Biotic and abiotic drivers of intraspecific trait variation within plant populations of three herbaceous plant species along a latitudinal gradient

Background: The importance of intraspecific trait variation (ITV) is increasingly acknowledged among plant ecologists. However, our understanding of what drives ITV between individual plants (ITVBI) at the population level is still limited. Contrasting theoretical hypotheses state that ITVBI can be either suppressed (stress-reduced plasticity hypothesis) or enhanced (stress-induced variability hypothesis) under high abiotic stress. Similarly, other hypotheses predict either suppressed (niche packing hypothesis) or enhanced ITVBI (individual variation hypothesis) under high niche packing in species rich communities. In this study we assess the relative effects of both abiotic and biotic niche effects on ITVBI of four functional traits (leaf area, specific leaf area, plant height and seed mass), for three herbaceous plant species across a 2300 km long gradient in Europe. The study species were the slow colonizing Anemone nemorosa, a species with intermediate colonization rates, Milium effusum, and the fast colonizing, non-native Impatiens glandulifera. Results: Climatic stress consistently increased ITVBI across species and traits. Soil nutrient stress, on the other hand, reduced ITVBI for A. nemorosa and I. glandulifera, but had a reversed effect for M. effusum. We furthermore observed a reversed effect of high niche packing on ITVBI for the fast colonizing non-native I. glandulifera (increased ITVBI), as compared to the slow colonizing native A. nemorosa and M. effusum (reduced ITVBI). Additionally, ITVBI in the fast colonizing species tended to be highest for the vegetative traits plant height and leaf area, but lowest for the measured generative trait seed mass. Conclusions: This study shows that stress can both reduce and increase ITVBI, seemingly supporting both the stress-reduced plasticity and stress-induced variability hypotheses. Similarly, niche packing effects on ITVBI supported both the niche packing hypothesis and the individual variation hypothesis. These results clearly illustrates the importance of simultaneously evaluating both abiotic and biotic factors on ITVBI. This study adds to the growing realization that within-population trait variation should not be ignored and can provide valuable ecological insights

The social cognition of medical knowledge, with special reference to childhood epilepsy

This paper arose out of an engagement in medical communication courses at a Gulf university. It deploys a theoretical framework derived from a (critical) sociocognitive approach to discourse analysis in order to investigate three aspects of medical discourse relating to childhood epilepsy: the cognitive processes that are entailed in relating different types of medical knowledge to their communicative context; the types of medical knowledge that are constituted in the three different text types analysed; and the relationship between these different types of medical knowledge and the discursive features of each text type. The paper argues that there is a cognitive dimension to the human experience of understanding and talking about one specialized from of medical knowledge. It recommends that texts be studied in medical communication courses not just in terms of their discrete formal features but also critically, in terms of the knowledge which they produce, transmit and reproduce

Phänotypische Merkmalsvariation krautiger Waldarten entlang von Umweltgradienten im Kontext des globalen Klimawandels.

Temporal and spatial environmental variation affects every organism in manifold ways. Especially for sessile life forms like plants it poses a big challenge to deal with fluctuations in their environment, since they are hardly able to quickly escape unfavourable conditions. Recently, it has been shown that the combination of several human-induced, rapid changes in the environment (known as global environmental change) represents large novel selective pressures to which plants need to respond and possibly adapt. Amongst others, the rapid world-wide increase in temperature is assumed to have major ecological and evolutionary consequences being a major threat to species diversity. Hence, it is of great importance to get deeper knowledge about the ability of plant species to react to environmental changes, especially in climate. One way of plant populations to avoid extinction is tracking the shift in climate either in time or space (e.g. shifts in phenology or to higher latitudes / altitudes). Such a response, however, may be impeded by low migration rates of many species and / or current human-induced habitat fragmentation (possibly combined with reduced genetic variation in fragmented populations). Thus, the ability of plant species to adapt themselves to new climatic conditions, via a combination of adaptive and non-adaptive phenotypic plasticity, genetic diversity or local adaptation, may provide an alternative vital strategy for their survival and long-term persistence. To examine the response of plant species to different environmental conditions, fitness-related plant functional traits are commonly used. So far, the variability of these traits within a species (i.e. intraspecific variation), however, has been mostly neglected. Still, there is recent awareness that i) intraspecific variation may differ substantially across different scales (among regions, between populations, within populations or even within individuals) and ii) that it may reflect the general potential of a species' ability to adapt to a new environment via phenotypic plasticity, genetic diversity or local adaptation. Therefore, the major objective of this study was to enlighten patterns and underlying causes of intraspecific variation within and among populations of temperate forest under-storey herbs with regard to different environmental conditions and climatic variation in particular. The forest understorey comprises mainly specialist species, which may be notably threatened by global change due to their low migration rates and colonization success. These species may thus especially rely on their ability to adjust themselves to a changing environment. Overall, phenotypic responses differed between species and plant functional types used in this study. Therefore, impacts of global change on different species are likely diverse and will potentially strongly affect forest community structures. Further research integrating experimental studies and examination of numerous species in natural plant communities and especially the consideration of several (human-induced) environmental changes is required to allow generalization and more explicit prospects for specific species. In summary, this thesis emphasizes the importance of taking intraspecific variation into account when using plant functional traits as proxies for species performance related to environmental variation

Phenotypic trait variation in forest herbs along environmental gradients in the context of climate change

Temporal and spatial environmental variation affects every organism in manifold ways. Especially for sessile life forms like plants it poses a big challenge to deal with fluctuations in their environment, since they are hardly able to quickly escape unfavourable conditions. Recently, it has been shown that the combination of several human-induced, rapid changes in the environment (known as global environmental change) represents large novel selective pressures to which plants need to respond and possibly adapt. Amongst others, the rapid world-wide increase in temperature is assumed to have major ecological and evolutionary consequences being a major threat to species diversity. Hence, it is of great importance to get deeper knowledge about the ability of plant species to react to environmental changes, especially in climate. One way of plant populations to avoid extinction is tracking the shift in climate â either in time or space (e.g. shifts in phenology or to higher latitudes / altitudes). Such a response, however, may be impeded by low migration rates of many species and / or current human-induced habitat fragmentation (possibly combined with reduced genetic variation in fragmented populations). Thus, the ability of plant species to adapt themselves to new climatic conditions, via a combination of adaptive and non-adaptive phenotypic plasticity, genetic diversity or local adaptation, may provide an alternative vital strategy for their survival and long-term persistence. To examine the response of plant species to different environmental conditions, fitness-related plant functional traits are commonly used. So far, the variability of these traits within a species (i.e. intraspecific variation), however, has been mostly neglected. Still, there is recent awareness that i) intraspecific variation may differ substantially across different scales (among regions, between populations, within populations or even within individuals) and ii) that it may reflect the general potential of a species' ability to adapt to a new environment â via phenotypic plasticity, genetic diversity or local adaptation. Therefore, the major objective of this study was to enlighten patterns and underlying causes of intraspecific variation within and among populations of temperate forest under-storey herbs with regard to different environmental conditions and climatic variation in particular. The forest understorey comprises mainly specialist species, which may be notably threatened by global change due to their low migration rates and colonization success. These species may thus especially rely on their ability to adjust themselves to a changing environment. Overall, phenotypic responses differed between species and plant functional types used in this study. Therefore, impacts of global change on different species are likely diverse and will potentially strongly affect forest community structures. Further research integrating experimental studies and examination of numerous species in natural plant communities and especially the consideration of several (human-induced) environmental changes is required to allow generalization and more explicit prospects for specific species. In summary, this thesis emphasizes the importance of taking intraspecific variation into account when using plant functional traits as proxies for species performance related to environmental variation

Latitudinal variation of life-history traits of an exotic and a native impatiens species in Europe

International audienceUnderstanding the responses of invasive and native populations to environmental change is crucial for reliable predictions of invasions in the face of global change. While comparisons of responses across invasive species with different life histories have been performed before, comparing functional traits of congeneric native and invasive species may help to reveal driving factors associated with invasion. Here we compared morphological functional trait patterns of an invasive species (Impatiens parviflora) with its congeneric native species (I. noli-tangere) along an approximately 1600 km European latitudinal gradient from France (49 degrees 34'N) to Norway (63 degrees 40'N). Soil nitrogen was recorded during six weeks of the growing season, and light, soil moisture, and nutrient availability were estimated for each sampled population using community weighted means of indicator values for co-occurring species. Temperature data were gathered from nearby weather stations. Both the native and invasive species are taller at higher latitudes and this response is strongest in the invasive species. Seed mass and number of seeds per capsule increase in I. noli-tangere but decrease in I. parviflora towards higher latitudes. Surprisingly, plant height in the invasive I. parviflora decreases with increasing soil nitrogen availability. The latitudinal pattern in seed mass is positively related to temperature in I. noli-tangere and negatively in I. parviflora. Leaf area of both species decreases with increasing Ellenberg indicator values for nitrogen and light but increases with increasing soil moisture. Soil nitrogen concentrations and Ellenberg indicator values for nitrogen have significant positive (I. nolitangere) and negative (I. parviflora) effects on the number of seeds per capsule. Our results show that the native I. noli-tangere has efficient reproduction at its range edge while the invasive I. parviflora shows a marked decrease in seed size and seed number per capsule. These patterns are unrelated to the growth and obtained size of the plants: even low soil nitrogen availability in the north seemed not to limit plant growth and size. Our results suggest that the invasive I. parviflora tends to become more invasive at lower latitudes by producing heavier seeds and more seeds per capsule. 0 2017 Elsevier Masson SAS. All rights reserved

Small forest patches as pollinator habitat : oases in an agricultural desert?

Context: Small forest fragments are often the most abundant type of semi-natural habitat in intensive agricultural landscapes. Wild pollinators can use these forest patches as nesting or foraging habitat. However, the importance of small forest fragments as pollinator habitat has been neglected so far. Objectives: We evaluated the role of these forest patches as pollinator habitat, focusing on the effect of nesting and foraging resources, both at a local and at a landscape scale. Methods: Pollinators were sampled with pan traps in 78 forest patches, spread over five study regions in Northwestern Europe. We evaluated effect of forest and landscape characteristics on bee and hoverfly species richness, diversity and activity-abundance. Results: We showed that the bee community is influenced by both microsite conditions and landscape characteristics. Species richness and activity-abundance were higher when suitable nesting resources, such as sloped terrain and bare soil were available. This suggests that forest edges are important in providing nesting sites, but that most species forage in different habitats. Hoverfly species richness was higher in old forest fragments. This relation was mainly caused by the presence of forest specialist hoverflies in old forest fragments. Conclusions: Small forest fragments in agricultural landscapes can harbour a diverse pollinator community. Increasing the amount of nesting habitat, such as bare soil and sloped terrains is expected to have beneficial effects on the bee community, whereas older forest fragments should be conserved to sustain a rich hoverfly community

Biological flora of the British Isles : Milium effusum

1. This account presents information on all aspects of the biology of Milium effusum L. (Wood Millet) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history, and conservation. 2. The grass Milium effusum is a common species of mature woodland in central and southern England, but is less common in the wetter parts of northern England, Wales, Scotland and Ireland. Worldwide, the species is native to many temperate, boreal, subarctic and subalpine parts of the northern hemisphere: from eastern North America across most of Europe (excluding Mediterranean climates) to the Ural Mountains and Black Sea, extending eastwards to the Himalaya, Korea and Japan. 3. Wood Millet is a shade-tolerant, relatively tall grass (up to 1.8 m) producing up to 700 caryopses per individual. It is characteristic of temperate deciduous woodland, but can also occur in other woodland and forest types and even in scrub, alpine meadows, along railways and roads, and on rocks. In woods, it is one of the most conspicuous plants of the herb layer in the early summer after the disappearance of spring flowering species. While the species is generally considered an ancient woodland indicator in England and western Europe, it is also known to colonize secondary, post-agricultural forests relatively rapidly in other areas such as Denmark, southern Sweden and Poland. 4. The species has a wide amplitude in terms of soil acidity and nutrient availability, but predominantly grows on soils of intermediate soil fertility and soil pH and with high organic matter concentration. However, M. effusum can tolerate large quantities of tree-leaf litter on the forest floor and is able to grow on very acidic soils. 5. Changes in land use, climate, densities of large herbivores and atmospheric deposition of nitrogen are having effects on populations of Wood Millet. Significant responses of the life-history traits and population characteristics have been detected in response to environmental variation and to experimental treatments of temperature, nutrients, light and acidity. In many of its habitats across its range, M. effusum is currently becoming more frequent. During the last century, its mean elevation of occurrence in upland areas of Europe has also increased by several hundreds of metres. Typically, management actions are directed towards the conservation of its main habitat type (e.g. ancient woodlands of the Milio-Fagetum association) rather than to the species specifically

Where does the community start, and where does it end? : including the seed bank to reassess forest herb layer responses to the environment

Question: Below-ground processes are key determinants of above-ground plant population and community dynamics. Still, our understanding of how environmental drivers shape plant communities is mostly based on above-ground diversity patterns, bypassing below-ground plant diversity stored in seed banks. As seed banks may shape above-ground plant communities, we question whether concurrently analysing the above- and below-ground species assemblages may potentially enhance our understanding of community responses to environmental variation. Location: Temperate deciduous forests along a 2000km latitudinal gradient in NW Europe. Methods: Herb layer, seed bank and local environmental data including soil pH, canopy cover, forest cover continuity and time since last canopy disturbance were collected in 129 temperate deciduous forest plots. We quantified herb layer and seed bank diversity per plot and evaluated how environmental variation structured community diversity in the herb layer, seed bank and the combined herb layer-seed bank community. Results: Seed banks consistently held more plant species than the herb layer. How local plot diversity was partitioned across the herb layer and seed bank was mediated by environmental variation in drivers serving as proxies of light availability. The herb layer and seed bank contained an ever smaller and ever larger share of local diversity, respectively, as both canopy cover and time since last canopy disturbance decreased. Species richness and -diversity of the combined herb layer-seed bank community responded distinctly differently compared to the separate assemblages in response to environmental variation in, e.g. forest cover continuity and canopy cover. Conclusions: The seed bank is a below-ground diversity reservoir of the herbaceous forest community, which interacts with the herb layer, although constrained by environmental variation in e.g. light availability. The herb layer and seed bank co-exist as a single community by means of the so-called storage effect, resulting in distinct responses to environmental variation not necessarily recorded in the individual herb layer or seed bank assemblages. Thus, concurrently analysing above- and below-ground diversity will improve our ecological understanding of how understorey plant communities respond to environmental variation

Data from: Low genetic diversity despite multiple introductions of the invasive plant species Impatiens glandulifera in Europe

Background: Invasive species can be a major threat to native biodiversity and the number of invasive plant species is increasing across the globe. Population genetic studies of invasive species can provide key insights into their invasion history and ensuing evolution, but also for their control. Here we genetically characterise populations of Impatiens glandulifera, an invasive plant in Europe that can have a major impact on native plant communities. We compared populations from the species’ native range in Kashmir, India, to those in its invaded range, along a latitudinal gradient in Europe. For comparison, the results from 39 other studies of genetic diversity in invasive species were collated. Results: Our results suggest that I. glandulifera was established in the wild in Europe at least twice, from an area outside of our Kashmir study area. Our results further revealed that the genetic diversity in invasive populations of I. glandulifera is unusually low compared to native populations, in particular when compared to other invasive species. Genetic drift rather than mutation seems to have played a role in differentiating populations in Europe. We find evidence of limitations to local gene flow after introduction to Europe, but somewhat less restrictions in the native range. I. glandulifera populations with significant inbreeding were only found in the species’ native range and invasive species in general showed no increase in inbreeding upon leaving their native ranges. In Europe we detect cases of migration between distantly located populations. Human activities therefore seem to, at least partially, have facilitated not only introductions, but also further spread of I. glandulifera across Europe. Conclusions: Although multiple introductions will facilitate the retention of genetic diversity in invasive ranges, widespread invasive species can remain genetically relatively invariant also after multiple introductions. Phenotypic plasticity may therefore be an important component of the successful spread of Impatiens glandulifera across Europe