Oecologia
AbstractAssessing the relative contributions to seed set for each of a plant species floral visitors provides an indication of the relative influence of these visitors on the plants reproductive success. This study examined pollinator activity and seed set in a population of Heterotheca subaxillaris, a species that exhibits a floret dimorphism (heads bearing disk and ray florets), and that is visited...
AbstractOn the black cotton soils of the Laikipia ecosystem in Kenya, two swollen-thorn acacia species support nine ant species, four of which are apparently obligate plant-ants. Among the ants, there are five species of Crematogaster, two species of Camponotus, and one each of Tetraponera and Lepisota. Acacia drepanolobium is host to four ant species that are both common and mutually exclusive. These...
AbstractNitrogen (N) limits plant growth in many terrestrial ecosystems, potentially constraining terrestrial ecosystem response to elevated CO2. In this study, elevated CO2 stimulated gross N mineralization and plant N uptake in two annual grasslands. In contrast to other studies that have invoked increased C input to soil as the mechanism altering soil N cycling in response to elevated CO2, increased...
AbstractThis study evaluated a possible fitness advantage, specifically time savings, that might account for an unusual propensity in walnut flies (Rhagoletis spp.) to superparasitize their walnut hosts and to place eggs into existing egg-laying cavities. The first part of this study demonstrated that, in laboratory assays, females of two walnut fly species, R. boycei and R. juglandis, save time when...
AbstractFluorogenic substrate analogues (MUF substrates) are very sensitive in detecting hydrolytic enzymes. This method was adapted for the quantitative analysis of extracellular enzymes in snails and other animals. It was then used to determine cellobiase, chitobiase, protease, esterase, phosphatase and lipase in the digestive tract of Radix peregra and Bithynia tentaculata. The method was sensitive...
AbstractTo determine whether stable isotopes can be used for identifying the geographic origins of migratory bird populations, we examined the isotopic composition of hydrogen (deuterium, D), carbon (13C), and strontium (87Sr) in tissues of a migratory passerine, the black-throated blue warbler (Dendroica caerulescens), throughout its breeding range in eastern North America. D and 13C values in feathers,...
AbstractWe tested the hypothesis that changed microclimate at induced forest edges causes reduced growth of epiphytic lichens. Two foliose, green algal lichens were transplanted to the lower canopy of a mature Picea abies forest at six distances (2, 6.25, 12.5, 25, 50 and 100m) from a clearcut. The biomass growth in Platismatia glauca (6.2% in 16 months) was 41% higher than in Lobaria pulmonaria (4...
Abstract Studies of the ecology of mangroves show that a wide variety of factors, including salinity, desiccation, disturbance, competition and predation, may affect the distribution and abundance of species. Field studies were done to examine the relative importance of several of these factors in the establishment and early survival of Ceriops tagal, a species common in mid-to high-shore regions...
AbstractI investigated the effects of tannin consumption, using plant tannins naturally occurring in the diet, on a herbivorous mammal, the North American pika, Ochotona princeps. The objectives were to determine if a high-tannin diet influenced protein and dry matter apparent digestibility, fiber digestibility and production of detoxification by-products. Additionally, I examined the possibility...
AbstractUsing ratio-tracking data obtained at three sites, we assessed the effects of season and of neighbour avoidance on the activity and patterns of home range use by European moles (Talpa europaea). The home ranges of non-breeding male and female moles did not differ significantly in size, and averaged 2324 m2 (minimum convex polygon). Although overlap between ranges was small (an average of 12...
AbstractAtmospheric CO2 concentration has increased by 25% over the preindustrial level. A parallel increase in C concentration and decreases in N concentration and 13C of plants grown throughout this century have been observed in plant specimens stored in herbaria. We tested our previous results in a study of 12 more species collected in the western Mediterranean throughout this century (19201930,...
AbstractSeedlings of Eucalyptus tereticornis (Smith) were grown under two levels of availability each of CO2 (352 and 793mol mol1), soil nutrients (1/24 and 1/4 Hoaglands solution) and light (full and 30% sunlight). Low soil nutrient availability or high light increased the C:N ratio of leaves, leading to lower leaf nitrogen concentrations, higher leaf specific weights and higher levels of both total...
AbstractPhotosynthetic and respiratory CO2 gas exchange was measured under controlled climate conditions in the laboratory in two epiphytic lichens, Lobaria pulmonaria and Platismatia glauca, with the aim of modelling their net productivity using field microclimate data. For both, the thallus water content (WC) and the light intensity had the greatest impact on photosynthesis. L. pulmonaria had optimum...
AbstractRecent studies have shown that stable hydrogen isotope ratios (D) in the tissues of animals often correlate with D of local precipitation. Here we examined the relationship between D in feathers and growing season precipitation for neotropical migrant songbirds breeding over a continent-wide isotopic gradient. D values were determined on feathers of 140 individuals of 6 species of wild insectivorous...
AbstractThe light environment within tropical rain forests varies considerably both spatially and temporally, and photon flux density (PFD) is considered to be an important factor determining the growth and survival of rain forest tree seedlings. In this paper we examine the ability of four ecologically contrasting dipterocarps (Dryobalanops lanceolata, Shorea leprosula, Hopea nervosa and Vatica oblongifolia)...
Abstract Seedlings of nine southern Chilean trees were grown at three nutrient supply rates, to examine the roles of growth rate, biomass distribution and nutrient use traits in determining species natural distributions on resource gradients. Relative growth rate (RGR) showed no overall relationship with species site requirements, although RGR of fertile-site species tended to be more responsive to...
AbstractThe objective of this study was to determine if pond permanence and vertebrate predation (by fish and waterfowl) affect invertebrate community structure in the mudflat habitat of floodplain ponds. Invertebrate communities were studied for 1 year in four Mississippi River floodplain ponds with different hydroperiods. Pond 1 experienced five dry periods, pond 2 experienced four, pond 3 dried...
AbstractWe investigated the effects of cohort, sex, litter size and time of birth on birth weights and postnatal growth rates of roe deer fawns in a highly reproductive Norwegian population. By repeatedly recapturing radio-collared individuals, a total of 950 weights were obtained from 231 fawns of known age. In accordance with earlier studies, there was a period of linear growth during the first...
AbstractWe investigated the occurrence of freezing-induced cavitation in the evergreen desert shrub Larrea tridentata and compared it to co-occurring, winter-deciduous Prosopis velutina. Field measurements indicated that xylem sap in L. tridentata froze at temperatures below c. 5C, and that this caused no measurable cavitation for minimum temperatures above 7C. During the same period P. velutina cavitated...
AbstractQuantifying pathways of energy transfer between plants, pests, and beneficial insects is a necessary step toward maintaining pest stable agroecosystems in the absence of chemical subsidies. A diet switching experiment utilizing a predatory ladybird beetle, Hippodamia variegata (Goeze), evaluated the use of naturally occurring stable C and N isotopes as an economically feasible and safe method...