Interactive life‐history traits predict sensitivity of plants and animals to temporal autocorrelation

Temporal autocorrelation in demographic processes is an important aspect of population dynamics, but a comprehensive examination of its effects on different life‐history strategies is lacking. We use matrix population models from 454 plant and animal populations to simulate stochastic population growth rates (log λ_s) under different temporal autocorrelations in demographic rates , using simulated and observed covariation among rates. We then test for differences in sensitivities, or changes of log λ_s to changes in autocorrelation among two major axes of life‐history strategies, obtained from phylogenetically informed principal component analysis: the fast‐slow and reproductive‐strategy continua. Fast life histories exhibit highest sensitivities to simulated autocorrelation in demographic rates across reproductive strategies. Slow life histories are less sensitive to temporal autocorrelation, but their sensitivities increase among highly iteroparous species. We provide cross‐taxonomic evidence that changes in the autocorrelation of environmental variation may affect a wide range of species, depending on complex interactions of life‐history strategies.     

Population estimates of Alfred mantas (<Emphasis Type="Italic">Manta alfredi</Emphasis>) in central Maldives atolls: North Male,Ari and Baa

The Alfred manta, Manta alfredi, is economically important in the Maldives due to the large number of tourists attracted to SCUBA dive and snorkel with them. It is important to understand the size of populations around main diving points and throughout the Maldives so that manta based tourism activities can be developed more successfully and the impact of tourism can be monitored. Using natural markings to identify individual manta rays, Petersen and Jolly-Seber probabilistic estimators were used to assess population size for main dive sites and the central atolls of North Male, Ari and Baa. Between 2000 and 2009, 1835 individual mantas were identified from 3373 sightings. There was a significant gender bias with a male: female ratio of 1:1.8. Only 24.7% of manta rays were re-sighted between 1 and 34 times with a maximum gap of 7 years and 11 months between sightings. Estimates for populations around main dive sites were 181–562. The estimated population of M. alfredi for North Male atoll is 537 (SE ± 53.2). Estimated atoll populations were extrapolated to obtain an estimate of Manta alfredi population for the entire Maldives of 9,677 individuals.     

Manta rays in the Marquesas Islands: first records of Manta birostris in French Polynesia and most easterly location of Manta alfredi in the Pacific Ocean,with notes on their distribution

Based on direct observations of free‐ranging specimens, the giant manta ray Manta birostris is reported from the Marquesas Islands, the first sighting in French Polynesia. Sightings of its sister species, the reef manta ray Manta alfredi, are also reported at the most easterly location in the Pacific Ocean. Preliminary individual identification as well as notes on their distribution are also reported.     

Comparing survey and multiple recruitment–mortality models to assess growth rates and population projections

Estimation of population trends and demographic parameters is important to our understanding of fundamental ecology and species management, yet these data are often difficult to obtain without the use of data from population surveys or marking animals. The northeastern Minnesota moose (Alces alces Linnaeus, 1758) population declined 58% during 2006–2017, yet aerial surveys indicated stability during 2012–2017. In response to the decline, the Minnesota Department of Natural Resources (MNDNR) initiated studies of adult and calf survival to better understand cause‐specific mortality, calf recruitment, and factors influencing the population trajectory. We estimated population growth rate (λ) using adult survival and calf recruitment data from demographic studies and the recruitment–mortality (R‐M) Equation and compared these estimates to those calculated using data from aerial surveys. We then projected population dynamics 50 years using each resulting λ and used a stochastic model to project population dynamics 30 years using data from the MNDNR's studies. Calculations of λ derived from 2012 to 2017 survey data, and the R‐M Equation indicated growth (1.02 ± 0.16 [SE] and 1.01 ± 0.04, respectively). However, the stochastic model indicated a decline in the population over 30 years (λ = 0.91 ± 0.004; 2014–2044). The R‐M Equation has utility for estimating λ, and the supporting information from demographic collaring studies also helps to better address management questions. Furthermore, estimates of λ calculated using collaring data were more certain and reflective of current conditions. Long‐term monitoring using collars would better inform population performance predictions and demographic responses to environmental variability.     

Demographic consequences of greater clonal than sexual reproduction in Dicentra canadensis

Clonality is a widespread life history trait in flowering plants that may be essential for population persistence, especially in environments where sexual reproduction is unpredictable. Frequent clonal reproduction, however, could hinder sexual reproduction by spatially aggregating ramets that compete with seedlings and reduce inter‐genet pollination. Nevertheless, the role of clonality in relation to variable sexual reproduction in population dynamics is often overlooked. We combined population matrix models and pollination experiments to compare the demographic contributions of clonal and sexual reproduction in three Dicentra canadensis populations, one in a well‐forested landscape and two in isolated forest remnants. We constructed stage‐based transition matrices from 3 years of census data to evaluate annual population growth rates, λ. We used loop analysis to evaluate the relative contribution of different reproductive pathways to λ. Despite strong temporal and spatial variation in seed set, populations generally showed stable growth rates. Although we detected some pollen limitation of seed set, manipulative pollination treatments did not affect population growth rates. Clonal reproduction contributed significantly more than sexual reproduction to population growth in the forest remnants. Only at the well‐forested site did sexual reproduction contribute as much as clonal reproduction to population growth. Flowering plants were more likely to transition to a smaller size class with reduced reproductive potential in the following year than similarly sized nonflowering plants, suggesting energy trade‐offs between sexual and clonal reproduction at the individual level. Seed production had negligible effects on growth and tuber production of individual plants. Our results demonstrate that clonal reproduction is vital for population persistence in a system where sexual reproduction is unpredictable. The bias toward clonality may be driven by low fitness returns for resource investment in sexual reproduction at the individual level. However, chronic failure in sexual reproduction may exacerbate the imbalance between sexual and clonal reproduction and eventually lead to irreversible loss of sex in the population.     

Fitness measures in selection analyses: sensitivity to the overall number of offspring produced in a lifetime

Age at first (α) and last (ω) breeding are important life‐history traits; however, the direction and strength of selection detected on traits may vary depending on the fitness measure used. We provide the first estimates of lifetime breeding success (LBS) and λ_ind (the population growth rate of an individual) of European badgers Meles meles, by genotyping 915 individuals, sampled over 18 years, for 22 microsatellites. Males are slightly larger than females, and the opportunity for selection was slightly greater for males, as predicted. λ_ind and LBS both performed well in predicting the number of grand‐offspring, and both detected selection for a late ω, until the age of eight. Differential selection (S′_α) for an early α, however, was only detected using LBS, not with λ_ind. In declining populations (λ_ind < 1) selection favours reproduction later in life, whereas early reproduction is selected in increasing populations (λ_ind > 1). As 41% of badgers were assigned only one offspring (λ_ind < 1), whereas 40% were assigned more than two (λ_ind > 1), this cancelled out S′_α measured by λ_ind.     

Behavioural and population responses to changing availability of <Emphasis Type="Italic">Artemia</Emphasis> prey by moulting black-necked grebes, <Emphasis Type="Italic">Podiceps nigricollis</Emphasis>

Chemical communication may inform about the location of prey, predators, co-specifics, and mate partners in zooplankton. In this study, we evaluated several life-history traits of the rotifer, Brachionus calyciflorus, exposed to conditioned media by a rotifer predator (Asplanchna brightwelli) and a cladocera competitor (Daphnia similis), quantifying population growth and life-table demography at two algal food levels (2.0 and 0.5 × 10⁶ cells ml⁻¹ of Chlorella pyrenoidosa). At both food levels, B. calyciflorus grown in predator-conditioned media had lower population abundance and slower population growth rate than controls. Conversely, the competitor-conditioned media treatments produced both higher rotifer population abundance and faster population growth rate than controls. Life-history parameters varied significantly depending on the presence of predator and competitor-conditioned media. The Asplanchna-conditioned media significantly decreased gross reproductive rate (GRR): 8–9 offsprings per female; net reproductive rate (R ₀): 6–7 offsprings per female; population growth rate (r): 0.34–0.37 day⁻¹; and increased generation time (T): 5.5–5.6 days. On the other hand, The Daphnia-conditioned media significantly increased the GRR (13–14 offsprings per female); net reproductive rate (8–9 offsprings per female); population growth rate (0.42–0.43 day⁻¹); and decreased generation time (4.9–5.0 days). However, the effects of food level on the life-history characteristic were not significant in both treatments. Maximum values of the population abundance and the population growth rate are significantly influenced by the predator densities and pre-culture time. This study suggests that rotifers use variable life-history strategies (low reproduction and high survivorship versus high reproduction and low survivorship) based on the presence of predators and competitors.     

Accounting for uncertainty in dormant life stages in stochastic demographic models

Dormant life stages are often critical for population viability in stochastic environments, but accurate field data characterizing them are difficult to collect. Such limitations may translate into uncertainties in demographic parameters describing these stages, which then may propagate errors in the examination of population‐level responses to environmental variation. Expanding on current methods, we 1) apply data‐driven approaches to estimate parameter uncertainty in vital rates of dormant life stages and 2) test whether such estimates provide more robust inferences about population dynamics. We built integral projection models (IPMs) for a fire‐adapted, carnivorous plant species using a Bayesian framework to estimate uncertainty in parameters of three vital rates of dormant seeds – seed‐bank ingression, stasis and egression. We used stochastic population projections and elasticity analyses to quantify the relative sensitivity of the stochastic population growth rate (log λs) to changes in these vital rates at different fire return intervals. We then ran stochastic projections of log λs for 1000 posterior samples of the three seed‐bank vital rates and assessed how strongly their parameter uncertainty propagated into uncertainty in estimates of log λs and the probability of quasi‐extinction, P_q(t). Elasticity analyses indicated that changes in seed‐bank stasis and egression had large effects on log λs across fire return intervals. In turn, uncertainty in the estimates of these two vital rates explained > 50% of the variation in log λs estimates at several fire‐return intervals. Inferences about population viability became less certain as the time between fires widened, with estimates of P_q(t) potentially > 20% higher when considering parameter uncertainty. Our results suggest that, for species with dormant stages, where data is often limited, failing to account for parameter uncertainty in population models may result in incorrect interpretations of population viability.     

Population dynamics of the reef manta ray Manta alfredi in eastern Australia

The reef manta ray Manta alfredi aggregates at several sites along the east coast of Australia. Photographic identification and mark–recapture methods were used to report on the site affinity, size and structure of this population of M. alfredi. A total of 716 individuals were identified in 1982–2012, including 636 at Lady Elliot Island (LEI), southern Great Barrier Reef. Over 60 % of individuals identified were resighted at least once during the study period. Multiple resightings within and among years imply a high degree of site affinity by individuals to aggregation sites. One individual was sighted 11 times at LEI over a 30-yr period. The sex ratio of this population was significantly biased towards females (1.2:1 female-to-male ratio), and females were more commonly resighted than males. Robust design population models were used to estimate the population size of the winter aggregation at LEI over a 4-yr period. The models estimated up to 456 (95 % CI 399–535) M. alfredi individuals in the population within one winter season and a high annual apparent survival. This study demonstrated that waters around LEI form a key aggregation site for a large portion of the M. alfredi population in east Australian waters.     

Climate‐driven vital rates do not always mean climate‐driven population

Current climatic changes have increased the need to forecast population responses to climate variability. A common approach to address this question is through models that project current population state using the functional relationship between demographic rates and climatic variables. We argue that this approach can lead to erroneous conclusions when interpopulation dispersal is not considered. We found that immigration can release the population from climate‐driven trajectories even when local vital rates are climate dependent. We illustrated this using individual‐based data on a trans‐equatorial migratory seabird, the Scopoli's shearwater Calonectris diomedea, in which the variation of vital rates has been associated with large‐scale climatic indices. We compared the population annual growth rate λ_i, estimated using local climate‐driven parameters with ρ_i, a population growth rate directly estimated from individual information and that accounts for immigration. While λ_i varied as a function of climatic variables, reflecting the climate‐dependent parameters, ρ_i did not, indicating that dispersal decouples the relationship between population growth and climate variables from that between climatic variables and vital rates. Our results suggest caution when assessing demographic effects of climatic variability especially in open populations for very mobile organisms such as fish, marine mammals, bats, or birds. When a population model cannot be validated or it is not detailed enough, ignoring immigration might lead to misleading climate‐driven projections.     

Growth and reproduction of the non‐native icefish Neosalanx taihuensis Chen, 1956 (Salangidae) in a plateau lake,southwestern China

Growth, reproduction and abundance traits of the invasive icefish Neosalanx taihuensis Chen, 1956 were investigated monthly from July 2009 to May 2011 in Lake Erhai on the Yunnan‐Guizhou Plateau, south‐western China, in order to explore the changes in life‐history traits after translocation. The results indicated that the icefish exhibited obvious plasticity in growth and reproduction traits. Growth of the fish in Lake Erhai was faster than that in native waters and in other translocated reservoirs. By fitting the von Bertalanffy growth model to the data, it was estimated that icefish obtain an asymptotic size of 96.12 mm, a K of 1.61, and a t₀ of ‐0.26; the calculated overall growth performance index φ′ was 4.17. The strategy of reproduction changed from multiple‐ to single‐spawning. The spawning period was from October to December with the absolute and relative fecundities of 1250 ± 169 eggs per ind and 2557 ± 245 eggs per g, respectively. Plasticity in icefish growth and reproduction in Lake Erhai greatly facilitated its population establishment, making it one of the most abundant fish species. The icefish invasion in the lake may be one of the reasons for the decrease or extinction of native fish species populations, and some measures for the control of this invasive fish are suggested.     

Demographic processes of upward range contraction in a long‐lived Mediterranean high mountain plant

We analyzed demographic data of a long‐lived high mountain Mediterranean plant, Silene ciliata Poirret, over a 4‐yr period. Selected populations were located at contrasting altitudes at the southernmost margin of the species (Sierra de Guadarrama, central Spain), representing a local altitudinal range at the rear edge of its overall distribution. Previous studies have suggested that differences in the reproduction and performance of individuals at upper and lower populations may have implications for population dynamics. We used matrix analysis to assess their demographic behaviour. Life Table Response Experiments were used to identify the life history stages most relevant to observed differences in population growth rates between populations. Transition matrices revealed great spatio‐temporal variability in demographic traits. Seedling recruitment was very low each year in all populations. Maximum longevity of S. ciliata individuals in the lower peripheral population was much lower compared to the central population, probably due to higher adult mortality. Population growth rate (λ) showed a declining trend at the lowest altitude and a relatively stable trend at the central population. Long‐term simulations also indicated a great risk of quasi‐extinction at the lowest population. Our results suggest that rear edge populations of S. ciliata at Sierra de Guadarrama are suffering demographic processes that may be leading to the latitudinal displacement of the species' range.     

On the possible role of nonreproductive traits for the evolution of unisexuality: Life‐history variation among males,females, and hermaphrodites in Opuntia robusta (Cactaceae)

In angiosperms, dioecy has arisen in 871–5,000 independent events, distributed in approximately 43% of the flowering families. The reproductive superiority of unisexuals has been the favorite explanation for the evolution of separate sexes. However, in several instances, the observed reproductive performance of unisexuals, if any, does not seem to compensate for the loss of one of the sex functions. The involvement of fitness components not directly associated with reproduction is a plausible hypothesis that has received little attention. Life‐history traits recently recognized as predictors of plant performance were compared among males, females, and hermaphrodites of a rare trioecious Opuntia robusta population in the field, using the cladode as the study unit. Cladode mortality by domestic herbivores was common and higher in females and hermaphrodites than in males. Males, females, or both displayed lower shrinkage and higher rates of survival, growth, and reproductive frequency than hermaphrodites. Unisexuals simultaneously outperformed hermaphrodites in demographic traits known to compete for common limiting resources, such as the acceleration of reproductive maturation (progenesis) and survival. A meta‐analysis combining the outcomes of each of the analyzed life‐history traits revealed a tendency of males (d₊₊ = 1.03) and females (d₊₊ = 0.93) to outperform hermaphrodites in presumably costly demographic options. Clonality is induced by human or domestic animal plant sectioning; and males and females highly exceeded hermaphrodites in their clonality potential by a factor of 8.3 and 5.3, respectively. The performances of unisexuals in the analyzed life‐history traits may enhance their reproductive potential in the long run and their clonality potential and could explain the observed increase of unisexuality in the population. Life‐history traits can be crucial for the evolution of unisexuality, but their impact appears to be habitat specific and may involve broad ontogenetic changes.     

Reproductive ecology of the reef manta ray Manta alfredi in southern Mozambique

The application of a photographic identification methodology using the unique ventral surface markings (natural spot patterns) of an observed population in southern Mozambique enabled many aspects of the reproductive ecology of reef manta rays Manta alfredi to be examined. The region encompassing the study site was identified as a mating ground for M. alfredi based on observations of mating events and fresh mating scars on females. The distribution of these pectoral fin scars was highly biased and indicated a strong lateralized behavioural trait, with 99% of these scars occurring only on the left pectoral fin. No other elasmobranch has been reported to display behavioural lateralization. The study region also acts as a birthing ground, with individuals typically giving birth in the austral summer period after a gestation of c. 1 year. Reproductive periodicity in M. alfredi was most commonly biennial, but a few individuals were pregnant in consecutive years, confirming an annual ovulatory cycle. The production of a single pup appears to be the normal situation, although observations in the wild as well as during opportunistic dissections of individuals killed by fisheries revealed that two pups are conceived on occasion. Many aspects of the study have contributed to the limited baseline data currently available for this species and have highlighted the potential need for more conservative conservation strategies.     

Variation in the demographics of a rare central Oregon endemic, Astragalus peckii Piper (Fabaceae), with fluctuating levels of herbivory

Understanding variation in plant vital rates (survival, growth, and reproduction) and population demographic parameters for rare plant taxa facilitates effective management for long-term persistence. We evaluated demographics of the rare plant Astragalus peckii (Fabaceae), a state-listed Threatened plant in Oregon, USA, with particular emphasis on how a microlepidopteran herbivore, Sparganothis tunicana, impacted vital rates and population growth. Stage-based transition matrix models were used to compute population growth rate (λ) and elasticity from 2006 to 2009 at two populations: Bull Flat, which was located in the main population center; and Chiloquin, a naturally isolated population. Population growth at Bull Flat was stable to slightly declining (λ = 0.96, 95 % CI 0.91–1.00) whereas at Chiloquin, the isolated population, population growth was increasing (λ = 1.20, 95 % CI 1.15–1.24). Microlepidopteran herbivory was associated with different plant responses in each population. At Bull Flat, plant survival was lower with greater herbivore presence. At Chiloquin, reproduction was reduced in plants when herbivores were active earlier in the growing season. Despite these effects on plant vital rates, we found lower population growth only during one transition period at Bull Flat when we compared matrices with and without herbivory. In addition to herbivory, we also address the potential role precipitation plays as a contributor to site differences and temporal variation within sites. Overall, we illustrate how two populations can have different responses to the same disturbance factor and highlight implications for management of different populations across the landscape.     

Population responses to observed climate variability across multiple organismal groups

A major challenge in ecology is to understand how populations are affected by increased climate variability. Here, we assessed the effects of observed climate variability on different organismal groups (amphibians, insects, mammals, herbaceous plants and reptiles) by estimating the extent to which interannual variation in the annual population growth rates (CV_λ) and the absolute value of the long-term population growth rate (|log λ|) were associated with short-term climate variability. We used empirical data (≥ 20 consecutive years of annual abundances) from 59 wild populations in the Northern Hemisphere, and quantified variabilities in population growth rates and climatic conditions (temperature and precipitation in active and inactive seasons) calculated over four- and eight-year sliding time windows. We observed a positive relationship between the variability of growth rate (CV_λ) and the variability of temperature in the active season at the shorter timescale only. Moreover, |log λ| was positively associated with the variability of precipitation in the inactive season at both timescales. Otherwise, the direction of the relationships between population dynamics and climate variability (if any) depended largely on the season and organismal group in question. Both CV_λ and |log λ| correlated negatively with species' lifespan, indicating general differences in population dynamics between short-lived and long-lived species that were not related to climate variability. Our results suggest that although temporal variation in population growth rates and the magnitude of long-term population growth rates are partially associated with short-term interannual climate variability, demographic responses to climate fluctuations might still be population-specific rather than specific to given organismal groups, and driven by other factors than the observed climate variability.     

Running the Gauntlet: Regional Movement Patterns of Manta alfredi through a Complex of Parks and Fisheries

Manta rays (Genus Manta) are economically important for fisheries and tourism in Indonesia. These species have been listed by the International Union for the Conservation of Nature Red List as Vulnerable to extinction; therefore, human exploitation of manta rays must be regulated. A better understanding of the habitat use and movement patterns of manta rays in Indonesia is needed in order to employ effective conservation measures. To gain better insight into the movements of Manta alfredi we used ‘Manta Matcher’, an online database with an integrated automated matching algorithm, to compare photographs from 2,604 encounters of M. alfredi collected by recreational divers and dive operators throughout Indonesia over a nine-year period. This photographic comparison revealed that manta rays migrated between regional sanctuaries such as Nusa Penida, the Gili Islands, and the Komodo National Park (up to 450 km straight-line distance). The areas between these sanctuaries are heavily fished and trafficked by ships, and when manta rays travel through these regions they risk being fished and injured by ship strikes. These long-range manta ray movements suggest connectivity between M. alfredi populations in neighboring islands and raise concerns about the future management of regional populations. It is recommended that a national conservation strategy be developed to protect the remaining populations in the country.     

Spatial data replacing temporal data in population viability analyses: An empirical investigation for plants

In conservation management, there is an urgent need for estimates of population viability and for knowledge of the contributions of different life-history stages to population growth rates. Collection of long-term demographic data from a study population is time-consuming and may considerably delay the start of proper management actions. We examined the possibility of replacing a long-term temporal data set (demographic data from several years within a population) with a short-term spatial data set (demographic data from different populations for the same subset of two continuous years) for stochastic estimates of population viability. Using matrix population models for ten perennial plant species, we found that the matrix elements of spatial data sets often deviated from those of temporal data sets and that matrix elements generally varied more spatially than temporally. The appropriateness of replacing temporal data with spatial data depended on the subset of years and populations used to estimate stochastic population growth rates (log λ_s). Still, the precision of log λ_s estimates measured as variation in the yearly change of logarithmic population size rarely differed significantly between the spatial and temporal data sets. Since a spatiotemporal comparison of matrix elements and their variation cannot be used to assess whether spatial and temporal data sets are interchangeable, we recommend further research on the topic.     

Transient Population Dynamics of Two Epiphytic Orchid Species after Hurricane Ivan: Implications for Management

Populations of epiphytic orchids in disturbance‐prone environments rarely reach stable‐stage equilibrium. We characterized the post‐disturbance, transient dynamics of two epiphytic orchids, Broughtonia cubensis, and the leafless Dendrophylax lindenii, comparing the following indices: reactivity/first‐time attenuation, maximal amplification/attenuation, and amplified/attenuated inertia. We also assessed the effects of reintroducing only seeds or only adults, by examining the elasticity of the inertia on the vital rates. For 2006–2010, the stochastic growth rate of D. lindenii was λ_s = 0.94, or a 6 percent decrease per annum. First‐time step attenuation indicates that in 1 year, the population could decrease by an additional 16 percent, and in the worst‐case scenario could decrease by almost half, relative to the stable‐stage distribution, in 10 years. Broughtonia cubensis had a λ_s = 1.03; reactivity and first‐time step attenuation indicates that in 1 year, the population should not change by more than 14 percent of the estimated stable‐stage distribution. However, the worst‐case scenario projected a reduction of 40 percent relative to the stable‐stage distribution within 8 years. A comparison of reintroduction strategies assessed by elasticity of the population momentum showed that adults performed better when relocated to new habitats.     

Effects of combined ozone and nitrogen deposition on the in situ properties of eleven key plant species of a subalpine pasture

Tropospheric O₃ and deposition of reactive N threaten the composition and function of natural and semi-natural vegetation even in remote regions. However, little is known about effects of these pollutants individually or in combination on plant species in alpine habitats. We analyzed 11 frequent plant species of a subalpine Geo-Montani-Nardetum pasture exposed at 2,000 m a.s.l. in the Swiss Alps during 3 years using a factorial free-air exposure system with three concentrations of O₃ and five rates of N application. The aim was to detect subtle effects on leaf chlorophyll and N concentrations, leaf weight, specific leaf area (SLA), and δ¹⁸O and δ¹³C as proxies for gas exchange. We expected that the species’ responsiveness to O₃ and N would be related to their functional traits and that N-induced changes in these traits would modify the species’ response to O₃ via increased growth and higher leaf conductance (g _s). Most species reacted to N supply with the accumulation of N and chlorophyll, but with no change in SLA, g _s, and growth, except Carex sempervirens which showed increased water use efficiency and leaf weight. Elevated O₃ reduced g _s in most species, but this was not related to a reduction in leaf weight, which was recorded in half of the species. Contrary to our expectation, the magnitude of the response to both O₃ and N was not related to species-specific traits such as SLA or g _s. No pronounced O₃ × N interactions were observed. In conclusion, since for most species neither N nor gas exchange limited growth, their short-term response to O₃ and N and to their combination was small. O₃ × N interactive effects are expected to be more pronounced in habitats where species are more responsive to N due to favorable growth conditions in terms of nutrient availability and temperature. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.