Search results for " Predation"
showing 10 items of 56 documents
A stochastic model of seed dispersal pattern to assess seed predation by ants in annual dry grasslands
2005
A combined field experiment and modelling approach has been used to provide evidence that ants may be responsible for an observed lower patchiness and higher plant diversity in the neighbourhood of ant nests, within Mediterranean dry grasslands belonging to the phytosociological class Tuberarietea guttatae. The hypothesis was that seeds occurring in clumps may have an higher probability to be harvested than seeds having a scattered distribution. In order to test this hypothesis, four analysis steps have been performed. First, the seed productivity and dispersal pattern was recorded for four plant species found, either more abundant beside the ant nests (Tuberaria guttata, Euphorbia exigua) …
Importance of water-level fluctuation on population dynamics of cladocerans in a hypertrophic reservoir (Lake Arancio, south-west Sicily, Italy)
1997
During a period of three years (1990-1991 and 1993), we studied the population dynamics of planktonic cladocerans in a hypertrophic reservoir. Weekly sampling revealed that the five most common species followed a trend which reflects the peculiar hydrological characteristics of the reservoir and their key position in the pelagic food web. In particular, 1991 was characterized by a strong water inflow which probably interfered with the reproductive activities of the dominant fish population (Rutilus rubilio) and reduced the concentration of inedible planktonic algae allowing the development of small Chlorococcales. This event was associated with higher population densities of Daphnia hyalina…
Limited behavioural effects of ocean acidification on a Mediterranean anemone goby (Gobius incognitus) chronically exposed to elevated CO2 levels
2022
An in situ reciprocal transplant experiment was carried around a volcanic CO2 vent to evaluate the anti-predator responses of an anemone goby species exposed to ambient (∼380 μatm) and high (∼850 μatm) CO2 sites. Overall, the anemone gobies displayed largely unaffected behaviors under high-CO2 conditions suggesting an adaptive potential of Gobius incognitus to ocean acidification (OA) conditions. This is also supported by its 3-fold higher density recorded in the field under high CO2. However, while fish exposed to ambient conditions showed an expected reduction in the swimming activity in the proximity of the predator between the pre- and post-exposure period, no such changes were detected…
A Case of Predation of a Eurasian Eagle-Owl by a Bonelli's Eagle
2016
Although some of these hypotheses are not mutually exclusive, in light of our field observations and experience with both species in the study area, we would favor the first hypothesis as food availability is low in our study area (P. López-López, C. García-Ripollés, J. Giménez, and V. Urios unpubl. data). The second and third hypotheses could also account for this behavior, especially considering previous events of nestling Bonelli's Eagles being killed by eagle-owls (Real and Manosa 1990). Notwithstanding, if the''predatorremoval hypothesis'' were true, the frequency of lethal interactions among both species would be probably much higher and thus previously reported in the literature. Unf…
Macroalgal assemblage type affects predation pressure on sea urchins by altering adhesion strength.
2010
In the Mediterranean, sea breams are the most effective Paracentrotus lividus and Arbacia lixula predators. Generally, seabreams dislodge adult urchins from the rocky substrate, turn them upside down and crush their tests. Sea urchins may respond to fish attacks clinging tenaciously to the substratum. This study is the first attempt to investigate sea urchin adhesion strength in two alternative algal assemblages of the rocky infralittoral and valuated its possible implication for fish predation. We hypothesized that (1) sea urchin adhesion strength is higher in rocky shores dominated by encrusting macro-algae (ECA) than in erected macro algae (EMA); (2) predation rates upon sea urchins are …
Indirect effects of invasive crayfish on native fish parasites
2013
Interactions between invasive and native species are often modified by parasites. One little-studied scenario is that invasive species affect parasite transmission to native hosts by altering the relative abundance of hosts needed in parasite life cycles, for example by predation on these hosts. Here we show that presence of an invasive crayfish species, Pacifastacus leniusculus, decreases the mean abundance of native parasites transmitted from snails and aquatic isopods to perch, Perca fluviatilis, in two large boreal lakes in Finland. In contrast, parasites transmitted to the fish from planktonic copepods or mussels, hosts not readily preyed on by crayfish, were not affected by crayfish p…
John Bates Clark on trusts: New light from the Columbia archives
2005
Public concern over the so called “trust problem” in the United States between the end of the nineteenth century and 1914, the year of the passage of the Clayton and Federal Trade Commission (FTC) Acts, was reflected in the considerable contemporary literature on the subject. Not surprisingly, professional economists actively participated in this debate. Their thinking directly and indirectly influenced the legislation of 1914 in a way that cannot be said of the Sherman Act of 1890 (Mayhew 1998). A survey of the most important of these professional writings shows that, among the several voices animating the discussion, John Bates Clark's was perhaps the most influential. In this connection,…
The role of biotic interactions in a prey-predator system : the case of predation and regulation of weed seeds by carabids.
2020
For the transition towards agricultural production systems that are less dependent on herbicides, the use of weed regulation by seed-eating carabids is of great interest. Weed seed predation by carabids is variable and occurs within a complex context of many biotic interactions. This complexity partly explains our current inability to predict levels of in-field weed regulation. In this thesis, I analysed variations in the levels of predation and biological regulation of weeds and determined how they respond to two classes of biotic interactions: 1) the availability of alternative prey; and, 2) intra- and inter-specific interactions between the carabids themselves. Field measurements carried…
Does Forest Fragmentation and Selective Logging Affect Seed Predators and Seed Predation Rates of Prunus africana (Rosaceae)?
2007
Forest fragmentation and selective logging can influence the life cycle of tropical tree species at several levels, e.g., by lowering pollination, by limiting seed dispersal, and by increasing seed predation. Understanding human-induced modifications in ecosystem processes such as seed predation is essential for conservation management of threatened species. We studied the impact of forest fragmentation and selective logging on seed predation of the endangered tree Prunus africana in the tropical rain forest of Kakamega, Kenya. We quantified the activity of seed predators in the main forest, forest fragments, and in sites of different logging intensity in the dry and rainy seasons of 2003 a…
Predation of two Mediterranean phytoseiid species (Parasitiformes, Phytoseiidae) upon eggs of tetranychid mites (Acariformes, Tetranychidae)
2012
Laboratory trials were carried out to verify the predatory capacity of two generic phytoseiid predators upon eggs of the two most important tetranychids damaging Citrus orchards in Sicily: Tetranychus urticae and Panonychus citri. Both Typhlodromus laurentii and Typhlodromus rhenanoides are autochthonous and common species on spontaneous and cultivated plants. The research aimed at investigating the predatory behaviour of the phytoseiids upon the prey stage considered more vulnerable. The predation rate of the two phytoseiids was different on the two prey eggs, both on each observation day and for the whole observation period. Both phytoseiids clearly preferred T. urticae eggs, on which the…