The demographic effects of functional traits: an integral projection model approach reveals population‐level consequences of reproduction‐defence trade‐offs

Quantitatively linking individual variation in functional traits to demography is a necessary step to advance our understanding of trait‐based ecological processes. We constructed a population model for Asclepias syriaca to identify how functional traits affect vital rates and population growth and whether trade‐offs in chemical defence and demography alter population growth. Plants with higher foliar cardenolides had lower fibre, cellulose and lignin levels, as well as decreased sexual and clonal reproduction. Average cardenolide concentrations had the strongest effect on population growth. In both the sexual and clonal pathway, the trade‐off between reproduction and defence affected population growth. We found that both increasing the mean of the distribution of individual plant values for cardenolides and herbivory decreased population growth. However, increasing the variance in both defence and herbivory increased population growth. Functional traits can impact population growth and quantifying individual‐level variation in traits should be included in assessments of population‐level processes.     

Functional roles of remnant plant populations in communities and ecosystems

A hypothesis is suggested for functional roles of remnant plant populations in communities and ecosystems. A remnant population is capable of persistence during extended time periods, despite a negative population growth rate, due to long‐lived life stages and life‐cycles, including loops that allow population persistence without completion of the whole life cycle. A list of critera is suggested to help identification of remnant plant populations. Several community and ecosystem features may result from the presence of remnant plant populations. Apart from increasing community and ecosystem resilience just by being present, remnant populations may contribute to resilience through enhancing colonization by other plant species, by providing a persistent habitat for assemblages of animals and microorganisms, and by reducing variation in nutrient cycling. It is suggested that the common ability of plants to develop remnant populations is a contributing factor to ecosystem stability. Remnant populations are important for the capacity of ecosystems to cope with the present‐day impact caused by human society, and their occurrence should be recognized in surveys of threatened plant species and communities.     

Improving plant drought tolerance and growth under water limitation through combinatorial engineering of signalling networks

Agriculture is by far the biggest water consumer on our planet, accounting for 70 per cent of all freshwater withdrawals. Climate change and a growing world population increase pressure on agriculture to use water more efficiently (‘more crop per drop’). Water‐use efficiency (WUE) and drought tolerance of crops are complex traits that are determined by many physiological processes whose interplay is not well understood. Here, we describe a combinatorial engineering approach to optimize signalling networks involved in the control of stress tolerance. Screening a large population of combinatorially transformed plant lines, we identified a combination of calcium‐dependent protein kinase genes that confers enhanced drought stress tolerance and improved growth under water‐limiting conditions. Targeted introduction of this gene combination into plants increased plant survival under drought and enhanced growth under water‐limited conditions. Our work provides an efficient strategy for engineering complex signalling networks to improve plant performance under adverse environmental conditions, which does not depend on prior understanding of network function.     

Increasing plant diversity of experimental grasslands alters the age and growth of Plantago lanceolata from younger and faster to older and slower

The persistence of plant populations depends on the ability of individuals to cope with the conditions provided by the community. So far, it is not known whether differences in the diversity and composition of plant communities affect the age structure of plant populations or the expression of stem anatomical traits reflecting investment into plant growth and storage. We analyzed annual growth rings in the secondary xylem and measured stem anatomical traits in individuals from 18 populations of Plantago lanceolata growing in a 12‐year old grassland biodiversity experiment (Jena Experiment). Plant individuals of P. lanceolata were on average older and reproduced later with increasing species richness. Individuals of P. lanceolata were slightly younger and the age distribution within populations skewed to younger individuals in the presence of grasses. The presence of legumes did not affect mean age, but led to a more even age distribution within populations. The width of growth‐related tissues (xylem, phloem, phellem) decreased with increasing species richness. Plant diversity‐effects on storage‐related tissues (pith, cortex) were less consistent, as pith showed increasing width with species richness, while cortex did not change with plant diversity. Our results imply that plant diversity effects on population age structure and the expression of stem anatomical traits of P. lanceolata reflect a tradeoff: growth and turnover is fast at low diversity (younger age, higher allocation to growth‐related tissue, faster generative reproduction), while it is slow at high diversity (older age, higher allocation to storage‐related tissue, later generative reproduction).     

A pre‐adaptive approach for tropical forest restoration during climate change using naturally occurring genetic variation in response to water limitation

Effective reforestation of degraded tropical forests depends on selecting planting material suited to the stressful environments typical at restoration sites that can be exacerbated by increased duration and intensity of dry spells expected with climate change. While reforestation efforts in nontropical systems are incorporating drought‐adapted genotypes into restoration programs to cope with drier conditions, such approaches have not been tested or implemented in tropical forests. As the first effort to examine genetic variation in plant response to drought in a tropical wet forest, we established a watering experiment using five replicated maternal lines (i.e. seedlings from different maternal trees) of five dipterocarp species native to Borneo. Apart from the expected species level variation in growth and herbivory (3‐fold variation in both cases), we also found intraspecific variation so that growth in some cases varied 2‐fold, and herbivory 3‐fold, among genetically different maternal lines. In two species we found that among‐maternal line variation in growth rate was negatively correlated with tolerance to water limitation, that is, the maternal lines that performed the best in the high water treatment lost proportionally more of their growth during water limitation. We argue that selection for tolerance to future drier conditions is not only likely to impact population genetics of entire forests, but likely extends from forest trees to the communities of canopy arthropods associated with these trees. In tropical reforestation efforts where increased drought is predicted from climate change, including plant material resilient to drier conditions may improve restoration effectiveness.     

Utility of Microcosm Studies for Predicting Phylloplane Bacterium Population Sizes in the Field

Population sizes of two ice nucleation-active strains of Pseudomonas syringae were compared on leaves in controlled environments and in the field to determine the ability of microcosm studies to predict plant habitat preferences in the field. The P. syringae strains investigated were the parental strains of recombinant deletion mutant strains deficient in ice nucleation activity that had been field tested for their ability to control plant frost injury. The population size of the P. syringae strains was measured after inoculation at three field locations on up to 40 of the same plant species that were studied in the growth chamber. There was seldom a significant relationship between the mean population size of a given P. syringae strain incubated under either wet or dry conditions in microcosms and the mean population size which could be recovered from the same species when inoculated in the field. Specifically, on some plant species, the population size recovered from leaves in the field was substantially greater than from that species in a controlled environment, while for other plant species field populations were significantly smaller than those observed under controlled conditions. Population sizes of inoculated P. syringae strains, however, were frequently highly positively correlated with the indigenous bacterial population size on the same plant species in the field, suggesting that the ability of a particular plant species to support introduced bacterial strains is correlated with its ability to support large bacterial populations or that indigenous bacteria enhance the survival of introduced strains. Microcosm studies therefore seem most effective at assessing possible differences between parental and recombinant strains under a given environmental regime but are limited in their ability to predict the specific population sizes or plant habitat preferences of bacteria on leaves under field conditions.     

Predicting Plant Height of Greenhouse Grown Crops with a Polynomial Growth Rate Model

A prediction model for the growth of plant height is developed, using polynomials in time to describe the growth rate. The growth rate is affected by forcing factors through the polynomial coefficients. A random slope model is used to describe the difference in growth rate for plants grown under similar conditions. Maximum likelihood estimates of model parameters are obtained and a selection procedure is employed to estimate the model complexity using Schwarz' bayesian criterion as a measure of predictive power. The procedure is applied to data sets for greenhouse grown poinsettias. The use of polynomials to describe the time effects on the growth rate makes the strategy versatile, and it can be used to predict the growth of many different crops. Many forcing factors of different types can be incorporated simultaneously in the model. Confidence of predictions are also quantifies, which is important when the results are applied in a practical situation, e.g. in climate control of commercial greenhouses.     

Signs of stabilisation and stable coexistence

Many empirical studies motivated by an interest in stable coexistence have quantified negative density dependence, negative frequency dependence, or negative plant–soil feedback, but the links between these empirical results and ecological theory are not straightforward. Here, we relate these analyses to theoretical conditions for stabilisation and stable coexistence in classical competition models. By stabilisation, we mean an excess of intraspecific competition relative to interspecific competition that inherently slows or even prevents competitive exclusion. We show that most, though not all, tests demonstrating negative density dependence, negative frequency dependence, and negative plant–soil feedback constitute sufficient conditions for stabilisation of two‐species interactions if applied to data for per capita population growth rates of pairs of species, but none are necessary or sufficient conditions for stable coexistence of two species. Potential inferences are even more limited when communities involve more than two species, and when performance is measured at a single life stage or vital rate. We then discuss two approaches that enable stronger tests for stable coexistence‐invasibility experiments and model parameterisation. The model parameterisation approach can be applied to typical density‐dependence, frequency‐dependence, and plant–soil feedback data sets, and generally enables better links with mechanisms and greater insights, as demonstrated by recent studies.     

A life‐history perspective on the demographic drivers of structured population dynamics in changing environments

Current understanding of life‐history evolution and how demographic parameters contribute to population dynamics across species is largely based on assumptions of either constant environments or stationary environmental variation. Meanwhile, species are faced with non‐stationary environmental conditions (changing mean, variance, or both) created by climate and landscape change. To close the gap between contemporary reality and demographic theory, we develop a set of transient life table response experiments (LTREs) for decomposing realised population growth rates into contributions from specific vital rates and components of population structure. Using transient LTREs in a theoretical framework, we reveal that established concepts in population biology will require revision because of reliance on approaches that do not address the influence of unstable population structure on population growth and mean fitness. Going forward, transient LTREs will enhance understanding of demography and improve the explanatory power of models used to understand ecological and evolutionary dynamics.     

The maximum relative growth rate of common UK plant species is positively associated with their global invasiveness

Aim An emerging consensus in invasion ecology is that faster‐growing alien plant species tend to be more invasive than slower‐growing species. However, phylogenetic non‐independence and the precision of growth‐rate measures often remain unaccounted for in comparative studies. We tested whether global invasiveness was related to mean and maximum relative growth rate of 105 plant species (101 native and 4 introduced) commonly occurring in the UK. Location Global. Methods We combined a unique experimental dataset of relative growth rates (RGR) measured under standardized experimental conditions for plant species that occur widely in the UK with our global measures of invasiveness, which were the number of references in the Global Compendium of Weeds (GCW) and the number of world regions invaded. We weighted mean RGR measures per species by including variances of RGR in our analyses, and we also conducted analyses with and without phylogenetic structure, to account for potential phylogenetic non‐independence in RGR. Results We found a positive association between global invasiveness and maximum RGR. In addition, this association was not confounded by phylogenetic correlation, or by species seed mass. Main conclusions The results from this study suggest that faster‐growing species are more widespread at a global scale, adding support to other studies that suggest faster‐growing alien plant species tend to be more invasive in the introduced range.     

Site‐to‐site variation in the demography of a fire‐affected perennial. Acacia suaveolens,at Ku‐ring‐gai Chase National Park,New South Wales,Australia

Abstract Acacia suaveolens (Sm.) Willd is a perennial shrub that forms even‐aged stands, recruited from a soil seed‐bank following fire. It has previously been subject to demographic studies, which used a space‐for‐time substitution to investigate temporal patterns following fire. In the present study the potential for spatial variation across sites was investigated by sampling at several similarly aged populations in Ku‐ring‐gai Chase National Park, northern Sydney, Australia. Significant variation in mean size and fecundity of A. suaveolens individuals was observed among sites, over a 2‐4.6‐fold range in plant size, and a sevenfold range in mean fecundity. The observed variation at 3 years after fire encapsulated most of the variation previously observed among sites 0‐17 years since fire, emphasizing the importance of spatial variation in this species. For each site a two‐stage (seed, plant) matrix model was constructed, and projected from 3 to 25 years following fire. Population growth was measured as number of seeds per 3‐year‐old plant, and found to vary 1.4‐fold across models for different sites. This site‐to‐site variation, as well as that in size, fecundity and survival, was statistically significant. Variation in projected seeds per plant could mostly be attributed to differences in fecundity rather than plant survival. Sensitivity analyses emphasized the biological significance of the variation in fecundity. Whereas previous studies have focused on temporal variation, this work demonstrates the importance of extending our understanding of a species to include the spatial component of population dynamics.     

Stochastic LTRE analysis of the effects of herbivory on the population dynamics of a perennial grassland herb

Herbivores can have strong deleterious effects on vital rates (growth, reproduction, and survival) and thus negatively impact the population dynamics of plant species. In practice, however, these effects might be strongly correlated, for example as a result of tradeoffs between vital rates. To get better insights into the effects of herbivory on the population dynamics of the long‐lived grassland plant Primula veris population projection matrices were constructed from demographic data collected between 1999 and 2008 (nine annual transitions). Data were collected in two large grassland populations, each of which was subjected to two treatments (grazing by cattle versus a mowing treatment), yielding a total of 36 matrices. We applied a lower‐level vital rate life table response experiment (LTRE) using the small noise approximation (SNA) of the stochastic population growth rate to disentangle the contributions of changes in mean vital rates, variability in vital rates, correlations between vital rates and vital rate elasticities to the difference in the stochastic growth rate. Stochastic growth rates (a= log λ_S) were significantly lower in grazed than in mown plots (a= 0.0185 and 0.1019, respectively). SNA LTRE analysis showed that contributions of mean vital rates by far made the largest contribution to the observed difference in a between grazed and control plots. In particular, changes in sexual reproduction rates made the largest contributions to lower the stochastic growth rate in grazed plots: both adult flowering probabilities and flower and seed production were importantly lower in grazed populations, but these negative effects were largely buffered by increased establishment and seedling survival rates. Among the stochastic terms of the SNA decomposition, contributions of covariance and correlations between vital rates had the largest impact, whereas contributions of elasticities were smaller. The strongest correlation driver was the association between adult survival and seedling establishment, suggesting that environmental conditions favouring adult survival also are beneficial for seedling establishment. Overall, our results show that herbivory had a strong negative effect on the long‐term population growth rate of P. veris that was primarily mediated by differences in fecundity (flower and seed production) and germination.     

The role of climate and plant functional trade‐offs in shaping global biome and biodiversity patterns

Aim Two of the oldest observations in plant geography are the increase in plant diversity from the poles towards the tropics and the global geographic distribution of vegetation physiognomy (biomes). The objective of this paper is to use a process‐based vegetation model to evaluate the relationship between modelled and observed global patterns of plant diversity and the geographic distribution of biomes. Location The global terrestrial biosphere. Methods We implemented and tested a novel vegetation model aimed at identifying strategies that enable plants to grow and reproduce within particular climatic conditions across the globe. Our model simulates plant survival according to the fundamental ecophysiological processes of water uptake, photosynthesis, reproduction and phenology. We evaluated the survival of an ensemble of 10,000 plant growth strategies across the range of global climatic conditions. For the simulated regional plant assemblages we quantified functional richness, functional diversity and functional identity. Results A strong relationship was found (correlation coefficient of 0.75) between the modelled and the observed plant diversity. Our approach demonstrates that plant functional dissimilarity increases and then saturates with increasing plant diversity. Six of the major Earth biomes were reproduced by clustering grid cells according to their functional identity (mean functional traits of a regional plant assemblage). These biome clusters were in fair agreement with two other global vegetation schemes: a satellite image classification and a biogeography model (kappa statistics around 0.4). Main conclusions Our model reproduces the observed global patterns of plant diversity and vegetation physiognomy from the number and identity of simulated plant growth strategies. These plant growth strategies emerge from the first principles of climatic constraints and plant functional trade‐offs. Our study makes important contributions to furthering the understanding of how climate affects patterns of plant diversity and vegetation physiognomy from a process‐based rather than a phenomenological perspective.     

Ploidy level interacts with population size and habitat conditions to determine the degree of herbivory damage in plant populations

Recently it has been suggested that ploidy level of a plant population may have important effects on plant‐animal interactions. Plant‐animal interactions can also be strongly altered by factors such as plant population size and habitat conditions. It is, however, not known how these factors interact to shape the overall pattern of plant‐animal interactions. I studied the interaction between a perennial plant, Aster amellus, and a monophagous herbivorous moth, Coleophora obscenella, and investigated the effect of ploidy level of the plant population, plant population size, isolation and habitat conditions on density of the insect, damage by the insect, and plant performance. Ploidy level, plant population size and habitat conditions, but not isolation, strongly influence plant‐herbivore interactions. Furthermore, there are significant interactions between effects of ploidy level and plant population size and between ploidy level and isolation. Hexaploid plants suffer higher seed damage by the herbivore, but their seed production is still higher than that of diploids. Herbivores thus partly limit the evolutionary success of the hexaploid plants. Plant‐animal interactions are also strongly determined by plant population size. Small populations of A. amellus (below forty flowering ramets) host no C. obscenella larvae, indicating a minimum A. amellus population size that can sustain a viable C. obscenella population. Negative and positive effects of plant population size balance and result in no relationship between plant population size and number of developed seeds per flower head. The results also show a significant interaction between ploidy level and plant population size, indicating that the increase in density of C. obscenella larvae with plant population size is greater in hexaploid than in diploid populations. The results also indicate that the effect of ploidy level on plant‐herbivore interactions can be altered by plant population size, which suggests that plant‐herbivore interactions are driven by a complex of interactions among different factors. Studying each factor separately could thus lead to biased conclusions about patterns of interactions in such systems.     

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.     

Local Adaptation of Metallicolous and Non‐Metallicolous Anthyllis vulneraria Populations: Their Utilization in Soil Restoration

Restoration of metalliferous mine soils requires using plant species tolerant to high metal concentrations and adapted to nutrient‐poor soil. Legumes can increase plant productivity through N₂‐fixation, but they are often scarce in metalliferous sites. We examined survival, growth, and tolerance of four populations of a legume, Anthyllis vulneraria, from two metalliferous (MET) Zn‐Pb mine sites, Avinières (AV) ([Zn‐EDTA] = 26,000 mg/kg) and Eylie (EY) ([Zn‐EDTA] = 4,632 mg/kg), and two non‐metalliferous (NMET) sites located in the south of France with the aim to select the most appropriate populations for restoration of mined soils. In a common garden experiment, plants from each population were reciprocally grown in soil from the provenance of each population. The two NMET populations exhibited high mortality and low growth rates in soil from the mined sites. The AV MET exhibited a high growth rate in metalliferous soils, but showed high mortality in non‐metalliferous soils. The growth of the EY MET was very low in the AV‐contaminated soil, but was the highest of all populations in moderately and non‐metalliferous soils. Plants from the AV MET population showed a high growth and survival in metalliferous soil and would be appropriate in the restoration of metal‐contaminated sites (>30,000 mg Zn kg^?1). The EY MET population would be adapted to the restoration of moderate metal‐contaminated soils (<30,000 mg Zn kg^?1). Taking into account the broad distribution of A. vulneraria, these two populations could be suitable for the restoration of derelict mine sites in mediterranean and temperate regions of Europe and North America.     

Sea ice predicts long‐term trends in Adélie penguin population growth,but not annual fluctuations: Results from a range‐wide multiscale analysis

Understanding the scales at which environmental variability affects populations is critical for projecting population dynamics and species distributions in rapidly changing environments. Here we used a multilevel Bayesian analysis of range‐wide survey data for Adélie penguins to characterize multidecadal and annual effects of sea ice on population growth. We found that mean sea ice concentration at breeding colonies (i.e., “prevailing” environmental conditions) had robust nonlinear effects on multidecadal population trends and explained over 85% of the variance in mean population growth rates among sites. In contrast, despite considerable year‐to‐year fluctuations in abundance at most breeding colonies, annual sea ice fluctuations often explained less than 10% of the temporal variance in population growth rates. Our study provides an understanding of the spatially and temporally dynamic environmental factors that define the range limits of Adélie penguins, further establishing this iconic marine predator as a true sea ice obligate and providing a firm basis for projection under scenarios of future climate change. Yet, given the weak effects of annual sea ice relative to the large unexplained variance in year‐to‐year growth rates, the ability to generate useful short‐term forecasts of Adélie penguin breeding abundance will be extremely limited. Our approach provides a powerful framework for linking short‐ and longer term population processes to environmental conditions that can be applied to any species, facilitating a richer understanding of ecological predictability and sensitivity to global change.     

An Analysis of Seasonal Variation of Vegetative Propagation and the Relationships Between Biomass and Population Density of Aneurolepidium chinense in Songnen Plain of China

Aneurolepidium chinense (Trin.) Kitag. is a perennial rhizome grass with fertile vegetative propagation. According to the field-investigation at fixed locations in fixed period, the seasonal change of vegetative propagation of A. chinense population and the autopopulation were specifically analysed. The results showed that both A. chinense population and the autopopulation could continuously make vegetative propagation in the entire growh season. The vegetative propagation brought more potential into play in the autopopulation of planting tillering than in the autopopulation of planting seedling, and the dynamics conformed to the Logistic curve growth for every experimental autopopulation in the planting growth season. The vegetative propagation of the population and the autopopulation was more seriously affected by the sexual development and the growth. The plant size was rigorously restricted by the population density, and the change of regularity followed–0.6699 power between mean weight per plant and the population density in the period of maximum biomass in the natural cutting grassland. The comprehensive analysis showed that A. chinense population depended on vegetative propagation and the population regeneration of the self-regulation, but the population hadnt far reached the most density which could be accommodated by standing conditions in the natural cutting grassland in the Songnen Plain of China.     

松嫩平原羊草种群营养繁殖的季节动态及其生物量与密度关系的分析

本文根据野外定位定期观测,分析了羊草[Aneurolepidium chinense(Trin.)Kitag.]种群和羊草个体群营养繁殖的特点。结果表明,在整个生长季,羊草能不断地进行营养繁殖。在移植当年,羊草分蘖株个体群的营养繁殖潜力比实生苗个体群的更大,两个实验个体群的数量均符合于逻辑斯谛曲线增长。生殖生长对羊草的营养繁殖有较大的影响。天然割草场上的羊草种群在生物量达最高时期,种群植株的大小受密度的制约,平均单株重量与密度之间遵循-0.6699 幂的规律性变化。综合分析表明,在松嫩平原天然割草场上,羊草种群依靠营养繁殖更新延续、自我调节,但该种群尚未达到环境所能容纳的最大数量。     

Temperature adaptation in a geographically widespread zooplankter,Daphnia magna

Evidence for temperature adaptation in Daphnia magna was inferred from variation in the shape of temperature reaction norms for somatic growth rate, a fitness‐related trait. Ex‐ephippial clones from eight populations across Europe were grown under standardized conditions after preacclimation at five temperatures (17–29 °C). Significant variation for grand mean growth rates occurred both within populations (among clones) and between populations. Genetic variation for reaction norm shape was found within populations, with temperature‐dependent trade‐offs in clone relative fitness. However, the population average responses to temperature were similar, following approximately parallel reaction norms. The among‐population variation is not evidence for temperature adaptation. Lack of temperature adaptation at the population level may be a feature of intermittent populations where environmentally terminated diapause can entrain the planktonic stage of the life‐history within a similar range of temperatures.