Search results for "animal ecology"
showing 10 items of 120 documents
Minimum message length clustering: an explication and some applications to vegetation data
2001
In this paper, we examine the application of a particular approach to induction, the minimum message length principle and illustrate some of the problems that can be addressed through its use. The MML principle seeks to identify an optimal model within some specified parameterised class of models and for this paper we have chosen to concentrate on a single model class, that of mixture separation or fuzzy clustering. The first section presents, in outline, an MML methodology for fuzzy clustering. We then present some applications, including the nature of the within-cluster model, examination of the univocality of results for different groups of species and the effectiveness of presence data …
Sediment features, macrozoobenthic assemblages and trophic relationships (δ13C and δ15N analysis) following a dystrophic event with anoxia and sulphi…
2007
Macrozoobenthic assemblages and stable carbon (delta C-13) and nitrogen (delta N-15) isotope values of various primary producers (macroalgae and angiosperms) and consumers (macroinvertebrate filter/suspension feeders, deposit feeders, detritivores/omnivores and carnivores and fishes) were studied in the Santa Giusta lagoon (Sardinia, Italy) before (spring) and after (autumn) a dystrophic event which occurred in the summer of 2004. A few days after the dystrophy, the physico-chemical characteristics of sediments and macrozoobenthic assemblages were also investigated. In the latter occasion, high total organic carbon (3.9%) and organic matter (15.9%) contents of surface sediments went togethe…
Biometric variability of Hadwenius tursionis (Marchi, 1873) (Digenea, Campulidae) from the intestine of the bottlenose dolphin Tursiops truncatus (Mo…
1995
The species discrimination in the family Campulidae is largely based on morphometric characters (absolute measurements and ratios). To assess the variability of this characters we have studied the campulid species Hadwenius tursionis from four Mediterranean bottlenose dolphins Tursiops truncatus from the Western Mediterranean. In H. tursionis most absolute measurements differed significantly across the infrapopulations, showing high coefficients of variation. Only egg dimensions appeared to be fairly conservative. Body ratios were less variable than absolute measurements, but growth patterns did vary significantly between the infrapopulations studied. None of the ratios previously used in r…
Feeding habits, post-embryonic and adult survival, mating, virility and fecundity of the predacious miteAmblyseius swirskii [Acarina: Phytoseiidae] o…
1977
The nutritional value forAmblyseius swirskiiAthias-Henriot, of eggs or crawlers ofCoccus hesperidum L.,Saissetia oleae (Olivier),S. coffeae (Walker),Pseudococcus citriculusGreen, andP. longispinusTarg.-Tozz, even with the addition of honeydew, was low; only a few young reached adulthood and the oviposition rate was negligible. However, addition of honeydew toTetranychus cinnabarinusBoisd. enhanced the oviposition rate ofAmblyseius swirskii. Honeydew was a favourite food forA. swirskii, whereas the eggs and crawlers tested were not eagerly attacked and consumed. Females and males fed honeydew ofSaissetia oleae mated readily and the females were inseminated, but fecundity was negligible.
Risultati della lotta biologica contro ilDacus oleae Gmel. a mezzo dell'Opius concolor Sz. siculus Mon.
1965
The Author reports on the essays of artificial biological control of the olive fly (Dacus oleaeGmel.) made by himself andGenduso with the specific parasiteOpius c. siculusMon. found in Sicily. The Authors followingDelanoue's technic have bred theseOpius in laboratory on larvae ofCeratitis capitataWied; so they were able to release: in 1961 — 1000Opius in a small olive plantation near Palermo; in 1962 — 24000Opius in the island of Pantelleria (Sicily); in 1963 — 40000Opius in the island of Salina (Eolic Islands-Sicily); in 1964 — 180000Opius also in the island of Salina.
Female Oviposition Decisions and Their Impact on Progeny Life-History Traits
2008
An important factor affecting the life-history of an organism is parental investment in reproduction: reproductive decisions are almost invariably costly. Therefore, reproductive decisions should be beneficial in terms of increased offspring number or fitness. For example, egg laying decisions in many insects can influence resource availability of the offspring through changes in the larval density, and resource availability will have effects on many life-history traits. Here we studied whether female reproductive decisions affect offspring fitness in Callosobruchus maculatus seed beetles. Females laid more eggs on black-eye beans than on mung beans. However, when the difference in the surf…
Mate sampling behaviour of black grouse females (Tetrao tetrix)
1995
We studied female mate sampling behaviour in lekking black grouse (Tetrao tetrix). Females mainly visited males occupying territories in the centre of the lek with relatively large territories. They were also more likely to visit males that had high attendance. The same factors were also correlated with male mating success. A multiple regression model including these factors explained more of the variance in female visits per male (53%) than in mating success (33%). The pattern of female sampling conformed with a pool comparison (best-of-n) tactic. Such a tactic is expected if the costs of sampling are low. Females of high body mass visited more males than lighter females, however, which in…
The effects of parasites on male ornaments and female choice in the lek-breeding black grouse (Tetrao tetrix)
1992
We describe the results of two studies of parasitic infection in the black grouse (Tetrao tetrix). The first deals with our own observations of lekking black grouse in which the parasite levels of two blood parasites, the protozoan Leucocytozoon lovati and microfilaria, probably produced by a nematode worm Splendidofilaria tuvensis, were scored. We also obtained measures of age, survival, number of copulations, body mass and length of the ornamental tail feathers (the lyre) of the lekking males. The second study analysed the data from Lund (1954) which involved eight gut parasites obtained from birds which were killed. In the first study we found higher levels of infection of Leucocytozoon …
Influence of landscape composition and diversity on contaminant flux in terrestrial food webs: a case study of trace metal transfer to European black…
2012
13 pages; International audience; Although understanding the influence of the spatial arrangement of habitats and interacting communities on the processes of pollutant flux and impacts is critical for exposure and risk assessment, to date few studies have been devoted to this emergent topic. We tested the hypothesis that landscape composition and diversity affect the transfer of trace metals to vertebrates. Bioaccumulation of Cd and Pb in blood and feathers of European blackbirds Turdus merula (n=138) was studied over a smelter-impacted area (Northern France). Landscape composition (type and occurrence of the different habitats) and diversity (number of different habitat types and the propo…
Biological and life table parameters of Typhlodromus laurentii and Iphiseius degenerans (Acari, Phytoseiidae) fed on Panonychus citri and pollen of O…
2015
Typhlodromus laurentii and Iphiseius degenerans are two generalist phytoseiid mites, broadly spread in the Mediterranean area, especially in citrus orchards. In the present work we report results on various biological and life table parameters of the two phytoseiids, fed on pollen of Oxalis pes-caprae and various stages of the tetranychid Panonychus citri. Iphiseius degenerans had the shortest post embryonic development (6.53 days), the highest oviposition rate (1.83 eggs/female/day) and the shortest mean time between eggs laid (0.55 day) on Oxalis pollen, whereas the two food types did not influence these parameters in T. laurentii. However, Oxalis pollen showed a positive effect on the su…