Variation In Mean Annual Temperature Research Articles

Species richness: A pivotal factor mediating the effects of land use intensification and climate on grassland multifunctionality

Abstract Temperate seminatural grasslands harbour unique biodiversity, support livestock farming through forage production, and deliver many essential ecosystem services (ESs) to human society; they are highly multifunctional. However, temperate grassland ecosystems are also among the most threatened ecosystems on earth due to land use and climate changes. Understanding how biodiversity, climate and land use intensification impact grassland multifunctionality through complex direct and indirect pathways is critical to better anticipate the future of these fragile ecosystems. Here, we evaluate how local plant species richness (SR) modulates the effect of land use intensification and climate on grassland multifunctionality (using six key ESs: biomass productivity and stability, forage quality, carbon storage, pollination and local plant rarity) in the French Massif Central, the largest grassland in Western Europe. We sampled 100 grasslands with contrasted fertilization rates and SR, over large elevational and latitudinal gradients related to variation in mean annual temperature (MAT), and drought severity (DS), two key climate change drivers predicted to increase in the future. Using a confirmatory path analysis, we found that SR was the main driver of multifunctionality. We also found significant SR × MAT and SR × fertilization interactions suggesting that warm climate and high fertilization rates alter the biodiversity–ecosystem multifunctionality relationships. Furthermore, increasing temperature and fertilization indirectly influenced multifunctionality by decreasing SR and consequent multifunctionality in warm lowland and highly fertilized grasslands compared to colder montane grasslands or less fertilized ones. DS only impacted some ES individually (e.g. forage quality). Synthesis and applications: We identified species richness (SR) as a pivotal factor mediating the effects of land use intensification and climate on multifunctionality through both direct and indirect pathways. Failing to account for changes in SR could thus bias any prediction of, or aggravate, the effects of land use intensification and climate change on ecosystem services delivery in temperate grassland ecosystems. Considering that SR, mean annual temperature and fertilization are major proxies of three main global change drivers (biodiversity loss, climate change and land use intensification) our study may help to better anticipate the effect of multiple interacting global change drivers on grassland ecosystems.

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

AbstractAnthropogenic 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.

Winter Diet of Montezuma Quail in Arizona and New Mexico

Investigating the diet composition of Montezuma quail (Cyrtonyx montezumae) is fundamental for unveiling how food resources limit the species’ population size and may provide relevant tools for their harvest and habitat management. The objective of this research was to determine the composition and geographic variation of the winter diet of the Montezuma quail in Arizona and New Mexico, USA, from quail crops harvested during the hunting seasons of 2008–2017. In addition, we used beta regression analyses to determine the effect of environmental factors and ecological variables (annual mean precipitation, annual mean temperature, landscape diversity, diet diversity, time of hunt, longitude, latitude, and elevation) on Montezuma quail diet composition. We found that acorns (Quercus spp.) and sedge rhizomes (Cyperus fendlerianus) are the most frequent food items of Montezuma quail in Arizona and New Mexico, respectively, followed by tepary beans (Phaseolus acutifolius), woodsorrel tubers (Oxalis spp.) and insects in both states. Individual crop wet mass is positively associated with time of day during winter. Geographic variation in Montezuma quail diet composition in Arizona and New Mexico was associated with mean annual precipitation for acorns and with geographic variation in mean annual temperature for rhizomes and tubers of sedge (Cyperus spp.). Geographic variation of other food items was not associated with those environmental factors. These functional relationships between the species’ diet and environmental factors suggest that Montezuma quail preference towards these two principal food items is subject to climatic control. Therefore, warmer and drier environments in the southwestern United States and northern Mexico may affect the species’ distribution through changes in food availability.

Chemical Similarity of Co-occurring Trees Decreases With Precipitation and Temperature in North American Forests

Plant diversity varies immensely over large-scale gradients in temperature, precipitation, and seasonality at global and regional scales. This relationship may be driven in part by climatic variation in the relative importance of abiotic and biotic interactions to the diversity and composition of plant communities. In particular, biotic interactions may become stronger and more host specific with increasing precipitation and temperature, resulting in greater plant species richness in wetter and warmer environments. This hypothesis predicts that the many defensive compounds found in plants’ metabolomes should increase in richness and decrease in interspecific similarity with precipitation, temperature, and plant diversity. To test this prediction, we compared patterns of chemical and morphological trait diversity of 140 woody plant species among seven temperate forests in North America representing 16.2°C variation in mean annual temperature (MAT), 2,115 mm variation in mean annual precipitation (MAP), and from 10 to 68 co-occurring species. We used untargeted metabolomics methods based on data generated with liquid chromatography-tandem mass spectrometry to identify, classify, and compare 13,480 unique foliar metabolites and to quantify the metabolomic similarity of species in each community with respect to the whole metabolome and each of five broad classes of metabolites. In addition, we compiled morphological trait data from existing databases and field surveys for three commonly measured traits (specific leaf area [SLA], wood density, and seed mass) for comparison with foliar metabolomes. We found that chemical defense strategies and growth and allocation strategies reflected by these traits largely represented orthogonal axes of variation. In addition, functional dispersion of SLA increased with MAP, whereas functional richness of wood density and seed mass increased with MAT. In contrast, chemical similarity of co-occurring species decreased with both MAT and MAP, and metabolite richness increased with MAT. Variation in metabolite richness among communities was positively correlated with species richness, but variation in mean chemical similarity was not. Our results are consistent with the hypothesis that plant metabolomes play a more important role in community assembly in wetter and warmer climates, even at temperate latitudes, and suggest that metabolomic traits can provide unique insight to studies of trait-based community assembly.

The spatial scaling of food web structure across European biogeographical regions.

The species-area relationship (SAR) is one of the most well-established scaling patterns in ecology. Its implications for understanding how communities change across spatial gradients are numerous, including the effects of habitat loss on biodiversity. However, ecological communities are not mere collections of species. They are the result of interactions between these species forming complex networks that tie them together. Should we aim to grasp the spatial scaling of biodiversity as a whole, it is fundamental to understand the changes in the structure of interaction networks with area. In spite of a few empirical and theoretical studies that address this challenge, we still do not know much about how network structure changes with area, or what are the main environmental drivers of these changes. Here, using the meta-network of potential interactions between all terrestrial vertebrates in Europe (1140 species and 67 201 feeding interactions), we analysed network-area relationships (NARs) that summarize how network properties scale with area. We do this across ten biogeographical regions, which differ in environmental characteristics. We found that the spatial scaling of network complexity strongly varied across biogeographical regions. However, once the variation in SARs was accounted for, differences in the shape of NARs vanished. On the other hand, the proportion of species across trophic levels remained remarkably constant across biogeographical regions and spatial scales, despite the great variation in species richness. Spatial variation in mean annual temperature and habitat clustering were the main environmental determinants of the shape of both SARs and NARs across Europe. Our results suggest new avenues in the exploration of the effects of environmental factors on the spatial scaling of biodiversity. We argue that NARs can provide new insights to analyse and understand ecological communities.

Plant diversity loss reduces soil respiration across terrestrial ecosystems.

The rapid global biodiversity loss has led to the decline in ecosystem function. Despite the critical importance of soil respiration (Rs) in the global carbon and nutrient cycles, how plant diversity loss affects Rs remains uncertain. Here we present a meta-analysis using 446 paired observations from 95 published studies to evaluate the effects of plant and litter mixtures on Rs and its components. We found that total Rs and heterotrophic respiration (Rh) were, on average, greater in plant mixtures than expected from those of monocultures. These mixture effects increased with increasing species richness (SR) in both plant and litter mixtures. While the positive effects of species mixtures remained similar over time for total Rs, they increased over time for Rh in plant mixtures but decreased in litter mixtures. Despite the wide range of variations in mean annual temperature, annual aridity index, and ecosystem types, the plant mixture effects on total Rs and Rh did not change geographically, except for a more pronounced increase of total Rs in species mixtures with reduced water availability. Our structural equation models suggested that the positive effects of SR and stand age on total and Rh were driven by increased plant inputs and soil microbial biomass. Our results suggest that plant diversity loss has ubiquitous negative impacts on Rs, one of the fundamental carbon-cycle processes sustaining terrestrial element cycling and ecosystem function.

The role of climate on floristic composition in a latitudinal gradient in the Brazilian Atlantic Forest

Background and aims – Latitudinal gradients have an important influence on species distribution reflecting the effects of environmental factors such as temperature, rainfall, soil, and geographical distance. In the southeastern Brazilian Atlantic Forest, the role of climatic variables in the floristic composition is better known for altitudinal gradients of the Serra do Mar Mountains rather than for the latitudinal gradient. Here, we investigated the effects of mean annual temperature and rainfall on tree species distribution and composition in a latitudinal gradient in the Atlantic forest.Methods – We calculated each species frequency of occurrence and the latitudinal range. We used multivariate analyses (direct ordination, Hierarchical Clustering followed by Indicator Species analysis and NMDS) to investigate variation in floristic composition, and regression analyses to evaluate mean annual temperatures and rainfall effects on tree species composition along the latitudinal gradient (21°S to 28°S).Key results – A total of 789 species were registered, of which a majority (646 species) were present in less than 20% of the sampled areas, and only four species (0.5%) were present in more than 80% of the sampled areas. Only ten species (1.3%) reached the maximum latitudinal range (~6°). We found a strong correlation between variation in floristic composition and the spatial position in the latitudinal gradient. The cluster analyses detected two main floristic groups, one composed by the forests from Rio de Janeiro (21°S to 23°S) and the second by the forests from São Paulo, Paraná and Santa Catarina States (23°S to 28°S). The multiple regression analysis revealed a strong effect of the climatic variables on the variation of the floristic composition along the latitudinal gradient (r2 = 0.81, P < 0.001), where 62.82% of the variation were explained by mean annual temperature, 8.27% by annual rainfall and 10.45% by both variables together.Conclusions – The restricted distribution of most species may be explained by variations in mean annual temperature and annual rainfall along the latitudinal gradient. For instance, the decreasing mean annual temperature along the coast and the occurrence of frosts at higher latitudes may limit the southward distribution of some species while the lower annual rainfall (with marked seasonality) in the north of the gradient may limit the northward distribution of other species. Although mean annual temperature explained most of the variation in species composition along the latitudinal gradient, the abrupt variation in annual rainfall may explain the high floristic dissimilarity detected in the north of the gradient.

Dominance-diversity relationships in ant communities differ with invasion.

The relationship between levels of dominance and species richness is highly contentious, especially in ant communities. The dominance-impoverishment rule states that high levels of dominance only occur in species-poor communities, but there appear to be many cases of high levels of dominance in highly diverse communities. The extent to which dominant species limit local richness through competitive exclusion remains unclear, but such exclusion appears more apparent for non-native rather than native dominant species. Here we perform the first global analysis of the relationship between behavioral dominance and species richness. We used data from 1,293 local assemblages of ground-dwelling ants distributed across five continents to document the generality of the dominance-impoverishment rule, and to identify the biotic and abiotic conditions under which it does and does not apply. We found that the behavioral dominance-diversity relationship varies greatly, and depends on whether dominant species are native or non-native, whether dominance is considered as occurrence or relative abundance, and on variation in mean annual temperature. There were declines in diversity with increasing dominance in invaded communities, but diversity increased with increasing dominance in native communities. These patterns occur along the global temperature gradient. However, positive and negative relationships are strongest in the hottest sites. We also found that climate regulates the degree of behavioral dominance, but differently from how it shapes species richness. Our findings imply that, despite strong competitive interactions among ants, competitive exclusion is not a major driver of local richness in native ant communities. Although the dominance-impoverishment rule applies to invaded communities, we propose an alternative dominance-diversification rule for native communities.

Intra-Specific Latitudinal Clines in Leaf Carbon, Nitrogen, and Phosphorus and their Underlying Abiotic Correlates in Ruellia Nudiflora

While plant intra-specific variation in the stoichiometry of nutrients and carbon is well documented, clines for such traits have been less studied, despite their potential to reveal the mechanisms underlying such variation. Here we analyze latitudinal variation in the concentration of leaf nitrogen (N), phosphorus (P), carbon (C) and their ratios across 30 populations of the perennial herb Ruellia nudiflora. In addition, we further determined whether climatic and soil variables underlie any such latitudinal clines in leaf traits. The sampled transect spanned 5° latitude (ca. 900 km) and exhibited a four-fold precipitation gradient and 2 °C variation in mean annual temperature. We found that leaf P concentration increased with precipitation towards lower latitudes, whereas N and C did not exhibit latitudinal clines. In addition, N:P and C:P decreased towards lower latitudes and latitudinal variation in the former was weakly associated with soil conditions (clay content and cation exchange capacity); C:N did not exhibit a latitudinal gradient. Overall, these results emphasize the importance of addressing and disentangling the simultaneous effects of abiotic factors associated with intra-specific clines in plant stoichiometric traits, and highlight the previously underappreciated influence of abiotic factors on plant nutrients operating under sharp abiotic gradients over smaller spatial scales.

Remote Sensing of Glacier Change in the Central Qinghai-Tibet Plateau and the Relationship with Changing Climate

The widely distributed glaciers over the Qinghai-Tibet Plateau (QTP) represent important freshwater reserves and the meltwater feeds many major rivers of Asia. Glacier change over the QTP has shown high temporal and spatial variability in recent decades, and the driving forces of the variability are not yet clear. This study examines the area and thickness change of glaciers in the Dongkemadi (DKMD) region over central QTP by exploring all available Landsat images from 1976 to 2013 and satellite altimetry data over 2003–2008, and then analyzes the relationships between glacier variation and local and macroscale climate factors based on various remote sensing and re-analysis data. Results show that the variation of glacier area over 1976–2013 is characterized by significant shrinkage at a linear rate of −0.31 ± 0.04 km2·year−1. Glacier retreat slightly accelerated in the 2000s, and the mean glacier surface elevation lowered at a rate of −0.56 m·year−1 over 2003–2008. During the past 38 years, glacier change in the DKMD area was dominated by the variation of mean annual temperature, and was influenced by the state of the North Atlantic Oscillation (NAO). The mechanism linking climate variability over the central QTP and the state of NAO is most likely via changes in the strength of westerlies and Siberian High. We found no evidence supporting the role of summer monsoons (Indian summer monsoon and East Asian monsoon) in driving local climate and glacier changes. In addition, El Niño Southern Oscillation (ENSO) may be associated with the extreme weather (snow storm) in October 1986 and 2000 which might have led to significant glacier expansion in the following years. Further research is needed to better understand the physical mechanisms linking NAO, ENSO and climate variability over the mid-latitude central QTP.

The demography of tree species response to climate: sapling and canopy tree growth

AbstractDespite the clear need to predict the effects of climate change on the distribution and abundance of temperate tree species, there is still only a rudimentary understanding of how climate influences key demographic processes that determine the current distribution and abundance of tree species. We use data from the U.S. Forest Service Forest Inventory and Analysis (FIA) program to quantify the relationships between two key climate variables—mean annual temperature and effective growing season precipitation—and rates of sapling and canopy tree growth for the 50 most common tree species in the eastern United States. Our models include the effects of tree size, competition, and anthropogenic nitrogen (N) deposition, both to avoid confounding effects and to provide context for the importance of variation in climate relative to other factors known to influence tree growth. The 50 species show a broad range of relationships between size and growth, in contrast to predictions of metabolic theory. The 50 species differ widely in shade tolerance, and both saplings and canopy trees show a wide range of competitive responses to total stand basal area. The competitive responses of canopy trees were more sensitive than were saplings to the size of an individual relative to the median size of trees in the stand. As has been shown in other studies with FIA data, species responses to N deposition also varied widely and were related to the type of mycorrhizal association of the tree species. Relationships between the two climate variables and tree growth were surprisingly modest, and bore little obvious relationship to the distributions of the species along climate gradients. For over a quarter of the species, there was no statistical support for a relationship between 5‐yr average growing season precipitation and 5‐yr average growth, and for most of the remaining species, the relationship was effectively flat over a wide range of precipitation. Responses to regional variation in mean annual temperature were stronger, but again showed little obvious correlation with the distribution of abundance of most species along the temperature gradient.

Climatic controls on the isotopic composition and availability of soil nitrogen across mountainous tropical forest

AbstractWhile tropical forests play a critical role in global carbon (C) and nitrogen (N) cycles, how their biogeochemical dynamics will respond to changes in climate, especially warming, is uncertain. To shed light on links between climate and N cycling in tropical forests, we measured bulk surface soil C and N concentrations and isotopic content at 40 forested sites spanning an 1800 m elevation transect in Central America, possessing wide variation in mean annual temperature (MAT; range = 10°C) and precipitation (MAP; range = 1.2 m). Climate and terrain attributes were extracted from gridded data sets and regressed against soil variables, and then, empirical relationships were combined with a mass balance model to scale up to the larger landscape. Across the remote study region, elevation and soil δ15N values displayed a strong negative relationship, while elevation was positively related to percent of soil C, N, and C:N ratios. As elevation was tightly correlated with MAT and MAP, soil chemical and isotopic content varied strongly with climate. For example, for every degree increase in MAT, soil δ15N values—an indicator of relative gaseous N losses—increased by a factor of 0.4, and soil C:N ratios, which affect net N mineralization and N availability, declined by a factor of 1.1. With the 40 sites binned into bioclimatic life zones, montane, premontane, and wet‐premontane transition forests showed distinct clustering of soil chemical and isotopic properties, yet forest type alone explained less variation compared to continuous elevation–climate parameters. Results of the spatially applied 15N mass balance model implied shifts in the contribution of gaseous‐to‐total N loss, from 10% or less in cool, wet high‐elevation forests to upwards of 60% at warmer, drier, low‐elevation sites. Climate variation was thus associated with significant shifts in N dynamics across this montane tropical region, yet more work is needed to decouple direct vs. indirect climatic controls. While the mechanisms deserve further study, observed shifts in indicators of N availability and gaseous loss may be useful in managing and modeling tropical forests under climate change.

Forest structure in low-diversity tropical forests: a study of Hawaiian wet and dry forests.

The potential influence of diversity on ecosystem structure and function remains a topic of significant debate, especially for tropical forests where diversity can range widely. We used Center for Tropical Forest Science (CTFS) methodology to establish forest dynamics plots in montane wet forest and lowland dry forest on Hawai‘i Island. We compared the species diversity, tree density, basal area, biomass, and size class distributions between the two forest types. We then examined these variables across tropical forests within the CTFS network. Consistent with other island forests, the Hawai‘i forests were characterized by low species richness and very high relative dominance. The two Hawai‘i forests were floristically distinct, yet similar in species richness (15 vs. 21 species) and stem density (3078 vs. 3486/ha). While these forests were selected for their low invasive species cover relative to surrounding forests, both forests averaged 5–>50% invasive species cover; ongoing removal will be necessary to reduce or prevent competitive impacts, especially from woody species. The montane wet forest had much larger trees, resulting in eightfold higher basal area and above-ground biomass. Across the CTFS network, the Hawaiian montane wet forest was similar to other tropical forests with respect to diameter distributions, density, and aboveground biomass, while the Hawai‘i lowland dry forest was similar in density to tropical forests with much higher diversity. These findings suggest that forest structural variables can be similar across tropical forests independently of species richness. The inclusion of low-diversity Pacific Island forests in the CTFS network provides an ∼80-fold range in species richness (15–1182 species), six-fold variation in mean annual rainfall (835–5272 mm yr−1) and 1.8-fold variation in mean annual temperature (16.0–28.4°C). Thus, the Hawaiian forest plots expand the global forest plot network to enable testing of ecological theory for links among species diversity, environmental variation and ecosystem function.

Ecosystem CO2 fluxes of arbuscular and ectomycorrhizal dominated vegetation types are differentially influenced by precipitation and temperature

Here, we explore how interannual variations in environmental factors (i.e. temperature, precipitation and light) influence CO(2) fluxes (gross primary production and ecosystem respiration) in terrestrial ecosystems classified by vegetation type and the mycorrhizal type of dominant plants (arbuscular mycorrhizal (AM) or ectomycorrhizal (EM)). We combined 236 site-year measurements of terrestrial ecosystem CO(2) fluxes and environmental factors from 50 eddy-covariance flux tower sites with information about climate, vegetation type and dominant plant species. Across large geographical distances, interannual variations in ecosystem CO(2) fluxes for EM-dominated sites were primarily controlled by interannual variations in mean annual temperature. By contrast, interannual variations in ecosystem CO(2) fluxes at AM-dominated sites were primarily controlled by interannual variations in precipitation. This study represents the first large-scale assessment of terrestrial CO(2) fluxes in multiple vegetation types classified according to dominant mycorrhizal association. Our results support and complement the hypothesis that bioclimatic conditions influence the distribution of AM and EM systems across large geographical distances, which leads to important differences in the major climatic factors controlling ecosystem CO(2) fluxes.

Contributions of climate, leaf area index and leaf physiology to variation in gross primary production of six coniferous forests across Europe: a model-based analysis

Gross primary production (GPP) is the primary source of all carbon fluxes in the ecosystem. Understanding variation in this flux is vital to understanding variation in the carbon sink of forest ecosystems, and this would serve as input to forest production models. Using GPP derived from eddy-covariance (EC) measurements, it is now possible to determine the most important factor to scale GPP across sites. We use long-term EC measurements for six coniferous forest stands in Europe, for a total of 25 site-years, located on a gradient between southern France and northern Finland. Eddy-derived GPP varied threefold across the six sites, peak ecosystem leaf area index (LAI) (all-sided) varied from 4 to 22 m(2) m(-2) and mean annual temperature varied from -1 to 13 degrees C. A process-based model operating at a half-hourly time-step was parameterized with available information for each site, and explained 71-96% in variation between daily totals of GPP within site-years and 62% of annual total GPP across site-years. Using the parameterized model, we performed two simulation experiments: weather datasets were interchanged between sites, so that the model was used to predict GPP at some site using data from either a different year or a different site. The resulting bias in GPP prediction was related to several aggregated weather variables and was found to be closely related to the change in the effective temperature sum or mean annual temperature. High R(2)s resulted even when using weather datasets from unrelated sites, providing a cautionary note on the interpretation of R(2) in model comparisons. A second experiment interchanged stand-structure information between sites, and the resulting bias was strongly related to the difference in LAI, or the difference in integrated absorbed light. Across the six sites, variation in mean annual temperature had more effect on simulated GPP than the variation in LAI, but both were important determinants of GPP. A sensitivity analysis of leaf physiology parameters showed that the quantum yield was the most influential parameter on annual GPP, followed by a parameter controlling the seasonality of photosynthesis and photosynthetic capacity. Overall, the results are promising for the development of a parsimonious model of GPP.

Macroecological patterns of spider species richness across Europe

We analysed the pattern of covariation of European spider species richness with various environmental variables at different scales. Four layers of perception ranging from single investigation sites to the whole European continent were selected. Species richness was determined using published data from all four scales. Correlation analyses and stepwise multiple linear regression were used to relate richness to topographic, climatic and biotic variables. Up to nine environmental variables were included in the analyses (area, latitude, elevation range, mean annual temperature, local variation in mean annual temperature, mean annual precipitation, mean July temperature, local variation in mean July temperature, plant species richness). At the local and at the continental scale, no significant correlations with surface area were found, whereas at the landscape and regional scale, surface area had a significant positive effect on species richness. Factors that were positively correlated with species richness at both broader scales were plant species richness, elevation range, and specific temperature variables (regional scale: local variation in mean annual, and mean July temperature; continental scale: mean July temperature). Latitude was significantly negatively correlated with the species richness at the continental scale. Multiple models for spider species richness data accounted for up to 77% of the total variance in spider species richness data. Furthermore, multiple models explained variation in plant species richness up to 79% through the variables mean July temperature and elevation range. We conclude that these first continental wide analyses grasp the overall pattern in spider species richness of Europe quite well, although some of the observed patterns are not directly causal. Climatic variables are expected to be among the most important direct factors, although other variables (e.g. elevation range, plant species richness) are important (surrogate) correlates of spider species richness.

800-yr-long records of annual air temperature and precipitation over southern Siberia inferred from Teletskoye Lake sediments

A unique 800-yr-long record of annual temperatures and precipitation over the south of western Siberia has been reconstructed from the bottom sediments of Teletskoye Lake, Altai Mountains using an X-ray fluorescence scanner (XRF) providing 0.1-mm resolution timeseries of elemental composition and X-ray density (XRD). Br content appears to be broadly correlative with mean annual temperature variations because of changes in catchment vegetation productivity. Sr/Rb ratio reflects the proportion of the unweathered terrestrial fraction. XRD appears to reflect water yield regime and sediment flux. Sedimentation is rather continuous because annual clastic supply and deposited mass are the same. The artificial neural networks method was applied to convert annual sedimentary time-series of XRD, Br content, and Sr/Rb ratio to annual records of temperature and precipitation using a transfer function. Comparison of these reconstructed Siberian records with the annual record of air temperature for the Northern Hemisphere shows similar trends in climatic variability over the past 800 yr. Estimated harmonic oscillations of temperature and precipitation values for both historical and reconstructed periods reveal subdecadal cyclicity.

Dichroplus vittatus(Orthoptera: Acrididae) follows the converse to Bergmann's rule although male morphological variability increases with latitude

Geographic body size variation was analysed in males and females of 19 populations of the South American grasshopper Dichroplus vittatus Bruner spanning 20 degrees of latitude and 2700 m of altitude. Using mean and maximum body length of each sex and factors obtained from principal components analyses of six morphometric linear characters it was shown that D. vittatus followed the converse to Bergmann's rule latitudinally but not altitudinally where no significant trends were observed. For males, variability of body size increased with latitude but not with altitude. Both types of trends were significantly correlated with mean annual temperature and minimum annual temperature (positive correlations), and two estimators of seasonality, the coefficients of variation of mean annual temperature (negative) and mean annual precipitation (positive). Some allometric relationships also showed geographic variation. It is suggested that the observed decrease in size with latitude together with the increase in morphological variability is a consequence of a number of factors: the shortening of the growing season southwards; the increasing seasonality and climatic unpredictability; and the fact that the species exhibits protandry which contributes to smaller and more variable size in males and smaller but more constant body size in females.

Geographical divergence for quantitative traits in colonising populations of Drosophila kikkawai from India.

There are significant geographical variations for four quantitative traits among eight natural populations of Drosophila kikkawai along the Indian latitudinal transect (8.29 to 33 degrees N). Body weight, wing length, thorax length, and ovariole number exhibit significant clinal variation with increase in latitutde. Genetic correlations between all the four traits are significantly higher. Slope values for body weight and wing length are higher (2.32 per degree latitude) while lower for thorax length (0.70) and ovariole number (0.56). South Indian populations are characterised by lower mean values but higher variances as well as CV values as compared with northern populations. Multiple regression analyses (on the basis of temperature related climatic variables) evidence significantly higher association between all the four traits and coefficient of variation of mean annual temperature (seasonal thermal amplitude; TCV). Thus, genetic differentiations for quantitative traits in D. kikkawai are due to selective pressure from variable seasonal environmental conditions occurring on the southern tropical versus northern subtropical regions of the Indian subcontinent.

Valley floor climate observations from the McMurdo dry valleys, Antarctica, 1986–2000

Climate observations from the McMurdo dry valleys, East Antarctica are presented from a network of seven valley floor automatic meteorological stations during the period 1986 to 2000. Mean annual temperatures ranged from −14.8°C to −30.0°C, depending on the site and period of measurement. Mean annual relative humidity is generally highest near the coast. Mean annual wind speed increases with proximity to the polar plateau. Site‐to‐site variation in mean annual solar flux and PAR is due to exposure of each station and changes over time are likely related to changes in cloudiness. During the nonsummer months, strong katabatic winds are frequent at some sites and infrequent at others, creating large variation in mean annual temperature owing to the warming effect of the winds. Katabatic wind exposure appears to be controlled to a large degree by the presence of colder air in the region that collects at low points and keeps the warm less dense katabatic flow from the ground. The strong influence of katabatic winds makes prediction of relative mean annual temperature based on geographical position (elevation and distance from the coast) alone, not possible. During the summer months, onshore winds dominate and warm as they progress through the valleys creating a strong linear relationship (r2 = 0.992) of increasing potential temperature with distance from the coast (0.09°C km−1). In contrast to mean annual temperature, summer temperature lends itself quite well to model predictions, and is used to construct a statistical model for predicting summer dry valley temperatures at unmonitored sites.