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951.
Thomas J. Habib Evelyn H. MerrillM.J. Pybus David W. Coltman 《Ecological modelling》2011,222(15):2722-2732
Managing wildlife diseases requires an understanding of disease transmission, which may be strongly affected by host population density and landscape features. Transmission models are typically fit from time-series disease prevalence data and modelled based on how the contact rate among hosts is affected by density, which is often assumed to be a linear (density-dependent transmission) or constant (frequency-dependent transmission) relationship. However, long-term time-series data is unavailable for emerging diseases, and this approach cannot account for independent effects of landscape. We developed a mechanistic model based on ecological data to empirically derive the contact rate-density relationship in white-tailed and mule deer in an enzootic region of chronic wasting disease (CWD) in Alberta, Canada and to determine whether it was affected by landscape. Using data collected from aerial surveys and GPS-telemetry, we developed empirical relationships predicting deer group size, home range size, and habitat selection to iteratively simulate deer distributions across a range of densities and landscapes. We calculated a relative measure of total per-capita contact rate, which is proportional to the number of other deer contacted per individual per unit time, for each distribution as the sum of pairwise contact rates between a target deer and all other individuals. Each pairwise contact rate was estimated from an empirical relationship developed from GPS-telemetry data predicting pairwise contact rates as a function of home range overlap and landscape structure. Total per-capita contact rates increased as a saturating function of density, supporting a transmission model intermediate between density- and frequency-dependent transmission. This pattern resulted from group sizes that reached an asymptote with increasing deer density, although this relationship was mediated by tree and shrub coverage in the landscape, such that in heavily wooded areas, the contact rate saturated at much lower densities. These results suggest that CWD management based on herd reductions, which require a density-dependent contact rate to be effective, may have variable effects on disease across a single management region. The novel mechanistic approach we employed for estimating effects of density and landscape on transmission is a powerful complement to typical data-fitting approaches for modelling disease transmission. 相似文献
952.
Using simulation to explore the functional relationships of terrestrial carnivore population indices
Population indices based on visits to detection stations commonly are used to monitor wildlife populations. Inferences about populations are based on 1 of 2 measures: (1) change in the proportion of stations visited at least once or (2) change in the cumulative number of visits by unique individuals. The functional relationships between index responses and population density is poorly understood and can lead to misinterpretation of index data when an incorrect functional relationship (e.g. linear) is assumed. We created a flexible simulation environment to study the response of detection-based population indices under a wide variety of conditions meant to reflect species life history and study design. Proportional indices exhibited non-linear saturating responses to changes in population density while cumulative indices responded linearly. Shapes of responses were functions of home range sizes, individual detection probabilities, and spatial arrangement of animals and sampling stations. Non-linear relationships of proportional indices lead to under-estimation of mean population density when data are aggregated from multiple detection stations deployed in a heterogeneous landscape. Cumulative indices have significant statistical advantages over proportional indices including smaller sample sizes required to detect density change, linearity, consistent index responses across a wide range of densities, and ability to aggregate data to meet minimum sample size requirements. Our simulation provides a flexible tool for the interpretation of station-based population indices. 相似文献
953.
Calculating ecological carrying capacity of shellfish aquaculture using mass-balance modeling: Narragansett Bay, Rhode Island 总被引:1,自引:0,他引:1
Increasing growth in the aquaculture industry demands ecosystem-based techniques for management if that growth is to be ecologically sustainable and promote equity among users of the ecosystems in which it occurs. Models of carrying capacity can be used to responsibly limit the growth of aquaculture in increasingly crowded coastal areas. Narragansett Bay, Rhode Island, USA is one such crowded coastal region experiencing a rapid increase in bivalve aquaculture. An ecosystem mass-balance model was used to calculate the ecological carrying capacity of bivalve aquaculture. Cultured oyster biomass is currently at 0.47 t km−2 and could be increased 625 times without exceeding the ecological carrying capacity of 297 t km−2. This translates to approximately 38,950 t of harvested cultured oysters annually which is 4 times the total estimated annual harvest of finfish. This potential for growth is due to the high primary productivity and large energy throughput to detritus of this ecosystem. Shellfish aquaculture has potential for continued growth and is unlikely to become food limited due, in part, to the large detritus pool. 相似文献
954.
Effects of urbanization and urban stream restoration on the physical and biological structure of stream ecosystems 总被引:1,自引:0,他引:1
Violin CR Cada P Sudduth EB Hassett BA Penrose DL Bernhardt ES 《Ecological applications》2011,21(6):1932-1949
Streams, as low-lying points in the landscape, are strongly influenced by the stormwaters, pollutants, and warming that characterize catchment urbanization. River restoration projects are an increasingly popular method for mitigating urban insults. Despite the growing frequency and high expense of urban stream restoration projects, very few projects have been evaluated to determine whether they can successfully enhance habitat structure or support the stream biota characteristic of reference sites. We compared the physical and biological structure of four urban degraded, four urban restored, and four forested streams in the Piedmont region of North Carolina to quantify the ability of reach-scale stream restoration to restore physical and biological structure to urban streams and to examine the assumption that providing habitat is sufficient for biological recovery. To be successful at mitigating urban impacts, the habitat structure and biological communities found in restored streams should be more similar to forested reference sites than to their urban degraded counterparts. For every measured reach- and patch-scale attribute, we found that restored streams were indistinguishable from their degraded urban stream counterparts. Forested streams were shallower, had greater habitat complexity and median sediment size, and contained less-tolerant communities with higher sensitive taxa richness than streams in either urban category. Because heavy machinery is used to regrade and reconfigure restored channels, restored streams had less canopy cover than either forested or urban streams. Channel habitat complexity and watershed impervious surface cover (ISC) were the best predictors of sensitive taxa richness and biotic index at the reach and catchment scale, respectively. Macroinvertebrate communities in restored channels were compositionally similar to the communities in urban degraded channels, and both were dissimilar to communities in forested streams. The macroinvertebrate communities of both restored and urban degraded streams were correlated with environmental variables characteristic of degraded urban systems. Our study suggests that reach-scale restoration is not successfully mitigating for the factors causing physical and biological degradation. 相似文献
955.
Jonathan N. Pruitt Susan E. Riechert David J. Harris 《Behavioral ecology and sociobiology》2011,65(10):1957-1966
Relatively few investigations explicitly test for concordant versus conflicting selection pressures from intrasexual versus
intersexual selection. Here, we examine the effects of male body mass and behavioral type (BT) on reproductive success in
the spider Anelosimus studiosus, with emphasis placed on the potential interaction between intrasexual and intersexual selection influences. Female A. studiosus exhibit either an aggressive-active or docile-passive BT, both of which co-occur in multifemale colonies. Males, in contrast, exhibit a more continuous distribution of
behavioral tendencies. We investigated the male traits favored by females in five trial types: one docile female, one aggressive
female, four docile females, four aggressive females, and two docile and two aggressive females. Male reproductive success
was estimated by the number eggs produced by females following staged mating trials. In previous work, it was established
that large aggressive males are favored in male–male contests, an intrasexual effect. However, large aggressive males were
not universally favored here. We failed to detect an effect of male body mass or aggressiveness on reproductive success in
trials with all docile females; however, in situations involving aggressive females, large aggressive males experienced diminished
reproductive success relative to small docile males. Large, aggressive males were also more likely to be attacked and killed
by aggressive females in the first 20 min of staged encounters and were more likely to be found dead after 72 h of unobserved
interactions. Taken together, our data suggest that the reproductive consequences of male traits differ based on (1) the aspect
of sexual selection being considered (intrasexual versus intersexual) and (2) the BT of their prospective mates: large aggressive
males enjoy advantages in intrasexual selection and when courting docile females and small docile males experience reduced
risk of cannibalism and increased reproductive success with aggressive females. 相似文献
956.
Knowledge gain and behavioral change in citizen-science programs 总被引:1,自引:0,他引:1
Citizen-science programs are often touted as useful for advancing conservation literacy, scientific knowledge, and increasing scientific-reasoning skills among the public. Guidelines for collaboration among scientists and the public are lacking and the extent to which these citizen-science initiatives change behavior is relatively unstudied. Over two years, we studied 82 participants in a three-day program that included education about non-native invasive plants and collection of data on the occurrence of those plants. Volunteers were given background knowledge about invasive plant ecology and trained on a specific protocol for collecting invasive plant data. They then collected data and later gathered as a group to analyze data and discuss responsible environmental behavior with respect to invasive plants. We tested whether participants without experience in plant identification and with little knowledge of invasive plants increased their knowledge of invasive species ecology, participation increased knowledge of scientific methods, and participation affected behavior. Knowledge of invasive plants increased on average 24%, but participation was insufficient to increase understanding of how scientific research is conducted. Participants reported increased ability to recognize invasive plants and increased awareness of effects of invasive plants on the environment, but this translated into little change in behavior regarding invasive plants. Potential conflicts between scientific goals, educational goals, and the motivation of participants must be considered during program design. 相似文献
957.
David L. Clark J. Andrew Roberts Meghan Rector George W. Uetz 《Behavioral ecology and sociobiology》2011,65(6):1237-1247
Animal color patterns often reflect a compromise between natural selection for crypsis or inconspicuousness to predators and
sexual selection for conspicuousness to potential mates. In leaf litter-dwelling wolf spider species like Schizocosa ocreata, body coloration often closely matches the background coloration of a generally brown environment. However, body parts used
in communication should exhibit high contrast against background coloration. We used spectral analysis to examine male and
female S. ocreata for matching and contrasting coloration against leaf litter. Values were plotted in multivariate color space, based on reflectivity
in different frequency ranges. When viewed from above, colors of both males and females overlap with values for dead brown
leaf litter and soil, suggesting cryptic coloration when viewed by potential predators. However, when viewed from a lateral
perspective, both males and females show color values that are polar opposites of litter backgrounds, suggesting higher contrast
when viewed by other spiders. Moreover, male secondary characters used in visual signaling by S. ocreata (tibia brushes) show the highest level of background contrast. These findings suggest that S. ocreata wolf spiders have color patterns that provide both crypsis and background contrast at the same time, depending on receiver
viewing perspective. 相似文献
958.
AIC model selection and multimodel inference in behavioral ecology: some background,observations, and comparisons 总被引:4,自引:0,他引:4
Kenneth P. Burnham David R. Anderson Kathryn P. Huyvaert 《Behavioral ecology and sociobiology》2011,65(1):23-35
We briefly outline the information-theoretic (I-T) approaches to valid inference including a review of some simple methods
for making formal inference from all the hypotheses in the model set (multimodel inference). The I-T approaches can replace
the usual t tests and ANOVA tables that are so inferentially limited, but still commonly used. The I-T methods are easy to compute and
understand and provide formal measures of the strength of evidence for both the null and alternative hypotheses, given the
data. We give an example to highlight the importance of deriving alternative hypotheses and representing these as probability
models. Fifteen technical issues are addressed to clarify various points that have appeared incorrectly in the recent literature.
We offer several remarks regarding the future of empirical science and data analysis under an I-T framework. 相似文献
959.
American black bears frequently abandon their home ranges in late summer and move to feeding areas to fatten themselves for
hibernation. We examined seasonal movements of 206 radio-collared bears in north-central Minnesota during 1981–1990. We exploited
the variability in this long-term data set to test tradeoffs for animals leaving their home range. Late summer movements were
common for both sexes and all ages (39% of females, 44% of males), but were variable from year-to-year in prevalence, timing,
and destination. Bears typically left their summer home ranges in August and returned ~6 weeks later in September or October.
Most traveled southward, where acorns were more plentiful (median = 10 km for females, 26 km for males; maximum = 168 km).
These facultative migrations were most common when rich resources were available outside home ranges. Bears were least apt
to leave when foods were scarce in their home range, possibly sensing a risk of migrating during a widespread food failure.
Among females, those whose body mass was close to a reproductive threshold were most prone to migrate. Migrating bears were
less likely to be killed by hunters, suggesting that they were especially vigilant. 相似文献
960.
David Lindstr?m Inger Odnevall Wallinder 《Environmental monitoring and assessment》2011,173(1-4):139-153
Galvanized steel structures are used in a large variety of external constructions in the modern urban society, and their beneficial properties from a corrosion and oxidation perspective are well known. Less investigated is the extent of their contribution to the diffuse dispersion of zinc in the society and also to the environmental fate of corrosion-induced released zinc. This paper presents long-term runoff rates of zinc from galvanized steel surfaces with main focus on hot-dipped galvanized steel exposed for up to 10 years at nonsheltered urban atmospheric conditions. The long-term capacities of a naturally formed patina and the presence of surface treatments and coatings to hinder and reduce corrosion-induced zinc runoff from galvanized steel are elucidated. The environmental interaction of zinc runoff and concrete surfaces in pavement and urban storm drain systems is highlighted and the high capacity of concrete to retain released zinc presented. 相似文献