Subalpine-nival gradient of species richness for vascular plants, lichens and bryophytes in the Swiss Inner Alps

In the European GLORIA project, 12 summits (treeline to nival belt) were inventoried in three regions of Switzerland: two in the Swiss National Park Graubünden and one in Valais. Vascular plants were recorded in all three regions and bryophytes and lichens were recorded only in Valais. On each summit, vegetation and temperature data were sampled using sampling protocols for the GLORIA project (Global Observation Research Initiative in Alpine environment) on large summit sections and in clusters of four 1x1-m quadrats. We observed a general decrease of species richness for all three systematic groups with increasing elevation in the summit sections, but only for vascular plants in the quadrats. In Valais, there was higher species richness for vascular plants than for bryophytes and lichens on the lower summits, but as the decrease in species richness was less pronounced for cryptogams, the latter were more numerous than vascular plants on the highest summit. Vascular species showed a clear shift of the dominant life form with elevation, with chamaephytes replacing hemicryptophytes. Bryophytes and lichens showed a weak trend among the life forms at the summit section scale, but a stronger shift of the dominant forms was seen in the quadrats, with cushion replacing turf bryophytes and crustaceous replacing fruticose lichens. Altogether, these results sustain the temperature-physiographic hypothesis to explain the species richness decrease along the altitudinal gradient: the harsh climatic conditions of the alpine-nival belts act as a filter for species, but the diminishing diversity of microhabitats is also an important factor. Because cryptogams depend more on humidity than temperature and more on smaller microhabitats than vascular plants, the decrease of species richness is more gradual with elevation for bryophytes and lichens.

Heat perception and signalling in plants: a tortuous path to thermotolerance.

An accurate assessment of the rising ambient temperature by plant cells is crucial for the timely activation of various molecular defences before the appearance of heat damage. Recent findings have allowed a better understanding of the early cellular events that take place at the beginning of mild temperature rise, to timely express heat-shock proteins (HSPs), which will, in turn, confer thermotolerance to the plant. Here, we discuss the key components of the heat signalling pathway and suggest a model in which a primary sensory role is carried out by the plasma membrane and various secondary messengers, such as Ca(2+) ions, nitric oxide (NO) and hydrogen peroxide (H(2) O(2) ). We also describe the role of downstream components, such as calmodulins, mitogen-activated protein kinases and Hsp90, in the activation of heat-shock transcription factors (HSFs). The data gathered for land plants suggest that, following temperature elevation, the heat signal is probably transduced by several pathways that will, however, coalesce into the final activation of HSFs, the expression of HSPs and the onset of cellular thermotolerance.

Polymers of 3-hydroxyacids in plants

Polyhydroxyalkanoates (PHA) are polyesters of bacterial origin that have properties of biodegradable plastics and elastomers. Synthesis of PHA in crop plants would allow the large-scale production and use of these biodegradable and renewable polymers as substitutes for petroleum-derived plastics. Synthesis of a diversity of PHAs in plants, such as Arabidopsis thaliana, rapeseed, corn and cotton, has been demonstrated through the genetic engineering of metabolic pathways in the cytoplasm, plastid and peroxisome. PHA can also be used as a novel tool to study various aspects of plant metabolism, such as the regulation of carbon flux to the fatty acid biosynthetic and degradation pathways.

Cell polarity in plants: a PARspective on PINs.

Plants have acquired the ability for organized multicellular development independent from animals. Because of this, they represent an independent example in nature for the development of coordinated, complex cell polarity from the simple polarity found in unicellular eukaryotes. Plants display a striking array of polarized cell types, with different axes of polarity being defined in one cell. The most investigated and best understood aspect of plant polarity is the apical-basal polarity of the PIN family of auxin efflux facilitators, which are of crucial importance for the organization of the entire plant body. Striking differences exist between the PAR-polarity modules known in animals and the ways PINs polarize plant cells. Nonetheless, a common regulatory logic probably applies to all polarizing eukaryotic cells, which includes self-reinforcing, positive feedback loops, intricate interactions between membrane-attached proteins, lipid signatures, and the targeting of transmembrane proteins to the correct domains of the plasma membrane.

Assessment of airborne virus contamination in wastewater treatment plants

INTRODUCTION: Occupational exposure to bioaerosols in wastewater treatment plants (WWTP) and its consequence on workers׳ health are well documented. Most studies were devoted to enumerating and identifying cultivable bacteria and fungi, as well as measuring concentrations of airborne endotoxins, as these are the main health-related factors found in WWTP. Surprisingly, very few studies have investigated the presence and concentrations of airborne virus in WWTP. However, many enteric viruses are present in wastewater and, due to their small size, they should become aerosolized. Two in particular, the norovirus and the adenovirus, are extremely widespread and are the major causes of infectious gastrointestinal diseases reported around the world. The third one, hepatitis E virus, has an emerging status. GOAL AND METHODS: This study׳s objectives were to detect and quantify the presence and concentrations of 3 different viruses (adenovirus, norovirus and the hepatitis E virus) in air samples from 31 WWTPs by using quantitative polymerase chain reaction (qPCR) during two different seasons and two consecutive years. RESULTS: Adenovirus was present in 100% of summer WWTP samples and 97% of winter samples. The highest airborne concentration measured was 2.27×10(6) genome equivalent/m(3) and, on average, these were higher in summer than in winter. Norovirus was detected in only 3 of the 123 air samples, and the hepatitis E virus was not detected. CONCLUSIONS: Concentrations of potentially pathogenic viral particles in WWTP air are non-negligible and could partly explain the work-related gastrointestinal symptoms often reported in employees in this sector.

Metabolic engineering of plants for the synthesis of polyhydroxyalkanoates

Synthesis of polyhydroxyalkanoates (PHAs) in crop is viewed as an attractive approach for the production of this family of biodegradable plastics in large quantities and at low costs. Synthesisof PHAs containing various monomers has so far been demonstrated in the cytosol, plastids, and peroxisomes of plants. Several biochemical pathways have been modifies to achieve this, including the isoprenois pathway, the fatty acid biosynthetic pathway, and the fatty acid

Environment and dispersal paths override life strategies and residence time in determining regional patterns of invasion by alien plants.

We describe a novel dissimilarity framework to analyze spatial patterns of species diversity and illustrate it with alien plant invasions in Northern Portugal. We used this framework to test the hypothesis that patterns of alien invasive plant species richness and composition are differently affected by differences in climate, land use and landscape connectivity (i.e. Geographic distance as a proxy and vectorial objects that facilitate dispersal such as roads and rivers) between pairs of localities at the regional scale. We further evaluated possible effects of plant life strategies (Grime's C-S-R) and residence time. Each locality consisted of a 1 km(2) landscape mosaic in which all alien invasive species were recorded by visiting all habitat types. Multi-model inference revealed that dissimilarity in species richness is more influenced by environmental distance (particularly climate), whereas geographic distance (proxies for dispersal limitations) is more important to explain dissimilarity in species composition, with a prevailing role for ecotones and roads. However, only minor differences were found in the responses of the three C-S-R strategies. Some effect of residence time was found, but only for dissimilarity in species richness. Our results also indicated that environmental conditions (e.g. climate conditions) limit the number of alien species invading a given site, but that the presence of dispersal corridors determines the paths of invasion and therefore the pool of species reaching each site. As geographic distances (e.g. ecotones and roads) tend to explain invasion at our regional scale highlights the need to consider the management of alien invasions in the context of integrated landscape planning. Alien species management should include (but not be limited to) the mitigation of dispersal pathways along linear infrastructures. Our results therefore highlight potentially useful applications of the novel multimodel framework to the anticipation and management of plant invasions. (C) 2013 Elsevier GmbH. All rights reserved.

Detritivorous crustaceans become herbivores on jasmonate-deficient plants.

The jasmonate signal pathway is known to control defenses against herbivores, such as leaf eaters (folivores). Does the reach of the pathway extend to defense against other types of animal? Among the arthropods attracted to seed baits placed below flowering Arabidopsis thaliana plants are 2 largely nocturnal isopod crustaceans generally considered as detritivores: Porcellio scaber and Armadillidium vulgare. Parallel laboratory experiments identified the isopods as being capable of predation on intact plants. Isopod feeding was strongly facilitated in jasmonate-deficient Arabidopsis and rice plants. The feeding activity of isopods revealed potentially detritivore-sensitive, jasmonate-protected Achilles' heels in these architecturally different plants (petioles and inflorescence stems in Arabidopsis, and lower stem and mesocotyl in rice). The work addresses the question of what stops 2 detritivores from attacking living plants and provides evidence that it is, in part, the jasmonate signal pathway. Furthermore, senescent leaves from an Arabidopsis jasmonate mutant were consumed more rapidly than senescent wild-type leaves, suggesting that past activity of the jasmonate signal pathway in leaves may slow carbon recycling through detritivory.

Plants respond to pathogen infection by enhancing the antifungal gene expression of root-associated bacteria.

Plant health and fitness widely depend on interactions with soil microorganisms. Some bacteria such as pseudomonads can inhibit pathogens by producing antibiotics, and controlling these bacteria could help improve plant fitness. In the present study, we tested whether plants induce changes in the antifungal activity of root-associated bacteria as a response to root pathogens. We grew barley plants in a split-root system with one side of the root system challenged by the pathogen Pythium ultimum and the other side inoculated with the biocontrol strain Pseudomonas fluorescens CHA0. We used reporter genes to follow the expression of ribosomal RNA indicative of the metabolic state and of the gene phlA, required for production of 2,4-diacetylphloroglucinol, a key component of antifungal activity. Infection increased the expression of the antifungal gene phlA. No contact with the pathogen was required, indicating that barley influenced gene expression by the bacteria in a systemic way. This effect relied on increased exudation of diffusible molecules increasing phlA expression, suggesting that communication with rhizosphere bacteria is part of the pathogen response of plants. Tripartite interactions among plants, pathogens, and bacteria appear as a novel determinant of plant response to root pathogens.

Plants and tortoises: mutations in the Arabidopsis jasmonate pathway increase feeding in a vertebrate herbivore.

Photosynthetic tissues, the major food source of many invertebrates and vertebrates, are well defended. Many defence traits in leaves are controlled via the jasmonate signalling pathway in which jasmonate acts as a hormone by binding to a receptor to activate responses that lead to increased resistance to invertebrate folivores. We predicted that mutations in jasmonate synthesis might also increase the vulnerability of leaves to vertebrate folivores and tested this hypothesis using the Eastern Hermann's tortoise (Eurotestudo boettgeri) and an Arabidopsis thaliana (Brassicaceae) allene oxide synthase (aos) mutant unable to synthesize jasmonate. Tortoises preferred the aos mutant over the wild type (WT). Based on these results, we then investigated the effect of mutating jasmonate perception using a segregating population of the recessive A. thaliana jasmonate receptor mutant coronatine insensitive1-1 (coi1-1). Genotyping of these plants after tortoise feeding revealed that the homozygous coi1-1 receptor mutant was consumed more readily than the heterozygous mutant or the WT. Therefore, the plant's ability to synthesize or perceive jasmonate reduces feeding by a vertebrate herbivore. We also tested whether or not tortoise feeding behaviour was influenced by glucosinolates, the principal defence chemicals in Arabidopsis leaves with known roles in defence against many generalist insects. However, in contrast to what has been observed with such insects, leaves in which the levels of these compounds were reduced genetically were consumed at a similar rate to those of the WT.

Analysis of the alternative pathways for the beta-oxidation of unsaturated fatty acids using transgenic plants synthesizing polyhydroxyalkanoates in peroxisomes.

Degradation of fatty acids having cis-double bonds on even-numbered carbons requires the presence of auxiliary enzymes in addition to the enzymes of the core beta-oxidation cycle. Two alternative pathways have been described to degrade these fatty acids. One pathway involves the participation of the enzymes 2, 4-dienoyl-coenzyme A (CoA) reductase and Delta(3)-Delta(2)-enoyl-CoA isomerase, whereas the second involves the epimerization of R-3-hydroxyacyl-CoA via a 3-hydroxyacyl-CoA epimerase or the action of two stereo-specific enoyl-CoA hydratases. Although degradation of these fatty acids in bacteria and mammalian peroxisomes was shown to involve mainly the reductase-isomerase pathway, previous analysis of the relative activity of the enoyl-CoA hydratase II (also called R-3-hydroxyacyl-CoA hydro-lyase) and 2,4-dienoyl-CoA reductase in plants indicated that degradation occurred mainly through the epimerase pathway. We have examined the implication of both pathways in transgenic Arabidopsis expressing the polyhydroxyalkanoate synthase from Pseudomonas aeruginosa in peroxisomes and producing polyhydroxyalkanoate from the 3-hydroxyacyl-CoA intermediates of the beta-oxidation cycle. Analysis of the polyhydroxyalkanoate synthesized in plants grown in media containing cis-10-heptadecenoic or cis-10-pentadecenoic acids revealed a significant contribution of both the reductase-isomerase and epimerase pathways to the degradation of these fatty acids.

The ecological significance of arbuscular mycorrhizal fungal effects on clonal reproduction in plants

The population ecology of clonal plants depends on the number and distribution of ramets formed during growth. Variation in clonal reproduction has previously been explained by variation in effects of abiotic resource heterogeneity and by plant genotypic variation. Different co-occurring species of the mutualistic arbuscular mycorrhizal fungi (AMF) have been shown to differentially alter growth traits of Prunella vulgaris which we hypothesize would lead to changes in clonal reproduction. Two experiments were carried out to test whether different co-occurring mycorrhizal fungi significantly influence clonal reproduction of P. vulgaris whether this effect also occurs when P. vulgaris is growing in an artificial plant community and how the effects compare with plant genotype effects on clonal growth of P. vulgaris. In the first experiment the number of ramets of P. vulgaris growing in a plant community of simulated calcareous grassland was significantly affected by inoculation with different mycorrhizal fungi. The number of ramets produced by P. vulgaris differed by a factor of up to 1.8 with different mycorrhizal fungi. The fungal effects on the number of new ramets were independent of their effects on the biomass of P. vulgaris. In a second experiment 17 different genotypes of P. vulgaris were inoculated with different mycorrhizal fungi. There were significant main effects of genotypes and mycorrhizal fungi on clonal reproduction of P. vulgaris. The effect of different mycorrhizal fungi contributed more than the effect of plant genotype to variation in size and ramet production. However mean stolon length and spacer length which determine the spatial arrangement of ramets were only significantly affected by plant genotype. There were no mycorrhizal fungal X plant genotype interactions on clonal growth of P. vulgaris indicating that there is no obvious evidence that selection pressures would favor further coevolution between P. vulgaris and mycorrhizal fungal species. In natural communities plants can be colonized by several different AMF at the same time. The effect of the mixed AMF treatment on the growth and clonal reproduction of P. vulgaris could not be predicted from the responses of the plants to the single AMF To what extent however the patterns of colonization by different AMF differ among plants in a natural community is unknown. Since the effects of AMF on growth and clonal reproduction occur on a population of P. vulgaris in a microcosm plant community and because the effects are also as great as those caused by plant genotypic variation we conclude that the effects are strong enough to potentially affect population size and variation of clonal plants in communities.

Predicting future distributions of mountain plants under climate change: does dispersal capacity matter?

Many studies have investigated the impacts that climate change could potentially have on the distribution of plant species, but few have attempted to constrain projections through plant dispersal limitations. Instead, most studies published so far have been using the simplification of considering dispersal as either unlimited or null. However, depending on a species' dispersal capacity, landscape fragmentation, and the rate of climatic change, these assumptions can lead to serious over- or underestimation of a species' future distribution. To quantify the discrepancies between unlimited, realistic, and no dispersal scenarios, we carried out projections of future distribution over the 21st century for 287 mountain plant species in a study area of the Western Swiss Alps. For each species, simulations were run for four dispersal scenarios (unlimited dispersal, no dispersal, realistic dispersal and realistic dispersal with long-distance dispersal events) and under four climate change scenarios. Although simulations accounting for realistic dispersal limitations did significantly differ from those considering dispersal as unlimited or null in terms of projected future distribution, using the unlimited dispersal simplification nevertheless provided good approximations for species extinctions under more moderate climate change scenarios. Overall, simulations accounting for dispersal limitations produced, for our mountainous study area, results that were significantly closer to unlimited dispersal than to no dispersal. Finally, analyzing the temporal pattern of species extinctions over the entire 21st century showed that, due to the possibility of a large number of species shifting their distribution to higher elevation, important species extinctions for our study area might not occur before the 2080-2100 time periods.

Niche, distribution and global change : modeling insights into biogeography and conservation biology Olivier Broennimann

RESUME Les évidences montrant que les changements globaux affectent la biodiversité s'accumulent. Les facteurs les plus influant dans ce processus sont les changements et destructions d'habitat, l'expansion des espèces envahissantes et l'impact des changements climatiques. Une évaluation pertinente de la réponse des espèces face à ces changements est essentielle pour proposer des mesures permettant de réduire le déclin actuel de la biodiversité. La modélisation de la répartition d'espèces basée sur la niche (NBM) est l'un des rares outils permettant cette évaluation. Néanmoins, leur application dans le contexte des changements globaux repose sur des hypothèses restrictives et demande une interprétation critique. Ce travail présente une série d'études de cas investiguant les possibilités et limitations de cette approche pour prédire l'impact des changements globaux. Deux études traitant des menaces sur les espèces rares et en danger d'extinction sont présentées. Les caractéristiques éco-géographiques de 118 plantes avec un haut degré de priorité de conservation sont revues. La prévalence des types de rareté sont analysées en relation avec leur risque d'extinction UICN. La revue souligne l'importance de la conservation à l'échelle régionale. Une évaluation de la rareté à échelle globale peut être trompeuse pour certaine espèces car elle ne tient pas en compte des différents degrés de rareté que présente une espèce à différentes échelles spatiales. La deuxième étude test une approche pour améliorer l'échantillonnage d'espèces rares en incluant des phases itératives de modélisation et d'échantillonnage sur le terrain. L'application de l'approche en biologie de la conservation (illustrée ici par le cas du chardon bleu, Eryngium alpinum), permettrait de réduire le temps et les coûts d'échantillonnage. Deux études sur l'impact des changements climatiques sur la faune et la flore africaine sont présentées. La première étude évalue la sensibilité de 227 mammifères africains face aux climatiques d'ici 2050. Elle montre qu'un nombre important d'espèces pourrait être bientôt en danger d'extinction et que les parcs nationaux africains (principalement ceux situé en milieux xériques) pourraient ne pas remplir leur mandat de protection de la biodiversité dans le futur. La seconde étude modélise l'aire de répartition en 2050 de 975 espèces de plantes endémiques du sud de l'Afrique. L'étude propose l'inclusion de méthodes améliorant la prédiction des risques liés aux changements climatiques. Elle propose également une méthode pour estimer a priori la sensibilité d'une espèce aux changements climatiques à partir de ses propriétés écologiques et des caractéristiques de son aire de répartition. Trois études illustrent l'utilisation des modèles dans l'étude des invasions biologiques. Une première étude relate l'expansion de la laitue sáuvage (Lactuca serriola) vers le nord de l'Europe en lien avec les changements du climat depuis 250 ans. La deuxième étude analyse le potentiel d'invasion de la centaurée tachetée (Centaures maculosa), une mauvaise herbe importée en Amérique du nord vers 1890. L'étude apporte la preuve qu'une espèce envahissante peut occuper une niche climatique différente après introduction sur un autre continent. Les modèles basés sur l'aire native prédisent de manière incorrecte l'entier de l'aire envahie mais permettent de prévoir les aires d'introductions potentielles. Une méthode alternative, incluant la calibration du modèle à partir des deux aires où l'espèce est présente, est proposée pour améliorer les prédictions de l'invasion en Amérique du nord. Je présente finalement une revue de la littérature sur la dynamique de la niche écologique dans le temps et l'espace. Elle synthétise les récents développements théoriques concernant le conservatisme de la niche et propose des solutions pour améliorer la pertinence des prédictions d'impact des changements climatiques et des invasions biologiques. SUMMARY Evidences are accumulating that biodiversity is facing the effects of global change. The most influential drivers of change in ecosystems are land-use change, alien species invasions and climate change impacts. Accurate projections of species' responses to these changes are needed to propose mitigation measures to slow down the on-going erosion of biodiversity. Niche-based models (NBM) currently represent one of the only tools for such projections. However, their application in the context of global changes relies on restrictive assumptions, calling for cautious interpretations. In this thesis I aim to assess the effectiveness and shortcomings of niche-based models for the study of global change impacts on biodiversity through the investigation of specific, unsolved limitations and suggestion of new approaches. Two studies investigating threats to rare and endangered plants are presented. I review the ecogeographic characteristic of 118 endangered plants with high conservation priority in Switzerland. The prevalence of rarity types among plant species is analyzed in relation to IUCN extinction risks. The review underlines the importance of regional vs. global conservation and shows that a global assessment of rarity might be misleading for some species because it can fail to account for different degrees of rarity at a variety of spatial scales. The second study tests a modeling framework including iterative steps of modeling and field surveys to improve the sampling of rare species. The approach is illustrated with a rare alpine plant, Eryngium alpinum and shows promise for complementing conservation practices and reducing sampling costs. Two studies illustrate the impacts of climate change on African taxa. The first one assesses the sensitivity of 277 mammals at African scale to climate change by 2050 in terms of species richness and turnover. It shows that a substantial number of species could be critically endangered in the future. National parks situated in xeric ecosystems are not expected to meet their mandate of protecting current species diversity in the future. The second study model the distribution in 2050 of 975 endemic plant species in southern Africa. The study proposes the inclusion of new methodological insights improving the accuracy and ecological realism of predictions of global changes studies. It also investigates the possibility to estimate a priori the sensitivity of a species to climate change from the geographical distribution and ecological proprieties of the species. Three studies illustrate the application of NBM in the study of biological invasions. The first one investigates the Northwards expansion of Lactuca serriola L. in Europe during the last 250 years in relation with climate changes. In the last two decades, the species could not track climate change due to non climatic influences. A second study analyses the potential invasion extent of spotted knapweed, a European weed first introduced into North America in the 1890s. The study provides one of the first empirical evidence that an invasive species can occupy climatically distinct niche spaces following its introduction into a new area. Models fail to predict the current full extent of the invasion, but correctly predict areas of introduction. An alternative approach, involving the calibration of models with pooled data from both ranges, is proposed to improve predictions of the extent of invasion on models based solely on the native range. I finally present a review on the dynamic nature of ecological niches in space and time. It synthesizes the recent theoretical developments to the niche conservatism issues and proposes solutions to improve confidence in NBM predictions of the impacts of climate change and species invasions on species distributions.