Search results for "NVA"
showing 10 items of 3653 documents
Occurrence of Two-Year Cyclicity, “Saw-Blade Fluctuation”, in Vendace Populations in Finland
2021
The tendency towards two-year cyclicity is considered typical of many Fennoscandian vendace populations, especially in fluctuation of recruitment, based on time series of individual lakes. We used two robust indicators to identify and quantify two-year cycles in vendace population proxy time series at different life-stages — spawning stock biomass (SB), density of newly hatched larvae (LD) and recruitment (REC) — from 22 Finnish lakes. Then we applied Fisher’s meta-analytical test to assess the adequacy of the evidence to support the hypothesis that vendace population dynam-ics include two-year cyclicity. The results supported this hypothesis for RECbut not for SB or LD. Yet, the indicators…
Lack of molluscan host diversity and the transmission of an emerging parasitic disease in Bolivia.
2001
Fasciolosis is a re-emerging parasitic disease that affects an increasing number of people in developing countries. The most severe endemic affects the Bolivian Altiplano, where the liver fluke (Fasciola hepatica) and its hermaphroditic snail host, Lymnaea truncatula, have been introduced from Europe. To achieve a better understanding of the epidemiological situation and the consequences of the colonization event of this invasive species, genetic analysis of Bolivian snail populations was needed. Here we compare the genetic diversity and population structure of snail samples from the Bolivian Altiplano with samples from the Old World at six polymorphic microsatellite loci. Whereas some vari…
EUNIS Habitat Classification: Expert system, characteristic species combinations and distribution maps of European habitats
2020
Aim The EUNIS Habitat Classification is a widely used reference framework for European habitat types (habitats), but it lacks formal definitions of individual habitats that would enable their unequivocal identification. Our goal was to develop a tool for assigning vegetation-plot records to the habitats of the EUNIS system, use it to classify a European vegetation-plot database, and compile statistically-derived characteristic species combinations and distribution maps for these habitats. Location Europe. Methods We developed the classification expert system EUNIS-ESy, which contains definitions of individual EUNIS habitats based on their species composition and geographic location. Each ha…
Assessing escapes from short rotation plantations of the invasive tree species Robinia pseudoacacia L. in Mediterranean ecosystems: a study in centra…
2016
Abstract: Black locust (Robinia pseudoacacia L.) is a fast growing tree species native to temperate North America, and widely diffused and naturalized in Europe. It is one of the candidate species for establishing bioenergy plantations on marginal lands in temperate and sub-Mediterranean regions. This potential is in contrast to its well-known invasive habit, leading to a potential damage to plant biodiversity in many European countries. Advise against black locust plantation in regions where it is already invasive has been issued by several international reports, as well as the adoption of mitigation measures (e.g., “containment” buffer zones) to prevent the spread of the species into natu…
Standardization proposal for the mapping of Caulerpa taxifolia expansion in the Mediterranean sea
1999
Fourteen years after the first observation of Caulerpa taxifolia (Valh) C. Agardh in the northwestern Mediterranean Sea, this green alga of tropical origin is now present in five countries (Spain, France, Monaco, Italy and Croatia). By the end of 1997, more than 46 km(2), at depths of between 0 and 50 m, were found to be affected by this expansion. A standardization of the cartographic procedure is proposed here. Such a standardization is necessary to compare maps produced by various organizations from different countries. For a given independent station, it is based on the definition of three levels of colonization:Level I refers to a station where one or several colonies less than 100 m a…
Multiple paths to cold tolerance: the role of environmental cues, morphological traits and the circadian clock gene vrille
2021
AbstractBackgroundTracing the association between insect cold tolerance and latitudinally and locally varying environmental conditions, as well as key morphological traits and molecular mechanisms, is essential for understanding the processes involved in adaptation. We explored these issues in two closely-related species, Drosophila montana and Drosophila flavomontana, originating from diverse climatic locations across several latitudes on the coastal and mountainous regions of North America. We also investigated the association between sequence variation in one of the key circadian clock genes, vrille, and cold tolerance in both species. Finally, we studied the impact of vrille on fly cold…
Invasive bees and their impact on agriculture
2020
Fil: Aizen, Marcelo A. Universidad Nacional del Comahue. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Fil: Aizen, Marcelo A. Consejo Nacional de Investigaciones Científicas y Técnica. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Fil: Arbetman, Marina P. Universidad Nacional del Comahue. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Fil: Arbetman, Marina P. Consejo Nacional de Investigaciones Científicas y Técnica. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Fil: Chacoff, Natacha P. Universidad Nacional de Tucumán. Instituto de Ecología Regional; Argentina. Fil: Chalcoff, Vanin…
Can the large ecological amplitude of Ambrosia artemisiifolia explain its invasive success in France?
2008
International audience; In order to understand the successful spread of Ambrosia artemisiifolia in France, the variability of colonised habitat by this species was studied at 48 locations, from its central to peripheral area of distribution. Each site was characterised by a vegetation survey, a description of the A. artemisiifolia population and a soil analysis. Differences in the number of species, Shannon diversity index, evenness index and plant life form spectra were compared among the sites. A total of 276 species occurring along with A. artemisiifolia was observed. Therophytes and hemicryptophytes represented more than 80% of all the species. The two most frequent species occurring al…
Native and invasive hosts play different roles in host–parasite networks
2020
Parasites are often key players in biological invasions since they can mediate the impact of host invasions or can themselves become invasive species. However, the nature and extent of parasite‐mediated invasions are often difficult to delineate. Here, we used individual‐based, weighted bipartite networks to study the roles (degrees of interactions of individuals in a modular network according to their within‐ and among‐module connections) played by native and invasive host individuals to their parasite communities. We studied two phylogenetically and ecologically close fish species, Mugil cephalus s.l. and Planiliza haematocheilus (Teleostei: Mugilidae). Planiliza haematocheilus is native …
Functional and energetic consequences of climate change on a predatory whelk
2017
Abstract The increasing rise in sea surface temperature caused by human activities currently represents the major threat to biodiversity and natural food webs. In this study we used the Lessepsian mussel Brachidontes pharaonis, one of the most recent invaders of the Mediterranean Sea, as a model to investigate the effect of a novel prey and a chronic increase in temperatures on functional parameters of local consumers, compared to the native mytilid species Mytilaster minimus. In particular we focused on the whelk Stramonita haemastoma, a widespread Mediterranean intertidal predator that actively preys on bivalves, barnacles and limpets, by studying the direct effects of such multiple stres…