Search results for "Colon"
showing 10 items of 2038 documents
A niche perspective on the range expansion of symbionts.
2020
Range expansion results from complex eco-evolutionary processes where range dynamics and niche shifts interact in a novel physical space and/or environment, with scale playing a major role. Obligate symbionts (i.e. organisms permanently living on hosts) differ from free-living organisms in that they depend on strong biotic interactions with their hosts which alter their niche and spatial dynamics. A symbiotic lifestyle modifies organism–environment relationships across levels of organisation, from individuals to geographical ranges. These changes influence how symbionts experience colonisation and, by extension, range expansion. Here, we investigate the potential implications of a symbiotic…
Habitat- and density-dependent demography of a colonial raptor in Mediterranean agro-ecosystems
2016
Agricultural intensification is considered the major cause of decline in farmland bird populations, especially in the Mediterranean region. Food shortage increased by the interaction between agricultural intensification and density-dependent mechanisms could influence the population dynamics of colonial birds.Weused demographic data on lesser kestrels (Falco naumanni), a key species of Mediterranean pseudo-steppes, to understand the importance of land-use changes and density-dependent mechanisms in the light of its fluctuating conservation status in the Western Palearctic. Our analysis indicated an important influence of land uses (artichokes, arable and grassland fields) and colony size on…
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…
Emigration speed and the production of sexuals in colonies of the ant Temnothorax crassispinus under high and low levels of disturbance
2015
A nest relocation is costly for social insects, and involves hazards. Emigrations were studied in Temnothorax crassispinus ant colonies, which inhabit ephemeral nest sites, and which frequently change their nests. In a laboratory experiment, ant colonies from one group were forced to change their nest sites 10 times over a ca. 3-month period, whilst colonies from the second group were forced to adopt this practice twice (on the beginning of May, and in the second half of July). Colonies of the ant from both the groups reduced their total emigration duration. However, the duration of the transport phase remained unchanged. In the case of colonies with higher level of disturbance, there was n…
Mitochondrial phylogeography of the edible dormouse (Glis glis) in the western Palearctic region
2010
International audience; This study describes in detail the phylogeoraphic pattern Of the edible dormouse (Glis glis) a European rodent With pronounced hibernating behavior We Used sequences of 831 base pairs of the mitochondrial DNA cytochrome-b gene from 130 edible dormice collected at 43 localities (throughout Its distribution. Our results reveal presence of 3 main haplogroups: Sicilian, South Italian (restricted to the Calabrian region) (a widespread lineage corresponding to all remaining western, central. and eastern European populations). Examination of paleontological data confirms refugial regions for G,Its in the 3 Mediterranean peninsulas, although overall low genetic diversity is …
Colonisation of newly established habitats by soil decomposer organisms: the effect of habitat corridors in relation to colonisation distance and hab…
2005
Abstract The aim of the present 2.5-year-long field experiment was to explore the ability of various members of the detrital food web to colonise newly established habitat patches in field conditions, either in the presence or absence of habitat corridors. Patch size and distance to the “mainland” (colonisation source) were manipulated to explore the scale dependency of the corridor effects. Sterilised humus patches, embedded in mineral soil regarded as uninhabitable (or non-preferred) matrix for the soil organisms, functioned as newly established habitats. Intact forest soil served as the source of colonisers. Three kinds of patches were established: large ones situated at relatively long …
Temperature differences associated with colour do not determine where the acorn ant Temnothorax crassispinus (Hymenoptera: Formicidae) chooses to nest
2021
Temperature is an important factor for invertebrates. Social insects build nests, which along with their ability to thermoregulate, provide shelter from extreme temperatures. However, for many species of ants the most common method of controlling the temperature inside a nest is to choose a suitable nest site. During a fi eld experiment, the choice of nest site by the acorn ant Temnothorax crassispinus, a species which lives in coniferous and mixed forests, was studied. It typically occupies ephemeral nest sites and can move to a new nest site several times in one season. It was predicted that in early spring, dark coloured nest sites would be warmer and thus more frequently occupied by ant…
Application of a new protocol to evaluate the benthic impacts of aquaculture: Colonization of experimental units for monitoring by polychaeta
2019
A range of different protocols and indices have been developed in recent years for the definition of Environmental Quality Standards in aquaculture. However, it can be difficult to compare these protocols or indices between different regions or different habitats due to spatial heterogeneity at different scales. We carried out a field study to estimate the effectiveness of experimental units (sediment-filled trays) as an environmental management tool. The experimental units were filled with two different sediments - sand and mud - and placed underneath two fish farm facilities for one month. Using polychaetes to assess the ecological status, AMBI and multidimensional analysis showed clear r…
Symmetry breaking in mass-recruiting ants: extent of foraging biases depends on resource quality.
2016
Abstract The communication involved in the foraging behaviour of social insects is integral to their success. Many ant species use trail pheromones to make decisions about where to forage. The strong positive feedback caused by the trail pheromone is thought to create a decision between two or more options. When the two options are of identical quality, this is known as symmetry breaking, and is important because it helps colonies to monopolise food sources in a competitive environment. Symmetry breaking is thought to increase with the quantity of pheromone deposited by ants, but empirical studies exploring the factors affecting symmetry breaking are limited. Here, we tested if (i) greater …
Colonization of adventitious roots ofMedicago truncatulabyPseudomonas fluorescensC7R12 as affected by arbuscular mycorrhiza
2008
Pseudomonas fluorescens C7R12 was previously shown to promote colonization of Medicago truncatula roots by Glomus mosseae BEG12. To gain more insight into the interaction between C7R12 and BEG12, the cell organization of C7R12 was characterized on adventitious roots mycorrhized or not with BEG12 and on extraradical hyphae. Bacterial cell observations were made using the immuno-fluorescence technique and confocal laser scanning microscopy. Five types of cell organization, so-called organization types (OT), were identified: small or large single cells, cells by pair and cells in microcolonies or in strings. The frequencies of each OT on the roots were expressed as the percentage of observatio…