Response of aquatic hyphomycete communities to enhanced stream retention in areas impacted by commercial forestry

1. Aquatic hyphomycetes are an important component of detritus processing in streams. Their response to enhanced stream retentiveness was tested by manipulating three streams located in Kielder Forest (northern England), a large plantation of exotic conifers, and two streams in Montagne Noire (south-west France) dominated by native broadleaf woodland. Treatment was by placement of logs or plastic litter traps into a 10–20 m stream section. Fungal spores were collected from stream water upstream and downstream of the treated sections over 1–2 years. 2.The average concentration of fungal spores in reference sections was nearly 10x greater in the French streams than in the English streams. The number of hyphomycete species was also higher in the French streams. These differences between regions were probably a consequence of the much lower standing stock and diversity of leaf litter in the English streams. 3. Despite these large regional differences, the treatment had a clear effect in all streams. Detrital standing stocks were enhanced in treated sections by up to 90% in French streams and 70% in English streams. 4. Mean spore density below treated sections increased by 1.8–14.8% in French streams and 10.2–28.9% in the naturally less retentive English streams. The number of fungal species increased significantly below the treated sections of the English streams, although not the French ones. 5. In biologically impoverished plantation streams, input of woody debris can increase detritus retention and enhance hyphomycete diversity and productivity. This may have consequent benefits for detritus processing and macroinvertebrate production

Processus écologiques et évolutifs influençant la colonisation de l'ambroisie à feuilles d'armoise (Ambrosia artemisiifolia L.) en France

La compréhension des mécanismes déterminant le succès des espèces invasives est une étape essentielle dans la gestion des invasions biologiques actuelles et la prédiction des futurs risques d invasion. En adoptant un cadre d étude conceptuel intégrant les processus écologiques et évolutifs, l objectif de ce travail était d analyser les déterminants de la colonisation de l ambroisie à feuilles d armoise en France. Tout d abord, l étude des interactions biotiques et abiotiques a permis de montrer la capacité de tolérance de l ambroisie à l herbivorie et au stress hydrique. L ambroisie est capable de tolérer la défoliation grâce à une croissance compensatoire efficace, sans que sa reproduction en soit affectée. Cette forte tolérance à l herbivorie est maintenue chez les populations introduites, malgré la faible pression des ennemis naturels dans la zone d introduction. En condition de stress hydrique, l ambroisie produit une biomasse racinaire supérieure aux espèces présentes dans les communautés qu elle envahit. De plus, les différences dans les valeurs moyennes pour les traits mesurés suggèrent une occupation différente par l ambroisie des niches écologiques disponibles. La comparaison en jardins communs de populations de l aire d origine avec des populations de l aire d introduction isolées et issues du foyer central d invasion a montré que l adaptation de l ambroisie à son environnement reposait principalement sur la plasticité phénotypique plutôt que sur la différenciation des traits. Les études de génétiques quantitatives ont mis en évidence un potentiel évolutif élevé pour les traits liés à la germination. Les traits liés à la morphologie, à la phénologie et à la physiologie de la plante montrent une variance additive et une héritabilité plus faibles et donc un potentiel évolutif moindre. En revanche, la variation dans les normes de réaction indique un potentiel évolutif important de la plasticité phénotypique. La tolérance au stress hydrique et à l herbivorie sont des facteurs qui potentiellement augmentent la capacité de l ambroisie à coloniser une large gamme d habitat. De plus, la plasticité phénotypique et le potentiel évolutif important peuvent favoriser une augmentation ou un déplacement de la niche écologique de l espèce et ainsi favoriser l expansion de son aire de répartitionUnderstanding of the mechanisms behind the success of the invasive species is essential to manage current biological invasions and to prevent the risks of the futures ones. Using a conceptual framework integrating ecological and evolutionary processes, this work aimed to analyse the factors of the common ragweed colonization in France. First of all, the study of biotic and abiotic interactions has shown the ability of common ragweed to tolerate herbivory and water stress. Common ragweed is able to buffer defoliation through an efficient compensatory growth with no consequence on the reproduction. Herbivory tolerance has been maintained in introduced populations even if herbivory pressure is low in the introduction area. Under water stress conditions, common ragweed displayed higher root biomass than the other species present in the communities it invades. In addition, differences in mean trait values suggest different niche occupation by common ragweed compared with its companion species. Common garden experiments comparing native populations vs. invasive isolated and invasive core populations have shown that adaptation ability is mainly due to phenotypic plasticity rather than trait differentiations. Quantitative genetic studies suggest a high evolutionary potential for germination traits. Morphological, phenological and physiological traits exhibit lower standard genetic variation and lower heritability and thus a lower evolutionary potential. However, variation in reaction norms suggests a high evolutionary potential for phenotypic plasticity. Herbivory and water stress tolerance are factors that potentially increase the ability to colonize à large range of habitats. Furthermore, phenotypic plasticity and evolutionary potential may also favour an increase or a shift in species ecological niche and hence may favour the distribution range expansionDIJON-BU Doc.électronique (212319901) / SudocSudocFranceF

Genetic diversity in Tetrachaetum elegans, a mitosporic aquatic fungus.

Tetrachaetum elegans Ingold is a saprobic aquatic hyphomycete for which no sexual stage has yet been described. It occurs most commonly during the initial decay of tree leaves in temperate freshwater habitats and typically sporulates under water. Dispersal of the aquatic fungus takes place primarily in the water column and has a large passive component. Differences in substrate composition (e.g. quality of leaf litter) may also play a role in the distribution of different species or genotypes. The population genetic structure of T. elegans was studied using amplified fragment length polymorphism (AFLP) multilocus fingerprints. The populations were isolated from the leaf litter of three different tree genera, sampled in nine streams distributed throughout a mixed deciduous forest. Molecular markers were developed for 97 monosporic isolates using four selective primer pairs. A total of 247 fragments were scored, of which only 32 were polymorphic. Significant stream differentiation was detected for the isolates considered in this study. Analysis of molecular variance revealed that 20% of the genetic variation observed was the result of differences between streams. No correlation between genetic and geographical distances was found but a few multilocus genotypes were observed in different locations. Altogether these results suggest that environmental barriers play a role in the population structure of this aquatic fungus. No clear-cut effect of leaf litter composition on genetic variation could be demonstrated. Finally, tests of linkage disequilibrium between the 32 polymorphic AFLP loci as well as simulations did not provide a final answer regarding clonality in T. elegans. Indeed, it was possible to reject linkage equilibrium at different sampling levels and show that full linkage was unlikely

Biological Flora of the British Isles: Ambrosia artemisiifolia

1. This account presents information on all aspects of the biology of Ambrosia artemisiifolia L. (Common ragweed) that are relevant to understanding its ecology. 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, and history, conservation, impacts and management. 2. Ambrosia artemisiifolia is a monoecious, wind-pollinated, annual herb native to North America whose height varies from 10 cm to 2.5 m, according to environmental conditions. It has erect, branched stems and pinnately lobed leaves. Spike-like racemes of male capitula composed of staminate (male) florets terminate the stems, while cyme-like clusters of pistillate (female) florets are arranged in groups in the axils of main and lateral stem leaves. 3. Seeds require prolonged chilling to break dormancy. Following seedling emergence in spring, the rate of vegetative growth depends on temperature, but development occurs over a wide thermal range. In temperate European climates, male and female flowers are produced from summer to early autumn (July to October). 4. Ambrosia artemisiifolia is sensitive to freezing. Late spring frosts kill seedlings and the first autumn frosts terminate the growing season. It has a preference for dry soils of intermediate to rich nutrient level. 5. Ambrosia artemisiifolia was introduced into Europe with seed imports from North America in the 19th century. Since World War II, it has become widespread in temperate regions of Europe and is now abundant in open, disturbed habitats as a ruderal and agricultural weed. 6. Recently, the North American ragweed leaf beetle (Ophraella communa) has been detected in southern Switzerland and northern Italy. This species appears to have the capacity to substantially reduce growth and seed production of A. artemisiifolia. 7. In heavily infested regions of Europe, A. artemisiifolia causes substantial crop-yield losses and its copious, highly allergenic pollen creates considerable public health problems. There is a consensus among models that climate change will allow its northward and uphill spread in Europe

Vegetation diversity increases species richness of leaf-decaying fungal communities in woodland streams

Submerged leaf litter is a vital resource for many aquatic species in wood- land streams. However, forestry tends to lower the diversity of litter entering streams, which potentially impacts leaf-dependent species and the entire detritus-based food web. To overcome this problem, a guideline for sustainable forestry and ecosystem conservation lies in increasing litter diversity in managed forests. However, the way in and the extent to which such an increase changes the leaf decomposer communities are mostly unknown. In the present study, fungal communities were surveyed bimonthly in ten woodland headwater streams with contrasting tree diversity resulting in various proportions of leaf species in litter. A total of 79 aquatic hyphomycete species identified from conidia in stream water were listed. The differences in conidial abundance, richness and diversity between communities from the ten streams suggested a strong effect of local abundance and composition of leaf litter. Conidial abundance clearly distinguished two sets of streams, one dominated by oaks and hazel and the other by beech. The fungal richness in the ten streams showed a positive and significant correlation with the leaf species richness, accounting for 44 % of the total variance among streams. About 50 % more fungal species were found in streams with the highest leaf litter diversity, and several species were more frequent in such streams. No distinct species assemblages were however associated with any particular leaf species. These findings were interpreted as resulting from substrate preferences, but not specificity by the fungal species. This is supported by a manipulation in which the addition of a bulk of hazel leaves in a stream dominated by beech did not result in an increase in fungal richness over three months. Seasonal changes appeared to be the main factor controlling fungal species abundance. Overall, the results suggest a hierarchical pattern between riparian and aquatic biodiversity and provide an argument for the conservation of diverse tree species along streams

Mise en garde des scientifiques du monde à l'humanité : deuxième avertissement [french translation of Ripple et al., 2017. World Scientists’ Warning to Humanity: A Second Notice. BioScience, 67 (12):1026-1028]

Traduction Française de l'article: Ripple et al., 2017. World Scientists’ Warning to Humanity: A Second Notice. BioScience, 67 (12):1026-1028Cette traduction est publiée sur le site: http://scientistswarning.forestry.oregonstate.edu/En 1992, l'Union of Concerned Scientists a appelé à une meilleure gestion de l'environnement. Vingt-cinq ans plus tard, face à l’urgence de l’état environnemental de la planète, plus de 15 000 scientifiques internationaux engagés dans l’Alliance of Word Scientists émettent un deuxième avertissement à l'humanité. Cette mise en garde scientifique a été publiée sous la forme d’un article exceptionnel dans la revue BioScience (Ripple et al., 2017. World Scientists’ Warning to Humanity: A Second Notice. BioScience, 67 (12):1026-1028). Tous les scientifiques préoccupés par l’évolution du climat et la dégradation de l’environnement de la planète sont désormais invités à lire et à approuver cet article et à s'engager dans l’Alliance of Word Scientists : http://scientistswarning.forestry.oregonstate.edu/ Pour accéder à la version Française de l’article : http://scientistswarning.forestry.oregonstate.edu/sites/sw/files/French_Scientists%20_Warning_Laitung_Fumanal.pd

Diversité des communautés et populations d'hyphomycètes aquatiques de cours d'eau forestiers (influence de la végétation riveraine)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Invasive and native populations of common ragweed exhibit strong tolerance to foliar damage.

8 pagesInternational audienceTolerance and resistance are defence strategies evolved by plants to cope with damage due to herbivores. The introduction of exotic species to a new biogeographical range may alter the plant herbivore interactions and induce selection pressures for new plant defence strategies with a modified resource allocation. To detect evolution in tolerance to herbivory in common ragweed, we compared 3 native (North America) and 3 introduced (France) populations, grown in a common garden environment. We explored the effect of leaf herbivory on plant vegetative and reproductive traits. Plants were defoliated by hand, simulating different degrees of insect grazing by removing 0%, 50% or 90% of each leaf blade. Total and shoot dry biomasses were not affected by increasing defoliation, whereas root dry biomass and root:shoot ratio decreased significantly for native and introduced populations. Furthermore, defoliation treatments did not affect any of the plant reproductive traits measured. Hence, common ragweed displayed an efficient reallocation of resources in shoot biomass at the expense of roots following defoliation, which allows the species to tolerate herbivory without obvious costs for fitness. We did not detect any difference in herbivory tolerance between introduced and native populations, but significant differences were found in reproduction with invasive populations producing more seeds than native populations. As a result, tolerance to herbivory has been maintained in the introduced plant populations. We discuss some implications of these preliminary results for biological control strategies dedicated to common ragweed

Verbascum birjandense and V. urumiense (Scrophulariaceae), two new endemic species for Flora of Iran

International audienceVerbascum birjandense and V. urumiense are described as new endemic species of Verbascum from eastern and northwestern Iran. It was not possible to assign the samples of these two taxa to any of the known Verbascum species in Iran and adjacent regions. Collating the morphological characters of the samples against the specialized and pertinent literature of the genus led us to propose them as new species. Both belong to section Bothrosperma, subsection Fasciculata. These new species are morphologically close to V. erianthum and V. songaricum based on some key characteristics, but show some differences in basal leaves shape, pedicel size, the ratio of pedicel to calyx, presence of hairs inside the corolla, and the hair color of the stamen’s filaments. Distribution map and details of important characters are also presented

Biological flora of the British Isles: Ambrosia artemisiifolia

1. This account presents information on all aspects of the biology of Ambrosia artemisiifolia L. (Common ragweed) that are relevant to understanding its ecology. 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, and history, conservation, impacts and management. 2. Ambrosia artemisiifolia is a monoecious, wind-pollinated, annual herb native to North America whose height varies from 10 cm to 2.5 m, according to environmental conditions. It has erect, branched stems and pinnately lobed leaves. Spike-like racemes of male capitula composed of staminate (male) florets terminate the stems, while cyme-like clusters of pistillate (female) florets are arranged in groups in the axils of main and lateral stem leaves. 3. Seeds require prolonged chilling to break dormancy. Following seedling emergence in spring, the rate of vegetative growth depends on temperature, but development occurs over a wide thermal range. In temperate European climates, male and female flowers are produced from summer to early autumn (July to October). 4. Ambrosia artemisiifolia is sensitive to freezing. Late spring frosts kill seedlings and the first autumn frosts terminate the growing season. It has a preference for dry soils of intermediate to rich nutrient level. 5. Ambrosia artemisiifolia was introduced into Europe with seed imports from North America in the 19th century. Since World War II, it has become widespread in temperate regions of Europe and is now abundant in open, disturbed habitats as a ruderal and agricultural weed. 6. Recently, the North American ragweed leaf beetle (Ophraella communa) has been detected in southern Switzerland and northern Italy. This species appears to have the capacity to substantially reduce growth and seed production of A. artemisiifolia. 7. In heavily infested regions of Europe, A. artemisiifolia causes substantial crop-yield losses and its copious, highly allergenic pollen creates considerable public health problems. There is a consensus among models that climate change will allow its northward and uphill spread in Europe