Species richness generally decreases with increasing latitude,a biodiversity gradient that has long been considered as one of the few laws in ecology.This latitudinal diversity gradient has been observed in many major...Species richness generally decreases with increasing latitude,a biodiversity gradient that has long been considered as one of the few laws in ecology.This latitudinal diversity gradient has been observed in many major groups of organisms.In plants,the latitudinal diversity gradient has been observed in vascular plants,angiosperms,ferns,and liverworts.However,a conspicuous latitudinal diversity gradient in mosses at a global or continental scale has not been observed until now.Here,we analyze a comprehensive data set including moss species in each band of 20° in latitude worldwide.Our results show that moss species richness decreases strongly with increasing latitude,regardless of whether the globe is considered as a whole or different longitudinal segments(e.g.,Old World versus New World) are considered separately.This result holds when variation in area size among latitudinal bands is taken into account.Pearson's correlation coefficient between latitude and species richness is-0.99 for both the Northern and Southern Hemispheres.Because bryophytes are an extant lineage of early land plants and because mosses not only include most of extant species of bryophytes but also are important constituents of most terrestrial ecosystems,understanding geographic patterns of mosses is particularly important The finding of our study fills a critical knowledge gap.展开更多
Human commensal species take advantage of anthropogenic conditions that are less likely to be challenged by the selective pressures of natural environments.Their morphological and physiological phenotypes can therefor...Human commensal species take advantage of anthropogenic conditions that are less likely to be challenged by the selective pressures of natural environments.Their morphological and physiological phenotypes can therefore dissociate from habitat characteristics.Understanding how these species adjust their morphological and physiological traits across latitudinal gradients is fundamental to uncovering the eco-physiological strategies underlying coping mechanisms.Here,we studied morphological traits in breeding Eurasian tree sparrows(ETSs;Passer montanus)among low-latitude(Yunnan and Hunan)and middle-latitude(Hebei)localities in China.We then compared body mass;lengths of bill,tarsometatarsus,wing,total body,and tail feather;and baseline and capture stress-induced levels of plasma corticosterone(CORT)and the metabolites including glucose(Glu),total triglyceride(TG),free fatty acid(FFA),total protein,and uric acid(UA).None of the measured morphological parameters varied with latitude except in the Hunan population,which demonstrated longer bills than those in other populations.Stress-induced CORT levels significantly exceeded baseline levels and decreased with increasing latitude,but total integrated CORT levels did not vary with latitude.Capture stress-induced significantly increased Glu levels and decreased TG levels,independent of site.However,the Hunan population had significantly higher baseline CORT,baseline and stress-induced FFA levels,but lower UA levels,which differed from other populations.Our results suggest that rather than morphological adjustments,physiological adjustments are mainly involved in coping mechanisms for middle-latitude adaptation in ETSs.It is worth investigating whether other avian species also exhibit such dissociation from external morphological designs while depending on physiological adjustments.展开更多
Aims Invasive species occurrence and their effects on biodiversity may vary along latitudes.We examined the occurrence(species cover)and relative dominance(importance value)of invasive alligator weed,Alternanthera phi...Aims Invasive species occurrence and their effects on biodiversity may vary along latitudes.We examined the occurrence(species cover)and relative dominance(importance value)of invasive alligator weed,Alternanthera philoxeroides,in its terrestrial habitat in China through a large-scale latitudinal field investigation.Methods We established 59 plots along the latitudinal transect from 21°N to 37°N.We recorded species name,abundance,height and individual species coverage of plants in every quadrat.We then measuredα-species diversity variations associated with the A.philoxeroides community across the latitudinal range.We also analyzed the effect of latitude on plant species’distributions in this community by using canonical correspondence analysis(CCA).Important Findings We found that species cover and importance value of A.philoxe-roides increased in areas<35°N,but decreased at higher latitudes.Lower latitudes supported greater species diversity than higher latitudes.Small-scale invasion of A.philoxeroides was associated with higher species diversity,but community diversity was lower when A.philoxeroides species cover exceeded 36%.Community plant species changed from mesophyte to hygrophyte gradually from low to high latitude.Our research suggests that latitude had significant influences on community diversity which interacted with the biotic resistance of a community and impact of invasion.Consequently,A.philoxeroides may become more invasive and have greater negative impacts on community species diversity in higher latitudes as global climate changes.展开更多
In forest ecosystems,plant communities shape soil fungal communities through the provisioning of carbon.Although the variation in forest composition with latitude is well established,little is known about how soil fun...In forest ecosystems,plant communities shape soil fungal communities through the provisioning of carbon.Although the variation in forest composition with latitude is well established,little is known about how soil fungal communities vary with latitude.We collected soil samples from 17 forests,along a latitudinal transect in western China.Forest types covered included boreal,temperate,subtropical and tropical forests.We used 454 pyrosequencing techniques to analyze the soil communities.These data were correlated with abiotic and biotic variables to determine which factors most strongly influenced fungal community composition.Our results indicated that temperature,latitude,and plant diversity most strongly influence soil fungal community composition.Fungal diversity patterns were unimodal,with temperate forests(mid latitude)exhibiting the greatest diversity.Furthermore,these diversity patterns indicate that fungal diversity was highest in the forest systems with the lowest tree diversity(temperate forests).Different forest systems were dominated by different fungal subgroups,ectomycorrhizal fungi dominated in boreal and temperate forests;endomycorrhizal fungi dominated in the tropical rainforests,and non-mycorrhizal fungi were best represented in subtropical forests.Our results suggest that soil fungal communities are strongly dependent on vegetation type,with fungal diversity displaying an inverse relationship to plant diversity.展开更多
Aims We analyze two continental data sets of forest communities from across the New World to examine the latitudinal gradients of beta diversity after accounting for gamma diversity and the latitudinal gradient of gam...Aims We analyze two continental data sets of forest communities from across the New World to examine the latitudinal gradients of beta diversity after accounting for gamma diversity and the latitudinal gradient of gamma diversity after accounting for beta diversity.Methods Correlation and regression analyses were used to relate beta and gamma diversity to latitude along two latitudinal gradients in the New World(one including 72 forest sites located south of the equator and the other including 79 forest sites located north of the equator).Important Findings Beta diversity and gamma diversity were negatively correlated with latitude.Beta diversity was strongly and positively correlated with gamma diversity(Pearson’s correlation coefficient:0.783 for New World North and 0.848 for New World South).When beta diversity was regressed on latitude and gamma diversity,69.8 and 85.7%of the variation in beta diversity were explained,respectively,for New World North and New World South.When gamma diversity was regressed on latitude and beta diversity,81.8 and 84.3%of the variation in gamma diversity were explained,respectively,for New World North and New World South.After statistically removing the relationship between beta and gamma diversity,latitude has weak or no relationships with beta and gamma diversity.However,strong positive correlations between beta and gamma diversity may not be considered as evidence of one driving the other along a latitudinal gradient.展开更多
The timing of flowering is an important driver of species distribution and community assembly patterns.However,we still have much to learn about the factors that shape flowering diversity(i.e.,number of species flower...The timing of flowering is an important driver of species distribution and community assembly patterns.However,we still have much to learn about the factors that shape flowering diversity(i.e.,number of species flowering per period) in plant communities.One potential explanation of flowering diversity is the mid-domain effect,which states that geometric constraints on species ranges within a bounded domain(space or time) will yield a mid-domain peak in diversity regardless of ecological factors.Here,we determine whether the mid-domain effect explains peak flowering time(i.e.,when most species of communities are flowering) across China.We used phenological data of 16,267 herbaceous and woody species from the provincial Flora in China and species distribution data from the Chinese Vascular Plant Distribution Database to determine relationships between the observed number of species flowering and the number of species flowering as predicted by the mid-domain effect model,as well as between three climatic variables(mean minimum monthly temperature,mean monthly precipitation,and mean monthly sunshine duration).We found that the mid-domain effect explained a significant proportion of the temporal variation in flowering diversity across all species in China.Further,the mid-domain effect explained a greater proportion of variance in flowering diversity at higher latitudes than at lower latitudes.The patterns of flowering diversity for both herbaceous and woody species were related to both the mid-domain effect and environmental variables.Our findings indicate that including geometric constraints in conjunction with abiotic and biotic predictors will improve predictions of flowering diversity patterns.展开更多
Beta diversity(β-diversity)is the scalar between local(α)and regional(γ)diversity.Understanding geographic patterns ofβ-diversity is central to ecology,biogeography,and conservation biology.A full understanding of...Beta diversity(β-diversity)is the scalar between local(α)and regional(γ)diversity.Understanding geographic patterns ofβ-diversity is central to ecology,biogeography,and conservation biology.A full understanding of the origin and maintenance of geographic patterns ofβ-diversity requires exploring both taxonomic and phylogeneticβ-diversity,as well as their respective turnover and nestedness components,and exploring phylogenetic p-diversity at different evolutionary depths.In this study,we explore and map geographic patterns ofβ-diversity for angiosperm genera in regional floras across the world.We examine both taxonomic and phylogeneticβ-diversity and their constituent components,and both tip-weighted and basal-weighted phylogeneticβ-diversity,and relate them to latitude.On the one hand,our study found that the global distribution ofβ-diversity is highly heterogeneous.This is the case for both taxonomic and phylogeneticβ-diversity,and for both tip-weighted and basal-weighted phylogeneticβ-diversity.On the other hand,our study found that there are highly consistent geographic patterns among different metrics ofβ-diversity.In most cases,metrics ofβ-diversity are negatively associated with latitude,particularly in the Northern Hemisphere.Different metrics of taxonomicβ-diversity are strongly and positively correlated with their counterparts of phylogeneticβ-diversity.展开更多
In eastern Asian subtropical forests,leaf habit shifts from evergreen to deciduous broad-leaved woody plants toward higher latitudes.This shift has been largely explained by the greater capacity of deciduous broad-lea...In eastern Asian subtropical forests,leaf habit shifts from evergreen to deciduous broad-leaved woody plants toward higher latitudes.This shift has been largely explained by the greater capacity of deciduous broad-leaved plants to respond to harsh climatic conditions(e.g.,greater seasonality).The advantages of deciduous leaf habit over evergreen leaf habit in more seasonal climates have led us to hypothesize that leaf habits would shift in response to climate changes more conspicuously in forest canopy trees than in forest understory shrubs.Furthermore,we hypothesize that in the forests of the subtropics,plants at higher latitudes,regardless of growth form,would better tolerate seasonal harsh climates,and hence show less differentiation in leaf habit shift,compared to those at lower latitudes.To test these two hypotheses,we modelled the proportion of deciduous broad-leaved species and the incidence of deciduous and evergreen broad-leaved species in woody angiosperm species compositions of ten largesized forest plots distributed in the Chinese subtropics.We found that the rate of leaf habit shift along a latitudinal gradient was higher in forest trees than in forest shrubs.We also found that the differentiation in leaf habit shift between trees and shrubs is greater at lower latitudes(i.e.,warmer climates)than at higher latitudes(i.e.,colder climates).These findings indicate that specialized forest plants are differentially affected by climate in distinct forest strata in a manner dependent on latitudinal distribution.These differences in forest plant response to changes in climate suggest that global climate warming will alter growth forms and geographical distributions and ranges of forests.展开更多
Plant communities are shaped by multiple factors along environmental gradients;however,studies are limited on how environmental filtering drives community composition and species richness on tropical inselbergs.We eva...Plant communities are shaped by multiple factors along environmental gradients;however,studies are limited on how environmental filtering drives community composition and species richness on tropical inselbergs.We evaluate the influence of altitude and climatic variables related to temperature and precipitation on plant community composition and species richness on Brazilian inselbergs.We assume as a premise that both climate and altitude would induce changes on plant community composition and species richness at the local level.We used plant inventory data from 370 sampling units across four inselberg sites in the Atlantic Forest of Espírito Santo State,south-eastern Brazil.We tested the univariate and multivariate effects of altitude and climate variables on community composition and species richness with multiple models.Differences in species richness between inselbergs were evaluated using sample-based data to estimate rarefaction and extrapolation curves.In addition,differences in species composition and taxonomic beta diversity were examined via novel frequency-based metrics.A contrasting climate pattern was observed between the inselberg sites,with south sites being wet compared to the dry conditions found in northern sites.Species richness by rarefaction showed a similar pattern within regional sites;however,there were marked differences between regions.Species richness and beta diversity showed significant differences among sites,with higher values in southern sites than in northern sites.In a multi-model comparison between inselberg sites,altitude significantly influenced community composition and species richness and explained more variance than climate models.This finding suggested that climate could act to some extent on these tropical inselbergs;however,altitude was a better predictor of plant community composition and species richness at the local level.展开更多
Background:Equatorward,rear-edge tree populations are natural monitors to estimate species vulnerability to climate change.According to biogeographical theory,exposition to drought events increases with increasing ari...Background:Equatorward,rear-edge tree populations are natural monitors to estimate species vulnerability to climate change.According to biogeographical theory,exposition to drought events increases with increasing aridity towards the equator and the growth of southern tree populations will be more vulnerable to drought than in central populations.However,the ecological and biogeographical margins can mismatch due to the impact of ecological factors(topography,soils)or tree-species acclimation that can blur large-scale geographical imprints in trees responses to drought making northern populations more drought limited.Methods:We tested these ideas in six tree species,three angiosperms(Fagus sylvatica,Quercus robur,Quercus petraea)and three gymnosperms(Abies alba,Pinus sylvestris and Pinus uncinata)by comparing rear-edge tree populations subjected to different degrees of aridity.We used dendrochronology to compare the radial-growth patterns of these species in northern,intermediate,and southern tree populations at the continental rear edge.Results and conclusions:We found marked variations in growth variability between species with coherent patterns of stronger drought signals in the tree-ring series of the southern populations of F.sylvatica,P.sylvestris,and A.alba.This was also observed in species from cool-wet sites(P.uncinata and Q.robur),despite their limited responsiveness to drought.However,in the case of Q.petraea the intermediate population showed the strongest relationship to drought.For drought-sensitive species as F.sylvatica and P.sylvestris,southern populations presented more variable growth which was enhanced by cool-wet conditions from late spring to summer.We found a trend of enhanced vulnerability to drought in these two species.The response of tree growth to drought has a marked biogeographical component characterized by increased drought sensitivity in southern populations even within the species distribution rear edge.Nevertheless,the relationship between tree growth and drought varied between species suggesting that biogeographical and ecological limits do not always overlap as in the case of Q.petraea.In widespread species showing enhanced vulnerability to drought,as F.sylvatica and P.sylvestris,increased vulnerability to climate warming in their rear edges is forecasted.Therefore,we encourage the monitoring and conservation of such marginal tree populations.展开更多
Background: Forest biodiversity is the foundation of many ecosystem services, and the effect of biodiversity on ecosystem functioning and processes (BEF) has been a central issue in biodiversity studies. Although m...Background: Forest biodiversity is the foundation of many ecosystem services, and the effect of biodiversity on ecosystem functioning and processes (BEF) has been a central issue in biodiversity studies. Although many hypotheses have been developed to interpret global gradients of biodiversity, there has not been complete agreement on mechanisms controlling biodiversity patterns and distributions. Differences may be due to limited observation data and inconsistencies of spatial scales in analysis. Methods: In this study, we take advantage of USDA Forest Service forest inventory and analysis (FIA) data for exploring regional forest biodiversity and BEF in New England forests. The FIA data provide detailed information of sampled plots and trees for the region, including 6000 FIA plots and more than 33,000 individual trees. Biodiversity models were used to analyze the data. Results: Tree species diversity increases from the north to the south at a rate about 2-3 species per latitudinal degree. Tree species diversity is better predicted by tree height than forest age or biomass. Very different distribution patterns of two common maple species, sugar maple (Acer sdcchorum) and red maple (Acer rubrum), highlight the vulnerability of sugar maple and its potential replacement by red maple on New England landscapes. Red maple generally already outperforms sugar maple, and will likely and continuously benefit from a changing climate in New England. Conclusions: We conclude that forest structure (height) and resources (biomass) are more likely foundational characteristics supporting biodiversity rather than biodiversity determining forest productivity and/or biomass. The potential replacement of red maple for sugar maple in the New England areas could affect biodiversity and stability of forest ecosystem functioning because sugar maple plays important ecological roles distinct from red maple that are beneficial to other tree species in northern hardwood forests. Such a change may not affect forest resilience in terms of forest productivity and biomass as these are similar in red maple and sugar maple, however, it would almost certainly alter forest structure across the landscape.展开更多
The evolution of the latitudinal diversity gradient(LDG),characterized by a peak in diversity toward the tropics,has captured significant attention in evolutionary biology and ecology.However,the inverse LDG(i-LDG)mec...The evolution of the latitudinal diversity gradient(LDG),characterized by a peak in diversity toward the tropics,has captured significant attention in evolutionary biology and ecology.However,the inverse LDG(i-LDG)mechanism,wherein species richness increases toward the poles,remains inadequately explored.Cycads are among one of the oldest lineages of extant seed plants and have undergone extensive diversification in the tropics.Intriguingly,the extant cycad abundance exhibits an i-LDG pattern,and the underlying causes for this phenomenon remain largely elusive.Here,using 1,843 nuclear genes from a nearly complete sampling,we conducted comprehensive phylogenomic analyses to establish a robust species-level phylogeny for Cycas,the largest genus within cycads.We then reconstructed the spatial-temporal dynamics and integrated global environmental data to evaluate the roles of species ages,diversification rates,contemporary environment,and conservatism to ancestral niches in shaping the i-LDG pattern.We found Cycas experienced decreased diversification rates,coupled with the cooling temperature since its origin in the Eocene from continental Asia.Different regions have distinctively contributed to the formation of i-LDG for Cycas,with the northern hemisphere acting as evolutionary museums and the southern hemisphere serving as cradles.Moreover,water-related climate variables,specifically precipitation seasonality and potential evapotranspiration,were identified as paramount factors constraining Cycas species richness in the rainforest biome near the equator.Notably,the adherence to ancestral monsoonal climates emerges as a critical factor in sustaining the diversity pattern.This study underscores the imperative of integrating both evolutionary and ecological approaches to comprehensively unravel the mechanisms underpinning global biodiversity patterns.展开更多
Higher biodiversity is often assumed to be a more desirable scenario for maintaining the functioning of ecosystems,but whether species-richer communities are also more disturbance-tolerant remains controversial.In thi...Higher biodiversity is often assumed to be a more desirable scenario for maintaining the functioning of ecosystems,but whether species-richer communities are also more disturbance-tolerant remains controversial.In this study,we investigated the bacterial communities based on 472 soil samples from 28 forests across China with associated edaphic and climatic properties.We developed two indexes(i.e.,community mean tolerance breadth[CMTB]and community mean response asynchrony[CMRA])to explore the relationship between diversity and community resistance potential.Moreover,we examined this resistance potential along the climatic and latitudinal gradients.We revealed that CMTB was significantly and negatively related to species richness,resulting from the changes in balance between relative abundances of putative specialists and generalists.In comparison,we found a unimodal relationship between CMRA and richness,suggesting that higher biodiversity might not always lead to higher community resistance.Moreover,our results showed differential local patterns along latitude.In particular,local patterns in the northern region mainly followed general relationships rather than those for the southern forests,which may be attributed to the differences in annual means and annual variations of climate conditions.Our findings highlight that the community resistance potential depends on the composition of diverse species with differential environmental tolerance and responses.This study provides a new,testable evaluation by considering tolerance breadth and response asynchrony at the community level,which will be helpful in assessing the influence of disturbance under rapid shifts in biodiversity and species composition as a result of global environmental change.展开更多
The search for pattern in the ecology and evolutionary biology of insect-plant associations has fascinated biologists for centuries. High levels of tropical (tow-latitude) plant and insect diversity relative to pole...The search for pattern in the ecology and evolutionary biology of insect-plant associations has fascinated biologists for centuries. High levels of tropical (tow-latitude) plant and insect diversity relative to poleward latitudes and the disproportionate abundance of host-specialized insect herbivores have been noted. This review addresses several aspects of local insect specialization, host use abilities (and loss of these abilities with specialization), host-associated evolutionary divergence, and ecological (including "hybrid") speciation, with special reference to the generation of biodiversity and the geographic and taxonomic identification of "species borders" for swallowtail butterflies (Papilionidae). From ancient phytochemically defined angiosperm affiliations that trace back millions of years to recent and very local specialized populations, the Papilionidae (swallowtail butterflies) have provided a model for enhanced tmderstanding of localized ecological patterns and genetically based evolutionary processes. They have served as a useful group for evaluating the feeding specialization/physiological efficiency hypothesis. They have shown how the abiotic (thermal) environment interacts with host nutritional suitability to generate "voltinisrn/suitability" gradients in specialization or preference latitudinally, and geographical mosaics locally. Several studies reviewed here suggest strongly that the oscillation hypothesis for speciation does have considerable merit, but at the same time, some species-level host specializations may lead to evolutionary dead-ends, especially with rapid environmental/habitat changes involving their host plants. Latitudinal gradients in species richness and degree of herbivore feeding specialization have been impacted by recent developments in ecological genetics and evolutionary ecology. Localized insect- plant associations that span the biospectrum from polyphenisms, polymorphisms, biotypes, demes, host races, to cryptic species, remain academically contentious, with simple definitions still debated. However, molecular analyses combined with ecological, ethological and physiological studies, have already begun to unveil some answers for many important ecological/evolutionary questions.展开更多
Aims the impact of global warming on belowground processes,espe-cially on fine root production,is poorly understood in comparison with its aboveground counterpart.Methods Here,we compiled 227 measurements to assess th...Aims the impact of global warming on belowground processes,espe-cially on fine root production,is poorly understood in comparison with its aboveground counterpart.Methods Here,we compiled 227 measurements to assess the influence of temperature and precipitation on fine root biomass of Norway spruce(Picea abies[L.]Karst)forest ecosystems in the Eurasia boreal region.Important Findings We found that fine root biomass decreased significantly with lati-tudes.there was a biomass increase of 0.63 Mg ha−1 and 0.32 Mg ha−1 for fine roots<2 and<1 mm in diameter,respectively,with 1°C increase of mean annual temperature.there was an increase of 0.5 and 0.1 Mg ha−1 per 100 mm year−1 precipitation for the two size classes of fine roots.If the adaption of root production can match the pace of global warming and water is not a limiting factor for plant growth,fine root biomass would be expected to increase by 40-140%in response to the predicted increase in tem-perature(3-10°C)over the next century.Our analyses highlighted the strongly positive influences of temperature and precipitation on belowground function,suggesting that predicted future climate change could substantially enhance belowground biomass in the boreal region where the greatest warming is anticipated.this potential increase of belowground biomass,coupled with aboveground biomass,may provide a better understanding of climate-ecosystem feedbacks.展开更多
The climatic niche is a central concept for understanding species distribution,with current and past climate interpreted as strong drivers of present and historical-geographical ranges.Our aim is to understand whether...The climatic niche is a central concept for understanding species distribution,with current and past climate interpreted as strong drivers of present and historical-geographical ranges.Our aim is to understand whether Atlantic Forest snakes follow the general geographical pattern of increasing species climatic niche breadths with increasing latitude.We also tested if there is a tradeoff between temperature and precipitation niche breadths of species in order to understand if species with larger breadths of one niche dimension have stronger dispersal constraints by the other due to narrower niche breadths.Niche breadths were calculated by the subtraction of maximal and minimal values of temperature and precipitation across species ranges.We implemented Phylogenetic Generalized Least Squares to measure the relationship between temperature and precipitation niche breadths and latitude.We also tested phylogenetic signals by Lambda statistics to analyze the degree of phylogenetic niche conservatism to both niche dimensions.Temperature niche breadths were not related to latitude.Precipitation niche breadths decreased with increasing latitude and presented a high phylogenetic signal,that is,significant phylogenetic niche conservatism.We rejected the tradeoff hypotheses of temperature and precipitation niche breadths.Our results also indicate that precipitation should be an important ecological constraint affecting the geographical distribution of snake lineages across the South American Atlantic Forest.We then provide a general view of how phylogenetic niche conservatism could impact the patterns of latitudinal variation of climatic niches across this biodiversity hotspot.展开更多
Aims Seeds of Rumex crispus from six provenances were studied in relation to their germination under drought and presence of nitrogen in the germination and emergence media.We also investigated whether adaptation to s...Aims Seeds of Rumex crispus from six provenances were studied in relation to their germination under drought and presence of nitrogen in the germination and emergence media.We also investigated whether adaptation to soil increases the ability of the species to colonize and establish in contrasting environments along a longitudinal gradient in western Spain by means of a reciprocal transplantation experiment.Methods We conducted a germination trial in the lab to test for the germination responses to water scarcity along a polyethylene glycol gradient and to varying concentrations of nitrogen compounds.Simultaneously reciprocal transplantations experiment was conducted,where seeds from six provenances were grown in the soils from the very same provenances.Seedling emergence,survivorship and fitness-related variables were measured in all plots.Important Findings We found that R.crispus has a cold-stratification requirement that enhances its germination.Significant differences between the six provenances were detected for time-to-germination,total seedling emergence,plant mortality and reproductive effort in all the experiments.The differences between provenances with respect to germination were confirmed by the significant statistical analyses of the variance,thus providing evidence that seeds from parent plants grown in different environmental conditions have an intrinsically different abilities to germinate and establish.Soil nitrogen content where seed germination and seedlings establish also play an important role in their performance in terms of survivorship and reproduction,being the higher levels of inorganic nitrogen and of microbial biomass those that increased biomass production,enhanced inflorescence formation and reduced plant mortality.We conclude that one of the main reasons for the spread and maintenance of R.crispus would be the increased levels of nitrogen in agricultural soils.展开更多
Biologists have considered both winter coldness and temperature seasonality as major determinants of the northern limits of plants and animals in the Northern Hemisphere,which in turn drive the well-known latitudinal ...Biologists have considered both winter coldness and temperature seasonality as major determinants of the northern limits of plants and animals in the Northern Hemisphere,which in turn drive the well-known latitudinal diversity gradient.However,few studies have tested which of the two climate variables is the primary determinant.In this study,we assess whether winter coldness or temperature seasonality is more strongly associated with the northern latitudinal limits of tree species and with tree species richness in North America.Tree species were recorded in each of 1198 quadrats of 110 km×110 km in North America.We used correlation and regression analyses to assess the relationship of the latitude of the northern boundary of each species,and of species richness per quadrat,with winter coldness and temperature seasonality.Species richness was analyzed within 38 longitudinal,i.e.,north-south,bands(each being>1100 km long and 110 km wide).The latitudes of the northern range limits of tree species were three times better correlated with minimum temperatures at those latitudes than with temperature seasonality.On average,minimum temperature and temperature seasonality together explained 81.5%of the variation in the northern range limits of the tree species examined,and minimum temperature uniquely explained six-fold(33.7%versus 5.8%)more of this variation than did temperature seasonality.Correlations of tree species richness with minimum temperatures were stronger than correlations with temperature seasonality for most of the longitudinal bands analyzed.Compared to temperature seasonality,winter coldness is more strongly associated with species distributions at high latitudes,and is likely a more important driver of the latitudinal diversity gradient.展开更多
文摘Species richness generally decreases with increasing latitude,a biodiversity gradient that has long been considered as one of the few laws in ecology.This latitudinal diversity gradient has been observed in many major groups of organisms.In plants,the latitudinal diversity gradient has been observed in vascular plants,angiosperms,ferns,and liverworts.However,a conspicuous latitudinal diversity gradient in mosses at a global or continental scale has not been observed until now.Here,we analyze a comprehensive data set including moss species in each band of 20° in latitude worldwide.Our results show that moss species richness decreases strongly with increasing latitude,regardless of whether the globe is considered as a whole or different longitudinal segments(e.g.,Old World versus New World) are considered separately.This result holds when variation in area size among latitudinal bands is taken into account.Pearson's correlation coefficient between latitude and species richness is-0.99 for both the Northern and Southern Hemispheres.Because bryophytes are an extant lineage of early land plants and because mosses not only include most of extant species of bryophytes but also are important constituents of most terrestrial ecosystems,understanding geographic patterns of mosses is particularly important The finding of our study fills a critical knowledge gap.
基金We thank Yinchao Hao and Wande Li for their assistance with sample collection.This study was funded by the National Natural Science Foundation of China(NSFC,31971413)Natural Science Foundation of Hebei Province(NSFHP,C2020205038)to D.L.Science and Technology Project of Hebei Education Department(QN2019103)to Y.S.
文摘Human commensal species take advantage of anthropogenic conditions that are less likely to be challenged by the selective pressures of natural environments.Their morphological and physiological phenotypes can therefore dissociate from habitat characteristics.Understanding how these species adjust their morphological and physiological traits across latitudinal gradients is fundamental to uncovering the eco-physiological strategies underlying coping mechanisms.Here,we studied morphological traits in breeding Eurasian tree sparrows(ETSs;Passer montanus)among low-latitude(Yunnan and Hunan)and middle-latitude(Hebei)localities in China.We then compared body mass;lengths of bill,tarsometatarsus,wing,total body,and tail feather;and baseline and capture stress-induced levels of plasma corticosterone(CORT)and the metabolites including glucose(Glu),total triglyceride(TG),free fatty acid(FFA),total protein,and uric acid(UA).None of the measured morphological parameters varied with latitude except in the Hunan population,which demonstrated longer bills than those in other populations.Stress-induced CORT levels significantly exceeded baseline levels and decreased with increasing latitude,but total integrated CORT levels did not vary with latitude.Capture stress-induced significantly increased Glu levels and decreased TG levels,independent of site.However,the Hunan population had significantly higher baseline CORT,baseline and stress-induced FFA levels,but lower UA levels,which differed from other populations.Our results suggest that rather than morphological adjustments,physiological adjustments are mainly involved in coping mechanisms for middle-latitude adaptation in ETSs.It is worth investigating whether other avian species also exhibit such dissociation from external morphological designs while depending on physiological adjustments.
基金Knowledge Innovation Program of Wuhan Botanical Garden(Y455437H05)supported by a National Science Foundation Postdoctoral Research Fellowship.
文摘Aims Invasive species occurrence and their effects on biodiversity may vary along latitudes.We examined the occurrence(species cover)and relative dominance(importance value)of invasive alligator weed,Alternanthera philoxeroides,in its terrestrial habitat in China through a large-scale latitudinal field investigation.Methods We established 59 plots along the latitudinal transect from 21°N to 37°N.We recorded species name,abundance,height and individual species coverage of plants in every quadrat.We then measuredα-species diversity variations associated with the A.philoxeroides community across the latitudinal range.We also analyzed the effect of latitude on plant species’distributions in this community by using canonical correspondence analysis(CCA).Important Findings We found that species cover and importance value of A.philoxe-roides increased in areas<35°N,but decreased at higher latitudes.Lower latitudes supported greater species diversity than higher latitudes.Small-scale invasion of A.philoxeroides was associated with higher species diversity,but community diversity was lower when A.philoxeroides species cover exceeded 36%.Community plant species changed from mesophyte to hygrophyte gradually from low to high latitude.Our research suggests that latitude had significant influences on community diversity which interacted with the biotic resistance of a community and impact of invasion.Consequently,A.philoxeroides may become more invasive and have greater negative impacts on community species diversity in higher latitudes as global climate changes.
基金This study was supported by grants from Ministry of Science and Technology(MOST)of China(973 Program No.2012CB416904)National Natural Science Foundation of China(No.90302013)+2 种基金Natural Science Foundation of Yunnan(2005C0056M)Wang K.C.Foundation,and grants(DEB-0620910,DEB-0218039)from U.S.National Science FoundationThe work was also partially funded by the CG Research Program 6:Forests,Trees and Agroforestry.ADNA sequence data are available via GenBank(accession no.KF411754-KF412201).
文摘In forest ecosystems,plant communities shape soil fungal communities through the provisioning of carbon.Although the variation in forest composition with latitude is well established,little is known about how soil fungal communities vary with latitude.We collected soil samples from 17 forests,along a latitudinal transect in western China.Forest types covered included boreal,temperate,subtropical and tropical forests.We used 454 pyrosequencing techniques to analyze the soil communities.These data were correlated with abiotic and biotic variables to determine which factors most strongly influenced fungal community composition.Our results indicated that temperature,latitude,and plant diversity most strongly influence soil fungal community composition.Fungal diversity patterns were unimodal,with temperate forests(mid latitude)exhibiting the greatest diversity.Furthermore,these diversity patterns indicate that fungal diversity was highest in the forest systems with the lowest tree diversity(temperate forests).Different forest systems were dominated by different fungal subgroups,ectomycorrhizal fungi dominated in boreal and temperate forests;endomycorrhizal fungi dominated in the tropical rainforests,and non-mycorrhizal fungi were best represented in subtropical forests.Our results suggest that soil fungal communities are strongly dependent on vegetation type,with fungal diversity displaying an inverse relationship to plant diversity.
文摘Aims We analyze two continental data sets of forest communities from across the New World to examine the latitudinal gradients of beta diversity after accounting for gamma diversity and the latitudinal gradient of gamma diversity after accounting for beta diversity.Methods Correlation and regression analyses were used to relate beta and gamma diversity to latitude along two latitudinal gradients in the New World(one including 72 forest sites located south of the equator and the other including 79 forest sites located north of the equator).Important Findings Beta diversity and gamma diversity were negatively correlated with latitude.Beta diversity was strongly and positively correlated with gamma diversity(Pearson’s correlation coefficient:0.783 for New World North and 0.848 for New World South).When beta diversity was regressed on latitude and gamma diversity,69.8 and 85.7%of the variation in beta diversity were explained,respectively,for New World North and New World South.When gamma diversity was regressed on latitude and beta diversity,81.8 and 84.3%of the variation in gamma diversity were explained,respectively,for New World North and New World South.After statistically removing the relationship between beta and gamma diversity,latitude has weak or no relationships with beta and gamma diversity.However,strong positive correlations between beta and gamma diversity may not be considered as evidence of one driving the other along a latitudinal gradient.
基金supported by the National Natural Science Foundation of China (Grant number 42261004)supported by the Jiangsu Social Development Project (BE2022792)。
文摘The timing of flowering is an important driver of species distribution and community assembly patterns.However,we still have much to learn about the factors that shape flowering diversity(i.e.,number of species flowering per period) in plant communities.One potential explanation of flowering diversity is the mid-domain effect,which states that geometric constraints on species ranges within a bounded domain(space or time) will yield a mid-domain peak in diversity regardless of ecological factors.Here,we determine whether the mid-domain effect explains peak flowering time(i.e.,when most species of communities are flowering) across China.We used phenological data of 16,267 herbaceous and woody species from the provincial Flora in China and species distribution data from the Chinese Vascular Plant Distribution Database to determine relationships between the observed number of species flowering and the number of species flowering as predicted by the mid-domain effect model,as well as between three climatic variables(mean minimum monthly temperature,mean monthly precipitation,and mean monthly sunshine duration).We found that the mid-domain effect explained a significant proportion of the temporal variation in flowering diversity across all species in China.Further,the mid-domain effect explained a greater proportion of variance in flowering diversity at higher latitudes than at lower latitudes.The patterns of flowering diversity for both herbaceous and woody species were related to both the mid-domain effect and environmental variables.Our findings indicate that including geometric constraints in conjunction with abiotic and biotic predictors will improve predictions of flowering diversity patterns.
文摘Beta diversity(β-diversity)is the scalar between local(α)and regional(γ)diversity.Understanding geographic patterns ofβ-diversity is central to ecology,biogeography,and conservation biology.A full understanding of the origin and maintenance of geographic patterns ofβ-diversity requires exploring both taxonomic and phylogeneticβ-diversity,as well as their respective turnover and nestedness components,and exploring phylogenetic p-diversity at different evolutionary depths.In this study,we explore and map geographic patterns ofβ-diversity for angiosperm genera in regional floras across the world.We examine both taxonomic and phylogeneticβ-diversity and their constituent components,and both tip-weighted and basal-weighted phylogeneticβ-diversity,and relate them to latitude.On the one hand,our study found that the global distribution ofβ-diversity is highly heterogeneous.This is the case for both taxonomic and phylogeneticβ-diversity,and for both tip-weighted and basal-weighted phylogeneticβ-diversity.On the other hand,our study found that there are highly consistent geographic patterns among different metrics ofβ-diversity.In most cases,metrics ofβ-diversity are negatively associated with latitude,particularly in the Northern Hemisphere.Different metrics of taxonomicβ-diversity are strongly and positively correlated with their counterparts of phylogeneticβ-diversity.
基金supported by the Natural Science and Technology Foundation of Guizhou Province[[2020]1Z013]the Joint Fund of the National Natural Science Foundation of Chinathe Karst Science Research Center of Guizhou Province[U1812401]。
文摘In eastern Asian subtropical forests,leaf habit shifts from evergreen to deciduous broad-leaved woody plants toward higher latitudes.This shift has been largely explained by the greater capacity of deciduous broad-leaved plants to respond to harsh climatic conditions(e.g.,greater seasonality).The advantages of deciduous leaf habit over evergreen leaf habit in more seasonal climates have led us to hypothesize that leaf habits would shift in response to climate changes more conspicuously in forest canopy trees than in forest understory shrubs.Furthermore,we hypothesize that in the forests of the subtropics,plants at higher latitudes,regardless of growth form,would better tolerate seasonal harsh climates,and hence show less differentiation in leaf habit shift,compared to those at lower latitudes.To test these two hypotheses,we modelled the proportion of deciduous broad-leaved species and the incidence of deciduous and evergreen broad-leaved species in woody angiosperm species compositions of ten largesized forest plots distributed in the Chinese subtropics.We found that the rate of leaf habit shift along a latitudinal gradient was higher in forest trees than in forest shrubs.We also found that the differentiation in leaf habit shift between trees and shrubs is greater at lower latitudes(i.e.,warmer climates)than at higher latitudes(i.e.,colder climates).These findings indicate that specialized forest plants are differentially affected by climate in distinct forest strata in a manner dependent on latitudinal distribution.These differences in forest plant response to changes in climate suggest that global climate warming will alter growth forms and geographical distributions and ranges of forests.
文摘Plant communities are shaped by multiple factors along environmental gradients;however,studies are limited on how environmental filtering drives community composition and species richness on tropical inselbergs.We evaluate the influence of altitude and climatic variables related to temperature and precipitation on plant community composition and species richness on Brazilian inselbergs.We assume as a premise that both climate and altitude would induce changes on plant community composition and species richness at the local level.We used plant inventory data from 370 sampling units across four inselberg sites in the Atlantic Forest of Espírito Santo State,south-eastern Brazil.We tested the univariate and multivariate effects of altitude and climate variables on community composition and species richness with multiple models.Differences in species richness between inselbergs were evaluated using sample-based data to estimate rarefaction and extrapolation curves.In addition,differences in species composition and taxonomic beta diversity were examined via novel frequency-based metrics.A contrasting climate pattern was observed between the inselberg sites,with south sites being wet compared to the dry conditions found in northern sites.Species richness by rarefaction showed a similar pattern within regional sites;however,there were marked differences between regions.Species richness and beta diversity showed significant differences among sites,with higher values in southern sites than in northern sites.In a multi-model comparison between inselberg sites,altitude significantly influenced community composition and species richness and explained more variance than climate models.This finding suggested that climate could act to some extent on these tropical inselbergs;however,altitude was a better predictor of plant community composition and species richness at the local level.
基金funding by project RTI2018–096884-B-C31(Spanish Ministry of Science)G.S-B.is supported by a Spanish Ministry of Economy,Industry+1 种基金Competitiveness Postdoctoral grant(FJCI 2016–30121FEDER funds)。
文摘Background:Equatorward,rear-edge tree populations are natural monitors to estimate species vulnerability to climate change.According to biogeographical theory,exposition to drought events increases with increasing aridity towards the equator and the growth of southern tree populations will be more vulnerable to drought than in central populations.However,the ecological and biogeographical margins can mismatch due to the impact of ecological factors(topography,soils)or tree-species acclimation that can blur large-scale geographical imprints in trees responses to drought making northern populations more drought limited.Methods:We tested these ideas in six tree species,three angiosperms(Fagus sylvatica,Quercus robur,Quercus petraea)and three gymnosperms(Abies alba,Pinus sylvestris and Pinus uncinata)by comparing rear-edge tree populations subjected to different degrees of aridity.We used dendrochronology to compare the radial-growth patterns of these species in northern,intermediate,and southern tree populations at the continental rear edge.Results and conclusions:We found marked variations in growth variability between species with coherent patterns of stronger drought signals in the tree-ring series of the southern populations of F.sylvatica,P.sylvestris,and A.alba.This was also observed in species from cool-wet sites(P.uncinata and Q.robur),despite their limited responsiveness to drought.However,in the case of Q.petraea the intermediate population showed the strongest relationship to drought.For drought-sensitive species as F.sylvatica and P.sylvestris,southern populations presented more variable growth which was enhanced by cool-wet conditions from late spring to summer.We found a trend of enhanced vulnerability to drought in these two species.The response of tree growth to drought has a marked biogeographical component characterized by increased drought sensitivity in southern populations even within the species distribution rear edge.Nevertheless,the relationship between tree growth and drought varied between species suggesting that biogeographical and ecological limits do not always overlap as in the case of Q.petraea.In widespread species showing enhanced vulnerability to drought,as F.sylvatica and P.sylvestris,increased vulnerability to climate warming in their rear edges is forecasted.Therefore,we encourage the monitoring and conservation of such marginal tree populations.
基金the project NRS-6“Climate,Fire,and Carbon Cycle Sciences”supported by the USDA Forest ServiceBeijing Forestry University for covering the trip to the conference and generous conference venue facilitating this study
文摘Background: Forest biodiversity is the foundation of many ecosystem services, and the effect of biodiversity on ecosystem functioning and processes (BEF) has been a central issue in biodiversity studies. Although many hypotheses have been developed to interpret global gradients of biodiversity, there has not been complete agreement on mechanisms controlling biodiversity patterns and distributions. Differences may be due to limited observation data and inconsistencies of spatial scales in analysis. Methods: In this study, we take advantage of USDA Forest Service forest inventory and analysis (FIA) data for exploring regional forest biodiversity and BEF in New England forests. The FIA data provide detailed information of sampled plots and trees for the region, including 6000 FIA plots and more than 33,000 individual trees. Biodiversity models were used to analyze the data. Results: Tree species diversity increases from the north to the south at a rate about 2-3 species per latitudinal degree. Tree species diversity is better predicted by tree height than forest age or biomass. Very different distribution patterns of two common maple species, sugar maple (Acer sdcchorum) and red maple (Acer rubrum), highlight the vulnerability of sugar maple and its potential replacement by red maple on New England landscapes. Red maple generally already outperforms sugar maple, and will likely and continuously benefit from a changing climate in New England. Conclusions: We conclude that forest structure (height) and resources (biomass) are more likely foundational characteristics supporting biodiversity rather than biodiversity determining forest productivity and/or biomass. The potential replacement of red maple for sugar maple in the New England areas could affect biodiversity and stability of forest ecosystem functioning because sugar maple plays important ecological roles distinct from red maple that are beneficial to other tree species in northern hardwood forests. Such a change may not affect forest resilience in terms of forest productivity and biomass as these are similar in red maple and sugar maple, however, it would almost certainly alter forest structure across the landscape.
基金funded by the National Natural Science Foundation of China(Nos.32270246 and 31900184 to J.L.)the Scientific Foundation of Urban Management Bureau of Shenzhen(Nos.202019 and 202208 to S.Z.)+1 种基金the Youth Innovation Promotion Association CAS,China(Grant No.:2023410)the Yunnan Fundamental Research Projects(Grant Nos.:202001AT070072 and 2019FD057 to J.L.)。
文摘The evolution of the latitudinal diversity gradient(LDG),characterized by a peak in diversity toward the tropics,has captured significant attention in evolutionary biology and ecology.However,the inverse LDG(i-LDG)mechanism,wherein species richness increases toward the poles,remains inadequately explored.Cycads are among one of the oldest lineages of extant seed plants and have undergone extensive diversification in the tropics.Intriguingly,the extant cycad abundance exhibits an i-LDG pattern,and the underlying causes for this phenomenon remain largely elusive.Here,using 1,843 nuclear genes from a nearly complete sampling,we conducted comprehensive phylogenomic analyses to establish a robust species-level phylogeny for Cycas,the largest genus within cycads.We then reconstructed the spatial-temporal dynamics and integrated global environmental data to evaluate the roles of species ages,diversification rates,contemporary environment,and conservatism to ancestral niches in shaping the i-LDG pattern.We found Cycas experienced decreased diversification rates,coupled with the cooling temperature since its origin in the Eocene from continental Asia.Different regions have distinctively contributed to the formation of i-LDG for Cycas,with the northern hemisphere acting as evolutionary museums and the southern hemisphere serving as cradles.Moreover,water-related climate variables,specifically precipitation seasonality and potential evapotranspiration,were identified as paramount factors constraining Cycas species richness in the rainforest biome near the equator.Notably,the adherence to ancestral monsoonal climates emerges as a critical factor in sustaining the diversity pattern.This study underscores the imperative of integrating both evolutionary and ecological approaches to comprehensively unravel the mechanisms underpinning global biodiversity patterns.
基金the National Natural Science Foundation of China(Nos.31600403,31800422,41673111,U1501232,41622106,31971553,and 31700470)the Natural Science Foundation of Guangdong Province,China(No.2016A030312003)+1 种基金the Natural Science Foundation of Guangxi Province,China(No.2017GXNSFBA198099)the U.S.National Science Foundation(NSF A22-0042).
文摘Higher biodiversity is often assumed to be a more desirable scenario for maintaining the functioning of ecosystems,but whether species-richer communities are also more disturbance-tolerant remains controversial.In this study,we investigated the bacterial communities based on 472 soil samples from 28 forests across China with associated edaphic and climatic properties.We developed two indexes(i.e.,community mean tolerance breadth[CMTB]and community mean response asynchrony[CMRA])to explore the relationship between diversity and community resistance potential.Moreover,we examined this resistance potential along the climatic and latitudinal gradients.We revealed that CMTB was significantly and negatively related to species richness,resulting from the changes in balance between relative abundances of putative specialists and generalists.In comparison,we found a unimodal relationship between CMRA and richness,suggesting that higher biodiversity might not always lead to higher community resistance.Moreover,our results showed differential local patterns along latitude.In particular,local patterns in the northern region mainly followed general relationships rather than those for the southern forests,which may be attributed to the differences in annual means and annual variations of climate conditions.Our findings highlight that the community resistance potential depends on the composition of diverse species with differential environmental tolerance and responses.This study provides a new,testable evaluation by considering tolerance breadth and response asynchrony at the community level,which will be helpful in assessing the influence of disturbance under rapid shifts in biodiversity and species composition as a result of global environmental change.
基金Acknowledgments This review reflects decades of personally treasured friendships and assistance from colleagues in the insectplant interactions field of study. The Papilionidae research from our lab was supported in part by the National Science Foundation (DEB-9201122 DEB-9510044+1 种基金 DEB 0716683 DEB 0918879) and the Michigan Agricultural Experiment Station (Project # 01644). I wish to thank all lab members and friends for their enthusiasm and assistance over the years, and most recently, Matthew Aardema, Rodrigo Mereader and Gabe Ording.
文摘The search for pattern in the ecology and evolutionary biology of insect-plant associations has fascinated biologists for centuries. High levels of tropical (tow-latitude) plant and insect diversity relative to poleward latitudes and the disproportionate abundance of host-specialized insect herbivores have been noted. This review addresses several aspects of local insect specialization, host use abilities (and loss of these abilities with specialization), host-associated evolutionary divergence, and ecological (including "hybrid") speciation, with special reference to the generation of biodiversity and the geographic and taxonomic identification of "species borders" for swallowtail butterflies (Papilionidae). From ancient phytochemically defined angiosperm affiliations that trace back millions of years to recent and very local specialized populations, the Papilionidae (swallowtail butterflies) have provided a model for enhanced tmderstanding of localized ecological patterns and genetically based evolutionary processes. They have served as a useful group for evaluating the feeding specialization/physiological efficiency hypothesis. They have shown how the abiotic (thermal) environment interacts with host nutritional suitability to generate "voltinisrn/suitability" gradients in specialization or preference latitudinally, and geographical mosaics locally. Several studies reviewed here suggest strongly that the oscillation hypothesis for speciation does have considerable merit, but at the same time, some species-level host specializations may lead to evolutionary dead-ends, especially with rapid environmental/habitat changes involving their host plants. Latitudinal gradients in species richness and degree of herbivore feeding specialization have been impacted by recent developments in ecological genetics and evolutionary ecology. Localized insect- plant associations that span the biospectrum from polyphenisms, polymorphisms, biotypes, demes, host races, to cryptic species, remain academically contentious, with simple definitions still debated. However, molecular analyses combined with ecological, ethological and physiological studies, have already begun to unveil some answers for many important ecological/evolutionary questions.
基金This work was financially supported by the National Natural Science Foundation of China(31370455 and 31570438)One Hundred Person Project of The Chinese Academy of Sciences(K318021405)the National Key Research and Development Program of China(2016YFA0600801).
文摘Aims the impact of global warming on belowground processes,espe-cially on fine root production,is poorly understood in comparison with its aboveground counterpart.Methods Here,we compiled 227 measurements to assess the influence of temperature and precipitation on fine root biomass of Norway spruce(Picea abies[L.]Karst)forest ecosystems in the Eurasia boreal region.Important Findings We found that fine root biomass decreased significantly with lati-tudes.there was a biomass increase of 0.63 Mg ha−1 and 0.32 Mg ha−1 for fine roots<2 and<1 mm in diameter,respectively,with 1°C increase of mean annual temperature.there was an increase of 0.5 and 0.1 Mg ha−1 per 100 mm year−1 precipitation for the two size classes of fine roots.If the adaption of root production can match the pace of global warming and water is not a limiting factor for plant growth,fine root biomass would be expected to increase by 40-140%in response to the predicted increase in tem-perature(3-10°C)over the next century.Our analyses highlighted the strongly positive influences of temperature and precipitation on belowground function,suggesting that predicted future climate change could substantially enhance belowground biomass in the boreal region where the greatest warming is anticipated.this potential increase of belowground biomass,coupled with aboveground biomass,may provide a better understanding of climate-ecosystem feedbacks.
基金Fundação de AmparoàPesquisa do Estado de São Paulo(FAPESP procs.2008/50068-2,2014/23677-9 and 2020/12658-4)Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq,405447/2016-7)RJS thanks CNPq for the research fellowship(312795/2018-1).
文摘The climatic niche is a central concept for understanding species distribution,with current and past climate interpreted as strong drivers of present and historical-geographical ranges.Our aim is to understand whether Atlantic Forest snakes follow the general geographical pattern of increasing species climatic niche breadths with increasing latitude.We also tested if there is a tradeoff between temperature and precipitation niche breadths of species in order to understand if species with larger breadths of one niche dimension have stronger dispersal constraints by the other due to narrower niche breadths.Niche breadths were calculated by the subtraction of maximal and minimal values of temperature and precipitation across species ranges.We implemented Phylogenetic Generalized Least Squares to measure the relationship between temperature and precipitation niche breadths and latitude.We also tested phylogenetic signals by Lambda statistics to analyze the degree of phylogenetic niche conservatism to both niche dimensions.Temperature niche breadths were not related to latitude.Precipitation niche breadths decreased with increasing latitude and presented a high phylogenetic signal,that is,significant phylogenetic niche conservatism.We rejected the tradeoff hypotheses of temperature and precipitation niche breadths.Our results also indicate that precipitation should be an important ecological constraint affecting the geographical distribution of snake lineages across the South American Atlantic Forest.We then provide a general view of how phylogenetic niche conservatism could impact the patterns of latitudinal variation of climatic niches across this biodiversity hotspot.
文摘Aims Seeds of Rumex crispus from six provenances were studied in relation to their germination under drought and presence of nitrogen in the germination and emergence media.We also investigated whether adaptation to soil increases the ability of the species to colonize and establish in contrasting environments along a longitudinal gradient in western Spain by means of a reciprocal transplantation experiment.Methods We conducted a germination trial in the lab to test for the germination responses to water scarcity along a polyethylene glycol gradient and to varying concentrations of nitrogen compounds.Simultaneously reciprocal transplantations experiment was conducted,where seeds from six provenances were grown in the soils from the very same provenances.Seedling emergence,survivorship and fitness-related variables were measured in all plots.Important Findings We found that R.crispus has a cold-stratification requirement that enhances its germination.Significant differences between the six provenances were detected for time-to-germination,total seedling emergence,plant mortality and reproductive effort in all the experiments.The differences between provenances with respect to germination were confirmed by the significant statistical analyses of the variance,thus providing evidence that seeds from parent plants grown in different environmental conditions have an intrinsically different abilities to germinate and establish.Soil nitrogen content where seed germination and seedlings establish also play an important role in their performance in terms of survivorship and reproduction,being the higher levels of inorganic nitrogen and of microbial biomass those that increased biomass production,enhanced inflorescence formation and reduced plant mortality.We conclude that one of the main reasons for the spread and maintenance of R.crispus would be the increased levels of nitrogen in agricultural soils.
基金supported by a grant form the National Key Research and Development Program,No.2019YFA0607302。
文摘Biologists have considered both winter coldness and temperature seasonality as major determinants of the northern limits of plants and animals in the Northern Hemisphere,which in turn drive the well-known latitudinal diversity gradient.However,few studies have tested which of the two climate variables is the primary determinant.In this study,we assess whether winter coldness or temperature seasonality is more strongly associated with the northern latitudinal limits of tree species and with tree species richness in North America.Tree species were recorded in each of 1198 quadrats of 110 km×110 km in North America.We used correlation and regression analyses to assess the relationship of the latitude of the northern boundary of each species,and of species richness per quadrat,with winter coldness and temperature seasonality.Species richness was analyzed within 38 longitudinal,i.e.,north-south,bands(each being>1100 km long and 110 km wide).The latitudes of the northern range limits of tree species were three times better correlated with minimum temperatures at those latitudes than with temperature seasonality.On average,minimum temperature and temperature seasonality together explained 81.5%of the variation in the northern range limits of the tree species examined,and minimum temperature uniquely explained six-fold(33.7%versus 5.8%)more of this variation than did temperature seasonality.Correlations of tree species richness with minimum temperatures were stronger than correlations with temperature seasonality for most of the longitudinal bands analyzed.Compared to temperature seasonality,winter coldness is more strongly associated with species distributions at high latitudes,and is likely a more important driver of the latitudinal diversity gradient.