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921.
Seymour I. SchwartzDavid E. Hansen Richard Green 《Journal of Environmental Economics and Management》1981,8(4):303-320
The effect of Petaluma, California's growth control program on new house prices is examined by a comparative (quasi-experimental) design, using statistical controls. The difference in price increases between Petaluma and two comparison cities is calculated for houses of standard quality and for average actual houses in each city. It was found that prices of standard quality houses increased significantly more in Petaluma than in one of the comparison cities but not the other. A similar pattern was observed for actual houses. Reasons for the observed results and specific causes of the growth control effect are analyzed. 相似文献
922.
Age structure,growth rates,movement patterns and feeding in an estuarine population of the cardinalfish Apogon rueppellii 总被引:1,自引:0,他引:1
The biology of a population of the cardinalfish Apogon rueppellii has been studied over several years (1977–1983) in the Swan Estuary in south-western Australia, using ramples collected monthly from the shallows by beach seine and from various depths by otter trawl. While the life cycle of this species typically lasts for one year, at the end of which time the mean length is 50 to 60 mm, some individuals survive for a further year and attain lengths up to 104 mm. A. rueppellii shows a marked tendency to move offshore into deeper water during the winter months. This tendency is more pronounced in the 1+ than in the 0+ year class and in larger than smaller 0+ individuals. An inshore movement of A. rueppellii in the spring is followed by spawning and by oral brooding by the males, which leads to the recruitment of large numbers of a new 0+ year class on to the banks during the summer. The offshore movement is correlated with changes in salinity and temperature. The larger catches taken by otter trawl during the day than at night indicate that A. rueppellii exhibits a diel pattern of activity. Mean fecundity ranged from 70 in the 45 to 49 mm size class to 345 in the 90 to 94 mm size class. Measurements of fecundity and the number of oral-brooded eggs demonstrated that the majority of the eggs released by the female are collected and incubated by the males. Copepods are ingested in relatively greater amounts by small than by large A. rueppellii, whereas the reverse situation occurs with larger crustaceans, polychaetes and small fish. The presence of greater amounts of copepods in the diet during the day and of amphipods at night probably reflects the diel activity patterns of the prey. 相似文献
923.
Summary Spatial relationships of white-footed mouse (Peromyscus leucopus) dams and their offspring and of littermates post-weaning were determined to evaluate if their dispersion was sufficient to prevent inbreeding. Mothers tended to leave their first nest site and establish another nest site within or near their original home range. Daughters inherited part of the maternal home range but sons dispersed. During the following breeding season, sons were not in proximity to their mothers or sisters. Daughters, however, frequently attained sexual maturity and bred within the home range of males that could have been their fathers. Differential dispersal of male and female juveniles reduces the probability of mother-son and brother-sister matings, but there is no obvious dispersal-related mechanism to prevent father-daughter matings. 相似文献
924.
925.
Carmen?Rossini Alexander?Bezzerides Andrés?González Maria?Eisner Thomas?EisnerEmail author 《Chemoecology》2003,13(4):199-205
Summary. Evidence is presented that pyrrolizidine alkaloid acquired
by Utetheisa ornatrix (Lepidoptera, Arctiidae) as a larva
from Crotalaria foodplants is incorporated in part into the scales
of the adult. A single forewing of a male or female moth may contain in
the order of 6 to 13 g monocrotaline in its scale cover or about 1 to 2%
of the moths systemic monocrotaline content. Based on estimates of the number
of scales per forewing, the monocrotaline content of individual scales is calculated
to be in the order of 0.1 and 0.2 ng monocrotaline per male and female scale,
respectively. This amounts to concentrations of about 1 and 3%, values roughly at
a par with the average systemic concentration (0.5-0.6%) previously determined
for monocrotaline in Utetheisa. It is argued that the presence of pyrrolizidine alkaloid
in the moths scale coating could account for the promptness with which adult Utetheisa are
rejected by spiders. It is suggested further that chemical impregnation of scales with substances
deterrent to predators may be more widespread among insects than generally assumed. 相似文献
926.
Georg Wohlfahrt Michael Bahn Christian Newesely Sigrid Sapinsky Ulrike Tappeiner Alexander Cernusca 《Ecological modelling》2003,170(2-3):407
The present paper aims at investigating how changes in canopy structure and species physiology associated with the abandonment of mountain meadows and pastures affect their net photosynthesis. For this purpose, a multi-layer vegetation–atmosphere transfer (VAT) model is employed, which explicitly takes into account the structural and functional properties of the various canopy components and species. Three sites differing in land use are investigated, a meadow, a pasture and an abandoned area. Model simulations agree reasonably with measured canopy net photosynthetic rates, the meadow featuring the highest daily net photosynthesis, followed by the pasture and, finally, the abandoned area. A detailed process analysis suggests this ranking to be mainly due to bulk canopy physiology, which decreases from the meadow to the pasture and the abandoned area, reflecting species composition and species-specific photosynthetic capacities. Differences between the canopies with regard to canopy structure are found to be of minor importance. The amounts of green, photosynthetically active plant matter are too similar at the three sites to be a major source of variation in net photosynthesis. Large differences exist between the canopies with regard to the amount of photosynthetically inactive phytoelements. Even though a model analysis showed them to be potentially important, most of them are accumulated close to the ground surface, where they exert little influence on canopy net photosynthesis. 相似文献
927.
Heather?R. Britt Bradley?P.?CarlinEmail author Traci?L.?Toomey Alexander?C.?Wagenaar 《Environmental and Ecological Statistics》2005,12(4):411-426
Misuse of alcohol is a significant public health problem, potentially resulting in unintentional injuries, motor vehicle crashes,
drownings, and, perhaps of greatest concern, serious acts of violence, including assaults, rapes, suicides, and homicides.
Although previous research establishes a link between alcohol consumption increased levels of violence, studies relating the
density of alcohol outlets (e.g., restaurants, bars, liquor stores) and the likelihood of violent crime have been less common.
In this paper we test for such a relationship at the small area level, using data from 79 neighborhoods in the city of Minneapolis,
Minnesota. We adopt a fully Bayesian point of view using Markov chain Monte Carlo (MCMC) computational methods as available
in the popular and freely available WinBUGS language. Our models control for important covariates (e.g., neighborhood racial
heterogeneity, age heterogeneity) and also account for spatial association in unexplained variability using conditionally
autoregressive (CAR) random effects. Our results indicate a significant positive relationship between alcohol outlet density
and violent crime, while also permitting easy mapping of neighborhood-level predicted and residual values, the former useful
for intervention in the most at-risk neighborhoods and the latter potentially useful in identifying covariates still missing
from the fixed effects portion of the model. 相似文献
928.
O. Barneah I. Brickner M. Hooge V. M. Weis T. C. LaJeunesse Y. Benayahu 《Marine Biology》2007,151(4):1215-1223
Epizoic worms were found to occur on certain coral colonies from reefs off the coast of Eilat (Red Sea). We identified 14
coral species infested by acoelomorph worms at a depth range of 2–50 m. The host corals were all zooxanthellate and included
both massive and branching stony corals and a soft coral. Worms from all hosts were identified as belonging to the genus Waminoa and contained two distinct algal symbionts differing in size. The smaller one was identified as Symbiodinium sp. and the larger one is presumed to belong to the genus Amphidinium. Worm-infested colonies of the soft coral, Stereonephthya cundabiluensis, lacked a mucus layer and exhibited distinct cell microvilli, a phenotype not present in colonies lacking Waminoa sp. In most cases, both cnidarian and Acoelomorph hosts displayed high specificity for genetically distinctive Symbiodinium spp. These observations show that the epizoic worms do not acquire their symbionts from the “host” coral. 相似文献
929.
930.
With the aim of improving the formulation of diets for early stages of marine fish, post-larval Hippoglossus hippoglossus (56 days after first feeding; 23 mg dry weight) were tube-fed liquid diets of radiolabelled L-(14C) free amino acids (FAA diet), peptides (PEPT diet) and protein (PROT diet), in order to compare the kinetics of transfer from gut into the liver and carcass. The test diets were prepared using equal concentrations of amino acids (AA) and fed as a single pulse (0.3 µl, 2.2 µg AA). The PROT diet consisted of methylated-14C-labelled (mainly lysine) bovine serum albumin (BSA), the PEPT diet was the PROT diet digested with trypsin and the FAA diet consisted of an amino acid mixture based on BSA composition with added 14C-lysine. The common labelling with 14C-lysine permitted a comparison of the three diets. Based on dissection and distribution of the tracer in each compartment, the FAA diet was almost completely absorbed 1 h after the tube-feeding; PEPT and PROT diets required more time before they were processed by the digestive tract. The FAA diet was absorbed about eight times as fast as protein and about six times as fast as peptides from the gut. A low retention of label in the liver for all diets at all sampling times suggests that the liver does not store the AA at these absorption rates. The FAA diet had a higher assimilation efficiency (about 90%) than the PEPT diet (about 12%) and PROT diet (about 32%). FAAs, thus, appear to be superior to protein and peptides as a dietary source of amino acids in post-larval Atlantic halibut. 相似文献