Soil microbial diversity and community structure across a climatic gradient in western Canada

Soil microbial functional diversity was assessed along a climatic gradient in Western Canada. Mineral soil samples were collected from jack pine (Pinus banksiana Lamb.) stands along an 800km transect between Prince Albert, Saskatchewan and Gillam, Manitoba. Microbial communities were isolated from the soil samples, washed and inoculated into wells of Gram-negative Biolog microplates. Optical density values were used to calculate Shannon diversity indices and to perform principal component analysis. Colour development rank plots (CDR) were created by expressing optical density values as a percentage of total colour development and plotting the wells in descending order. Soil microbial functional diversity decreased with increasing latitude and correlated positively with measures of atmospheric temperature and pH. Soil microbial diversity may be lower in northern sites due to decreased productivity, nutrient limitation and higher acidity. CDR plots are consistent with a trend of increasing environmental harshness moving north along the transect.     

Relationships between alpha diversity of plant species in bloom and climatic variables across an elevation gradient

This study analyzes a 20-year record of flowering observations collected near Tucson, Arizona, USA. In contrast to traditional phenological records, this dataset is a record of all species observed in bloom collected in five segments of approximately 1 mile (1.61 km) in length across a 4,158-ft (1,200-m) elevation gradient. The data showed differing seasonal and interannual patterns, demonstrating the influence of climatic factors and elevation on flowering. Miles at higher elevations showed bloom peaks in summer, consistent with temperate and montane communities. Conversely, lower miles demonstrated two distinct flowering seasons, typical of the surrounding Sonoran Desert. Interannual fluctuations in total species observed in bloom were not consistent across the 5 miles (c. 8 km), suggesting that these communities respond to different flowering cues. Consistent with documented flowering triggers in semi-arid systems, the alpha diversity of species in bloom at lower elevations in this study was strongly influenced by precipitation. Upper elevation bloom numbers were heavily influenced by temperature, correspondent with bloom triggers in temperate and montane systems. In general, different life forms exhibited similar bloom triggers within the study miles, believed to be a function of shallow soils. Multivariate community analyses showed that anomalous climate conditions yielded unique seasonal bloom compositions. Over the course of the study, average summer temperature showed an upward trend; the number of species in bloom in summer (July–October) in the highest mile (1,940–2,210 m) demonstrated a concurrent increasing trend. Community analysis suggested a gradual shift in the composition of species in bloom in this mile over the study period.     

Comparison of biodiversity and ground cover between a commercial rotationally grazed property and an adjacent nature reserve in semi‐arid rangeland

Continuous livestock grazing can have negative effects on biodiversity and landscape function in arid and semi‐arid rangelands. Alternative grazing management practices, such as rotational grazing, may be a viable option for broad‐scale biodiversity conservation and sustainable pastoral management. This study compared ground cover, plant species composition and floristic and functional diversity along gradients of grazing intensity between a pastoral property rotationally grazed by goats and an adjacent nature reserve (ungrazed by commercial livestock) in semi‐arid south‐eastern Australia. Understorey plant species composition differed significantly between the rotationally grazed property and the nature reserve, with a greater proportion and frequency of palatable species recorded in the nature reserve. Understorey plant species richness, diversity, functional biodiversity measures and ground cover declined with increasing grazing pressure close to water points under commercial rotational grazing management. However, at a whole‐paddock scale, there were few differences in plant biodiversity and ground cover between the rotationally grazed property and the nature reserve, despite differences in overall plant species composition. Flexible, adaptive, rotational grazing should be investigated further for its potential to achieve both socio‐economic and biodiversity conservation outcomes in semi‐arid rangelands to complement existing conservation reserves.     

Hierarchical partitioning of ant diversity: implications for conservation of biogeographical diversity in arid and semi‐arid areas

Aim The scale of observation is important in detecting the spatial variation of biological assemblages, which should be taken into consideration for an appropriate plan of biogeographical conservation. We investigated whether (1) World Wildlife Fund’s ecoregion units are the appropriate scale for conserving ant diversity in Iran, (2) each ecoregion represents a distinct ant community composition and (3) patterns of diversity partitioning differ among four ecoregions. Location Iran, a sampling transect along four arid and semi‐arid ecoregions. Methods We applied hierarchical partitioning to data collected from a nested sampling design including four hierarchical levels: ‘local’, ‘landscape’, ‘ecoregional’ and ‘whole‐region’. Observed alpha and beta diversity components were compared with values of null distributions. Hierarchical cluster analysis was applied to evaluate similarity of ant species composition among ecoregions. Results Partitioning of whole‐region species richness showed that 85% of the species richness was generated by beta diversity among ecoregions and landscapes. The highest value of diversity was generated by beta diversity among ecoregions. Unlike whole‐region partitioning, separate partitioning within each ecoregion revealed that beta component among localities contributed to species richness of each ecoregion. Ecoregions showed different patterns of diversity partitioning. The alpha component contributed largely to the total diversity of two ecoregions, but for two other ecoregions, beta component contributed more than alpha component. Cluster analysis identified four discrete ant species compositions; however, it split landscapes of one ecoregion into two distinct groups. Main conclusions Whole‐region diversity partitioning indicates that ecoregions represent the appropriate scale for conserving ant diversity and that each ecoregion has a distinct ant fauna. However, different conservation strategies should be considered for different ecoregions owing to the differing scales of variation within them. Boundaries of ecoregions remain a subject for further studies. The influence of climate change on ecoregional boundaries should be considered and should be predicted with respect to future conservation maps.     

Climatic variation and simulated patterns in seedling establishment of two dominant grasses at a semi‐arid‐arid grassland ecotone

Abstract. The objective of this study was to predict the effects of climatic variation at multiple temporal frequencies on seedling establishment by two congeneric C₄ perennial grasses (Bouteloua gracilis and B. eriopoda) at the ecotone between shortgrass steppe grassland and Chihuahuan desert grassland in central New Mexico, USA. The approach was to use a daily time‐step simulation model to determine the occurrence of a recruitment event in each year based upon the amount and timing of soil water required for establishment. Historical weather data were used to predict effects of seasonal and inter‐decadal variation in climate on establishment. A sensitivity analysis was used to predict effects of directional climate change on establishment. Bouteloua gracilis had a broad pattern of simulated establishment from May through September that included periods with high year‐to‐year variation in precipitation. B. eriopoda establishment events occurred primarily in July when precipitation amounts were most reliable. Climatic conditions from 1949 through 1968 were more favorable for B. eriopoda establishment compared to the cooler, wetter conditions from 1969 through 1988 that favored B. gracilis. Establishment of B. eriopoda was lowest in El Niño years whereas B. gracilis establishment was highest in La Niña years. Establishment of B. gracilis was most sensitive to temperature when precipitation was higher than current amounts. The greatest response to temperature by B. eriopoda for all precipitation amounts occurred at cooler temperatures than found currently. These results indicate that climatic variation at multiple frequencies has differential effects on seedling establishment for these two perennial grasses, and may account at least in part for patterns in dominance at this biome transition zone.     

Broad‐scale patterns in plant diversity vary between land uses in a variegated temperate Australian agricultural landscape

Plant diversity is threatened in many agricultural landscapes. Our understanding of patterns of plant diversity in these landscapes is mainly based on small‐scale (<1000 m²) observations of species richness. However, such observations are insufficient for detecting the spatial heterogeneity of vegetation composition. In a case‐study farm on the North‐West Slopes of New South Wales, Australia, we observed species richness at four scales (quadrat, patch, land use and landscape) across five land uses (grazed and ungrazed woodlands, native pastures, roadsides and crops). We applied two landscape ecological models to assess the contribution of these land uses to landscape species richness: (i) additive partitioning of diversity at multiple spatial scales, and (ii) a measure of habitat specificity – the effective number of species that a patch contributes to landscape species richness. Native pastures had less variation between patches than grazed and ungrazed woodlands, and hence were less species‐rich at the landscape scale, despite having similar richness to woodlands at the quadrat and patch scale. Habitat specificity was significantly higher for ungrazed woodland patches than all other land uses. Our results showed that in this landscape, ungrazed woodland patches had a higher contribution than the grazed land uses to landscape species richness. These results have implications for the conservation management of this landscape, and highlighted the need for greater consensus on the influence of different land uses on landscape patterns of plant diversity.     

Richness and diversity of Leguminosae in an altitudinal gradient in the tropical semi‐arid zone of Brazil

Abstract Many studies are based on the premise that, on a local scale, diversity is the result of ecological processes, whereas on a regional scale factors such as the topography, geology, hydrology, and historical and evolutionary events would influence this control. The Baturité Mountain Range (Ceará state), located in the Brazilian semi‐arid zone, is considered an area of extreme importance for conservation with its vegetation varying with the altitude and slope (windward vs. leeward). On the windward (wet) slope, rainforest dominates, whereas the leeward (dry) slope is dominated by seasonal forests and thorny woodland. The aim of this study was to contribute to the knowledge of the patterns of richness and diversity of the family Leguminosae on a local scale (Baturité Mountain Range) as well as a regional scale (northeastern Brazil). The two slopes present quite distinct floras. The dry slope presents higher richness and diversity indices for Leguminosae than the wet slope. The highest diversity of Leguminosae in the dry areas did not corroborate the ideas of other studies carried out in neotropical forests (total flora) that the higher species richness was predicted for wet areas. The present study indicates that the historical and evolutionary processes influence the diversity patterns on a local scale (Baturité Mountain Range), as well as on a regional scale (Brazilian semi‐arid). Our results reinforce the uniqueness of each portion of this area and its importance for conservation.     

Scale‐dependent complementarity of climatic velocity and environmental diversity for identifying priority areas for conservation under climate change

As most regions of the earth transition to altered climatic conditions, new methods are needed to identify refugia and other areas whose conservation would facilitate persistence of biodiversity under climate change. We compared several common approaches to conservation planning focused on climate resilience over a broad range of ecological settings across North America and evaluated how commonalities in the priority areas identified by different methods varied with regional context and spatial scale. Our results indicate that priority areas based on different environmental diversity metrics differed substantially from each other and from priorities based on spatiotemporal metrics such as climatic velocity. Refugia identified by diversity or velocity metrics were not strongly associated with the current protected area system, suggesting the need for additional conservation measures including protection of refugia. Despite the inherent uncertainties in predicting future climate, we found that variation among climatic velocities derived from different general circulation models and emissions pathways was less than the variation among the suite of environmental diversity metrics. To address uncertainty created by this variation, planners can combine priorities identified by alternative metrics at a single resolution and downweight areas of high variation between metrics. Alternately, coarse‐resolution velocity metrics can be combined with fine‐resolution diversity metrics in order to leverage the respective strengths of the two groups of metrics as tools for identification of potential macro‐ and microrefugia that in combination maximize both transient and long‐term resilience to climate change. Planners should compare and integrate approaches that span a range of model complexity and spatial scale to match the range of ecological and physical processes influencing persistence of biodiversity and identify a conservation network resilient to threats operating at multiple scales.     

Differentiation of spring carabid beetle assemblages between semi‐natural habitats and adjoining winter wheat

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Landscape context affects the relationship between local and landscape species richness of butterflies in semi‐natural habitats

Local species richness of butterflies can be expected to benefit from both local habitat properties as well as the availability of suitable habitats and source populations in the surrounding landscape. Whether local species richness is dependent on local or landscape factors can be assessed by examining the relationship between local and landscape species richness. Here we studied how local species richness is related to landscape‐level species richness in landscapes differing in agricultural intensity. The relationship was linear for field boundaries in intensively cultivated landscapes and non‐linear in less‐intensively cultivated landscapes. In landscapes containing semi‐natural grasslands (on average 4% of overall land‐use), the relationship was non‐linear for field boundaries, but linear when considering local species richness of the grasslands themselves. These results show that local factors are more important than landscape factors in determining local species richness in landscapes which contained semi‐natural grasslands. Local species richness was limited by landscape factors in intensively cultivated landscapes. This interpretation was supported by the relationship between local species richness and landscape‐scale average mobility and generalist percentage of butterfly assemblages. We conclude that the management of field boundary habitat quality for butterflies is expected to be most effective in landscapes with semi‐natural grasslands, the species composition of which in turn is dependent on the regional occurrence of grasslands. Based on our results, managing non‐crop habitats for the conservation of habitat specialists and species with poor mobility will be most efficient in regions where patches of semi‐natural grasslands occur.     

Environmental controls on the distribution and diversity of lentic Chironomidae (Insecta: Diptera) across an altitudinal gradient in tropical South America

To predict the response of aquatic ecosystems to future global climate change, data on the ecology and distribution of keystone groups in freshwater ecosystems are needed. In contrast to mid‐ and high‐latitude zones, such data are scarce across tropical South America (Neotropics). We present the distribution and diversity of chironomid species using surface sediments of 59 lakes from the Andes to the Amazon (0.1–17°S and 64–78°W) within the Neotropics. We assess the spatial variation in community assemblages and identify the key variables influencing the distributional patterns. The relationships between environmental variables (pH, conductivity, depth, and sediment organic content), climatic data, and chironomid assemblages were assessed using multivariate statistics (detrended correspondence analysis and canonical correspondence analysis). Climatic parameters (temperature and precipitation) were most significant in describing the variance in chironomid assemblages. Temperature and precipitation are both predicted to change under future climate change scenarios in the tropical Andes. Our findings suggest taxa of Orthocladiinae, which show a preference to cold high‐elevation oligotrophic lakes, will likely see range contraction under future anthropogenic‐induced climate change. Taxa abundant in areas of high precipitation, such as Micropsectra and Phaenopsectra, will likely become restricted to the inner tropical Andes, as the outer tropical Andes become drier. The sensitivity of chironomids to climate parameters makes them important bio‐indicators of regional climate change in the Neotropics. Furthermore, the distribution of chironomid taxa presented here is a vital first step toward providing urgently needed autecological data for interpreting fossil chironomid records of past ecological and climate change from the tropical Andes.     

Large‐scale longitudinal climate gradient across the Palearctic region affects passerine feather moult extent

Large‐scale spatial gradients of environmental conditions shape organisms, populations and ecosystems. Even though environmental gradients are a key research theme in macro‐ecology and biogeography, the effects of large‐scale, east–west, environmental gradients are largely overlooked compared with north–south gradients. Our study focused on feather moult, an important and energy demanding process in birds. By comparing Western and Eastern Palearctic populations of 21 species, we found that juvenile passerines in the Western and Eastern Palearctic differ in the number of feathers moulted as part of their post‐juvenile moult. This difference is most likely the result of a large‐scale climatic gradient in cold season duration and consequent differences in the time available for moulting. Eastern populations were characterized by a limited extent of feather moult that was additionally affected by migration distance and body mass. The longer migration distance in the Eastern Palearctic caused a generally less extensive moult while high body mass was correlated with a low difference in moult extent between the Western and Eastern Palearctic regions. These results highlight the importance of linking annual cycle processes at the organismal level to the specific environmental conditions within the distribution range of each species.