Allocation strategies and seed traits are hardly affected by nitrogen supply in 18 species differing in successional status

Species performance depends on ecological strategies, revealed by suites of traits, conferring different relative ecological advantages in different environments. Although current knowledge on plant strategies along successional gradients is derived from studies conducted in situ, actually quantifying these strategies requires disentangling the effects of environmental factors from intrinsic differences between species.Here we tested whether allocation strategies and seed traits differ among successional stages and nitrogen levels. To this aim, we assessed biomass and nitrogen allocations and seed traits variations for 18 species, differing in life history and belonging to three stages of a Mediterranean old-field succession. These species were grown as monocultures in an experimental garden under limiting and non-limiting nitrogen supply.Early successional species allocated allometrically more nitrogen and proportionally more biomass to reproduction, and set more seeds than later successional species. Seed mass increased with successional status and was negatively related to seed number. Early successional species thus produced more but less-provisioned seeds, suggesting better colonization abilities. These patterns were not the sole consequence of the replacement of annuals by perennials along the successional gradient, since comparable trends were also observed within each life history. Allocation patterns were generally not altered by nitrogen supply and the higher nitrogen content in vegetative organs of plants grown under high nitrogen supply was not retranslocated from leaves to seeds during seed development.We therefore conclude that differences in plant ecological strategies in species characteristics from contrasting successional stages appear to be intrinsic properties of the studied species, and independent from environmental conditions.     

Do bacterial and fungal communities assemble differently during primary succession?

High‐throughput sequencing technologies are now allowing us to study patterns of community assembly for diverse microbial assemblages across environmental gradients and during succession. Here we discuss potential explanations for similarities and differences in bacterial and fungal community assembly patterns along a soil chronosequence in the foreland of a receding glacier. Although the data are not entirely conclusive, they do indicate that successional trajectories for bacteria and fungi may be quite different. Recent empirical and theoretical studies indicate that smaller microbes (like most bacteria) are less likely to be dispersal limited than are larger microbes – which could result in a more deterministic community assembly pattern for bacteria during primary succession. Many bacteria are also better adapted (than are fungi) to life in barren, early‐successional sediments in that some can fix nitrogen and carbon from the atmosphere – traits not possessed by any fungi. Other differences between bacteria and fungi are discussed, but it is apparent from this and other recent studies of microbial succession that we are a long way from understanding the mechanistic underpinnings of microbial community assembly during ecosystem succession. We especially need a better understanding of global and regional patterns of microbial dispersal and what environmental factors control the development of microbial communities in complex natural systems.     

Leaf trait-environment relationships in a subtropical broadleaved forest in South-East China

Although trait analyses have become more important in community ecology, trait-environment correlations have rarely been studied along successional gradients. We asked which environmental variables had the strongest impact on intraspecific and interspecific trait variation in the community and which traits were most responsive to the environment. We established a series of plots in a secondary forest in the Chinese subtropics, stratified by successional stages that were defined by the time elapsed since the last logging activities. On a total of 27 plots all woody plants were recorded and a set of individuals of every species was analysed for leaf traits, resulting in a trait matrix of 26 leaf traits for 122 species. A Fourth Corner Analysis revealed that the mean values of many leaf traits were tightly related to the successional gradient. Most shifts in traits followed the leaf economics spectrum with decreasing specific leaf area and leaf nutrient contents with successional time. Beside succession, few additional environmental variables resulted in significant trait relationships, such as soil moisture and soil C and N content as well as topographical variables. Not all traits were related to the leaf economics spectrum, and thus, to the successional gradient, such as stomata size and density. By comparing different permutation models in the Fourth Corner Analysis, we found that the trait-environment link was based more on the association of species with the environment than of the communities with species traits. The strong species-environment association was brought about by a clear gradient in species composition along the succession series, while communities were not well differentiated in mean trait composition. In contrast, intraspecific trait variation did not show close environmental relationships. The study confirmed the role of environmental trait filtering in subtropical forests, with traits associated with the leaf economics spectrum being the most responsive ones.     

Primary succession of Bistorta vivipara (L.) Delabre (Polygonaceae) root‐associated fungi mirrors plant succession in two glacial chronosequences

Glacier chronosequences are important sites for primary succession studies and have yielded well‐defined primary succession models for plants that identify environmental resistance as an important determinant of the successional trajectory. Whether plant‐associated fungal communities follow those same successional trajectories and also respond to environmental resistance is an open question. In this study, 454 amplicon pyrosequencing was used to compare the root‐associated fungal communities of the ectomycorrhizal (ECM) herb Bistorta vivipara along two primary succession gradients with different environmental resistance (alpine versus arctic) and different successional trajectories in the vascular plant communities (directional replacement versus directional non‐replacement). At both sites, the root‐associated fungal communities were dominated by ECM basidiomycetes and community composition shifted with increasing time since deglaciation. However, the fungal community's successional trajectory mirrored the pattern observed in the surrounding plant community at both sites: the alpine site displayed a directional‐replacement successional trajectory, and the arctic site displayed a directional‐non‐replacement successional trajectory. This suggests that, like in plant communities, environmental resistance is key in determining succession patterns in root‐associated fungi. The need for further replicated study, including in other host species, is emphasized.     

Properties of native plant communities do not determine exotic success during early forest succession

Considerable research has been devoted to understanding how plant invasions are influenced by properties of the native community and to the traits of exotic species that contribute to successful invasion. Studies of invasibility are common in successionally stable grasslands, but rare in recently disturbed or seral forests. We used 16 yr of species richness and abundance data from 1 m² plots in a clearcut and burned forest in the Cascade Range of western Oregon to address the following questions: 1) is invasion success correlated with properties of the native community? Are correlations stronger among pools of functionally similar taxa (i.e. exotic and native annuals)? Do these relationships change over successional time? 2) Does exotic abundance increase with removal of potentially dominant native species? 3) Do the population dynamics of exotic and native species differ, suggesting that exotics are more successful colonists? Exotics were primarily annual and biennial species. Regardless of the measure of success (richness, cover, biomass, or density) or successional stage, most correlations between exotics and natives were non‐significant. Exotic and native annuals showed positive correlations during mid‐succession, but these were attributed to shared associations with bare ground rather than to direct biotic interactions. At peak abundance, neither cover nor density of exotics differed between controls and plots from which native, mid‐successional dominants were removed. Tests comparing nine measures of population performance (representing the pace, magnitude, and duration of population growth) revealed no significant differences between native and exotic species. In this early successional system, local richness and abundance of exotics are not explained by properties of the native community, by the presence of dominant native species, or by superior colonizing ability among exotics species. Instead natives and exotics exhibit individualistic patterns of increase and decline suggesting similar sets of life‐history traits leading to similar successional roles.     

Life History Traits of Lianas During Tropical Forest Succession

Tropical secondary forests form an important part of the landscape. Understanding functional traits of species that colonize at different points in succession can provide insight into community assembly. Although studies on functional traits during forest succession have focused on trees, lianas (woody vines) also contribute strongly to forest biomass, species richness, and dynamics. We examined life history traits of lianas in a forest chronosequence in Costa Rica to determine which traits vary consistently over succession. We conducted 0.1 ha vegetation inventories in 30 sites. To examine the establishment of young individuals, we only included small lianas (0.5–1.5 cm diameter at 1.3 m height). For each species, we identified seed size, dispersal mode, climbing mode, and whether or not the seedling is self‐supporting. We found a strong axis of variation determined by seed size and seedling growth habit, with early successional communities dominated by small‐seeded species with abiotic dispersal and climbing seedlings, while large‐seeded, animal‐dispersed species with free‐standing seedlings increased in abundance with stand age. Contrary to previous research and theory, we found a decrease in the abundance of stem twiners and no decrease in the abundance of tendril‐climbers during succession. Seed size appears to be a better indicator of liana successional stage than climbing mode. Liana life history traits change predictably over succession, particularly traits related to seedling establishment. Identifying whether these trait differences persist into the growth strategies of mature lianas is an important research goal, with potential ramifications for understanding the impact of lianas during tropical forest succession.     

Vegetation succession among and within structural layers following wildfire in managed forests

Question: How does vegetation develop during the initial period following severe wildfire in managed forests? Location: Southwestern Oregon, USA. Methods: In severely burned plantations, dynamics of (1) shrub, herbaceous, and cryptogam richness; (2) cover; (3) topographic, overstory, and site influences were characterized on two contrasting aspects 2 to 4 years following fire. Analysis of variance was used to examine change in structural layer richness and cover over time. Non‐metric multidimensional scaling, multi‐response permutation procedure, and indicator species analysis were used to evaluate changes in community composition over time. Results: Vegetation established rapidly following wildfire in burned plantations, following an initial floristics model of succession among structural layers. Succession within structural layers followed a combination of initial and relay floristic models. Succession occurred simultaneously within and among structural layers following wildfire, but at different rates and with different drivers. Stochastic (fire severity and site history) and deterministic (species life history traits, topography, and pre‐disturbance plant community) factors determined starting points of succession. Multiple successional trajectories were evident in early succession. Conclusions: Mixed conifer forests are resilient to interacting effects of natural and human‐caused disturbances. Predicting the development of vegetation communities following disturbances requires an understanding of the various successional components, such as succession among and within structural layers, and the fire regime. Succession among and within structural layers can follow different successional models and trajectories, occurs at different rates, and is affected by multiple interacting factors.     

A theory of the spatial and temporal dynamics of plant communities

An individual-based model of plant competition for light that uses a definition of plant functional types based on adaptations for the simultaneous use of water and light can reproduce the fundamental spatial and temporal patterns of plant communities. This model shows that succession and zonation result from the same basic processes. Succession is interpreted as a temporal shift in species dominance, primarily in response to autogenic changes in light availability. Zonation is interpreted as a spatial shift in species dominance, primarily in response to the effect of allogenic changes in water availability on the dynamics of competition for light. Patterns of succession at different points along a moisture gradient can be used to examine changes in the ecological roles of various functional types, as well as to address questions of shifts in patterns of resource use through time.Our model is based on the cost-benefit concept that plant adaptations for the simultaneous use of two or more resources are limited by physiological and life history constraints. Three general sets of adaptive constraints produce inverse correlations in the ability of plants to efficiently use (1) light at both high and low availability, (2) water at both high and low availability, and (3) both water and light at low availabilities.The results of this type of individual-based model can be aggregated to examine phenomena at several levels of system organization (i.e., subdisciplines of ecology), including (1) plant growth responses over a range of environmental conditions, (2) population dynamics and size structure, (3) experimental and field observations on the distribution of species across environmental gradients, (4) studies of successional pattern, (5) plant physiognomy and community structure across environmental gradients, and (6) nutrient cycling.     

CWM and Rao’s quadratic diversity: a unified framework for functional ecology

Assessing the effects of environmental constraints on community structure often relies on methods that consider changes in species functional traits in response to environmental processes. Various indices have been proposed to measure relevant aspects of community trait composition from different viewpoints and perspectives. Among these, the ‘community-weighted mean trait value’ (CWM) and the Rao coefficient have been widely used in ecological research for summarizing different facets of functional composition and diversity. Analyzing changes in functional diversity of bee communities along a post-fire successional gradient in southern Switzerland we show that these two measures may be used to describe two complementary aspects of community structure, such as the mean and the dispersion of functional traits within a given species assemblage. While CWM can be adequately used to summarize shifts in mean trait values within communities due to environmental selection for certain functional traits, the Rao coefficient can be effectively applied to analyze patterns of trait convergence or divergence compared to a random expectation.     

Dispersal traits as indicators of vegetation dynamics in long-term old-field succession

Succession is a key ecological process that supports our understanding of community assembly and biotic interactions. Dispersal potential and dispersal strategies, such as wind- or animal-dispersal, have been assumed to be highly relevant for the success of plant species during succession. However, research yielded varying results on changes in dispersal modes between successional stages. Here, we test the hypotheses that (a) vascular plant species that use a number of dispersal modes dominate in early stages of succession while species specialized on one/few dispersal modes increase in abundance towards later stages of succession; (b) species well adapted to wind-dispersal (anemochory) will peak in abundance in early successional stages and (c) species well adapted to adhesive dispersal (epizoochory) will increase with proceeding succession. We test these hypotheses in four sites within agriculturally dominated landscapes in Germany. Agricultural use in these sites was abandoned 20–28 years ago, leaving them to secondary succession. Sites have been monitored for plant biodiversity ever since. We analyze changes in plant species richness and abundance, number of dispersal modes and two ranking indices for wind- and adhesive dispersal by applying generalized linear mixed-effect models. We used both abundance-weighted and unweighted dispersal traits in order to gain a comprehensive picture of successional developments. Hypothesis (a) was supported by unweighted but not abundance-weighted data. Anemochory showed no consistent changes across sites. In contrast, epizoochory (especially when not weighted by abundance) turned out to be an indicator of the transition from early to mid-successional stages. It increased for the first 9–16 years of succession but declined afterwards. Species richness showed an opposing pattern, while species abundance increased asymptotically. We suggest that plant-animal interactions play a key role in mediating these processes: By importing seeds of highly competitive plant species, animals are likely to promote the increasing abundance of a few dominant, highly epizoochorous species. These species outcompete weak competitors and species richness decreases. However, animals should as well promote the subsequent increase of species richness by disturbing the sites and creating small open patches. These patches are colonized by weaker competitors that are not necessarily dispersed by animals. The changes in the presence of epizoochorous species indicate the importance of plant traits and related plant–animal interactions in the succession of plant communities.     

Individualistic patterns of annuals and biennials in early successional oldfields

The importance of Gleasonian species individuality, with its relation to life history strategies in succession, has been implied by studies lasting only a few years, or studies relying on chronosequences. Even in long-term studies, it has been addressed without statistical tests. Here, we examine the first six years of succession in permanent plots on ten contrasting oldfields to statistically determine the role of species individuality in early oldfield succession.Percent cover data were collected each summer in 48 permanent plots in ten oldfields as part of the Buell Succession Study at the Hutcheson Memorial Forest on the New Jersey Piedmont, USA. Congruent patterns of mean percent cover over time clearly reflect life history strategies of annuals and biennials. Kendall's coefficient of concordance, calculated for population patterns of annuals or biennials in each oldfield, confirms that population patterns within life form groups are similar and supports the contention that life history strategies are important in determining successional pattern once species become established in an oldfield.Profile analysis, a statistical test for parallelism among species patterns, performed on all population patterns in each oldfield, confirms that these patterns are individualistic. The individualistic pattern implies that succession may be driven by the different strategies of dispersal, growth, and resource use of the species involved.     

Correspondence of seed traits with niche position in glacier foreland succession

Changes in species composition during succession are driven by biotic and abiotic factors leading to a multitude of niches occupied by distinct species. Gradient analyses of plant communities provide opportunities to approximate the niche position of species along a successional gradient. Several plant traits have been used to explain mechanisms governing successional sequences, but generalising changes in species traits during primary succession is still controversial. This study examined whether the seed mass and the optimum temperature for germination could explain the niche position of several glacier foreland species along a primary successional gradient in the Austrian Central Alps. We hypothesised that pioneer species should possess lighter seeds and a lower optimum temperature for germination than late successional species. We found significant differences in the seed mass between species, but the seed mass did not correspond with the assigned niche position on the successional gradient. Germination responses to temperature also differed significantly between species. Pioneer species performed better at lower temperatures than late successional species, suggesting that the optimum temperature for germination is a driver of niche separation. We discuss the interactions between seed traits and environmental conditions along the primary successional gradient emphasising the importance of temperature requirements for the germination. Differences in the regeneration characteristics are a major cue governing species turnover in glacier foreland succession.     

Community assembly along a successional gradient in sub‐alpine meadows of the Qinghai‐Tibetan Plateau,China

Community assembly is a dynamic progression that reflects the interaction of several processes functioning at multiple scales. Understanding how these processes work in communities at different successional stages is important for identifying when regional or local processes are more important for community assembly, and for developing effective preservation and restoration strategies. We examined community assembly using a chronosequence of sub‐alpine meadows in Qinghai‐Tibetan Plateau that range from ‘natural’ (never farmed), to those that have been protected from agricultural exploitation for 1 to 10 years. We tested for shifts in species and traits among meadows and also for changes in environmental and spatial correlates of species distributions within meadows. We found that species richness increased and species composition returned to natural conditions within ten years of protection. These changes coincided with shifts in species traits; abundant species had high seed mass and specific leaf area in late‐successional meadows, whereas the opposite occurred in early‐successional meadows. Despite these shifts among meadows of different ages, spatial distributions of species within meadows did not change – when associated with abiotic variables, these spatial patterns reflected changes in soil pH and nitrogen. There was also no consistent change in the relative importance of environmental and spatial correlates of species distributions within meadows. These trends indicate that local processes of community assembly are similar within meadows even when species in those meadows differ. We conclude that successional change is a large‐scale process that alters the species pool and resulting suite of traits that are present within meadows. As a result, regional planning that incorporates successional age should be the focus for the conservation of diversity in this area. In contrast, local processes work within the constraints of the species pool set by successional age, producing consistent patterns within meadows of different ages.     

Life in harsh environments: carabid and spider trait types and functional diversity on a debris‐covered glacier and along its foreland

1. Patterns of species richness and species assemblage composition of ground‐dwelling arthropods in primary successions along glacier forelands are traditionally described using a taxonomic approach. On the other hand, the functional trait approach could ensure a better characterisation of their colonisation strategies in these types of habitat. 2. The functional trait approach was applied to investigate patterns of functional diversity and life‐history traits of ground beetles and spiders on an alpine debris‐covered glacier and along its forefield in order to describe their colonisation strategies. 3. Ground beetles and spiders were sampled at different successional stages, representing five stages of deglaciation. 4. The results show that the studied glacier hosts ground beetle and spider assemblages that are mainly characterised by the following traits: walking colonisers, ground hunters and small‐sized species. These traits are typical of species living in cold, wet, and gravelly habitats. The diversity of functional traits in spiders increased along the succession, and in both carabids and spiders, life‐history traits follow the ‘addition and persistence model’. Accordingly, there is no turnover but there is an addition of new traits and a variation in their proportion within each species assemblage along the succession. The distribution of ground beetles and spiders along the glacier foreland and on the glacier seems to be driven by dispersal ability and foraging strategy. 5. The proposed functional approach improves knowledge of the adaptive strategies of ground‐dwelling arthropods colonising glacier surfaces and recently deglaciated terrains, which represent landforms quickly changing due to global warming.     

Consequences of abandonment for a regional fen flora and mechanisms of successional change

Abstract. Until the 1960s, species-rich vegetation on minero-trophic peaty soüs (fen sites) were characteristic of the alluvial plains in Schleswig-Holstein (Northwest Germany). Today, many of these habitats undergo successional changes due to abandonment. Vegetation development after abandonment can be characterized as a sequence of different successional stages and described in terms of a successional model. Successional stage I includes grazed, mown and recently abandoned sites without dominants. Stages II and III are characterized by the dominance of highly competitive herbaceous species whüe stage IV consists of woody vegetation. Ca. 3000 phytosociological relevés were assigned to the respective successional stages. Mean cover values were calculated for 250 species of the regional fen flora and assigned to successional categories according to their changes in cover in the successional series. According to our results 141 species decrease during succession, while 100 species were restricted to early successional stages and 85 species increased. Abandonment of all fen sites in Schleswig-Holstein will probably lead to the regional loss of 23 species of the fen flora. To identify mechanisms underlying successional change, the successional categories were correlated with life history traits and ecological requirements of the species. Results indicate that both light competition and limitation of sexual reproduction of small-seeded species might play a major role in the decrease and extinction of species during succession. Finally, conservation strategies for endangered species in a cultural landscape are discussed.     

Fit for succession – community structure and life strategies of leafhoppers in urban brownfields

Abstract.  1. Urban brownfields offer an excellent opportunity to study successional processes. Changes in the frequencies of biological traits during succession are of particular interest. They shed light on the general reasons why species emerge and vanish during the course of succession.
2. Leafhopper (Hemiptera: Auchenorrhyncha) occurrence data (3763 species observations) of 194 species were studied. Data was collected on 246 brownfield plots, aged 0–40 years, in two cities in Northern Germany.
3. Four categorical traits were studied: host-plant type, phagy, dormancy, and voltinism. In these traits, two aspects were analysed: (1) changes in trait category frequencies during succession, and (2) distribution of trait categories (i) within the brownfield species pool versus the German species pool and (ii) within species observations.
4. Trait categories showed clear successional trends. Young successional stages were related to feeding on herbs, polyphagy, egg overwintering, and two generations per year.
5. By analysing combinations of two traits, species could be assigned to four functional groups: species associated with young, intermediate and old sites, and one group indifferent to site age. The pioneer group comprised the least number of species, but the highest number of observations.
6. Categories associated with young site age were over-represented in the brownfield species pool. Moreover, within this already biased species pool, species with pioneer trait categories occurred with higher frequency. For the slow colonisers among leafhoppers, brownfields seem to be habitats that are hard to exploit.     

Herb abundance and life-history traits in two contrasting alpine habitats in southern Norway

Colonisation is often a critical stage in the life history of plants, and recruitment success is expected to have a strong impact on plant frequencies especially among herbs. Several plant traits (seed size, plant height, leaf dry weight and specific leaf area) are suggested to be functionally important in early life stages, and the impact of such traits is expected to increase with habitat harshness. In this comparative study we examine the relative role of different plant traits for herb community patterns on both a local and regional scale in two contrasting alpine ecosystems in southern Norway: (1) a sub-continental region with more dry and productive, base-rich soils (Ho1, Hallingdal) and (2) an oceanic region, with humid acidic soils (Setesdal). Differences in species richness between regions were mainly due to higher herb richness in the base-rich region (n=55) than in the acidic region (n=13). Among traits, herb species seed weight was higher at the acidic site. The relative importance of traits for explaining herb local abundance and regional distribution tended to be stronger at the acidic site. No trait had a significant effect at the base-rich site, although seed weight and seed number were marginally non-significant. Plant clonality was positively related to local abundance and marginally to regional distribution at the acidic site. Plant frequency-trait correlations were generally higher in the acidic region then in the base-rich region. There was further a (marginal) increase of herbs with large seeds and with a dependence on sexual reproduction with increasing pH levels in Ho1. Soil pH was also the most important environmental variable for herb richness in Ho1, while no environmental variable was significantly related to herb richness in Setesdal. The study suggests that recruitment through seed is critical for the alpine herb community patterns especially in harsh habitats. Possible explanations for recruitment constraints include both soil acidity (low pH and Ca levels in addition to possible aluminium toxicity) and disturbance through grazing.     

Phylogenetic turnover during subtropical forest succession across environmental and phylogenetic scales

Although spatial and temporal patterns of phylogenetic community structure during succession are inherently interlinked and assembly processes vary with environmental and phylogenetic scales, successional studies of community assembly have yet to integrate spatial and temporal components of community structure, while accounting for scaling issues. To gain insight into the processes that generate biodiversity after disturbance, we combine analyses of spatial and temporal phylogenetic turnover across phylogenetic scales, accounting for covariation with environmental differences. We compared phylogenetic turnover, at the species‐ and individual‐level, within and between five successional stages, representing woody plant communities in a subtropical forest chronosequence. We decomposed turnover at different phylogenetic depths and assessed its covariation with between‐plot abiotic differences. Phylogenetic turnover between stages was low relative to species turnover and was not explained by abiotic differences. However, within the late‐successional stages, there was high presence‐/absence‐based turnover (clustering) that occurred deep in the phylogeny and covaried with environmental differentiation. Our results support a deterministic model of community assembly where (i) phylogenetic composition is constrained through successional time, but (ii) toward late succession, species sorting into preferred habitats according to niche traits that are conserved deep in phylogeny, becomes increasingly important.     

黔中喀斯特山区植物功能性状的变异与关联

认识植物功能性状随演替进展的变化规律和不同性状之间的关系, 有助于从功能生态学的角度来理解群落演替。该文调查了位于贵州省中部的普定县喀斯特山区26个样方的物种组成, 这些样方分别处于灌丛、落叶阔叶林、落叶常绿混交林3个演替阶段; 测量了分布于该区域的82种木本植物的3个功能性状值(叶面积、比叶面积、最大高度); 根据物种在样方中的多度加权计算得到26个样方的性状平均值, 在此基础上分析了随演替进展植物功能性状在群落水平上的变异格局和不同性状之间的相关性; 采用性状梯度分析法分析了各阶段优势物种的功能性状在群落间(β组分)和群落内(α组分)的变异格局及相关性。结果表明: 1)沿灌丛→落叶阔叶林→落叶常绿混交林这一演替顺序, 群落平均叶面积和平均高度逐渐增加, 而群落平均比叶面积则逐渐变小; 2)就群落平均性状值而言, 叶面积与最大高度呈较强的正相关关系, 最大高度与比叶面积、叶面积与比叶面积均呈较强的负相关关系; 3)物种功能性状的α组分之间没有显著的相关关系, 而β组分之间相关性显著。这说明: 随演替的进展, 群落优势物种对环境的适应策略由高速生长转向提高资源利用效率, 而同一群落内共存的物种采取不同的性状组合来适应共同的群落环境。     

The genetic variance but not the genetic covariance of life‐history traits changes towards the north in a time‐constrained insect

Seasonal time constraints are usually stronger at higher than lower latitudes and can exert strong selection on life‐history traits and the correlations among these traits. To predict the response of life‐history traits to environmental change along a latitudinal gradient, information must be obtained about genetic variance in traits and also genetic correlation between traits, that is the genetic variance‐covariance matrix, G . Here, we estimated G for key life‐history traits in an obligate univoltine damselfly that faces seasonal time constraints. We exposed populations to simulated native temperatures and photoperiods and common garden environmental conditions in a laboratory set‐up. Despite differences in genetic variance in these traits between populations (lower variance at northern latitudes), there was no evidence for latitude‐specific covariance of the life‐history traits. At simulated native conditions, all populations showed strong genetic and phenotypic correlations between traits that shaped growth and development. The variance–covariance matrix changed considerably when populations were exposed to common garden conditions compared with the simulated natural conditions, showing the importance of environmentally induced changes in multivariate genetic structure. Our results highlight the importance of estimating variance–covariance matrixes in environments that mimic selection pressures and not only trait variances or mean trait values in common garden conditions for understanding the trait evolution across populations and environments.