How to shorten scientific manuscripts.

Many journals have strict word limits, and authors therefore spend considerable time shortening manuscripts. Here, we provide pointers for efficiently doing so while retaining key content. We include general guidance, tips for condensing the different parts of a scientific paper, and advice on what to avoid when shortening manuscripts. We hope that readers will find our guidance helpful.

High-resolution data are necessary to understand the effects of climate on plant population dynamics of a forest herb.

Climate is assumed to strongly influence species distribution and abundance. Although the performance of many organisms is influenced by the climate in their immediate proximity, the climate data used to model their distributions often have a coarse spatial resolution. This is problematic because the local climate experienced by individuals might deviate substantially from the regional average. This problem is likely to be particularly important for sessile organisms like plants and in environments where small-scale variation in climate is large. To quantify the effect of local temperature on vital rates and population growth rates, we used temperature values measured at the local scale (in situ logger measures) and integral projection models with demographic data from 37 populations of the forest herb Lathyrus vernus across a wide latitudinal gradient in Sweden. To assess how the spatial resolution of temperature data influences assessments of climate effects, we compared effects from models using local data with models using regionally aggregated temperature data at several spatial resolutions (≥1 km). Using local temperature data, we found that spring frost reduced the asymptotic population growth rate in the first of two annual transitions and influenced survival in both transitions. Only one of the four regional estimates showed a similar negative effect of spring frost on population growth rate. Our results for a perennial forest herb show that analyses using regionally aggregated data often fail to identify the effects of climate on population dynamics. This emphasizes the importance of using organism-relevant estimates of climate when examining effects on individual performance and population dynamics, as well as when modeling species distributions. For sessile organisms that experience the environment over small spatial scales, this will require climate data at high spatial resolutions.

Spring temperature drives phenotypic selection on plasticity of flowering time.

In seasonal environments, a high responsiveness of development to increasing temperatures in spring can infer benefits in terms of a longer growing season, but also costs in terms of an increased risk of facing unfavourable weather conditions. Still, we know little about how climatic conditions influence the optimal plastic response. Using 22 years of field observations for the perennial forest herb Lathyrus vernus, we assessed phenotypic selection on among-individual variation in reaction norms of flowering time to spring temperature, and examined if among-year variation in selection on plasticity was associated with spring temperature conditions. We found significant among-individual variation in mean flowering time and flowering time plasticity, and that plants that flowered earlier also had a more plastic flowering time. Selection favoured individuals with an earlier mean flowering time and a lower thermal plasticity of flowering time. Less plastic individuals were more strongly favoured in colder springs, indicating that spring temperature influenced optimal flowering time plasticity. Our results show how selection on plasticity can be linked to climatic conditions, and illustrate how we can understand and predict evolutionary responses of organisms to changing environmental conditions.

Maladaptive plastic responses of flowering time to geothermal heating.

Phenotypic plasticity might increase fitness if the conditions under which it evolved remain unaltered, but becomes maladaptive if the environment no longer provides reliable cues for subsequent conditions. In seasonal environments, timing of reproduction can respond plastically to spring temperature, maximizing the benefits of a long season while minimizing the exposure to unfavorable cold temperatures. However, if the relationship between early spring temperatures and later conditions changes, the optimal response might change. In geothermally heated ecosystems, the plastic response of flowering time to springtime soil temperature that has evolved in unheated areas is likely to be non-optimal, because soil temperatures are higher and decoupled from air temperatures in heated areas. We therefore expect natural selection to favor a lower plasticity and a delayed flowering in these areas. Using observational data along a natural geothermal warming gradient, we tested the hypothesis that selection on flowering time depends on soil temperature and favors later flowering on warmer soils in the perennial Cerastium fontanum. In both study years, plants growing in warmer soils began flowering earlier than plants growing in colder soils, suggesting that first flowering date (FFD) responds plastically to soil temperature. In one of the two study years, selection favored earlier flowering in colder soils but later flowering in warmer soils, suggesting that the current level of plastic advance of FFD on warmer soils may be maladaptive in some years. Our results illustrate the advantages of using natural experiments, such as geothermal ecosystems, to examine selection in environments that recently have undergone major changes. Such knowledge is essential to understand and predict both ecological and evolutionary responses to climate warming.

Life-history characteristics and historical factors are important to explain regional variation in reproductive traits and genetic diversity in perennial mosses.

BACKGROUND AND AIMS: Plants have evolved an unrivalled diversity of reproductive strategies, including variation in the degree of sexual vs. clonal reproduction. This variation has important effects on the dynamics and genetic structure of populations. We examined the association between large-scale variation in reproductive patterns and intraspecific genetic diversity in two moss species where sex is manifested in the dominant haploid generation and sex expression is irregular. We predicted that in regions with more frequent realized sexual reproduction, populations should display less skewed sex ratios, should more often express sex and should have higher genetic diversity than in regions with largely clonal reproduction. METHODS: We assessed reproductive status and phenotypic sex in the dioicous long-lived Drepanocladus trifarius and D. turgescens, in 248 and 438 samples across two regions in Scandinavia with frequent or rare realized sexual reproduction, respectively. In subsets of the samples, we analysed genetic diversity using nuclear and plastid sequence information and identified sex with a sex-specific molecular marker in non-reproductive samples. KEY RESULTS: Contrary to our predictions, sex ratios did not differ between regions; genetic diversity did not differ in D. trifarius and it was higher in the region with rare sexual reproduction in D. turgescens. Supporting our predictions, relatively more samples expressed sex in D. trifarius in the region with frequent sexual reproduction. Overall, samples were mostly female. The degree of sex expression and genetic diversity differed between sexes. CONCLUSIONS: Sex expression levels, regional sex ratios and genetic diversity were not directly associated with the regional frequency of realized sexual reproduction, and relationships and variation patterns differed between species. We conclude that a combination of species-specific life histories, such as longevity, overall degree of successful sexual reproduction and recruitment, and historical factors are important to explain this variation. Our data on haploid-dominated plants significantly complement plant reproductive biology.

Forest edge effects on moss growth are amplified by drought.

Forest fragmentation increases the amount of edges in the landscape. Differences in wind, radiation, and vegetation structure create edge-to-interior gradients in forest microclimate, and these gradients are likely to be more pronounced during droughts and heatwaves. Although the effects of climate extremes on edge influences have potentially strong and long-lasting impacts on forest understory biodiversity, they are not well understood and are not often considered in management and landscape planning. Here we used a novel method of retrospectively quantifying growth to assess biologically relevant edge influences likely caused by microclimate using Hylocomium splendens, a moss with annual segments. We examined how spatio-temporal variation in drought across 3 years and 46 sites in central Sweden, affected the depth and magnitude of edge influences. We also investigated whether edge effects during drought were influenced by differences in forest structure. Edge effects were almost twice as strong in the drought year compared to the non-drought years, but we did not find clear evidence that they penetrated deeper into the forest in the drought year. Edge influences were also greater in areas that had fewer days with rain during the drought year. Higher levels of forest canopy cover and tree height buffered the magnitude of edge influence in times of drought. Our results demonstrate that edge effects are amplified by drought, suggesting that fragmentation effects are aggravated when droughts become more frequent and severe. Our results suggest that dense edges and buffer zones with high canopy cover can be important ways to mitigate negative drought impacts in forest edges.

Single, but not dual, attack by a biotrophic pathogen and a sap-sucking insect affects the oak leaf metabolome.

Plants interact with a multitude of microorganisms and insects, both below- and above ground, which might influence plant metabolism. Despite this, we lack knowledge of the impact of natural soil communities and multiple aboveground attackers on the metabolic responses of plants, and whether plant metabolic responses to single attack can predict responses to dual attack. We used untargeted metabolic fingerprinting (gas chromatography-mass spectrometry, GC-MS) on leaves of the pedunculate oak, Quercus robur, to assess the metabolic response to different soil microbiomes and aboveground single and dual attack by oak powdery mildew (Erysiphe alphitoides) and the common oak aphid (Tuberculatus annulatus). Distinct soil microbiomes were not associated with differences in the metabolic profile of oak seedling leaves. Single attacks by aphids or mildew had pronounced but different effects on the oak leaf metabolome, but we detected no difference between the metabolomes of healthy seedlings and seedlings attacked by both aphids and powdery mildew. Our findings show that aboveground attackers can have species-specific and non-additive effects on the leaf metabolome of oak. The lack of a metabolic signature detected by GC-MS upon dual attack might suggest the existence of a potential negative feedback, and highlights the importance of considering the impacts of multiple attackers to gain mechanistic insights into the ecology and evolution of species interactions and the structure of plant-associated communities, as well as for the development of sustainable strategies to control agricultural pests and diseases and plant breeding.

Selection against early flowering in geothermally heated soils is associated with pollen but not prey availability in a carnivorous plant.

PREMISE: In high-latitude environments, plastic responses of phenology to increasing spring temperatures allow plants to extend growing seasons while avoiding late frosts. However, evolved plasticity might become maladaptive if climatic conditions change and spring temperatures no longer provide reliable cues for conditions important for fitness. Maladaptative phenological responses might be related to both abiotic factors and mismatches with interacting species. When mismatches arise, we expect selection to favor changes in phenology. METHODS: We combined observations along a soil temperature gradient in a geothermally heated area with pollen and prey supplementation experiments and examined how phenotypic selection on flowering time in the carnivorous plant Pinguicula vulgaris depends on soil temperature, and pollen and prey availability. RESULTS: Flowering advanced and fitness decreased with increasing soil temperature. However, in pollen-supplemented plants, fitness instead increased with soil temperature. In heated soils, there was selection favoring later flowering, while earlier flowering was favored in unheated soils. This pattern remained also after artificially increasing pollen and prey availability. CONCLUSIONS: Plant-pollinator mismatches can be an important reason why evolved plastic responses of flowering time to increasing spring temperatures become maladaptive under novel environmental conditions, and why there is selection to delay flowering. In our study, selection for later flowering remained after artificially increasing pollen availability, suggesting that abiotic factors also contribute to the observed selection. Identifying the factors that make evolved phenological responses maladaptive under novel conditions is fundamental for understanding and predicting evolutionary responses to climate warming.

Interactive effects of drought and edge exposure on old-growth forest understory species.

Context: Both climatic extremes and land-use change constitute severe threats to biodiversity, but their interactive effects remain poorly understood. In forest ecosystems, the effects of climatic extremes can be exacerbated at forest edges. Objectives: We explored the hypothesis that an extreme summer drought reduced the richness and coverage of old-growth forest species, particularly in forest patches with high edge exposure. Methods: Using a high-resolution spatially explicit precipitation dataset, we could detect variability in drought intensity during the summer drought of 2018. We selected 60 old-growth boreal forest patches in central Sweden that differed in their level of drought intensity and amount of edge exposure. The year after the drought, we surveyed red-listed and old-growth forest indicator species of vascular plants, lichens and bryophytes. We assessed if species richness, composition, and coverage were related to drought intensity, edge exposure, and their interaction. Results: Species richness was negatively related to drought intensity in forest patches with a high edge exposure, but not in patches with less edge exposure. Patterns differed among organism groups and were strongest for cyanolichens, epiphytes associated with high-pH bark, and species occurring on convex substrates such as trees and logs. Conclusions: Our results show that the effects of an extreme climatic event on forest species can vary strongly across a landscape. Edge exposed old-growth forest patches are more at risk under extreme climatic events than those in continuous forests. This suggest that maintaining buffer zones around forest patches with high conservation values should be an important conservation measure. Supplementary information: The online version contains supplementary material available at 10.1007/s10980-022-01441-9.

Simultaneous selection on vegetative and reproductive phenology in a perennial herb.

The timing of different life-history events is often correlated, and selection might only rarely be exerted independently on the timing of a single event. In plants, phenotypic selection has often been shown to favor earlier flowering. However, little is known about to what extent this selection acts directly versus indirectly via vegetative phenology, and if selection on the two traits is correlational. We estimated direct, indirect, and correlational phenotypic selection on vegetative and reproductive phenology over 3 years for flowering individuals of the perennial herb Lathyrus vernus. Direct selection favored earlier flowering and shorter timespans between leaf-out and flowering in all years. However, early flowering was associated with early leaf-out, and the direction of selection on leaf-out day varied among years. As a result, selection on leaf-out weakened selection for early flowering in one of the study years. We found no evidence of correlational selection. Our results highlight the importance of including temporally correlated traits when exploring selection on the phenology of seasonal events.

The relationship between pathogen life-history traits and metapopulation dynamics.

Plant pathogen traits, such as transmission mode and overwintering strategy, may have important effects on dispersal and persistence, and drive disease dynamics. Still, we lack insights into how life-history traits influence spatiotemporal disease dynamics. We adopted a multifaceted approach, combining experimental assays, theory and field surveys, to investigate whether information about two pathogen life-history traits - infectivity and overwintering strategy - can predict pathogen metapopulation dynamics in natural systems. For this, we focused on four fungal pathogens (two rust fungi, one chytrid fungus and one smut fungus) on the forest herb Anemone nemorosa. Pathogens infecting new plants mostly via spores (the chytrid and smut fungi) had higher patch occupancies and colonization rates than pathogens causing mainly systemic infections and overwintering in the rhizomes (the two rust fungi). Although the rust fungi more often occupied well-connected plant patches, the chytrid and smut fungi were equally or more common in isolated patches. Host patch size was positively related to patch occupancy and colonization rates for all pathogens. Predicting disease dynamics is crucial for understanding the ecological and evolutionary dynamics of host-pathogen interactions, and to prevent disease outbreaks. Our study shows that combining experiments, theory and field observations is a useful way to predict disease dynamics.

Spring and autumn phenology in an understory herb are uncorrelated and driven by different factors.

PREMISE: Climate warming has altered the start and end of growing seasons in temperate regions. Ultimately, these changes occur at the individual level, but little is known about how previous seasonal life-history events, temperature, and plant-resource state simultaneously influence the spring and autumn phenology of plant individuals. METHODS: We studied the relationships between the timing of leaf-out and shoot senescence over 3 years in a natural population of the long-lived understory herb Lathyrus vernus and investigated the effects of spring temperature, plant size, reproductive status, and grazing on spring and autumn phenology. RESULTS: The timing of leaf-out and senescence were consistent within individuals among years. Leaf-out and senescence were not correlated with each other within years. Larger plants leafed out and senesced later, and size had no effect on growing season length. Reproductive plants leafed out earlier and had longer growing seasons than nonreproductive plants. Grazing had no detectable effects on phenology. Colder spring temperatures delayed senescence in two of three study years. CONCLUSIONS: The timing of seasonal events, such as leaf-out and senescence in plants can be expressed largely independently within and among seasons and are influenced by different factors. Growing season start and length can often be dependent on plant condition and reproductive status. Knowledge about the drivers of growing season length of individuals is essential to more accurately predict species and community responses to environmental variation.

Pathogen infection influences the relationship between spring and autumn phenology at the seedling and leaf level.

Seasonal life history events are often interdependent, but we know relatively little about how the relationship between different events is influenced by the abiotic and biotic environment. Such knowledge is important for predicting the immediate and evolutionary phenological response of populations to changing conditions. We manipulated germination timing and shade in a multi-factorial experiment to investigate the relationship between spring and autumn phenology in seedlings of the pedunculate oak, Quercus robur, and whether this relationship was mediated by natural colonization of leaves by specialist fungal pathogens (i.e., the oak powdery mildew complex). Each week delay in germination corresponded to about 2 days delay in autumn leaf senescence, and heavily shaded seedlings senesced 5-8 days later than seedlings in light shade or full sun. Within seedlings, leaves on primary-growth shoots senesced later than those on secondary-growth shoots in some treatments. Path analyses demonstrated that germination timing and shade affected autumn phenology both directly and indirectly via pathogen load, though the specific pattern differed among and within seedlings. Pathogen load increased with later germination and greater shade. Greater pathogen load was in turn associated with later senescence for seedlings, but with earlier senescence for individual leaves. Our findings show that relationships between seasonal events can be partly mediated by the biotic environment and suggest that these relationships may differ between the plant and leaf level. The influence of biotic interactions on phenological correlations across scales has implications for understanding phenotypic variation in phenology and for predicting how populations will respond to climatic perturbation.

Phenotypic plasticity masks range-wide genetic differentiation for vegetative but not reproductive traits in a short-lived plant.

Genetic differentiation and phenotypic plasticity jointly shape intraspecific trait variation, but their roles differ among traits. In short-lived plants, reproductive traits may be more genetically determined due to their impact on fitness, whereas vegetative traits may show higher plasticity to buffer short-term perturbations. Combining a multi-treatment greenhouse experiment with observational field data throughout the range of a widespread short-lived herb, Plantago lanceolata, we (1) disentangled genetic and plastic responses of functional traits to a set of environmental drivers and (2) assessed how genetic differentiation and plasticity shape observational trait-environment relationships. Reproductive traits showed distinct genetic differentiation that largely determined observational patterns, but only when correcting traits for differences in biomass. Vegetative traits showed higher plasticity and opposite genetic and plastic responses, masking the genetic component underlying field-observed trait variation. Our study suggests that genetic differentiation may be inferred from observational data only for the traits most closely related to fitness.

Plant-animal interactions mediate climatic effects on selection on flowering time.

Selection on flowering time in plants is often mediated by multiple agents, including climatic conditions and the intensity of mutualistic and antagonistic interactions with animals. These selective agents can have both direct and indirect effects. For example, climate might not only influence phenotypic selection on flowering time directly by affecting plant physiology, but it can also alter selection indirectly by modifying the seasonal activity and relative timing of animals interacting with plants. We used 21 yr of data to identify the drivers of selection on flowering time in the perennial herb Lathyrus vernus, and to examine if antagonistic plant-animal interactions mediate effects of climate on selection. We examined the fitness consequences of vertebrate grazing and predispersal seed predation, and how these effects varied among years and among individuals within years. Although both antagonistic plant-animal interactions had important negative effects on plant fitness, only grazing intensity was consistently related to plant phenology, being higher in early-flowering individuals. Spring temperature influenced the intensity of both plant-animal interactions, as well as the covariance between seed predation and plant phenology. However, only differences in grazing intensity among years were associated with differences in selection on flowering time; the strength of selection for early flowering being stronger in years with lower mean intensity of grazing. Our results illustrate how climatic conditions can influence plant-animal interactions that are important selective agents for plant traits. A broader implication of our findings is that both ecological and evolutionary responses to climatic changes might be indirect, and largely mediated by species interactions.

The timing and asymmetry of plant-pathogen-insect interactions.

Insects and pathogens frequently exploit the same host plant and can potentially impact each other's performance. However, studies on plant-pathogen-insect interactions have mainly focused on a fixed temporal setting or on a single interaction partner. In this study, we assessed the impact of time of attacker arrival on the outcome and symmetry of interactions between aphids (Tuberculatus annulatus), powdery mildew (Erysiphe alphitoides), and caterpillars (Phalera bucephala) feeding on pedunculate oak, Quercus robur, and explored how single versus multiple attackers affect oak performance. We used a multifactorial greenhouse experiment in which oak seedlings were infected with either zero, one, two, or three attackers, with the order of attacker arrival differing among treatments. The performances of all involved organisms were monitored throughout the experiment. Overall, attackers had a weak and inconsistent impact on plant performance. Interactions between attackers, when present, were asymmetric. For example, aphids performed worse, but powdery mildew performed better, when co-occurring. Order of arrival strongly affected the outcome of interactions, and early attackers modified the strength and direction of interactions between later-arriving attackers. Our study shows that interactions between plant attackers can be asymmetric, time-dependent, and species specific. This is likely to shape the ecology and evolution of plant-pathogen-insect interactions.

Global gene flow releases invasive plants from environmental constraints on genetic diversity.

When plants establish outside their native range, their ability to adapt to the new environment is influenced by both demography and dispersal. However, the relative importance of these two factors is poorly understood. To quantify the influence of demography and dispersal on patterns of genetic diversity underlying adaptation, we used data from a globally distributed demographic research network comprising 35 native and 18 nonnative populations of Plantago lanceolata Species-specific simulation experiments showed that dispersal would dilute demographic influences on genetic diversity at local scales. Populations in the native European range had strong spatial genetic structure associated with geographic distance and precipitation seasonality. In contrast, nonnative populations had weaker spatial genetic structure that was not associated with environmental gradients but with higher within-population genetic diversity. Our findings show that dispersal caused by repeated, long-distance, human-mediated introductions has allowed invasive plant populations to overcome environmental constraints on genetic diversity, even without strong demographic changes. The impact of invasive plants may, therefore, increase with repeated introductions, highlighting the need to constrain future introductions of species even if they already exist in an area.

Intraspecific variation influences performance of moss transplants along microclimate gradients.

Identifying the environmental drivers of population dynamics is crucial to predict changes in species abundances and distributions under climate change. Populations of the same species might differ in their responses as a result of intraspecific variation. Yet the importance of such differences remains largely unexplored. We examined the responses of latitudinally distant populations of the forest moss Hylocomiastrum umbratum along microclimate gradients in Sweden. We transplanted moss mats from southern and northern populations to 30 sites with contrasting microclimates (i.e., replicated field common gardens) within a forest landscape, and recorded growth and survival of individual shoots over 3 yr. To evaluate the importance of intraspecific variation in responses to environmental factors, we assessed effects of the interactions between population origin and microclimate drivers on growth and survival. Effects on overall performance of transplanted populations were estimated using the product of survival and growth. We found differences between southern and northern populations in the response to summer temperature and snowmelt date in one of three yearly transitions. In this year, southern populations performed better in warm, southern-like conditions than in cold, northern-like conditions; and the reverse pattern was true for northern populations. Survival of all populations decreased with evaporation, consistent with the high hydric demands and poikilohydric nature of mosses. Our results are consistent with population adaptation to local climate, and suggest that intraspecific variation among populations can have important effects on the response of species to microclimate drivers. These findings highlight the need to account for differential responses in predictions of species abundance and distribution under climate change.

Climate drives among-year variation in natural selection on flowering time.

To predict long-term responses to climate change, we need to understand how changes in temperature and precipitation elicit both immediate phenotypic responses and changes in natural selection. We used 22 years of data for the perennial herb Lathyrus vernus to examine how climate influences flowering phenology and phenotypic selection on phenology. Plants flowered earlier in springs with higher temperatures and higher precipitation. Early flowering was associated with a higher fitness in nearly all years, but selection for early flowering was significantly stronger in springs with higher temperatures and lower precipitation. Climate influenced selection through trait distributions, mean fitness and trait-fitness relationships, the latter accounting for most of the among-year variation in selection. Our results show that climate both induces phenotypic responses and alters natural selection, and that the change in the optimal phenotype might be either weaker, as for spring temperature, or stronger, as for precipitation, than the optimal response.

Biotic and anthropogenic forces rival climatic/abiotic factors in determining global plant population growth and fitness.

Multiple, simultaneous environmental changes, in climatic/abiotic factors, interacting species, and direct human influences, are impacting natural populations and thus biodiversity, ecosystem services, and evolutionary trajectories. Determining whether the magnitudes of the population impacts of abiotic, biotic, and anthropogenic drivers differ, accounting for their direct effects and effects mediated through other drivers, would allow us to better predict population fates and design mitigation strategies. We compiled 644 paired values of the population growth rate (λ) from high and low levels of an identified driver from demographic studies of terrestrial plants. Among abiotic drivers, natural disturbance (not climate), and among biotic drivers, interactions with neighboring plants had the strongest effects on λ However, when drivers were combined into the 3 main types, their average effects on λ did not differ. For the subset of studies that measured both the average and variability of the driver, λ was marginally more sensitive to 1 SD of change in abiotic drivers relative to biotic drivers, but sensitivity to biotic drivers was still substantial. Similar impact magnitudes for abiotic/biotic/anthropogenic drivers hold for plants of different growth forms, for different latitudinal zones, and for biomes characterized by harsher or milder abiotic conditions, suggesting that all 3 drivers have equivalent impacts across a variety of contexts. Thus, the best available information about the integrated effects of drivers on all demographic rates provides no justification for ignoring drivers of any of these 3 types when projecting ecological and evolutionary responses of populations and of biodiversity to environmental changes.