Search results for "ECOSYSTEM"
showing 10 items of 1752 documents
Möglichkeiten und Grenzen einer Ökosystem-Rekonstruktion am Beispiel des spätpaläozoischen lakustrinen Paläo-Ökosystems. 1. Theoretische und methodis…
1998
In analogy to ecosystems, palaeoecosystems are defined here as the palaeocommunities of a given area and their relationships to the abiotic variables of their respective environments. They are characterized by (a) their species diversity, (b) the trophic structure of their palaeocommunities, based on their food webs, and (c), based on their detailed historical development, ecosystem functions such as stability, resilience, and succession. Due to numerous taphonomic biases, palaeocommunities can only be reconstructed from very few fossil horizons (taphocoenoses). Important conditions for such reconstructions are an uninterrupted vertical sequence of taphocoenoses with little time-averaging, …
Environmental drivers of breeding sites in blackfly species of medical and veterinary importance in eastern Spain
2021
Geographical distribution and abundance of the pupae of six blackfly species of medical and veterinary concern were studied in eastern Spain according to three different sets of explanatory variables including in-stream variables, both (i) abiotic (i.e., physicochemical) and (ii) biotic (i.e., richness and abundance of either taxonomically or ecologically close related taxa), as well as (iii) meteorological and landscape variables. The results showed specific habitat requirements for pupation in Simulium (Boophthora) erythrocephalum (De Geer, 1776) and Simulium (Wilhelmia) equinum (Linnaeus, 1758), two of the six species studied regarding elevation and temperature. While the rest of the spe…
Genetic variation in growth and development time under two selection regimes in Leptinotarsa decemlineata
2008
It is possible to predict the potential range of a species on the basis of its ecological characteristics and those of the invaded ecosystem. The existence of genetic variation indicates a species' potential to respond to new environmental conditions, thus facilitating its success as an invader. Accordingly, evolutionary and ecological approaches are needed to identify the factors explaining both species' range and their potential to invade new areas. We combined these two approaches and studied whether genetic variation in life-history traits under abiotic (temperature) and biotic (host plant) selection pressures contributes to the potential range expansion of Leptinotarsa decemlineata Say…
Biodiversity, evolution and adaptation of fungi in exstreme environments
2013
Fungi play irreplaceable roles for ecosystem functioning. They may adopt different life styles, for example saprotrophs, symbionts or parasites: some species are cosmopolitan with a wide distribution and others, thanks to they ecological plasticity, may adapt to harsh environments precluded to most of life forms. In stressing conditions, their role is even more crucial for the recycling of organic matter or favouring nutrients uptake. When the conditions become really extreme and competion is low, fungi focus on extremotollerance and evolve peculiar competences to exploit natural or xenobiotic resources in the particular constraints imposed by the environment. This paper focuses on three di…
Host-based divergence in populations of the pea aphid: insights from nuclear markers and the prevalence of facultative symbionts.
2003
In North America, the pea aphid Acyrthosiphon pisum encompasses ecologically and genetically distinct host races that offer an ideal biological system for studies on sympatric speciation. In addition to its obligate symbiont Buchnera, pea aphids harbour several facultative and phylogenetically distant symbionts. We explored the relationships between host races of A. pisum and their symbiotic microbiota to gain insights into the historical process of ecological specialization and symbiotic acquisition in this aphid. We used allozyme and microsatellite markers to analyse the extent of genetic differentiation between populations of A. pisum on pea, alfalfa and clover in France. In parallel, we…
Does predation maintain eyespot plasticity in Bicyclus anynana?
2004
The butterfly Bicyclus anynana exhibits phenotypic plasticity involving the wet-season phenotype, which possesses marginal eyespots on the ventral surface of the wings, and the dry-season form, which lacks these eyespots. We examined the adaptive value of phenotypic plasticity of B. anynana in relation to the defence mechanisms of crypsis and deflection. We assessed the visibility differences between spotless and spotted butterflies against backgrounds of brown (dry season) or green (wet season) leaves. Spotless butterflies were highly cryptic and less predated by adult bird predators than were spotted ones when presented against brown leaf litter. However, the advantage of crypsis disappea…
Updated measurements in vineyards improves accuracy of soil erosion rates
2018
All rights reserved. Vineyards have proven to be one of the most degraded agricultural ecosystems due to very high erosion rates, which are typically measured at fine temporal and spatial scales. Long-term soil erosion measures are rare, but this information may be indispensable for a proper understanding of the vineyard soil system, landscape evolution, and crop production. The stock unearthing method (SUM) is a common topographical measurement technique developed to assess long-term erosion rates. The reliance of the SUM has been questioned and should be replaced by an improved measurement technique. In this paper, we demonstrate the added value (improved accurate, low cost, and faster th…
Combined effect of crop rotation and carabid beetles on weed dynamics in arable fields
2020
AbstractWeed management is a resource-intensive practice in arable agriculture, with direct and long-term impacts on both productivity and biodiversity (e.g. plant, pollinators and farmland wildlife). In conventional systems, weed control relies on crop management and herbicide inputs, but for more sustainable production systems, use of herbicides needs to be reduced. This requires a good understanding of the processes that regulate arable weed dynamics in arable fields.We adopted a systems framework to understand and model interacting components that drive the weed dynamics in 168 arable fields. Within this framework, we built a structural equation model (SEM) to quantify the direct and in…
Do properties and species of weed seeds affect their consumption by carabid beetles?
2019
International audience; Seed predators are an integral part of agroecosystems, where they can reduce the populations of weeds. The preference of predators for seeds and the observed predation rate may be affected by the properties of seeds (e.g. taxonomy, chemical composition, physical defence). In this work, we focused on seed consumption of Taraxacum officinale Web. and Stellaria media (L.) Vill., from France and the Czech Republic, by three species of ground beetle that are seed predators (Coleoptera: Carabidae): Poecilus cupreus (L.), Pterostichus melanarius (Illiger) and Anchomenus dorsalis (Pontoppidan). The seed species were offered in arenas, simultaneously, under three different ex…
Detecting crop water requirement indicators in irrigated agroecosystems from soil water content profiles: An application for a citrus orchard.
2022
Abstract Most perennial crops sensitive to water scarcity, such as citrus, can benefit from efficient water management, which allows for reduced water consumption while increasing crop production on a long-term basis. However, when implementing water-saving strategies, it is necessary to monitor soil and/or plant water status in order to determine crop water demand. A plethora of devices providing indirect measurements of volumetric soil water content, such as the “drill and drop” multi-sensors probes (Sentek, Inc., Stepney, Australia), have been developed over the last decade. The objective of the paper was to analyse time-series of soil water content profiles and meteorological data colle…