Search results for "CLASSIFICATION"
showing 10 items of 29475 documents
Competition for breeding sites and site-dependent population regulation in a highly colonial seabird, the common guillemot Uria aalge
2004
Summary 1. The hypothesis of site-dependent population regulation predicts that birds utilize available nesting sites in a pre-emptive (ideal despotic) manner, leading to density dependence in heterogeneous habitats as poorer sites are used at higher population densities. At small population sizes adaptive site choice protects populations against fluctuations (the buffer effect). 2. Common guillemots Uria aalge (Pontoppidan) breed at high density on sea-cliffs. The population breeding on the Isle of May, Scotland increased by 60% between 1981 and 2000. A good nest-site is a prerequisite for successful breeding and there is much competition for the best sites. Throughout this period, site us…
WHO BEARS THE COSTS OF INTERSPECIFIC COMPETITION IN AN AGE-STRUCTURED POPULATION?
2003
Social and density-dependent life history processes may differ according to age and the reproductive history of individuals. Arvicoline rodents have a typical, season-dependent, bimodal, age distribution of breeding individuals within a population. This distribution may influence population fluctuations. In this study, we measured effects of interspecific competition from field voles (Microtus agrestis) on various fitness components of female bank voles (Clethrionomys glareolus) in an age-structured breeding population in large (0.25 ha) outdoor enclosures. We monitored survival, reproduction, and space use of experimental bank vole populations with females from two different age groups. Wi…
RAPD differentiation between Borderea pyrenaica and B. chouardii (Dioscoreaceae), two relict endangered taxa
2001
As currently circumscribed, the genus Borderea Mieg. comprises two narrowly distributed European taxa, Borderea pyrenaica (Bub.) Mieg. and B. chouardii (Gaussen) Heslot. An accumulation of facts such as that both species share a very close overall morphology, that only a single population of Borderea chouardii is known, and that they live in contrasting environments has led some authors to suggest that B. chouardii is a mere ecotype of the more widespread B. pyrenaica. We tested this hypothesis using RAPD markers in four populations of Borderea, three of them identified as B. pyrenaica and the other one representing the only known population of B. chouardii. Eleven out of twenty assayed pri…
Population Dynamic of Algae and Bacteria in an Oxidation Channel
2003
A study on algae and bacteria population changes, as a function of time, was carried out in a pilot scale oxidation channel bioreactor using a carrousel system. Total Coliforms, Pseudomonas aeruginosa, and Streptococcus faecalis, the most common bacteria found in sewage, Scenedesmus obliquus and Chlorella vulgaris were the microalgae considered in this work. Physicochemical parameters such as COD, BOD, Chlorophyll a, nitrogen, and phosphorous compounds were studied and determined during the experiments. It was demonstrated that the level of wastewater contamination could be predicted based on the bacterial and algae composition. The relationships between the algae and bacteria population, a…
Biomarker responses by crucian carp () living in a pond of secondary treated pulp mill effluent
1999
Biochemical and histological biomarkers by the adult crucian carp ( Carassius carassius (L.)) living in a biologically treated pulp mill effluent were studied. Enocell pulp mill in Uimaharju, Finland, discharges its effluents through a waste water pond to the River Pielisjoki. This pond harbours an introduced crucian carp population that apparently reproduces on site. The objective of the present study was to measure possible hormonal effects of treated pulp mill effluent on crucian carps living in a wastewater pond. Adult fish were collected for analysis by traps. A reference population was sampled from a small natural pond. Blood and bile samples were taken for analyses of hemoglobin, hem…
Population dynamics using temporal series analysis in a industrial two-stage activated sludge pilot plant
1998
A time series analysis using an autocorrelation function (ACF) was used to assess the relative importance of density (DD) and non density-dependent - (NDD) factors on microfauna abundance of a two-stage activated sludge pilot plant treating industrial effluents. Although some previous work has detected a carrying capacity for the total microfauna abundance in both reactors, ACF showed a general pattern of non-density dependent abundance regulation. Stationarity due to density-dependent factors was observed for the two major species in the first reactor, the sessile Opercularia asymmetrica and the crawling Chilodonatella minuta. There was no evidence of bacterial competition and only weak ev…
A Study of the Health of Seafaring Workers of Valencia, Spain
1997
Under the auspices of the Service of Maritime Health of the Marine Social Institute of Valencia, Spain, the health status of seafaring workers from Valencia was evaluated. An epidemiologic study was carried out based on 707 pre-embarkation health examinations, collecting information about the health problems of these workers and their associated risk factors. The data were analyzed to estimate population frequencies and the corresponding 95% confidence intervals. Significance among groups was calculated by the chi-square test (p0.05). Relative risks were calculated in comparisons of the seafaring workers with the general population of Valencia. High incidences of ophthalmologic disorders we…
The role of local adaptation in the relationship between an endangered root hemiparasite Euphrasia rostkoviana, and its host, Agrostis capillaris
1999
We experimentally studied the role of local adaptation and the co-evolutionary relationship between an annual, endangered root hemiparasite Euphrasia rostkoviana and its main host Agrostis capillaris. According to our hypothesis, the existence of local adaptation in hemiparasites should be observable in better hemiparasite performance when attached to A. capillaris hosts originating from Euphrasia populations. After one month of growth, the height and the number of leaves of hemiparasites were not affected by the origin of their hosts. The differences in growth were due to between population effects. The situation remained constant after three months. Hemiparasite biomass was not affected b…
Susceptibility to Cry proteins of a SpanishOstrinia nubilalisglasshouse population repeatedly sprayed withBacillus thuringiensisformulations
2013
Ostrinia nubilalis Hubner (Lepidoptera: Crambidae), a major pest of corn in temperate climates, can feed on other crops due to its polyphagous behaviour. In particular, this species became a serious problem in some sweet pepper commercial glasshouses in south-eastern Spain repeatedly sprayed with Bacillus thuringiensis (Bt) products to control Spodoptera exigua Hubner (Lepidoptera: Noctuidae). The susceptibility of an O. nubilalis colony established from individuals collected in these Bt-sprayed glasshouses was compared with a reference laboratory colony. Differences in susceptibility between the two colonies to Cry1Aa, Cry1Ab, Cry1Ac and Cry2Aa proteins were found. However, our results ind…
Using probability of extinction to evaluate the ecological significance of toxicant effects
2000
A large component of uncertainty in ecological risk assessment (ERA) arises from the disparity between the time scale of toxicity measurements and the time scale of predictions of ERA models. It is difficult to make predictions about the persistence of populations from data from short-term toxicity tests. Reproductive toxicity tests provide data about how population growth rate (r) is reduced with toxicant exposure. Although reduction in r is believed to be one of the most important effects of toxicant exposure, its ecological significance has been difficult to quantify. For rotifers, r is typically reduced by 10 to 15% at no-observed-effect concentrations (NOEC). We investigated r reductio…