Trait dynamics of Mediterranean xerophytic shrub communities growing on stabilised inland dunes respond to nutrient and aridity gradients

Background: Understanding the processes that determine community assembly and their dynamics is a central issue in ecology. The analysis of functional diversity can improve our understanding of these dynamics by identifying community assembly processes.

Aims: We studied the effect of environment–community covariations on both functional diversity and functional structure of xerophytic shrub communities for inferring the community assembly processes shaping this vegetation type.

Methods: Functional diversity was quantified using (1) community-weighted mean of the studied traits, (2) functional groups, defined using Ward’s hierarchical agglomerative clustering method and (3) Rao’s quadratic entropy. Relationships between functional diversity and environmental gradients were identified by Spearman correlations and modelled using generalised additive models.

Results: Variations in community composition and functional diversity correlated with soil nutrient availability and aridity. Increasing nutrient availability resulted in both greater average plant height and higher abundance of plants with green photosynthetic organ colour, whereas the abundance of nanophanerophytes increases with aridity.

Conclusions: The species composition and trait structure of the studied Mediterranean xerophytic shrub communities varies along nutrient and aridity gradients. This supports the importance of environmental filters for the local assembly and dynamics of these inland dune communities.     

Linking plant genes to insect communities: Identifying the genetic bases of plant traits and community composition

Community genetics aims to understand the effects of intraspecific genetic variation on community composition and diversity, thereby connecting community ecology with evolutionary biology. Thus far, research has shown that plant genetics can underlie variation in the composition of associated communities (e.g., insects, lichen and endophytes), and those communities can therefore be considered as extended phenotypes. This work, however, has been conducted primarily at the plant genotype level and has not identified the key underlying genes. To address this gap, we used genome‐wide association mapping with a population of 445 aspen (Populus tremuloides) genets to identify the genes governing variation in plant traits (defence chemistry, bud phenology, leaf morphology, growth) and insect community composition. We found 49 significant SNP associations in 13 Populus genes that are correlated with chemical defence compounds and insect community traits. Most notably, we identified an early nodulin‐like protein that was associated with insect community diversity and the abundance of interacting foundation species (ants and aphids). These findings support the concept that particular plant traits are the mechanistic link between plant genes and the composition of associated insect communities. In putting the “genes” into “genes to ecosystems ecology”, this work enhances understanding of the molecular genetic mechanisms that underlie plant–insect associations and the consequences thereof for the structure of ecological communities.     

A trait-based experimental approach to understand the mechanisms underlying biodiversity–ecosystem functioning relationships

Plant functional characteristics may drive plant species richness effects on ecosystem processes. Consequently, the focus of biodiversity–ecosystem functioning (BEF) experiments has expanded from the manipulation of plant species richness to manipulating functional trait composition. Involving ecophysiological plant traits in the experimental design might allow for a better understanding of how species loss alters ecosystem processes. Here we provide the theoretical background, design and first results of the ‘Trait-Based Biodiversity Experiment’ (TBE), established in 2010 that directly manipulates the trait composition of experimental plant communities.Analysis of six plant traits related to resource acquisition and use were analyzed using principal component analysis of 60 grassland species. The resulting two main axes describe gradients in functional similarity, and were used as the basis for designing plant communities with different functional and species diversity levels. Using such an approach allowed us to manipulate different levels of complementarity in spatial and temporal plant resource acquisition. In contrast to previous biodiversity experiments, the TBE is designed according to more realistic scenarios of non-random species loss along orthogonal axes of species trait dissimilarities. This allows us to tease apart the relative importance of selection and complementarity effects on multiple ecosystem processes, and to mechanistically study the consequences of plant community simplification.     

Stress‐tolerator leaf traits determine population dynamics in the endangered New Caledonian conifer Araucaria muelleri

Demographic and ecophysiological data for the endangered New Caledonian conifer, Araucaria muelleri (Araucariaceae), were analysed to: (i) evaluate population viability in relation to site conditions and human impacts; and (ii) advance our understanding of how stress‐tolerator plant functional traits affect the population dynamic behaviour and conservation requirements of long‐lived tree species. Growth, survivorship and recruitment in four A. muelleri populations were monitored across 9 years. Demographic rates were analysed using stage‐based transition matrices. Leaf δ¹³C, %N and photosystem II stress (Fv/Fm) were measured for seedlings, saplings and trees, and leaf mass per area (LMA) for trees, and correlations among ecophysiological and demographic variables explored. Seedling, sapling and tree stem growth were among the slowest, and annual survivorship among the highest, reported for any tree. Transition matrix analyses yielded stable estimated population growth rates, λ, not significantly different from 1.0 for all populations. Leaf δ¹³C was positively correlated with seedling and sapling height growth, while daytime photosystem II stress (Fv/Fm) was high in seedlings, but low in saplings and trees. Ecophysiological measures suggest that individuals transition from moisture‐limited growth at the seedling stage to nutrient‐limited growth as adults. High levels of environmental stress result in slow stand dynamics, characterized by low recruitment and growth rates counterbalanced by equally low mortality rates. These dynamics result in populations with limited capacity to increase in size quickly, but potentially highly vulnerable to decline should the rate of adult mortality increase. This combination of traits is likely typical of extreme stress‐tolerator woody species and suggests a conservation focus on the preservation of mature individuals.     

Functional traits explain phytoplankton community structure and seasonal dynamics in a marine ecosystem

A fundamental yet elusive goal of ecology is to predict the structure of communities from the environmental conditions they experience. Trait‐based approaches to terrestrial plant communities have shown that functional traits can help reveal the mechanisms underlying community assembly, but such approaches have not been tested on the microbes that dominate ecosystem processes in the ocean. Here, we test whether functional traits can explain community responses to seasonal environmental fluctuation, using a time series of the phytoplankton of the English Channel. We show that interspecific variation in response to major limiting resources, light and nitrate, can be well‐predicted by lab‐measured traits characterising light utilisation, nitrate utilisation and maximum growth rate. As these relationships were predicted a priori, using independently measured traits, our results show that functional traits provide a strong mechanistic foundation for understanding the structure and dynamics of ecological communities.     

羊草基因型数目与氮添加对土壤微生物群落的交互影响

物种多样性(或同一物种遗传多样性)减少和氮富集都是影响陆地生态系统进程的主要因素,它们之间的交互作用是否对土壤微生物群落产生显著影响已成为研究者关心的主要科学问题。研究羊草基因型数目(1、2、4三种基因型数目组合)和氮添加(无氮添加、低氮添加和高氮添加3种水平)对土壤微生物群落的总磷脂脂肪酸(PLFA,Phospholipid Fatty Acid)含量、细菌PLFA生物标记含量、真菌PLFA生物标记含量、真菌/细菌比、以及基于每个PLFA生物标记相对含量百分比所得微生物群落的Shannon-Wiener多样性指数和Simpson优势度指数的影响。结果表明:氮添加对细菌PLFA生物标记含量,以及土壤微生物PLFA生物标记的Shannon-Wiener多样性指数和Simpson优势度指数具有显著影响(P0.05);基因型数目对所测变量无显著影响(P0.05),但基因型数目和氮添加的交互作用对细菌PLFA生物标记含量和真菌/细菌比具有显著影响(P0.05)。研究结果为全球变化背景下氮沉降及重要物种种群数量减少对土壤微生物群落的影响提供了科学数据,为合理解释群落动态变化提供了数据支持。     

Host‐plant genotypic diversity and community genetic interactions mediate aphid spatial distribution

Genetic variation in plants can influence the community structure of associated species, through both direct and indirect interactions. Herbivorous insects are known to feed on a restricted range of plants, and herbivore preference and performance can vary among host plants within a species due to genetically based traits of the plant (e.g., defensive compounds). In a natural system, we expect to find genetic variation within both plant and herbivore communities and we expect this variation to influence species interactions. Using a three‐species plant‐aphid model system, we investigated the effect of genetic diversity on genetic interactions among the community members. Our system involved a host plant (Hordeum vulgare) that was shared by an aphid (Sitobion avenae) and a hemi‐parasitic plant (Rhinanthus minor). We showed that aphids cluster more tightly in a genetically diverse host‐plant community than in a genetic monoculture, with host‐plant genetic diversity explaining up to 24% of the variation in aphid distribution. This is driven by differing preferences of the aphids to the different plant genotypes and their resulting performance on these plants. Within the two host‐plant diversity levels, aphid spatial distribution was influenced by an interaction among the aphid's own genotype, the genotype of a competing aphid, the origin of the parasitic plant population, and the host‐plant genotype. Thus, the overall outcome involves both direct (i.e., host plant to aphid) and indirect (i.e., parasitic plant to aphid) interactions across all these species. These results show that a complex genetic environment influences the distribution of herbivores among host plants. Thus, in genetically diverse systems, interspecific genetic interactions between the host plant and herbivore can influence the population dynamics of the system and could also structure local communities. We suggest that direct and indirect genotypic interactions among species can influence community structure and processes.     

Conservation of genetic diversity in old‐growth forest communities of the southeastern United States

Question: How do studies of the distribution of genetic diversity of species with different life forms contribute to the development of conservation strategies? Location: Old‐growth forests of the southeastern United States. Methods: Reviews of the plant allozyme literature are used to identify differences in genetic diversity and structure among species with different life forms, distributions and breeding systems. The general results are illustrated by case studies of four plant species characteristic of two widespread old‐growth forest communities of the southeastern United States: the Pinus palustris – Aristida stricta (Longleaf pine – wiregrass) savanna of the Coastal Plain and the Quercus – Carya – Pinus (Oak‐hickory‐pine) forest of the Piedmont. Genetic variation patterns of single‐gene and quantitative traits are also reviewed. Results: Dominant forest trees, represented by Pinus palustris(longleaf pine) and Quercus rubra (Northern red oak), maintain most of their genetic diversity within their populations whereas a higher proportion of the genetic diversity of herbaceous understorey species such as Sarracenia leucophylla and Trillium reliquum is distributed among their populations. The herbaceous species also tend to have more population‐to‐population variation in genetic diversity. Higher genetic differentiation among populations is seen for quantitative traits than for allozyme traits, indicating that interpopulation variation in quantitative traits is influenced by natural selection. Conclusion: Developing effective conservation strategies for one or a few species may not prove adequate for species with other combinations of traits. Given suitable empirical studies, it should be possible to design efficient conservation programs that maintain natural levels of genetic diversity within species of conservation interest.     

Nutrient stoichiometry and land use rather than species richness determine plant functional diversity

Plant functional traits reflect individual and community ecological strategies. They allow the detection of directional changes in community dynamics and ecosystemic processes, being an additional tool to assess biodiversity than species richness. Analysis of functional patterns in plant communities provides mechanistic insight into biodiversity alterations due to anthropogenic activity. Although studies have consi‐dered of either anthropogenic management or nutrient availability on functional traits in temperate grasslands, studies combining effects of both drivers are scarce. Here, we assessed the impacts of management intensity (fertilization, mowing, grazing), nutrient stoichiometry (C, N, P, K), and vegetation composition on community‐weighted means (CWMs) and functional diversity (Rao's Q) from seven plant traits in 150 grasslands in three regions in Germany, using data of 6 years. Land use and nutrient stoichiometry accounted for larger proportions of model variance of CWM and Rao's Q than species richness and productivity. Grazing affected all analyzed trait groups; fertilization and mowing only impacted generative traits. Grazing was clearly associated with nutrient retention strategies, that is, investing in durable structures and production of fewer, less variable seed. Phenological variability was increased. Fertilization and mowing decreased seed number/mass variability, indicating competition‐related effects. Impacts of nutrient stoichiometry on trait syndromes varied. Nutrient limitation (large N:P, C:N ratios) promoted species with conservative strategies, that is, investment in durable plant structures rather than fast growth, fewer seed, and delayed flowering onset. In contrast to seed mass, leaf‐economics variability was reduced under P shortage. Species diversity was positively associated with the variability of generative traits. Synthesis. Here, land use, nutrient availability, species richness, and plant functional strategies have been shown to interact complexly, driving community composition, and vegetation responses to management intensity. We suggest that deeper understanding of underlying mechanisms shaping community assembly and biodiversity will require analyzing all these parameters.     

Evidence of local adaptation despite strong drift in a Neotropical patchily distributed bromeliad

Both genetic drift and divergent selection are predicted to be drivers of population differentiation across patchy habitats, but the extent to which these forces act on natural populations to shape traits is strongly affected by species’ ecological features. In this study, we infer the genomic structure of Pitcairnia lanuginosa, a widespread herbaceous perennial plant with a patchy distribution. We sampled populations in the Brazilian Cerrado and the Central Andean Yungas and discovered and genotyped SNP markers using double-digest restriction-site associated DNA sequencing. In addition, we analyzed ecophysiological traits obtained from a common garden experiment and compared patterns of phenotypic and genetic divergence (P_ST–F_ST comparisons) in a subset of populations from the Cerrado. Our results from molecular analyses pointed to extremely low genetic diversity and a remarkable population differentiation, supporting a major role of genetic drift. Approximately 0.3% of genotyped SNPs were flagged as differentiation outliers by at least two distinct methods, and Bayesian generalized linear mixed models revealed a signature of isolation by environment in addition to isolation by distance for high-differentiation outlier SNPs among the Cerrado populations. P_ST–F_ST comparisons suggested divergent selection on two ecophysiological traits linked to drought tolerance. We showed that these traits vary among populations, although without any particular macro-spatial pattern, suggesting local adaptation to differences in micro-habitats. Our study shows that selection might be a relevant force, particularly for traits involved in drought stress, even for populations experiencing strong drift, which improves our knowledge on eco-evolutionary processes acting on non-continuously distributed species.Subject terms: Population genetics, Speciation     

Neighbours matter: natural selection on plant size depends on the identity and diversity of the surrounding community

Plant diversity can affect ecological processes such as competition and herbivory, and these ecological processes can act as drivers of evolutionary change. However, surprisingly little is known about how ecological variation in plant diversity can alter selective regimes on members of the community. Here, we examine how plant diversity at two different scales (genotypic and species diversity) impacts natural selection on a focal plant species, the common evening primrose (Oenothera biennis). Because competition is frequently relaxed in both genotypically and species rich plant communities, we hypothesized that increasing diversity would weaken selection on competitive ability. Changes in plant diversity can also affect associated arthropod communities. Therefore, we hypothesized that diversity would alter selection on plant traits mediating these interactions, such as herbivory related traits. We grew 24 focal O. biennis genotypes within four different neighbourhoods: genotypic monocultures or polycultures of O. biennis, and species monocultures or polycultures of old-field species that commonly co-occur with O. biennis. We then measured genotypic selection on nine plant traits known to be ecologically important for competition and herbivory. Focal O. biennis plants were smaller, flowered for shorter periods of time, had lower fitness, and experienced greater attack from specialist predispersal seed predators when grown with conspecifics versus heterospecifics. While neither conspecific nor heterospecific diversity altered trait means, both types of diversity altered the strength of selection on focal O. biennis plants. Specifically, selection on plant biomass was stronger in conspecific monocultures versus polycultures, but weaker in heterospecific monocultures versus polycultures. We found no evidence of selection on plant traits that mediate insect interactions, despite differences in arthropod communities on plants surrounded by conspecifics versus heterospecifics. Our data demonstrate that plant genotypic and species diversity can act as agents of natural selection, potentially driving evolutionary changes in plant communities.     

In situ marker‐based assessment of leaf trait evolutionary potential in a marginal European beech population

Evolutionary processes are expected to be crucial for the adaptation of natural populations to environmental changes. In particular, the capacity of rear edge populations to evolve in response to the species limiting conditions remains a major issue that requires to address their evolutionary potential. In situ quantitative genetic studies based on molecular markers offer the possibility to estimate evolutionary potentials manipulating neither the environment nor the individuals on which phenotypes are measured. The goal of this study was to estimate heritability and genetic correlations of a suite of leaf functional traits involved in climate adaptation for a natural population of the tree Fagus sylvatica, growing at the rear edge of the species range. Using two marker‐based quantitative genetics approaches, we obtained consistent and significant estimates of heritability for leaf phenological (phenology of leaf flush), morphological (mass, area, ratio mass/area) and physiological (δ¹³C, nitrogen content) traits. Moreover, we found only one significant positive genetic correlation between leaf area and leaf mass, which likely reflected mechanical constraints. We conclude first that the studied population has considerable genetic diversity for important ecophysiological traits regarding drought adaptation and, second, that genetic correlations are not likely to impose strong genetic constraints to future population evolution. Our results bring important insights into the question of the capacity of rear edge populations to evolve.     

The Microbial <Emphasis Type="BoldItalic">Phyllo</Emphasis>geography of the Carnivorous Plant <Emphasis Type="BoldItalic">Sarracenia alata</Emphasis>

Carnivorous pitcher plants host diverse microbial communities. This plant–microbe association provides a unique opportunity to investigate the evolutionary processes that influence the spatial diversity of microbial communities. Using next-generation sequencing of environmental samples, we surveyed microbial communities from 29 pitcher plants (Sarracenia alata) and compare community composition with plant genetic diversity in order to explore the influence of historical processes on the population structure of each lineage. Analyses reveal that there is a core S. alata microbiome, and that it is similar in composition to animal gut microfaunas. The spatial structure of community composition in S. alata (phyllogeography) is congruent at the deepest level with the dominant features of the landscape, including the Mississippi river and the discrete habitat boundaries that the plants occupy. Intriguingly, the microbial community structure reflects the phylogeographic structure of the host plant, suggesting that the phylogenetic structure of bacterial communities and population genetic structure of their host plant are influenced by similar historical processes.     

Genetic costructure in a meta‐community under threat of habitat fragmentation

Habitat fragmentation increasingly threatens the services provided by natural communities and ecosystem worldwide. An understanding of the eco‐evolutionary processes underlying fragmentation‐compromised communities in natural settings is lacking, yet critical to realistic and sustainable conservation. Through integrating the multivariate genetic, biotic and abiotic facets of a natural community module experiencing various degrees of habitat fragmentation, we provide unique insights into the processes underlying community functioning in real, natural conditions. The focal community module comprises a parasitic butterfly of conservation concern and its two obligatory host species, a plant and an ant. We show that both historical dispersal and ongoing habitat fragmentation shape population genetic diversity of the butterfly Phengaris alcon and its most limited host species (the plant Gentiana pneumonanthe). Genetic structure of each species was strongly driven by geographical structure, altitude and landscape connectivity. Strikingly, however, was the strong degree of genetic costructure among the three species that could not be explained by the spatial variables under study. This finding suggests that factors other than spatial configuration, including co‐evolutionary dynamics and shared dispersal pathways, cause parallel genetic structure among interacting species. While the exact contribution of co‐evolution and shared dispersal routes on the genetic variation within and among communities deserves further attention, our findings demonstrate a considerable degree of genetic parallelism in natural meta‐communities. The significant effect of landscape connectivity on the genetic diversity and structure of the butterfly also suggests that habitat fragmentation may threaten the functioning of the community module on the long run.     

A functional-structural model of rice linking quantitative genetic information with morphological development and physiological processes

Background and Aims

Although quantitative trait loci (QTL) analysis of yield-related traits for rice has developed rapidly, crop models using genotype information have been proposed only relatively recently. As a first step towards a generic genotype–phenotype model, we present here a three-dimensional functional–structural plant model (FSPM) of rice, in which some model parameters are controlled by functions describing the effect of main-effect and epistatic QTLs.

Methods

The model simulates the growth and development of rice based on selected ecophysiological processes, such as photosynthesis (source process) and organ formation, growth and extension (sink processes). It was devised using GroIMP, an interactive modelling platform based on the Relational Growth Grammar formalism (RGG). RGG rules describe the course of organ initiation and extension resulting in final morphology. The link between the phenotype (as represented by the simulated rice plant) and the QTL genotype was implemented via a data interface between the rice FSPM and the QTLNetwork software, which computes predictions of QTLs from map data and measured trait data.

Key Results

Using plant height and grain yield, it is shown how QTL information for a given trait can be used in an FSPM, computing and visualizing the phenotypes of different lines of a mapping population. Furthermore, we demonstrate how modification of a particular trait feeds back on the entire plant phenotype via the physiological processes considered.

Conclusions

We linked a rice FSPM to a quantitative genetic model, thereby employing QTL information to refine model parameters and visualizing the dynamics of development of the entire phenotype as a result of ecophysiological processes, including the trait(s) for which genetic information is available. Possibilities for further extension of the model, for example for the purposes of ideotype breeding, are discussed.Key words: Functional–structural plant model, ecophysiology, QTL analysis, plant modelling, quantitative genetics     

The ecophysiology of seed persistence: a mechanistic view of the journey to germination or demise

Seed persistence is the survival of seeds in the environment once they have reached maturity. Seed persistence allows a species, population or genotype to survive long after the death of parent plants, thus distributing genetic diversity through time. The ability to predict seed persistence accurately is critical to inform long‐term weed management and flora rehabilitation programs, as well as to allow a greater understanding of plant community dynamics. Indeed, each of the 420000 seed‐bearing plant species has a unique set of seed characteristics that determine its propensity to develop a persistent soil seed bank. The duration of seed persistence varies among species and populations, and depends on the physical and physiological characteristics of seeds and how they are affected by the biotic and abiotic environment. An integrated understanding of the ecophysiological mechanisms of seed persistence is essential if we are to improve our ability to predict how long seeds can survive in soils, both now and under future climatic conditions. In this review we present an holistic overview of the seed, species, climate, soil, and other site factors that contribute mechanistically to seed persistence, incorporating physiological, biochemical and ecological perspectives. We focus on current knowledge of the seed and species traits that influence seed longevity under ex situ controlled storage conditions, and explore how this inherent longevity is moderated by changeable biotic and abiotic conditions in situ, both before and after seeds are dispersed. We argue that the persistence of a given seed population in any environment depends on its resistance to exiting the seed bank via germination or death, and on its exposure to environmental conditions that are conducive to those fates. By synthesising knowledge of how the environment affects seeds to determine when and how they leave the soil seed bank into a resistance–exposure model, we provide a new framework for developing experimental and modelling approaches to predict how long seeds will persist in a range of environments.     

Invasion of an intact plant community: the role of population versus community level diversity

To improve the understanding of how native plant diversity influences invasion, we examined how population and community diversity may directly and indirectly be related to invasion in a natural field setting. Due to the large impact of the dominant C₄ grass species (Andropogon gerardii) on invasion resistance of tallgrass prairie, we hypothesized that genetic diversity and associated traits within a population of this species would be more strongly related to invasion than diversity or traits of the rest of the community. We added seeds of the exotic invasive C₄ grass, A. bladhii, to 1-m² plots in intact tallgrass prairie that varied in genetic diversity of A. gerardii and plant community diversity, but not species richness. We assessed relationships among genetic diversity and traits of A. gerardii, community diversity, community aggregated traits, resource availability, and early season establishment and late-season persistence of the invader using structural equation modeling (SEM). SEM models suggested that community diversity likely enhanced invasion indirectly through increasing community aggregated specific leaf area as a consequence of more favorable microclimatic conditions for seedling establishment. In contrast, neither population nor community diversity was directly or indirectly related to late season survival of invasive seedlings. Our research suggests that while much of diversity–invasion research has separately focused on the direct effects of genetic and species diversity, when taken together, we find that the role of both levels of diversity on invasion resistance may be more complex, whereby effects of diversity may be primarily indirect via traits and vary depending on the stage of invasion.     

高寒草甸植物群落功能多样性对不同生长期干旱的响应机制

植物对干旱胁迫的响应表现为各功能性状的差异化表达。全球气候变化下,青藏高原地区降水格局发生改变,高寒草甸群落功能性状及功能多样性在不同生长期干旱事件下的响应机制对加深高寒草甸适应气候变化认知具有重要意义。以藏北高寒草甸为研究对象,设置截雨棚模拟生长季前期（ED）、中期（MD）和非生长季时期（ND）干旱事件,通过观测群落物种功能性状,分析高寒草甸群落功能多样性对不同生长期干旱的响应机制。结果表明：（1）叶片功能性状对干旱存在差异响应,表现为叶片小而厚且寿命长,同化速率降低,并受氮元素限制加剧;（2）生长季前期干旱对高寒草甸群落功能性状的影响最强,生长季中期干旱次之,非生长季干旱的影响最弱;（3）生长季干旱处理显著改变了群落的功能多样性,ED处理下功能分散度指数（FDiv）和功能分异度指数（FDis）显著降低（P<0.05）,而Rao二次熵指数（RaoQ）显著升高（P<0.05）,MD处理下功能均匀度指数（FEve）显著降低（P<0.05）;（4）相关性分析得出,群落功能性状与功能多样性对干旱的响应之间存在着联系。本研究发现高寒草甸植物功能性状与群落功能多样性对生长季前期和中期干旱存在差异化响应,指示着高寒草甸植物群落在响应不同时期干旱时可能采取不同的生存策略,即对生长季前期干旱采用耐旱策略、对生长季中期干旱采用避旱策略。探讨了高寒草甸植物群落功能多样性对不同生长时期干旱胁迫的响应机制,为预测未来季节性干旱事件对青藏高原高寒草甸植物功能性状、群落特征和功能多样性的影响提供科学依据。     

Right here,right now: Populations of Actinotus helianthi differ in their early performance traits and interactions

Populations across the geographical distribution of a species are shaped by different local environments to produce distinctive patterns of variation in plant traits. Among‐population variation is, therefore, important for understanding potential shifts in distributions under changing environments, but is often not included in studies. In particular, critical data on the suitability of local environments for plant traits expressed at different life stages are lacking. To address this we performed two experiments to disentangle the influence of the local environment on multiple plant traits for populations of Actinotus helianthi from across its latitudinal range. A common environment experiment was used to compare early plant traits of germination, early seedling growth and survival for 17 populations of A. helianthi. To examine how biotic interactions vary across populations, we evaluated whether plant traits, including height and number of pseudanthia, influence visitor diversity and abundance, and if insect visitor abundance or diversity was associated with seed set success. We found that populations varied in germination success between 0.2 ± 0.1% and 64.2 ± 2.3%. Seedling growth and early survival varied among populations by as much as a factor of two and 44 respectively. We recorded variation in plant traits across hierarchical spatial scales from the maternal plant to biogeographical regions. The abundance and diversity of insect visitors also varied among populations and seed set was found to be site specific. There was a trend for populations with taller plants and larger floral display sizes to be more frequently visited by pollinators. We also identified a positive linear relationship between the number of visits by flies and seed set success. These results suggest that the local environment has a strong role in directly and indirectly influencing variation in plant traits within populations of A. helianthi, and potentially other perennial species.