Showing papers in "Oikos in 1975"
TL;DR: Shannon's information formula, H' = C~pi log2 pi, is found to be linearly related to evenness and to the log2 of the number of species.
Abstract: Species diversity was calculated using three different indices on sets of real and artificial data. Each index was analyzed to determine its relationship to the two component parts of diversity, richness and evenness. Shannon's information formula, H' = C~pi log2 pi, is found to be linearly related to evenness and to the log2 of the number of species. Simpson's Index, D = 1 n(n 1) and __ zg~~~~N(N -1) N V/ni2 McIntosh's Index, D' = N , when expressed in probits are found to
185 citations
TL;DR: This study shows how observations outside the main belt can be utilized to estimate densities of different species, including those of rarer species, in monitoring long-term fluctuations, and in analyzing species diversity.
Abstract: In line transect censuses of breeding birds, all observations are registered. Observations made within 25 m of the transect, about 20 % of total, constitute the "main belt" records, while "survey belt" records refer to all observations. This study shows how observations outside the main belt can be utilized to estimate densities of different species. Calculations are based on 1609 km of Finnish line transects, censused 1941 through 1974. Altogether 62905 individuals (pairs) were included. The effect of distance on the delectability of birds was approximated starting from three assumptions: delectability decreases according to a linear, a negative exponential, or a normal function of distance. The necessary parameters were estimated from main belt percentages and used to calculate relative density. Different models produce similar results for all species, except a few "shortdistance" species such as wildfowl. This correction method renders survey belt data suitable for estimating relative densities; a five-fold increase of data being available compared with main belt estimates alone. This is important in estimating densities of rarer species, in monitoring long-term fluctuations, and in analyzing species diversity.
162 citations
TL;DR: The results and the presumable preference of detritius-feeders for leaf areas with higheshyphal concentrations indicate that the significance of fungal substances in the diet of leaf-eating animals may be considerably higher than suggested by estimates of the average microbial biomass per unit weight of decomposing leaves.
Abstract: Dry weight, ash-free weight, protein and energy content of food and faeces of Gammarus pseudolimnaeus Bousfield on different diets were compared. When feeding on elm or maple leaves, approximatately 10 % of the dry weight, 14-18 % of the protein, and 17-19 % of the energy of the ingested material was assimilated. When mycelium of various fungi which commonly decompose leaves in streams was offered, Gammarus assimilated 42.6-75.6 % of the dry weight, 73.3-96.4 % of the protein, and 67.9-83.2 % of the energy of the food ingested. These results and the presumable preference of detritius-feeders for leaf areas with higheshyphal concentrations indicate that the significance of fungal substances in the diet of leaf-eating animals may be considerably higher than suggested by estimates of the average microbial biomass per unit weight of decomposing leaves.
144 citations
TL;DR: A significantly lower frequency of predators over this study plot than the others was recorded, and the rate of predation on the artificial nests in this plot was also significantly lower.
Abstract: Artificial birds' nests containing 2 eggs were placed in 5 study plots (area 4 ha) at densities of 1 to 4 nests ha-' and exposed for short periods (1-3 days) to predation, mainly by Corvus corone cornix L. and Larus argentatus Pont. Predation rates were high (75 to 96 % on average in 6 experiments) and positively correlated with nest density in 4 plots. In the fifth plot, individuals of Vanellus vanellus L. and, to a lesser extent, Numenius arquata L. were present and defended their ranges against predators. A significantly lower frequency of predators over this study plot than the others was recorded, and the rate of predation (26 %) on the artificial nests in this plot was also significantly lower. The importance of this result for some current hypotheses about the role of predation in bird communities is pointed out.
128 citations
TL;DR: Excess of males in decreasing weasel populations can be explained by their superior ability in hunting and in exploring alternative prey, and food segregation might be important due to the high food requirements of the weasels.
Abstract: Feeding habits in the field were examined by scat analysis. Experiments were carried out in an enclosure simulating natural habitats and containing prey species. Microtus agrestis L. was the staple food; other small rodents and lagomorphs were of secondary importance, and shrews, birds and lizards were occasionally taken. Small-rodent populations were exploited in proportion to their numbers, as the various flight reactions of the different prey species were, on the whole, more or less equally effective and the species were not subjected to descriminate hunting. Shrews were little depredated due to the weasels' distaste for them; the weasels also showed little interest in them when hunting. Food segregation between males and females was pronounced when basic food became scarce, causing males to swich to alternative prey. Segregation reflects the different body size and different hunting behaviour in males and females, and food segregation might be important due to the high food requirements of the weasels. Excess of males in decreasing weasel populations can be explained by their superior ability in hunting and in exploring alternative prey.
99 citations
TL;DR: Stream water temperature, air temperature and streamflow were monitored continuously over a 2-yr period in a 1 km2 drainage basin above 450 m O.D. in northern England and revealed more persistent local variations in stream temperature arising from other environmental factors.
Abstract: Stream water temperature, air temperature and streamflow were monitored continuously over a 2-yr period in a 1 km2 drainage basin above 450 m O.D. in northern England. At the basin outfall, daily maximum and minimum water temperatures generally correlated closely with the equivalent air temperatures under streamflow conditions which prevailed for 88 %0 of the time. The main discrepancies occurred during relatively short-term snowmelt or peak flow events. However, systematic sampling along the two major tributaries revealed more persistent local variations in stream temperature arising from other environmental factors. The effect of geology on baseflow contributions to the streams was particularly important and, with low flows during summer, ground water seepages produced local reductions of 4-50C.
97 citations
TL;DR: In this article, the authors describe the concentrations and total quantities of Pb and Zn in organic horizons of soils distributed over an elevational gradient in a remote area, and comparable with many heavily-travelled roadsides.
Abstract: Northern New England is subject to deposition of remotely derived air-borne pollutants. Mountain ecosystems of the region are particularly exposed because orographic precipitation and windy, cloudy conditions contribute to higher deposition rates. This study describes the concentrations and total quantities of Pb and Zn in organic horizons of soils distributed over an elevational gradient. Pb concentrations are high for a remote area, and comparable with many heavilytravelled roadsides. Zn concentrations fell within a broad range of levels presumed to represent natural conditions. The vertical distribution of Pb suggests that levels are still rising; the elevational distribution suggests that deposition rates are highest in subalpine forests where there is a combination of high winds and ample interceptive plant surfaces. High elevation ecosystems may serve a valuable role as amplifying systems for the detection of certain pollutants, and as convenient systems for understanding the pattern of deposition and the ecological effects of pollutants.
96 citations
TL;DR: In this article, the degree of exposure to predators is discussed in both intermediary and deep-burrowing species, and small juveniles of these species seem to be less exposed since they usually remain in the rhizosphere.
Abstract: in the intermediary and deep-burrowing species. They were superficially distributed at soil temperatures > 2-4?C (April-November). Juvenile deep-burrowers, especially small juveniles, were usually found more superficially than adults. This was probably due to the combined effect of poor burrowing ability, depth of hatching, and amount of food. The degree of exposure to predators is discussed. The surface-living species may be caught throughout the year, whereas adults of intermediary and deep-burrowing species are exposed to above-ground predators when they stay close to the soil surface and are highly active. Small juveniles of these species seem to be less exposed since they usually remain in the rhizosphere.
91 citations
TL;DR: Food palatability experiments suggest that there is a low specificity in the choice of 6 of the slug species but this, together with feeding zone separation, may be sufficient to explain niche separation.
Abstract: The palatability of food to 8 species of slug characteristic of lowland woodland on boulder clay soils, is discussed. Faecal analyses show that all 8 species feed largely on plant material but seasonal variations are important and reflect changing food availability. Food palatability experiments suggest that there is a low specificity in the choice of 6 of the slug species but this, together with feeding zone separation, may be sufficient to explain niche separation. The role of slugs as detritivores in woodlands is discussed.
77 citations
TL;DR: It was showed that lumbricid activity was seasonal, all species were more or less inactive during winter, while reduced activity or inactivity during summer was exclusively found in Allolobophora.
Abstract: Population densities and development throughout the year of different lumbricid species were estimated by handsorting, and compared with formaldehyde catches in order to estimate percentage of active individuals. Activity (= excitability, trappability) was defined as the number of individuals obtained by formaldehyde as a percentage of the actual population. The study showed that lumbricid activity was seasonal. All species were more or less inactive during winter, while reduced activity or inactivity during summer was exclusively found in Allolobophora. Dendrobaena and Lumbricus were active at 0-20?C when soil moisture was below pF 4.2. Allolobophora showed low activity below 2-4?C, and above 14-16?C when pF > 3.2-3.5. Differences in activity were seen between juvenile and adult Allolobophora and Lumbricus. Factors other than soil microclimate, e.g. food, are suggested to be important in the regulation of lumbricid activity.
67 citations
TL;DR: Metal analysis of soils collected near disused lead and zinc mines showed high concentrations of total iron, zinc, lead and available lead, together with free iron, and it is tentatively suggested that soil calcium may influence the uptake of metals by D. rubida.
Abstract: Metal analysis of soils collected near disused lead and zinc mines showed high concentrations of total iron, zinc, lead and available lead, together with free iron. Field and experimental studies on the metal content of the earthworm Dendrobaena rubida (Savigny) living in soils of high and low metal levels showed that the earthworms probably regulated the iron and zinc content of the tissues but retained lead. It is tentatively suggested that soil calcium may influence the uptake of metals by D. rubida while the results for tissue lead content appeared to show a direct effect of calcium on lead by the regulation of endogenous tissue calcium.
TL;DR: Fifth-instar larvae of the monarch butterfly Danaus chrysippus, when supplied with fresh leaves of milkweed Calotropis gigantea, attained maximum weights of 738, 721, 642 and 558 mg at 19?
Abstract: Fifth-instar larvae (165 ? 15 mg) of the monarch butterfly Danaus chrysippus, when supplied with fresh leaves of milkweed Calotropis gigantea, attained maximum weights of 738, 721, 642 and 558 mg at 19?, 27?, 32? and 37? C, respectively. Feeding rates, which did not differ significantly between males and females, were 210, 361, 592, and 548 mg dry food g-1 live larva d-1 at these temperatures. Assimilation efficiency decreased from 58% at 19?C, to 47% at 37?C. Conversion efficiency (K2) was 45% at 32?C, 40% at 27?C, 36% at 37?C, and 26% at 19?C. Fifth-instar larvae consumed about 480 mg dry food, assimilated about 230 mg of this at 27?, 32?, and 37?, and converted about 100 mg at 19?, 27?, and 32? C. Larvae consumed a maximum of 665 mg at 19?C and converted least (83 mg) at 37?C.
TL;DR: A model relating social behavior to population changes emphasizes behavioral density, a function of the number of animals of each behavioral type present in the population, as the factor controlling recruitment.
Abstract: Population dynamics and social behavior of 5 populations were studied for 10 yr. Agonistic behavior characterized social interactions among adult females and yearlings who were subordinate. Rates of amicable and of agonistic behavior varied widely within a harem from year to year and among harems in any given year. Mean interaction rate and mean number of residents were unrelated. Rates of amicable behavior were not related to population density in any colony; the rate of agonistic behavior was associated with population density only in one colony. Rates of amicable and of agonistic behavior between adult males and yearling females, between yearling females and adult females, and among adult females were independent of measures of population density whether data from all colonies were lumped or whether colonies were treated separately. There was no significant relationship between the mean size of home ranges and the mean number of resident adult females. The mean number of resident females was significantly and positively correlated with the percent overlap of home ranges. Patterns of social behavior and home range were slightly related. Female yearlings were more likely to become residents if their home ranges overlapped those of adult females by more than 50 %. Recruitment of females was associated with a high percentage overlap of home ranges and with social tolerance; decline in the number of residents, a small number of residents, or a lack of recruitment of new residents was associated with social intolerance. A model relating social behavior to population changes emphasizes behavioral density, a function of the number of animals of each behavioral type present in the population, as the factor controlling recruitment.
TL;DR: The dynamics of a larval population of Potamophylax cingulatus Steph.
Abstract: The dynamics of a larval population of Potamophylax cingulatus Steph. (Trichoptera) inhabiting a South Swedish stream was investigated. By far the greatest loss (83 %) of population was as "natural mortality", while drift and predation by Salmo trutta L. and Corvus corone cornix L. had only a minor influence. Only 1-2 % of larvae survived from instar I in October to imago in September the next year. Food available in the stream was calculated on a monthly basis by measuring the amounts of food imported, the food remaining from previous months, the living macrophyte vegetation and the loss of potential food as drift. Previous information about the energetic relationships on an individual basis and the present data permitted calculations of ecological efficiency, food chain efficiency, utilization efficiency and turnover rate. Monthly variations of these efficiency values were considerable. Total production was about 4500 cal m-2 yr-1.
TL;DR: A strong increase in bacterial numbers after oil application was observed both in field and model experiments, and this increase occurred within all groups of bacteria, except spore formers and streptomycetes.
Abstract: The influence of mineral oils and oily waste on the bacterial flora of soil was studied both in the field and in model experiments by plate counts followed by examination of the composition of the bacterial flora developing on the plates and by enrichment cultures followed by isolation of pure cultures. A strong increase in bacterial numbers after oil application was observed both in field and model experiments, and this increase occurred within all groups of bacteria, except spore formers and streptomycetes. The most important species of oil decomposing bacteria belonged to the genera Arthrobacter and Pseudomonas.
TL;DR: Comparison of respiration rates with cultured, acclimated animals showed considerable differences, and Cultured juveniles have much higher rates, especially above 5?
Abstract: Analyses are presented of 190 measurements of individual respiration rate for the complete size range of Cryptopygus antarcticus Willem. A Cartesian Diver micro-respirometer was used at Signy Island (Maritime Antarctic) during the austral summer 1971/72. Oxygen consumption per individual increased linearly with live weight on a log basis at 0?, 5? and 10?C. The 5? and 10?C regression lines differed significantly and the weight exponent b varied from 0.669 to 0.825. Mean oxygen uptake rates for 5 size classes ranged from 0.671 to 22.610 Al x 10-3 02 ind-1 h-1, and from 95.66 to 469.20 gl 02 g-~ h-1 over the temperature range studied. Juveniles showed least change in rate, and adults the maximum change, over 0? to 10?C. Egg respiration was 0.306 ul x 10-3 02 h-1 at 5?C. Data are compared with other Antarctic Collembola, and temperate species. Comparison of respiration rates with cultured, acclimated animals showed considerable differences. Cultured juveniles have much higher rates, especially above 5? C, than field animals. Population metabolism is estimated for a typical habitat and cold adaptation is discussed.
TL;DR: Elimination of 203Hg-labelled methylmercury by rainbow trout, studied by whole body counting, followed a bi-exponential equation, with a significant decrease in the biological half-time.
Abstract: Elimination of 203Hg-labelled methylmercury by rainbow trout, studied by whole body counting, followed a bi-exponential equation. The biological half-time of methylmercury varied from 202 to 516 d, depending on the retained dose and water temperature. An increase in the concentration of protein-bound methylmercury caused a significant decrease in the biological half-time. Between 0.5 and 4?C the excretion rate of methylmercury was about 1.5 times longer (516 ? 83 d) than at 16-19?C (348 ? 78 d).
TL;DR: Seasonal variations of physical and chemical factors were studied in the eutrophic, usually totally-circulated, Lake Vombsjon in South Sweden and a significant difference in the photosynthetic capacity of nannoplankton, as compared with netplankton was found.
TL;DR: A strong positive correlation between pH and water level of the river was partly due to the acidifying effect of rain and melt water, and to the abundance of peat in the area.
Abstract: Acidity of the weakly-buffered river Kiiminkijoki and its tributaries increases considerably in spring. In Nuorittajoki, the largest tributary, it may fall to pH 5.0, while it is pH 6.4-6.8 just before the flood and over pH 7.0 (maximum 7.8) in summer. Similar spring acidification of running water occurred at all other sites studied. Increased acidity was due to abundant melt water, generally at pH 4.5-5.0. River pH varied greatly at other times of the year. A strong positive correlation between pH and water level of the river was partly due to the acidifying effect of rain and melt water, and to the abundance of peat in the area.
TL;DR: Newly-emerged adult P. cingulatus (Steph.) in a South Swedish stream exhibited a strong correlation between the size of different body parts and total dry weight, and local differences in food supply during late winter and spring are probably important for the differences in body size.
Abstract: Newly-emerged adult P. cingulatus (Steph.) in a South Swedish stream exhibited a strong correlation between the size of different body parts and total dry weight. A 40 % seasonal decrease in weight, with no changes in linear measurements, was recorded in males. Mean body size of three sub-populations along the stream exhibited great between-year differences. Newly-emerged individuals from the sub-population with the smallest adults had an energy content of 60 to 70 % in comparison with those from the sub-population with the largest ones. In the uppermost part of the stream, with the most diverse habitat, specimens were on average intermediate or rather large, and showed the smallest between-year variations. Local differences in food supply during late winter and spring are probably important for the differences in body size of adult P. cingulatus along the stream. The flight period is probably adapted to temperature and the food requirements of the larvae.
TL;DR: In Jamaica Pachodynerus nasidens (Latr.) nest in disused cells of the solitary mudwasps Sceliphron assimile Dahlbom and Eumenes colona Saussure and is readily caught in trap-nests.
Abstract: In Jamaica Pachodynerus nasidens (Latr.) nest in disused cells of the solitary mudwasps Sceliphron assimile Dahlbom and Eumenes colona Saussure. P. nasidens is readily caught in trap-nests. Developmental mortality averaged 85.7 % in Sceliphron cells, 79.9 % in Eumenes cells, but only 45.7 % in trap-nests. Mean fecundity at a favourable site was 14.0 + 2.9. The sex-ratio was equivalent to 61.5 ? 4.7 % females. Mortality (and/or emigration) of pre-productive females ranged from 1 8.7 to 78.6 %o.
TL;DR: Small mammal catches at extensive (Small Quadrat) and intensive (StandardMinimum) trapping were compared and index catches were significantly correlated with density in the three rodent species Apodemus sylvaticus, Clethrionomys glareolus and Microtus agrestis, but such a correlation did not exist for the shrews.
Abstract: Small mammal catches at extensive (Small Quadrat) and intensive (StandardMinimum) trapping were compared. Population structures did not differ in the samples, whereas the species composition was very different. The latter was caused by different removal rates and trapping efficiencies at the two types of sampling. These differences are interpreted as due to different interest in the bait and different population densities of the various species. Index catches were significantly correlated with density in the three rodent species Apodemus sylvaticus (L.), Clethrionomys glareolus (Schreb.) and Microtus agrestis (L.) Such a correlation did not exist for the shrews. Short-time index trapping resulted in curvilinear, and longer periods in linear, relations between indices and density.
TL;DR: The litter stratum of the streamside forest ecosystem in Robert Allerton Park, Piatt County, Illinois, is described in relation to biotic and environmental gradients resulting from the flooding regime of the Sangamon River.
Abstract: The litter stratum of the streamside forest ecosystem in Robert Allerton Park, Piatt County, Illinois, is described in relation to biotic and environmental gradients resulting from the flooding regime of the Sangamon River. Composition, structure, and distribution of several components of the litter layer were determined at vertical increments of 0.304 m over an elevational gradient from near the river edge into upland, unflooded areas. A gradient of potential available energy source for decomposer organisms was determined from leaf litter components and caloric values. Special emphasis was placed on determining the relationship between the physical structure of the litter gradient and potential available habitat for litter-dwellin ginvertebrate populations and decomposer organisms.
TL;DR: Ingestion, egestion, production (growth) and respiration were determined for all developmental stages of the Chrysomelid beetle Melasoma collaris L. fed Salix herbacea.
Abstract: Ingestion, egestion, production (growth) and respiration were determined for all developmental stages of the Chrysomelid beetle Melasoma collaris L. fed Salix herbacea L. Gross efficiency of growth (100 x growth/ingestion) for the three larval instars were 32, 31, and 22, totally 24% (energy); and 26, 27, and 20, totally 21 % (dry weight). Assimilation efficiency (100 x assimilation/ingestion), based on collections of excrement, was 76, 77, and 65 % (energy) in the larval instars. Respiration calculated from the energy ingested, egested and stored as growth, was about 2-6 times higher than measured by respirometers.
TL;DR: Computer simulations suggest that availability of energy may be a critical factor for reproductive females (especially small ones) during the winter and several critical areas for further research are identified.
Abstract: A mathematical model is developed for the ecological energetics of individual brown lemmings. This model incorporates expressions for obtaining energy through grazing as a function of grass and sedge density, size of the lemming and its energy needs. Utilization of energy is divided into maintenance metabolism, growth, and reproduction. Expressions for energy spent in reproduction include growth of fetuses and growth of young before weaning. The consequences of the assumptions of the model are shown in a series of graphs relating groups of variables. Computer simulations suggest that availability of energy may be a critical factor for reproductive females (especially small ones) during the winter. During most summers availability of food should present no problem. On the basis of the simulation model several critical areas for further research are identified. Most important among these are the relationship between food density and consumption rate, deposition and utilization of fat, the time-activity budget of animals in their natural habitat, and the functional relationships between maximal growth rates and other variables such as age and sex.
TL;DR: Sulfide photosynthetic oxidation did not operate with fluorescent light, was less effective with any decrease in red light and was less efficient in infrared than inRed light indicating that green sulfur bacteria were more important than purple bacteria in oxidizing sulfide in the studied sediments.
Abstract: Sulfide concentration was measured at 1 mm intervals in marine sediment cores using Ag-AgS multiple electrodes. Illumination of the cores produced a marked decrease in sulfide concentration due to photosynthetic sulfur bacteria. These decreases were restricted to the upper 3 mm of the cores. After some time the cores lost their capacity to generate sulfide; they could be rejuvenated by the addition of cellulose, lactate or sulfide. The rate of utilization of sulfide was proportional to sulfide concentration up to 1.0 mmole the maximum rate being 0.25 mmoles 1-1 min-. Light saturation with incandescent light occurred above 2000 lx. Sulfide photosynthetic oxidation did not operate with fluorescent light, was less effective with any decrease in red light (640 nm) and was less efficient in infrared than in red light indicating that green sulfur bacteria were more important than purple bacteria in oxidizing sulfide in the studied sediments. Temperature had some effect on the photosynthetic oxidation of sulfide but there was a much greater effect on the rate of sulfide reappearance in the dark.
TL;DR: Results from four combined experiments using a capture-mark-recapture technique followed by Standard-Minimum removal were analysed and it was concluded that reproductive C. flavicollis and subadult C. glareolus are generally resident; as to subadult A. flaviollis no final conclusion can be made.
Abstract: Results from four combined experiments using a capture-mark-recapture technique followed by Standard-Minimum removal were analysed. Trappability of non-reproductive subadults and post-reproductive adults was lower than that of reproductive adults, and the removal of subadults was slower than the removal of adults, especially of reproductive adult males. Among subadult and reproductive C. glareolus (Schr.), 33 % and 8 % respectively were unmarked. In A. flavicollis (Melch.) 70 % of the subadults and 28 % of the reproductive adults were unmarked. A considerable edge-effect in Standard-Minimum removal was demonstrated for all groups except for subadult A. flavicollis. However, this effect could in all cases be ascribed to lower trappability of individuals with home-ranges partly overlapping the study area. It is concluded that reproductive C. glareolus and A. flavicollis and subadult C. glareolus are generally resident; as to subadult A. flavicollis no final conclusion can be made.