Ontogenetic trait variation and metacommunity effects influence species relative abundances during tree community assembly

Predicting species abundance is one of the most fundamental pursuits of ecology.Combining the information encoded in functional traits and metacommunities provides a new perspective to predict the abundance of species in communities.We applied a community assembly via trait selection model to predict quadrat-scale species abundances using functional trait variation on ontogenetic stages and metacommunity information for over 490 plant species in a subtropical forest and a lowland tropical forest in Yunnan,China.The relative importance of trait-based selection,mass effects,and stochasticity in shaping local species abundances is evaluated using different null models.We found both mass effects and trait selection contribute to local abundance patterns.Trait selection was detectable at all studied spatial scales(0.04e1 ha),with its strength stronger at larger scales and in the subtropical forest.In contrast,the importance of stochasticity decreased with spatial scale.A significant mass effect of the metacommunity was observed at small spatial scales.Our results indicate that tree community assembly is primarily driven by ontogenetic traits and metacommunity effects.Our findings also demonstrate that including ontogenetic trait variation into predictive frameworks allows ecologists to infer ecological mechanisms operating in community assembly at the individual level.

Intraspecific trait variation of woody species reduced in a savanna community,southwest China

Plants deploy various ecological strategies in response to environmental heterogeneity.In many forest ecosystems,plants have been reported to have notable inter-and intra-specific trait variation,as well as clear phylogenetic signals,indicating that these species possess a degree of phenotypic plasticity to cope with habitat variation in the community.Savanna communities,however,grow in an open canopy structure and exhibit little species diversification,likely as a result of strong environmental stress.In this study,we hypothesized that the phylogenetic signals of savanna species would be weak,the intraspecific trait variation(ITV)would be low,and the contribution of intraspecific variation to total trait variance would be reduced,owing to low species richness,multiple stresses and relatively homogenous community structure.To test these hypotheses,we sampled dominant woody species in a dry-hot savanna in southwestern China,focusing on leaf traits related to adaptability of plants to harsh conditions(yearround intense radiation,low soil fertility and seasonal droughts).We found weak phylogenetic signals in leaf traits and low ITV(at both individual and canopy-layer levels).Intraspecific variation(including leaf-,layer-and individual-scales)contributed little to the total trait variance,whereas interspecific variation and variation in leaf phenology explained substantial variance.Our study suggests that intraspecific trait variation is reduced in savanna community.Furthermore,our findings indicate that classifying species by leaf phenology may help better understand how species coexist under similar habitats with strong stresses.

Intraspecific trait variation improves the detection of deterministic community assembly processes in early successional forests,but not in late successional forests

Aims Intraspecific trait variation(ITV)has been increasingly recognized to play an important role in understanding the underlying processes influencing community assembly.However,gaps remain in our understanding of how incorporating ITV will influence the relative importance of deterministic(e.g.habitat filtering,limiting similarity)and stochastic processes in driving community assembly at different successional stages.Methods We used data for eight functional traits from 55 woody species in early(24 ha)and late(25 ha)successional temperate forest plot in northeast China.We employed an approximate Bayesian com-putation approach to assess the relative contribution of stochastic processes,habitat filtering and limiting similarity in driving commu-nity structure.We then compared the results with and without intra-specific trait variation to investigate how ITV influences the inferred importance of each process.Important Findings We found that when analyzing interspecific trait variation only(i.e.without ITV),stochastic processes were observed most frequently in driving community composition,followed by habitat filtering and limiting similarity in both forests.However,ITV analyses showed that the relative importance of both deterministic processes(habitat filtering and limiting similarity)increased in early successional for-est,but remained virtually unchanged in late successional forest.Our study reveals the distinctive influence of ITV on the inference of underlying processes in a context of succession and reinforces the need to estimate ITV for making correct inferences about underlying ecological processes.

Intraspecific trait variation in three common grass species reveals fine-scale species adjustment to local environmental conditions

Aims Studies along environmental gradients have shown that intraspecific trait variation(ITV)may contribute considerably to community-level trait variation.However,we lack knowledge about how the extent of ITV varies on a local scale and whether a varying extent of ITV is related to differences in local environmental site and plant commu-nity characteristics.Methods We investigated plant height,specific leaf area(SLA),leaf dry mat-ter content(LDMC)and leaf greenness of three common grass spe-cies(Arrhenatherum elatius,Dactylis glomerata,Poa pratensis)in 12 mown grasslands in a local study area around Jena(Thuringia,Germany)across three spatially hierarchical sampling levels:between sites,between subplots within site and within subplots.Important Findings Arrhenatherum elatius and D.glomerata had higher means in plant height and a lower variation in leaf traits than P.pratensis.The major proportions of variation in leaf traits of P.pratensis and D.glomerata were found within subplots,while the traits of A.elatius varied mainly between sites.Trait correlations across the hierarchical sam-pling levels were highly consistent in A.elatius,but more variable in D.glomerata and P.pratensis.Environmental site and plant commu-nity characteristics mostly explained a larger proportion of variation in trait means in A.elatius than in D.glomerata and P.pratensis,while metrics of ITV were generally less predictable.Our results suggest that trait variation in P.pratensis and D.glomerata is more strongly related to within-site conditions(i.e.biotic interactions),while differences in local environmental conditions between sites have a strong impact on trait variation in A.elatius.Since our study was limited to three grass species,further studies with a greater number of species are required to make generalizations about the importance of biotic interactions and environmental conditions as drivers of ITV at local scale.

Geographical differences of leaf traits of the endangered plant Litsea coreana Levl.var.sinensis and its relationship with climate

Seventeen morphological and anatomical characteristics of the leaves were selected from five natural populations to explore the variation in leaf traits of Lits ea core ana var.sinensis and the effects of geographical environment on these variations.Nested analysis of variance,multiple comparisons,principal component analysis(PCA),and correlation analysis were conducted to explore the variations within and between populations and their correlation with geographical and climatic factors.Significant differences in the 17 leaf traits were observed within and among populations.On average,the relative contribution of within population variation to total variation was 24.8%,which was lower than among population variation(54.6%).The average differentiation coefficient of the traits was 65.8%,and the average coefficient of variation 11.8%,ranging from6.7%for main vein thickness to 21.4%for petiole length.The PC A results showed that morphological characteristics were divided into two categories,and the level of variation was greater than that of leaf anatomy.Most of the leaf traits were significantly correlated with geography and climate and showed a gradual variation with longitude,latitude,and altitude.In areas with high temperatures,less rainfall,and strong seasonal rainfall,the leaves are larger,longer and thicker.This study shows that variations in leaf traits of L.coreana var.sinensis mainly come from variations among populations.The level of trait differentiation among populations is high and the level of variation within populations low.These findings help further understand leaf morphological characteristics of this species and can provide a valuable reference for the protection and sustainable utilization of this natural resource.

Species-specific traits determine shrub-annual interactions during a growing season

Stress gradient hypothesis predicted that facilitative interactions usually increase in intensity and are importance with abiotic stress.By contrast,facilitation may be lost in time,when it involves the growth of benefactors or beneficiaries.Less is known about which response pattern is more common in arid desert.We present an empirical study to explore shrub-annual interactions at the community and individual level along the course of a single growing season in a desert steppe in northwest China.Here the severity of drought stress may increase in time due to uneven precipitation during plant growing season.We assessed growth responses of annuals in understory where two dominant shrubs were removed.Annuals responses showed a switch from weakly positive to more strongly positive beneath Calligonum mongolicum,whereas from positive to negative beneath Nitraria sphaerocarpa during the growing season.Additionally,annual species with contrasting functional traits showed distinct growth responses to canopies removal.There was evidence of an increase in soil moisture below the canopy of shrubs,but a decrease in potential evaporation rate and photosynthetically active radiation,which can partly explain these species-specific responses.We conclude that the balance between competitive and facilitative effects in shrub-annual interactions is not only governed by the severity of stress but also determined by plant traits,such as canopy structure of shrubs and functional traits of their understory annuals.

Quantitative Trait Loci for Grain Chalkiness and Endosperm Transparency Detected in Three Recombinant Inbred Line Populations of Indica Rice

Quantitative trait loci（QTL） for percentage of chalky grain,degree of chalkiness,and endosperm transparency were detected using 3 recombinant inbred line populations derived from crosses between parental lines of commercial three-line hybrids of indica rice.Two of the populations showed great variations on heading date,and the other had a short range of heading date variation.A total of 40 QTLs were detected and fell into 15 regions of 10 chromosomes,of which 5 regions were detected for 1 or more same traits over different populations,2 were detected for different traits in different populations,3 were detected for 2 or all the 3 traits in a single population,and 5 were detected for a single trait in a single population.Most of these QTLs have been reported previously,but a region located on the long arm of chromosome 10 showing significant effects in all the 3 populations has not been reported before.It was shown that a number of gene cloned,including the Wx and Alk for the physiochemical property of rice grain,and GW2,GS3 and GW5 for grain weight and grain size,could have played important roles for the genetic control of grain chalkiness in rice,but there are many more QTLs exerting stable effects for rice chalkiness over different genetic backgrounds.It is worth paying more attentions to these regions which harbor QTL such as the qPCG5.2/qDC5.2/qET5.2 and qPCG10/qDC10/qET10 detected in our study.Our results also showed that the use of segregating populations having high-uniform heading date could greatly increase the efficiency of the identification of QTL responsible for traits that are subjected to great environmental influence.

Population isolation shapes plant genetics, phenotype and germination in naturally patchy ecosystems

Aims Habitat connectivity is important in conservation since isolation can diminish the potential of a population for adaptation and increase its risk of extinction.However,conservation of naturally patchy ecosystems such as peatlands has mainly focused on preserving specific sites with exceptional characteristics,neglecting the poten-tial interconnectivity between patches.In order to better under-stand plant dynamics within a peatland network,we assessed the effect of population isolation on genetic distinctiveness,phenotypic variations and germination rates using the peatland-obligate white-fringed orchid(Platanthera blephariglottis).Methods Fifteen phenotypic traits were measured for 24 individuals per pop-ulation(20 distinct populations,Quebec,Canada)and germination rates of nearly 20000 seeds were assessed.Genetic distinctiveness was quantified for 26 populations using single nucleotide polymor-phism markers obtained via a pooled genotyping-by-sequencing approach.Geographic isolation was measured as the distance to the nearest population and as the number of populations occurring in concentric buffer zones(within a radius of 2,5 and 10 km)around the studied populations.Important Findings All phenotypic traits showed significant differences among popu-lations.Genetic results also indicated a pattern of isolation-by-distance,which suggests that seed and/or pollen exchange is restricted geographically.Finally,all phenotypic traits,as well as a reduced germination rate,were correlated with either geographic isolation or genetic distance.We conclude that geographic iso-lation likely restricts gene flow,which in turn may affect germi-nation.Consequently,it is imperative that conservation programs take into account the patchy nature of such ecosystems,rather than targeting a few specific sites with exceptional character for preservation.