Climate, niche conservatism, and the global bird diversity gradient

We tested the proposition that there are more species in the tropics because basal clades adapted to warm paleoclimates have been lost in regions now experiencing cool climates. Molecular phylogenies were used to classify species as "basal" and "derived" based on their family, and their richness patterns were contrasted. Path models also evaluated environmental predictors of richness patterns. As predicted, basal clades are more diverse in the lowland tropics, whereas derived clades are more diverse in the extratropics and high-altitude tropics. Seventy-four percent of the variation in bird richness was explained by environmental variables, but models differed for basal and derived groups. The overall gradient is described by the spatial pattern of basal clades, although there are differences in the Old and New Worlds. We conclude that in ecological time, the global richness gradient reflects birds' responses to climatic gradients, partially operating via plants. Over evolutionary time, the gradient primarily reflects the extirpation of species in older clades from parts of the world that have become cooler in the present. A strong secondary effect arises from dispersal of clades from centers of origin and subsequent radiations. Overall, the diversity gradient is well explained by niche conservatism and the "time-for-speciation" hypothesis.     

Climate and vegetation controls on boreal zone energy exchange

The boreal forest, one of the world's larger biomes, is distinct from other biomes because it experiences a short growing season and extremely cold winter temperatures. Despite its size and impact on the earth's climate system, measurements of mass and energy exchange have been rare until the past five years. This paper overviews results of recent and comprehensive field studies conducted in Canada, Siberia and Scandinavia on energy exchanges between boreal forests and the atmosphere. How the boreal biosphere and atmosphere interact to affect the interception of solar energy and how solar energy is used to evaporate water and heat the air and soil is examined in detail. Specifically, we analyse the magnitudes, temporal and spatial patterns and controls of solar energy, moisture and sensible heat fluxes across the land–atmosphere interface. We interpret and synthesize field data with the aid of a soil–vegetation–atmosphere transfer model, which considers the coupling of the energy and carbon fluxes and nutrient status. Low precipitation and low temperatures limit growth of many boreal forests. These factors restrict photosynthetic capacity and lower root hydraulic conductivity and stomatal conductance of the inhabitant forests. In such circumstances, these factors interact to form a canopy that has a low leaf area index and exerts a significant resistance to evaporation. Conifer forests, growing on upland soils, for example, evaporate at rates between 25 and 75% of equilibrium evaporation and lose less than 2.5 mm day^?1 of water. The open nature of many boreal conifer forest stands causes a disproportionate amount of energy exchange to occur at the soil surface. The climatic and physiological factors that yield relatively low rates of evaporation over conifer stands also cause high rates of sensible heat exchange and the diurnal development of deep planetary boundary layers. In contrast, evaporation from broad‐leaved aspen stands and fen/wetlands approach equilibrium evaporation rates and lose up to 6 mm day^?1.     

Climate change and evolving human diversity in Europe during the last glacial

A link between climate change and human evolution during the Pleistocene has often been assumed but rarely tested. At the macro-evolutionary level Foley showed for hominids that extinction, rather than speciation, correlates with environmental change as recorded in the deep sea record. Our aim is to examine this finding at a smaller scale and with high-resolution environmental and archaeological archives. Our interest is in changing patterns of human dispersal under shifting Pleistocene climates during the last glacial period in Europe. Selecting this time frame and region allows us to observe how two hominid taxa, Neanderthals and Crô-Magnons, adapted to climatic conditions during oxygen isotope stage 3. These taxa are representative of two hominid adaptive radiations, termed terrestrial and aquatic, which exhibited different habitat preferences but similar tolerances to climatic factors. Their response to changing ecological conditions was predicated upon their ability to extend their societies in space and time. We examine this difference further using a database of all available radiocarbon determinations from western Europe in the late glacial. These data act as proxies for population history, and in particular the expansion and contraction of regional populations as climate changed rapidly. Independent assessment of these processes is obtained from the genetic history of Europeans. The results indicate that climate affects population contraction rather than expansion. We discuss the consequences for genetic and cultural diversity which led to the legacy of the Ice Age: a single hominid species, globally distributed.     

Climate change impacts on structure and diversity of fish communities in rivers

It is widely accepted that climate change constrains biota. Yet, because of the lack of consistent multisite and multitaxon surveys, few studies have addressed general rules about how climate change impacts on structure and diversity of animal communities. Especially, the relative influence of nonclimatic anthropogenic disturbances on this impact is fairly unknown. Here, we present for the first time a meta-analysis assessing the effect of global warming on stream organisms. Fish communities of large rivers in France undergoing various anthropogenic pressures showed significant increase in proportions of warm-water species and of specific richness during the last 15–25 years. Conversely, the equitability decreased, indicating a gradual decrease of the number of dominant species. Finally, the total abundance increased, coupled with rejuvenation and changes in size-structure of the communities. Interestingly, most of these effects were not depressed by the strength of nonclimatic anthropogenic disturbances. Conversely, geographical location of communities and especially closeness of natural barriers to migration could influence their response to climate change. Indeed, increase in the proportion of southern species seemed hindered at sites located close to the southern limit of the European species' geographical ranges. This work provides new evidence that climate change have deep impacts on communities which, by overtaking the effects of nonclimatic anthropogenic disturbances, could be more substantial than previously thought. Overall, our results stress the importance of considering climate change impacts in studies addressing community dynamics, even in disturbed sites.     

肠道微生物多样性与能量代谢调控及肥胖关系的研究进展

肠道微生物与宿主之间相互选择,构成了一个相对稳定的超有机体。宿主基因型和遗传关系影响肠道微生物的生态学特征,而肠道微生物发酵肠道内多糖,为宿主提供可吸收利用的养分,增强肠道对养分吸收的能力。同时,肠道微生物还影响一些转录因子的活性,调控宿主基因的表达,增强宿主甘油三酯的合成和脂肪沉积,减少脂肪酸氧化分解,调控宿主能量代谢。     

Archaeal diversity and geochemical energy yields in a geothermal well on Vulcano Island, Italy

The archaeal diversity in a shallow geothermal well on Vulcano Island, Italy was characterized using culture‐independent 16S rDNA sequence analysis. Environmental DNA was extracted from 56 °C well water, and the 16S ribosomal RNA gene was amplified with archaea‐specific primers. Restriction fragment length polymorphism (RFLP) analysis of ～250 clones revealed 35 unique patterns, which were sequenced and analyzed. These yielded 17 operational taxonomic units, of which 13, 3, and 1 were unique cren‐, eury‐, and korarchaeotal sequences, respectively. The majority of the crenarchaeotal phylotypes formed a novel, deeply‐branching clade that includes sequences from other hydrothermal environments, but no cultured representatives. Three phylotypes represent novel lineages in the Thermoproteales and two phylotypes represent a novel genus of Euryarchaeota. One euryarchaeotal phylotype was nearly identical (99%) to Palaeococcus helgesonii, an aerotolerant, hyperthermophilic fermenter previously isolated from the same well. To place this diverse archaeal community in the geochemical framework of this ecosystem, we calculate values of Gibbs free energy of 145 organic and inorganic redox reactions at in situ conditions. Energy yields ranged from 0 to 125 kJ per mole of electrons transferred. The most exergonic organic reactions were organic carbon oxidation with O₂ (>100 kJ/mol e^?), followed by oxidation with (61–93 kJ/mol e^?), Fe(III) (43–60 kJ/mol e^?), and S⁰/ (6–27 kJ/mol e^?) as terminal electron acceptors. Overall, energy yields from inorganic reactions were similar to those of the organic reactions considered, but were less systematic with respect to terminal electron acceptor. The oxidation of methane coupled with Fe(III) reduction yielded the most energy (123 kJ/mol e^?). However, the most exergonic inorganic reactions were predominantly O₂, , or reduction. Reduction of , S⁰, CO₂, and CO yielded significantly less energy (0–18 kJ/mol e^?). Metabolisms of the cultured organisms identified in the Pozzo Istmo archaeal clone library were exergonic. However, most of the archaeal diversity remains uncultured and energetic calculations reveal an extensive suite of potential lithotrophic and heterotrophic metabolisms that could be exploited by these novel organisms.     

Climate, altitude, and blood pressure.

The effects of climate and altitude on casual blood pressure are examined from the perspectives of initial exposure, acclimatization, long-term residence, and birthplace. Hot arid and hot humid climates seem to have little effect on blood pressure, although a slight reduction may be found in some naturally acclimatized groups. Exposure of the total body to mild cold likewise has little apparent effect. Local exposure of the extremities to severe cold occasions significant increases in blood pressure during exposure but not at other times. Acclimatization reduces but does not eliminate that response. The effects of altitude on blood pressure are variable. There is initial hypertension, followed by gradual normalization. After years of residence at high altitude blood pressure may actually be lower than that observed among residents at sea level.     

Climate and small scale factors determine functional diversity shifts of biological soil crusts in Iberian drylands

Understanding functional diversity is critical to manage and preserve biodiversity and ecosystem functioning in the face of global change. However, the efforts to characterize this functional component have been mostly directed to vascular vegetation. We sampled lichen-dominated biological soil crusts (BSCs) in semiarid grasslands along an environmental gradient in the Iberian Peninsula. We characterized five effect functional traits for 31 lichens species, and evaluated the influence of large scale (i.e. precipitation) and small scale factors (i.e. substrate type, shrub presence, Stipa tenacissima presence) on dominant trait values; i.e. community weighted means, and functional divergence; i.e. Rao quadratic entropy in 580 sampling quadrats. Across the gradient, we found multiple trait shifts and a general increase of functional divergence with increasing precipitation. We also observed that substrate type and small scale biotic factors determined shifts in all traits studied, while these factors affected less to functional divergence. Comparing functional diversity with taxonomic diversity, we found contrasting responses to both large and small scale factors. These findings suggest that BSC community trait composition is influenced by multi-scale abiotic and biotic factors with environmental filtering dominating at large spatial scales and limiting similarity at specific small scales. Also, our results emphasize the potential differences between taxonomic and functional diversity in response to environmental factors. We concluded that functional diversity of BSCs not only provides novel and critical knowledge of BSC community structure, but also it should be considered as a critical tool in biodiversity conservation strategies, ecosystem services assessment and ecological modelling.     

Bacterial diversity in the mountains of South-West China: Climate dominates over soil parameters

Certain patterns in soil bacterial diversity and community composition have become evident from metagenomics studies on a range of scales, from various parts of the world. For example, soil pH has generally been seen as dominating variation in bacterial diversity, above all other soil and climate parameters. It is important however to test the generality of these relationships by studying previously un-sampled areas. We compared soil bacterial diversity and community composition under a wide range of climatic and edaphic conditions in mountainous Yunnan Province, SW China. Soil samples were taken from a range of primary forest types and altitudes, reflecting the great variation of forest environments in this region. From each soil sample, DNA was extracted and pyrosequenced for bacterial 16S rRNA gene identification. In contrast to other recent studies from other parts of the world, pH was a weaker predictor of bacterial community composition and diversity than exchangeable Ca²⁺ concentration, and also the more poorly defined environmental parameter of elevation. Samples from within each forest type clustered strongly, showing the distinctive pattern of their microbial communities on a regional scale. It is clear that on a regional scale in a very heterogeneous environment, additional factors beyond pH can emerge as more important in determining bacterial diversity.     

Tectonics,topography, and mammalian diversity

Terrestrial vertebrates show striking changes in species richness across topographic gradients. For mammals, nearly twice as many species per unit area occur in topographically complex regions as in adjacent lowlands. The geological context of this pervasive biogeographic pattern suggests that tectonic processes have a first‐order impact on regional diversity. I evaluate ecological, evolutionary, and historical influences of tectonics and topography on the regional diversity of terrestrial mammals, focusing on the hypothesis that diversification rates are higher in active versus passive tectonic settings. Ten predictions follow from this hypothesis. 1) The timing of peaks in speciation should be congruent with the timescale for tectonic episodes. 2) The rates of speciation and genetic differentiation of populations should be greater for species inhabiting topographically complex regions than spatially continuous landscapes. 3) If topographic complexity per se promotes diversification, then a cluster of young divergences should occur for montane species compared to lowland relatives. 4) Endemism in tectonically active regions should reflect origination within the region rather than range reduction from larger areas. 5) Extinction rates should differ for lineages in tectonically active regions compared to adjacent lowlands. 6) The relationship between local and regional species richness should differ between topographic settings because of higher beta diversity in topographically complex regions. 7) Species originating in topographically complex regions should colonize adjacent lowlands more often than the reverse pattern. 8) North‐south mountain ranges should have higher regional species richness than east‐west mountain ranges. 9) Areas with multiple mountain ranges should have higher regional species richness than comparable areas with single mountain ranges. 10) Global climate changes should affect diversification in tectonically active regions. Research addressing these topics places elevational diversity gradients into a geohistorical context and integrates data from modern biotas and the fossil record.     

Restriction of energy intake, energy expenditure, and aging

Energy restriction (ER), without malnutrition, increases maximum life span and retards the development of a broad array of pathophysiological changes in laboratory rodents. The mechanism responsible for the retardation of aging by ER is, however, unknown. One proposed explanation is a reduction in energy expenditure (EE). Reduced EE may increase life span by decreasing the number of oxygen molecules interacting with mitochondria, thereby lowering reactive oxygen species (ROS) production. As a step toward testing this hypothesis, it is important to determine the effect of ER on EE. Several whole-body, organ, and cellular studies have measured the influence of ER on EE. In general, whole-body studies have reported an acute decrease in mass-adjusted EE that disappears with long-term ER. Organ-specific studies have shown that decreases in EE of liver and gastrointestinal tract are primarily responsible for initial reductions in EE with ER. These data, however, do not determine whether cellular EE is altered with ER. Three major processes contributing to resting EE at the cellular level are mitochondrial proton leak, Na(+)-K(+)-ATPase activity, and protein turnover. Studies suggest that proton leak and Na(+)-K(+)-ATPase activity are decreased with ER, whereas protein turnover is either unchanged or slightly increased with ER. Thus, two of the three major processes contributing to resting EE at the cellular level may be decreased with ER. Although additional cellular measurements are needed, the current results suggest that a lowering of EE could be a mechanism for the action of ER.