-use types with acidic soils. The four-times higher species richness at former building sites compared to the former gardens indicate the strong effect of soil pH and nutrient availability on plant species composition, even on the spatial scale of several square metres. Understanding recent patterns in soil properties and biodiversity in Central European forests requires detailed knowledge of former land use over centuries. Analysis of contemporary soil properties together with analysis of vegetation can help to identify former land-use types in deserted villages.     

Ice age climate, evolutionary constraints and diversity patterns of European dung beetles

Current climate and Pleistocene climatic changes are both known to be associated with geographical patterns of diversity. We assess their associations with the European Scarabaeinae dung beetles, a group with high dispersal ability and well-known adaptations to warm environments. By assessing spatial stationarity in climate variability since the last glacial maximum (LGM), we find that current scarab richness is related to the location of their limits of thermal tolerance during the LGM. These limits mark a strong change in their current species richness-environment relationships. Furthermore, northern scarab assemblages are nested and composed of a phylogenetically clustered subset of large-range sized generalist species, whereas southern ones are diverse and variable in composition. Our results show that species responses to current climate are limited by the evolution of assemblages that occupied relatively climatically stable areas during the Pleistocene, and by post-glacial dispersal in those that were strongly affected by glaciations.     

Exceptionally poor land snail fauna of central Yakutia (NE Russia): climatic and habitat determinants of species richness

There is an ongoing debate on the causes of the latitudinal diversity gradient, but diversity decline towards high latitudes is poorly documented for many invertebrate taxa. Therefore, we sampled land snail assemblages at 79 sites and in various habitat types in central Yakutia, a region with extremely continental, cool and dry climate. We tested whether habitats lacking suitable shelters for winter survival harbour less species than those with vegetation cover that softens climatic extremes. Both local species diversity and regional species diversity were extremely low: 13 species were recorded in total with an average of 1.4 species per site. While the majority of grassland sites were without snails (26 of 34 sites), forest sites supported at least one snail species in most cases (38 of 45 sites). Within grasslands, snail occurrences were associated with a higher herb-layer biomass. Numbers of snail species correlated with the amount of available calcium only in forests, in which species accumulation towards more favourable habitats was possible due to softening of climate harshness. As minute snails are known to be effective passive dispersers and the study area was not glaciated during the last glacial stage, there was certainly enough time for colonization of all favourable habitats. Our results suggest climatically driven limitations of both local and regional land snail diversity in central Yakutia. We conclude that the hypothesis of climate harshness remains the most probable explanation of a sharp drop in land snail diversity in high-latitude areas with cold climate.     

Climate as a determinant of dung beetle response to native forest replacement by cattle pastures in South America

Anthropogenic disturbance in natural ecosystems reduces the number of species in biological communities and homogenizes their composition across different regions. Climate is one of the main abiotic determinants of species distributions and different factors were proposed as the main climatic drivers. Here we explored the role of regional climate on the local response of dung beetle assemblages to the replacement of native forest by cattle pastures in South America by simultaneously contrasting three climatic hypotheses: energy, seasonality and heterogeneity. We compiled a database by searching published studies comparing dung beetle richness and composition between both native forests and cattle pastures. We calculated the proportional difference in species richness and composition between habitat types. As explanatory variables, we used seven abiotic variables grouped into the three climatic hypotheses. Energy/Productivity: mean annual temperature (°C/year) and total annual precipitation (mm/year). Seasonality: annual thermal amplitude (°C/year), the average coefficient of variation of monthly precipitation and the coefficient of average monthly variation in temperature. Heterogeneity: coefficient of variation of mean annual temperature, coefficient of variation of mean annual precipitation. Using regression analyses and a model selection procedure, we found differences in species richness between native forests and cattle pastures were explained by the coefficient of variation of mean annual precipitation, whereas changes in species composition were explained by total annual precipitation and the coefficient of variation of mean annual precipitation. The response of dung beetle assemblages to livestock grazing in South American forests was associated with precipitation variation. The heterogeneity hypothesis better explained changes in species richness following forest replacement by cattle pastures, while both energy/productivity and heterogeneity hypotheses explained the changes in species composition.     

Relative importance of climate vs local factors in shaping the regional patterns of forest plant richness across northeast China

Northeast (NE) China covers three climatic zones and contains all the major forest types of NE Asia. We sampled 108 forest plots in six nature reserves across NE China to examine the influence of climate and local factors (canopy seasonality, successional stage, topography and forest structure) on geographic patterns of plant richness. We analyzed the relative effects of different factors at two spatial scales: the regional scale (across both latitude and altitude) and the local scale (along the altitudinal gradient within site). Our results showed that the relative importance of climate vs local factors differed remarkably depending on scale and functional group. While total and tree species richness were mainly limited by climate, herb and shrub richness was more related to local factors (especially at the local scale). In the climatic factors, heat sum was the major correlate of tree, shrub and total species richness, while herb richness was more associated with winter coldness. Precipitation was not a limiting factor for forest plant richness in NE China. Climate accounted for 34–76% of variation in richness at the regional scale, but explained only 0–44% at the local scale. Among the local factors, shrub species richness was sensitive to seasonal canopy openness, with higher richness in deciduous forests than in the evergreen needle-leaf forest. On the other hand, herb richness was sensitive to forest successional stage, with higher richness in middle- successional forests than in the early and late-sucessional forests. Local topography (aspect and position on slope) and forest structure (tree density) also showed remarkable influence on species richness. Our results suggest the importance of including local factors when examining large scale diversity gradient (especially for understory species), and the necessity of comparing diversity patterns among functional groups at different spatial scales.