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Effects of elevated CO2 and P availability on plant growth of the legume Lotus corniculatus and consequences for the butterfly larvae of Polyommatus icarus feeding on L. corniculatus were investigated in screen-aided CO2 control chambers under natural conditions on a calcareous grassland in the Swiss Jura mountains. Elevated CO2 conditions and P fertilisation increased the biomass production of L...
This study examines the dispersal system of Guapira opposita in a tropical sandy rainforest in southeast Brazil. Guapira trees produce small fruits with a high protein content (28.4%) and low lipid content (0.3%), and the plant is primarily dispersed by birds. Mature fruits of G. opposita can fall spontaneously with the pulp intact, or be dropped by birds with bits of pulp attached. In either case,...
The effect of experimental manipulation of population density on home-range size was investigated in two free-ranging roe deer (Capreolus capreolus) populations under contrasting environmental conditions. In these two long-term monitoring studies, one in Bogesund, Sweden (12years) and one in Dourdan, France (10years), deer density varied fourfold through varying culling pressure. Home-range data were...
Although biological invasion by alien species is a major contributor to loss of indigenous biological diversity, few studies have examined the susceptibility of the boreal biome to invasion. Based on studies of other ecosystems, we hypothesized that alien plants will be restricted to disturbed areas near human activity and will not be found in natural areas of boreal ecosystems in Gros Morne National...
It has been hypothesised that climate change may affect vegetation by changing the outcome of competitive interactions. We use a space-for-time approach to evaluate this hypothesis in the context of alpine time-of-snowmelt gradients. Principal response curves, a multivariate repeated-measurement analysis technique, are used to analyse for compositional differences in local ridge-to-snowbed gradients...
Information on intra-specific variation in pollinator-attracting floral traits provides clues to selective pressures imposed by pollinators. However, these traits also reflect constraints related to floral phenology or morphology. The specific weevil pollinator Derelomus chamaeropsis of the dioecious Mediterranean dwarf palm Chamaerops humilis is attracted by volatile compounds that leaves, and not...
The positive relationship between local abundance and distribution of species is a widely recognized pattern in community ecology. However, it has been suggested that this relationship can simply be an artefact of sampling because locally rare species are less detectable then locally abundant ones, and hence their distribution can easily be underestimated. Here, we use count data to investigate the...
Variability in the size distributions of populations is usually studied in monocultures or in mixed plantings of two species. Variability of size distributions of populations in more complex communities has been neglected. The effects of seeding density (35 or 350seeds/species/m2) and presence of small vertebrates on the variability of size distributions were studied for a total of 1,920 individuals...
The effects of predators on the density of their prey can have positive indirect effects on the abundance of the preys resource via a trophic cascade. This concept has strongly influenced contemporary views of how communities are structured. However, predators also can transmit indirect effects by inducing changes in prey traits. We show that the mere presence of predator risk cues can initiate a...
Dispersal-assembly theories of species coexistence posit that environmental factors play no role in explaining community diversity and structure. Dispersal-assembly theories shed light on some aspects of community structure such as species-area and species-abundance relationships. However, species environmental associations also affect these measures of community structure. Measurements of species...
Life-history components may be food-limited. We supplemented food to 18 Ural owl, Strix uralensis, nests during the nestling period. Food supplementation led to a higher somatic condition in the female parent, but effects in males were moderate. Parents delivered less food to fed nests than to control nests. Offspring survival and fledging condition did not differ between control and fed nests. In...
Phenological synchrony of a consumer population with its resource populations is expected to affect interaction intensity. We quantified phenological variation and synchrony of populations of an invasive Eurasian flower head weevil, Rhinocyllus conicus, that consumes florets, ovules, and seeds of developing flower heads of a native North American thistle, Cirsium canescens, in Sand Hills prairie in...
We investigated leaf physiological traits of dominant canopy trees in four lowland Panamanian forests with contrasting mean annual precipitation (1,800, 2,300, 3,100 and 3,500mm). There was near complete turn-over of dominant canopy tree species among sites, resulting in greater dominance of evergreen species with long-lived leaves as precipitation increased. Mean structural and physiological traits...
Population size and structure, as well as individual growth rates, condition, and reproductive output, respond to environmental factors, particularly in short-lived and fast-growing squid species. We need to understand the mechanisms through which populations respond to environmental conditions, to predict when or if established relationships, used as management tools to forecast recruitment strength,...
Habitat structure is often assumed to be a predictor of habitat function. However, habitat structure may be insufficient to predict the functional significance of a habitat if the level of resources in the habitat is a consequence of the interaction between the habitat structure and physical or biological factors. In this study, we investigated whether depressions in tidal flat sediments generated...
We tested whether interspecific competition from Aedes albopictus had measurable effects on A. aegypti at the typical numbers of larval mosquitoes found in cemetery vases in south Florida. We also tested whether the effect of interspecific competition from A. albopictus on A. aegypti differed between sites where A. aegypti either persists or went extinct following invasion by A. albopictus. Similar...
We evaluated the effects of nutrient addition on interactions between the benthic microalgal community and a dominant herbivorous gastropod, Cerithidea californica (California horn snail), on tidal flats in Mugu Lagoon, southern California, USA. We crossed snail and nutrient (N and P) addition treatments in enclosures on two tidal flats varying from 71 to 92% sand content in a temporally replicated...
The influence of biotic interactions in structuring macroinfaunal communities of exposed sandy beaches, an unstable habitat characterized by strong physical forces, is generally considered negligible. We investigated the hypothesis that competitive interactions during burrowing could potentially affect the intertidal distribution and abundance of macroinfaunal animals of sandy beaches using two species...
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