bluuebunny/crossref_metadata_2025_split huggingface dataset:
Consequences of plant–soil feedbacks in invasion
Authors: Suding Katharine N. , Stanley Harpole William , Fukami Tadashi , Kulmatiski Andrew , MacDougall Andrew S. , Stein Claudia , van der Putten Wim H. 
Published: May 2013

Summary

Plant species can influence soil biota, which in turn can influence the relative performance of plant species. These plant–soil feedbacks (PSFs) have been hypothesized to affect many community‐level dynamics including species coexistence, dominance and invasion.

The importance of PSFs in exotic species invasion, although widely hypothesized, has been difficult to determine because invader establishment necessarily precedes invader‐mediated PSFs. Here, we combine a spatial simulation model of invasion that incorporates PSFs with a meta‐analysis that synthesizes published case studies describing feedbacks between pairs of native and exotic species.

While our spatial model confirmed the link between positive soil feedbacks (‘home’ advantage) for exotic species and exotic species spread, results were dependent on the initial abundance of the exotic species and the equivalence of dispersal and life history characteristics between exotic and native species.

The meta‐analysis of 52 native–exotic pairwise feedback comparisons in 22 studies synthesized measures of native and exotic performance in soils conditioned by native and exotic species. The analysis indicated that the growth responses of native species were often greater in soil conditioned by native species than in soil conditioned exotic species (a ‘home’ advantage). The growth responses of exotic species were variable and not consistently related to species soil‐conditioning effects.

Synthesis. Overlaying empirical estimates of pairwise PSFs with spatial simulations, we conclude that the empirically measured PSFs between native and exotic plant species are often not consistent with predictions of the spread of exotic species and mono‐dominance. This is particularly the case when exotic species are initially rare and share similar dispersal and average fitness characteristics with native species. However, disturbance and other processes that increase the abundance of exotic species as well as the inclusion of species dispersal and life history differences can interact with PSF effects to explain the spread of invasive species.
Biological Flora of the British Isles:Silene suecica
Authors: Nagy Laszlo 
Published: May 2013

SummaryThis account presents information on all aspects of the biology ofSilene suecica(Lodd.) Greuter & Burdet (Lychnis alpinaL.) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of theBiologicalFlora of theBritishIsles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history and conservation.Silene suecicais native to the British flora, being found in just two confirmed localities (one in north‐westEngland and the other inScotland) on open fell‐field and rocky outcrop habitats. It occurs on acid to neutral soil inBritain and elsewhere its circum‐arctic range. It often indicates elevated concentrations of copper or other heavy metals, whose presence in the soil restricts the growth of other species; therefore,S. suecicais perceived as a stress‐tolerant, competition‐avoiding species. Nonetheless, it also grows in more or less closed alpine grassland inEurope; inNorthAmerica andGreenland, it is known from tundra, rocky barrens, gulleys and river outwashes, grassy slopes and sea cliffs.Silene suecicais a (semi‐)rosette plant with a strong taproot, with no capacity for vegetative spread. The main perennating organ is the slightly lignified rootstock/taproot. The rosette has winter‐green leaves; after flowering the rosette leaves die, but new lateral rosettes may be produced in the following year. The longevity of the species is between 3 and 10 years, with the time of first flowering depending on rosette size. Plants that have flowered may die (semelparous individuals), but some are iteroparous and flower again on lateral shoots.Silene suecicaproduces protandrous hermaphrodite flowers, but self‐pollination may occur. InScotland about 10% of all plants flower in any year. Pollination is by a range of insects, including flies and bees. Capsules produce up to 80 seeds (mean = 30).Silene suecicahas probably not declined in theBritishIsles and, in fact, a slight population expansion in permanent plots was observed inScotland in the early 1990s. Nonetheless, it remains classed as vulnerable to extinction because of its restricted distribution. Both of itsBritish locations are protected asSSSIandSAC(Natura 2000) within national parks. It is common in many countries within its distribution range.
Variability in functional traits mediates plant interactions along stress gradients
Authors: Schöb Christian , Armas Cristina , Guler Manuela , Prieto Iván , Pugnaire Francisco I. 
Published: May 2013

Summary

Environmental gradients may influence a plant's physiological status and morphology, which in turn may affect plant–plant interactions. However, little is known about the relationship between environmental variation, physiological and morphological variability of plants and variation in the balance between competition and facilitation.

Mountain ranges in dry environments have opposing altitudinal environmental gradients of temperature and aridity, which limit plant growth at high and low elevations. This makes them particularly suitable for exploring the relationships between environmental conditions, plant phenotype and plant–plant interactions. We hypothesized that different environmental stressors will differently affect the physiological status of a nurse plant. This, then, manifests itself as variation in nurse plant morphological traits, which in turn mediates plant–plant interactions by altering microhabitat conditions for the nurse and associated species.

In an observational study, we measured a series of functional traits of Arenaria tetraquetra cushions as indicators of its physiological status (e.g. specific leaf area, relative water content) and morphology (e.g. cushion compactness, size). Measurements were taken along the entire elevation range where A. tetraquetra occurs. Furthermore, we analysed how these functional traits related to soil properties beneath cushions and the number of associated species and individuals compared with open areas.

Cushions at high elevation showed good physiological status; they were compact and large, had higher soil water and organic matter content compared with open areas and showed the strongest facilitation effect of the whole elevation gradient – that is, the highest increase in species richness and abundance of beneficiaries compared with open areas. Physiological data at low elevation indicated stressful abiotic conditions for A. tetraquetra, which formed loose and small cushions. These cushions showed less improved soil conditions and had reduced facilitative effects compared with those at high elevation.

Synthesis. Functional traits of the nurse species varied distinctively along the two opposing stress gradients, in parallel to the magnitude of differences in microenvironmental conditions between cushions and the surrounding open area, and also to the facilitation effect of cushions. Our data, therefore, provides a strong demonstration of the generally overlooked importance of a nurse plant's vigour and morphology for its facilitative effects.
Subordinate plant species enhance community resistance against drought in semi‐natural grasslands
Authors: Mariotte Pierre , Vandenberghe Charlotte , Kardol Paul , Hagedorn Frank , Buttler Alexandre 
Published: May 2013

Summary

According to the insurance hypothesis, more diverse plant communities are more likely to be resistant to drought. Whilst many experiments have been carried out to determine the effects of plant diversity on plant community insurance, the results are still contradictory.

Here, we conducted a drought experiment where we tested whether the presence of subordinate species increases plant community insurance. In Swiss Jura grassland, we combined a removal experiment of subordinate species with a summer drought event using rainout shelters.

Plant community composition was determined after the drought and based on biomass measurements; we estimated resistance, recovery and resilience of the plant community for each combination of treatments. Moreover, to assess drought impacts on water‐use efficiency (WUE), we analysed carbon isotope ratios (δ13C values) in plant leaves of two dominants and two subordinates collected at the end of the drought period.

We showed that subordinate species are more resistant to drought and increased community resistance by enhancing their above‐ground biomass production during the imposed drought. These patterns were associated with decreased competitiveness of dominant species whose biomass decreased during drought. Significant increase in δ13C values in plant tissue under drought indicated a better WUE for the measured species. Interestingly, the WUE was significantly higher in plots where subordinates were removed. Recovery and resilience were not affected by the summer drought, but the absence of subordinates reduced overall above‐ground biomass in both watered and drought plots.

Synthesis. We demonstrated that, independent of plant diversity, the presence of drought‐resistant subordinate species increases plant community insurance against drought and, hence, is important for the functioning of grassland ecosystems.
Convergent specialization – the sharing of pollinators by sympatric genera of sexually deceptive orchids
Authors: Phillips Ryan D. , Xu Tingbao , Hutchinson Michael F. , Dixon Kingsley W. , Peakall Rod 
Published: May 2013

Summary

Pollinator sharing can offer powerful insights into the floral traits associated with the evolution of a pollination system and the consequences of floral differences for pollinator behaviour. Here, we investigate the first known case of pollinator sharing between two sexually deceptive plant genera. Floral manipulations were used to test the importance of floral traits for pollinator behaviour and pollination efficiency. We also explored the ecological differences enabling species co‐occurrence.

Drakaea livida and Caladenia pectinata (Orchidaceae) exhibit dramatic differences in floral display and the insectiform appearance of the labellum, yet both are pollinated by sexually attracted males of the thynnine wasp Zaspilothynnis nigripes. Because of the prevalence of cryptic species in some genera of thynnine wasps, we confirmed pollinator sharing by a mark–recapture study and sequencing of the mtDNA CO1 region.

Floral dissections revealed that semiochemicals used to attract the pollinator are released from the labellum in D. livida and sepaline clubs in C. pectinata. Drakaea livida was more efficient at converting pollinator attraction into potential pollen deposition leading to higher fruit set. Floral manipulations showed that pollinator contact with the labellum increases when it is the point of semiochemical release. However, sexual attraction to the labellum remained infrequent in C. pectinata in all experimental treatments.

While their distribution and climatic range show extensive overlap, the differences in edaphic requirements of the two orchid species suggest that they rarely co‐occur. Therefore, the potential cost of sharing the same pollinator species is not realized.

Synthesis. This case of pollinator sharing confirms that morphological traits do not place a strong constraint on the evolution of sexual deception. However, interspecific differences in floral traits have important consequences for converting attraction into pollination, suggesting that selection can act to increase efficiency at multiple steps of the pollination process. This system provides a novel opportunity to elucidate the chemical, visual and morphological adaptations underpinning the evolution of sexual mimicry.
Evidence for transient dynamics in plant populations based on long‐term demographic data
Authors: Ellis Martha M. 
Published: May 2013

Summary

Recent interest in the importance of short‐term, transient responses in population dynamics has prompted the development of many new methods for describing transient responses in population models. Many of these methods focus on the largest possible responses for a model, thus providing a description of the ‘transient potential’ of a model that does not depend on knowledge of initial conditions in the population.

This study uses long‐term demographic data from five perennial plant species to evaluate how well measures of transient potential reflect actual transient responses in the populations. I used previously published matrix population models to create a set of initial conditions derived from empirically‐based simulations for each population. Maximum transient responses within this set of initial conditions were then compared with responses used in describing transient potential.

Transient responses based on empirical modeling results were smaller than responses used for measures of transient potential.

Realized responses were strongly correlated with the distance between the current demographic structure in the population and the asymptotically stable stage structure of the model (SSD).

Theoretical transient potential was predictive of the amount of variation in distance from SSD observed in each population in the simulations.

Synthesis. Methods based on largest possible responses tend to overemphasize the role of transient dynamics. These results suggest that traditional, asymptotic analyses may be appropriate in many cases. Measures of transient potential can be helpful for identifying species and situations that may be prone to larger transient responses, but do not necessarily indicate that transient dynamics are more important in those systems.
Preferences or plasticity in nitrogen acquisition by understorey palms in a tropical montane forest
Authors: Andersen Kelly M. , Turner Benjamin L. 
Published: May 2013

Summary

Soil nitrogen (N) occurs in a range of chemical forms from simple inorganic compounds, such as nitrate () and ammonium (), to organic compounds, such as amino acids. Plants differ in their capacity to use these various forms, which might influence the distribution of species across environmental nutrient gradients.

We tested the hypothesis that the distribution of understorey palm species along a soil N gradient in a tropical montane forest in Panama is related to preferences for different chemical forms of N. We conducted a field experiment using 15N‐labelled ammonium, nitrate and glycine to examine whether tropical plants show preferences for, or are flexible in, their use of chemical forms of soil N.

All species used N from inorganic and organic sources and showed no preference for chemical forms of N. However, across all species, the overall N acquisition pattern was glycine ≥ nitrate ≥ ammonium. Species from low‐nutrient sites dominated by ammonium and organic N forms had inherently slow N uptake rates.

Synthesis. Patterns in the distribution of understorey palms were related to nitrogen (N) uptake rates rather than preferences for N chemical forms. Down‐regulation of N uptake rates may be an important adaptation for plant species associated with low‐N soils, with plasticity in N acquisition patterns from various N sources important in alleviating competition for soil N.
Competitive interactions across a soil fertility gradient in a multispecies forest
Authors: Coates K. David , Lilles Erica B. , Astrup Rasmus 
Published: May 2013

Summary

Whether plant competition grows stronger or weaker across a soil fertility gradient is an area of great debate in plant ecology. We examined the effects of competition and soil fertility and their interaction on growth rates of the four dominant tree species in the sub‐boreal spruce forest of British Columbia.

We tested separate soil nutrient and moisture indices and found much stronger support for models that included the nutrient index as a measure of soil fertility.

Competition, soil fertility and their interaction affected radial growth rates for all species.

Each species supported a different alternate hypothesis for how competitive interactions changed with soil fertility and whether competition intensity was stronger or weaker overall as soil fertility increased depended on the context, specifically, species, neighbourhood composition and type of competition (shading vs. crowding).

The four species varied slightly in their growth response to soil fertility.

Individual species had some large variations in the shapes of their negative relationships between shading, crowding and tree growth, with one species experiencing no net negative effects of crowding at low soil fertility.

Goodness‐of‐fit was not substantially increased by models including competition–soil fertility interactions for any species. Tree size, soil fertility, shading and crowding predicted most of the variation in tree growth rates in the sub‐boreal spruce forest.

Synthesis. The intensity of competition among trees across a fertility gradient was species‐ and context‐specific and more complicated than that predicted by any one of the dominant existing theories in plant ecology.
Genetically based vertical transmission drives the frequency of the symbiosis between grasses and systemic fungal endophytes
Authors: Gibert Anaïs , Hazard Laurent 
Published: May 2013

Summary

Understanding the variation in hereditary symbiont frequency among host populations is a prerequisite to predict symbiont fixation processes. However, the mechanisms driving this variation remain elusive. Exploring the mechanisms responsible for the observed variability on an ecological time scale requires simultaneous study of fitness differentials between symbiotic (S) and non‐symbiotic (NS) hosts, and the symbiont transmission rates to host offspring.

We studied these two key mechanisms using a grass–endophyte symbiosis in the alpine grass Festuca eskia. Plants from four native populations varying in endophyte frequencies (ranging from 13% to 100%), and environmental conditions (water availability, and grazing pressure) were transplanted in a common garden. Soil nutrient levels were manipulated to assess genetic and environmental differences within and among populations in fitness‐related traits (i.e. traits linked to clonal growth, sexual reproduction and resource acquisition).

A fitness differential favouring S over NS plants was detected in all studied populations: in heavily grazed populations, sexual reproduction was higher in S compared with NS plants, whereas in minimally grazed populations, clonal growth increased. Results showed a positive correlation between endophyte transmission rates and population endophyte symbiotic frequencies. The population endophyte transmission rates were not affected by soil resource level.

According to selection pressures acting in each population, symbiotic plants appear to perform better in all F. eskia populations. The correlation between endophyte frequencies and transmission, and the positive effect of S on NS plants under our experimental conditions, indicated a predominant role of endophyte transmission in endophyte frequency variation in F. eskia. The endophyte transmission rate variation is genetically based at the population level and can be explained by a trade‐off with a specific host trait subjected to strong selection; here, we suspected traits linked to plant resource acquisition.

Synthesis: Our study provides evidence for the (i) dominant role of endophyte transmission and its responsibility for endophyte frequency variation in a native grass when compared with fitness differential process between S and NS plants at an ecological time scale, and (ii) genetically based variation in endophyte transmission rates. We also confirm the population specificity of positive endophyte effects in a native grass.
Pathogen accumulation and long‐term dynamics of plant invasions
Authors: Flory S. Luke , Clay Keith 
Published: May 2013

Summary

The diversity of pathogens on highly abundant introduced hosts has been positively correlated with time since introduction, geographical range of the introduced species and diversity of invaded habitats. However, little is known about the ecological effects of pathogen accumulation on non‐native invasive plants.

Pathogen accumulation on invasive plant species may result from ecological processes such as high plant densities, expanding geographical ranges and pathogen dispersal from the native range, or evolutionary mechanisms such as host range shifts and adaptation of native pathogens to invasive species.

Over time pathogen accumulation may cause decline in the density and distribution of invasive plants and facilitate recovery of native species. Alternatively, pathogens might build up on invasive species and then spill back onto co‐occurring native species, further exacerbating the effects of invasions.

Synthesis. Research efforts should focus on determining the long‐term outcomes of pathogen accumulation on invasive species. Such research will require multifaceted approaches including comparative studies of diverse invasive species and habitats, experimental manipulations of hosts and pathogens in nature and controlled environments, and predictive models of host‐pathogen interactions within an invasion framework. Results of this research will improve our understanding and ability to predict the outcomes of biological invasions.