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1.
JAY E. HOWELL JAMES T. PETERSON MICHAEL J. CONROY 《The Journal of wildlife management》2008,72(1):168-178
Abstract To predict the distributions of breeding birds in the state of Georgia, USA, we built hierarchical models consisting of 4 levels of nested mapping units of decreasing area: 90,000 ha, 3,600 ha, 144 ha, and 5.76 ha. We used the Partners in Flight database of point counts to generate presence and absence data at locations across the state of Georgia for 9 avian species: Acadian flycatcher (Empidonax virescens), brown-headed nuthatch (Sitta pusilla), Carolina wren (Thryothorus ludovicianus), indigo bunting (Passerina cyanea), northern cardinal (Cardinalis cardinalis), prairie warbler (Dendroica discolor), yellow-billed cuckoo (Coccyzus americanus), white-eyed vireo (Vireo griseus), and wood thrush (Hylocichla mustelina). At each location, we estimated hierarchical-level-specific habitat measurements using the Georgia GAP Analysis18 class land cover and other Geographic Information System sources. We created candidate, species-specific occupancy models based on previously reported relationships, and fit these using Markov chain Monte Carlo procedures implemented in OpenBugs. We then created a confidence model set for each species based on Akaike's Information Criterion. We found hierarchical habitat relationships for all species. Three-fold cross-validation estimates of model accuracy indicated an average overall correct classification rate of 60.5%. Comparisons with existing Georgia GAP Analysis models indicated that our models were more accurate overall. Our results provide guidance to wildlife scientists and managers seeking predict avian occurrence as a function of local and landscape-level habitat attributes. 相似文献
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Question: Is plant diversity in fragmented semi‐natural grasslands related to present and historical landscape context? Location: Southern Sweden. Methods: Plant diversity was described at 30 semi‐natural grassland sites in terms of total and specialist plant species richness at the site and species density at different scales (0.5–10 m2). These measures are commonly used to assess conservation value of semi‐natural grasslands. Landscape context was measured as contemporary connectivity to other semi‐natural grasslands, historical connectivity 50 years ago, amount of linear elements potentially suitable for dispersal (road verges, power line clearings), and amount of forest (inverse of the openness of the landscape). Results: The diversity measures were generally correlated with each other, implying that species richness in a subset of the grassland can predict the total richness. Plant species density at three scales (0.5 m2, 10 m2 and total) was related to the landscape context using an information theoretic approach. Results showed that total species richness increased with increased size of grasslands, contrary to earlier diversity studies in semi‐natural grasslands. Larger grasslands were more heterogeneous than smaller grasslands, and this is a likely reason for the species‐area relationship. Heterogeneity was also of high importance at the smaller scales (0.5 m2, 10 m2). With increased amount of forest, total species richness increased but species density on 10 m2 decreased. There was no influence of connectivity in either the contemporary or the historical landscape, contrary to previous studies. Conclusions: Grassland size and heterogeneity are of greater importance for plant diversity in semi‐natural grassland, than grassland connectivity in the landscape. 相似文献
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Mosses and vascular plants have been shown to be reliable indicators of wetland habitat delineation and environmental quality. Knowledge of the best ecological predictors of the quality of wetland moss and vascular plant communities may determine if similar management practices would simultaneously enhance both populations. We used Akaike's Information Criterion to identify models predicting a moss quality assessment index (MQAI) and a vascular plant index of biological integrity based on floristic quality (VIBI-FQ) from 27 emergent and 13 forested wetlands in Ohio, USA. The set of predictors included the six metrics from a wetlands disturbance index (ORAM) and two landscape development intensity indices (LDIs). The best single predictor of MQAI and one of the predictors of VIBI-FQ was an ORAM metric that assesses habitat alteration and disturbance within the wetland, such as mowing, grazing, and agricultural practices. However, the best single predictor of VIBI-FQ was an ORAM metric that assessed wetland vascular plant communities, interspersion, and microtopography. LDIs better predicted MQAI than VIBI-FQ, suggesting that mosses may either respond more rapidly to, or recover more slowly from, anthropogenic disturbance in the surrounding landscape than vascular plants. These results supported previous predictive studies on amphibian indices and metrics and a separate vegetation index, indicating that similar wetland management practices may result in qualitatively the same ecological response for three vastly different wetland biological communities (amphibians, vascular plants, and mosses). 相似文献
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Abstract We developed multiple a priori hypotheses to link the observed spatial patterns with colonisation processes in the high alpine cushion plant, Azorella madreporica. We conducted this study in the Molina River basin (33°20′ S, 70°16′ W, 3600 m a.s.l.), in the Andes of central Chile, approximately 50 km east of Santiago. We mapped and measured size (as a surrogate for age) of individual cushions in two populations and used a standard spatial analytical tool (semivariograms) to test our alternative a priori hypotheses related to colonisation mode of the cushion species. In both populations, the size distribution of A. madreporica reflected a negative exponential or inverse‐J pattern, typical of uneven‐aged populations, where most of the cushions belonged to relatively smaller size classes, in effect, a regular success in the establishment of seedlings, where all size classes of cushions were represented in the population. The results were site‐specific, where best‐fit semivariograms for spatial cushion's size distribution suggested a gradual colonisation in one population and an episodic colonisation in the other population. Microsite distribution proved to be homogeneous at both sites. Thus, the study of the spatial explicit size‐age population distribution of an alpine species provides valuable information about the frequency, magnitude and site variation of the reproductive pulses in these harsh environments. 相似文献
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ABSTRACT In spite of the wide use and acceptance of information theoretic approaches in the wildlife sciences, debate continues on the correct use and interpretation of Akaike's Information Criterion as compared to frequentist methods. Misunderstandings as to the fundamental nature of such comparisons continue. Here we agree with Steidl's argument about situation-specific use of each approach. However, Steidl did not make clear the distinction between statistical and biological hypotheses. Certainly model selection is not statistical, or null, hypothesis testing; importantly, it represents a more effective means to test among competing biological, or research, hypotheses. Employed correctly, it leads to superior strength of inference and reduces the risk that favorite hypotheses are uncritically accepted. 相似文献
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Age influences behavioral decisions such as reproductive timing and effort. In photoperiodic species, such age effects may be mediated, in part, by the individual's age‐accrued experience with photostimulation. In female European starlings (Sturnus vulgaris) that do not differ in age, experimental manipulation of photostimulation experience (photoexperience) affects hypothalamic, pituitary, and gonadal activity associated with reproductive development. Does photoexperience also affect activity in forebrain regions involved in processing a social cue, the song of males, which can influence mate choice and reproductive timing in females? Female starlings prefer long songs over short songs in a mate‐choice context, and, like that in other songbird species, their auditory telencephalon plays a major role in processing these signals. We manipulated the photoexperience of female starlings, photostimulated them, briefly exposed them to either long or short songs, and quantified the expression of the immediate‐early gene ZENK (EGR‐1) in the caudomedial nidopallium as a measure of activity in the auditory telencephalon. Using an information theoretic approach, we found higher ZENK immunoreactivity in females with prior photostimulation experience than in females experiencing photostimulation for the first time. We also found that long songs elicited greater ZENK immunoreactivity than short songs did. We did not find an effect of the interaction between photoexperience and song length, suggesting that photoexperience does not affect forebrain ZENK‐responsiveness to song quality. Thus, photoexperience affects activity in an area of the forebrain that processes social signals, an effect that we hypothesize mediates, in part, the effects of age on reproductive decisions in photoperiodic songbirds. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 2009 相似文献
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Fire is an important process in many ecosystems, but inappropriate fire regimes can adversely affect biodiversity. We identified a naturally flammable heathy woodland ecosystem where the use of planned fire had increased the extent of older vegetation, and quantified the abundance of two small native mammals in this landscape (silky mouse Pseudomys apodemoides and heath rat P. shortridgei). We defined four time‐since‐fire (TSF) categories representing a 2‐ to 55‐year post‐fire sequence and, on the basis of a habitat accommodation model, predicted that both species would select younger age‐classes over older ones. We also predicted that (i) much of the variance in vegetation structure would remain unexplained by TSF and (ii) statistical models of mammal abundance and occupancy including structural variables as predictors would be better than models including TSF. Pseudomys apodemoides selected 17‐ to 23‐year‐old sites, while there was no evidence that P. shortridgei selected a particular TSF category, findings that were inconsistent with our predictions. In line with our predictions, relatively large portions of the variance in vegetation structure remained unexplained by TSF (adjustedr2 for four structural variables: 0.24, 0.29, 0.35 and 0.57), and in three of four cases there was strong evidence that statistical models of mammal abundance and occupancy including structural variables were better than those including TSF. At the site scale (hectares), P. shortridgei abundance was positively related to the cover of dead material at the base of Xanthorrhoea plants and at the trap scale (metres), the trapability of both species was significantly related to vegetation volume at 0–20 cm. Our findings suggest that TSF may not be a good proxy for either vegetation structure or species abundance/occupancy. 相似文献
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KaKs_Calculator is a software package that calculates nonsynonymous （Ka） and synonymous （Ks） substitution rates through model selection and model averaging. Since existing methods for this estimation adopt their specific mutation （substitution） models that consider different evolutionary features, leading to diverse estimates, KaKs_Calculator implements a set of candidate models in a maximum likelihood framework and adopts the Akaike information criterion to measure fitness between models and data, aiming to include as many features as needed for accurately capturing evolutionary information in protein-coding sequences. In addition, several existing methods for calculating Ka and Ks are also incorporated into this software. KaKs_Calculator, including source codes, compiled executables, and documentation, is freely available for academic use at http：//evolution.genomics.org.cn/software.htm. 相似文献
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Abstract: Predators are the major cause of nest failure for prairie grouse, and corvids are widespread generalist predators that exploit land altered by humans where grouse are found. We studied how human-caused habitat change affected predator and prey by using habitat variables to model nest selection, corvid density, and nest success for sharp-tailed grouse (Tympanuchus phasianellus) in Alberta, Canada, 1999–2001. Habitat was quantified over a range of extents (radius of observation) from 2 to 2,265 m. We predicted that habitat features associated with corvid density at broad extents would also relate to grouse nest success, and that nesting cover and the presence of avian predator perch sites would be important at smaller extents. Corvid density was higher in landscapes with higher proportions of crop and sparse grassland (1,600-m extent). Conversely, nest success was markedly higher (≥4 times) in landscapes with <10% crop and <35% crop and sparse grassland (aggregated) at broad extents (1,600 m). Moreover, nests were 8 times more likely to succeed in landscapes with lower relative corvid densities (<3 vs. ≥3 corvids/km2). At smaller scales, nests were more likely to succeed with greater heights of concealment cover within 50-m of nests. Land managers can likely improve nest success for grouse in grassland systems by targeting concealment cover heights of at least 13 cm measured over a 50-m extent, and focusing efforts in landscapes with <10% crop and <35% crop and sparse grassland (1,600-m extent). 相似文献
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Mark-recapture methods cannot estimate both mortality and dispersal rates of a wild population simultaneously. However, when an artificially cultured population is released into an area, the initial population size and the initial population distribution are usually known. If artificially cultured individuals are released with marks or distinguished from wild individuals or if no wild individual exists in the study area, we can estimate both the mortality and dispersal rates of the artificial population. The numbers of dispersed and dead individuals are estimated from the dispersal rate from the diffusion model and the total decreasing rate estimated from a mark-recapture data. We can estimate both the time-dependent and time-independent dispersal rates from the data. We choose the best fit model that has the smallest value of Akaike's Information Criteria. We also consider ‘concentric circles approximation” of spatial distribution, in which the cumulative and frequency distributions are analytically obtained. 相似文献
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In the development of a species distribution model based on regression techniques such as generalized linear or additive modelling (GLM/GAM), a basic assumption is that records of species presence and absence are real. However, a common concern in many studies examining species distributions is that absences cannot be inferred with certainty. This is particularly the case where the species is rare, difficult to detect and/or does not occupy all available habitat considered suitable. The western ground parrot ( Pezoporus wallicus flaviventris ) of southern Western Australia, Australia, is a case in point, as not only is it rare and difficult to detect, but it is also unlikely to occupy all available suitable habitat. A recent survey of ground parrots provided the opportunity to develop a predictive distribution model. As the data were susceptible to false absences, these were replaced with randomly selected 'pseudo' absences and modelled using GLM. As a comparison, presence-only information was modelled using a relatively new approach, MAXENT, a machine-learning technique that has been shown to perform comparatively well. The predictive performance of both models, as assessed by the receiver operating characteristic plot (ROC) was high (AUC > 0.8), with MAXENT performing only marginally better than the GLM. These approaches both indicated that the ground parrot prefers areas relatively high in altitude, distant from rivers, gently sloping to level habitat, with an intermediate cover of vegetation and where there is a mosaic of vegetation ages. In this case, the use of presence-only information resulted in the identification of important environmental attributes defining the occurrence of the ground parrot, but additional factors that account for the inability of the bird to occupy all suitable habitat should be a component of model refinement. 相似文献
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Michael R. O’Farrell Mary M. Yoklavich Milton S. Love 《Environmental Biology of Fishes》2009,85(3):239-250
Habitat associations and the effect of predators on dwarf rockfishes (Sebastes spp.) were investigated in two large marine protected areas (MPAs) off southern California. Using data from submersible surveys, the occurrence and abundance of dwarf rockfishes were modeled using substrata types and the biomass of predators as predictor variables. The occurrence and abundance of dwarf rockfishes generally were positively associated with rock, boulder, and cobble substrata. The association between predators and occurrence of dwarf rockfishes differed substantially between species. Predator density and biomass levels were much lower in the southern California MPAs than in a de facto MPA off central California. Better inference about predator effects on dwarf rockfishes will be possible if the predator biomass and densities of southern California MPAs increase to that observed in the de facto MPA. 相似文献
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为了对我国城市水资源利用效率问题进行分析和评价,本文基于数据包络分析方法,从农业、工业、生活、社会等几个方面共选取了5个输入指标及6个输出指标,利用AIC信息准则(Akaike information criterion)进行了变量选择,构建了较为科学合理的用水效率评价指标体系.在此基础上,采用香农熵指数提升了传统CCR(由Charnes A,Cooper W W,Rhodes E提出)模型的识别能力,选取我国31个省会城市为研究对象,给出了省会城市水资源效率的完整排名。结果表明:①绝大部分城市综合效率得分(CES,Comprehensive efficiency score)普遍不高,投入产出比仍有较大的进步空间;②拉萨、北京、天津、银川、海口、上海等城市CES得分相对较高,这说明一个城市水资源利用效率的高低与经济发展水平可能没有必然的联系,其他城市应结合自身情况向CES得分靠前的城市进行学习;③重庆、南宁、南昌、长沙等水资源较丰富的城市CES得分反而较低,表明这些城市可能存在大量水资源被浪费,应建立起节水机制,同时优化产业结构。 相似文献
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Thomas R. Stanley Kenneth P. Burnham 《Biometrical journal. Biometrische Zeitschrift》1998,40(4):475-494
Specification of an appropriate model is critical to valid statistical inference. Given the “true model” for the data is unknown, the goal of model selection is to select a plausible approximating model that balances model bias and sampling variance. Model selection based on information criteria such as AIC or its variant AICc, or criteria like CAIC, has proven useful in a variety of contexts including the analysis of open-population capture-recapture data. These criteria have not been intensively evaluated for closed-population capture-recapture models, which are integer parameter models used to estimate population size (N), and there is concern that they will not perform well. To address this concern, we evaluated AIC, AICc, and CAIC model selection for closed-population capture-recapture models by empirically assessing the quality of inference for the population size parameter N. We found that AIC-, AICc-, and CAIC-selected models had smaller relative mean squared errors than randomly selected models, but that confidence interval coverage on N was poor unless unconditional variance estimates (which incorporate model uncertainty) were used to compute confidence intervals. Overall, AIC and AICc outperformed CAIC, and are preferred to CAIC for selection among the closed-population capture-recapture models we investigated. A model averaging approach to estimation, using AIC, AICc, or CAIC to estimate weights, was also investigated and proved superior to estimation using AIC-, AICc-, or CAIC-selected models. Our results suggested that, for model averaging, AIC or AICc should be favored over CAIC for estimating weights. 相似文献
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Urban amphibian assemblages as metacommunities 总被引：5，自引：0，他引：5
Parris KM 《The Journal of animal ecology》2006,75(3):757-764
1. Urban ecosystems are expanding throughout the world, and urban ecology is attracting increasing research interest. Some authors have questioned the value of existing ecological theories for understanding the processes and consequences of urbanization. 2. In order to assess the applicability of metacommunity theory to urban systems, I evaluated three assumptions that underlie the theory - the effect of patch area, the effect of patch isolation, and species-environment relations - using data on assemblages of pond-breeding amphibians in the Greater Melbourne area of Australia. I also assessed the relative impact of habitat fragmentation, habitat isolation, and changes to habitat quality on these assemblages. 3. Poisson regression modelling provided support for an important increase in species richness with patch area (pond size) and a decrease in species richness with increasing patch isolation, as measured by surrounding road cover. Holding all other variables constant, species richness was predicted to be 2.8-5.5 times higher at the largest pond than at the smallest, while the most isolated pond was predicted to have 12-19% of the species richness of the least isolated pond. Thus, the data were consistent with the first two assumptions of metacommunity theory evaluated. 4. The quality of habitat at a pond was also important, with a predicted 44-56% decrease in the number of species detected at ponds with a surrounding vertical wall compared with those with a gently sloping bank. This demonstrates that environmental differences between habitat patches were also influencing amphibian assemblages, providing support for the species-sorting and/or mass-effect perspectives of metacommunity theory. 5. Without management intervention, urbanization may lead to a reduction in the number of amphibian species persisting in urban ponds, particularly where increasing isolation of ponds by roads and associated infrastructure reduces the probability of re-colonization following local extinction. Journal of Animal Ecology (2006) 75, 757-764 doi: 10.1111/j.1365-2656.2006.01096.x. 相似文献
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FRED S. GUTHERY 《The Journal of wildlife management》2008,72(8):1872-1875
Abstract: I hypothesized that statistical ritual has supplanted knowledge accrual as the sine qua non of wildlife science. Under the hypothesis, I deduced occurrence of 1) significance testing of the obvious and inconsequential, 2) quantitative debasement of research problems, and 3) publication of papers that largely lacked information but were methodologically impeccable. Articles in past and recent wildlife literature fit the deductions and supported the hypothesis. Thus, wildlife science is operating inefficiently because quantitative formalities are supplanting ecological information in technical articles. This problem can be corrected by a change of mindset in authors, referees, and editors. The change entails less emphasis on quantitative ritual and more emphasis on information that aids in understanding and explaining nature and managing wildlife. 相似文献
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We present a Bayesian method for deriving species-sensitivity distributions (SSDs). We employed four Bayesian statistical models to consider differences in tolerance to toxic substances among different taxonomic groups. We first used a Malkov chain Monte Carlo simulation based on these models to estimate the SSD parameters. We then computed deviance information criterion values of the models and compared them in order to select the model with the best predictive ability. We applied this approach to seven substances (zinc, lead, hexavalent chromium, cadmium, nickel, short-chain chloride paraffin, and chloroform) as case examples, and then compared the derived SSDs from the selected models and a model that assumed no tolerance differences among taxonomic groups. We discuss the advantages and limitations of our approach on the basis of our results. 相似文献
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Kevin Gross William F. Morris Michael S. Wolosin Daniel F. Doak 《Population Ecology》2006,48(1):79-89
Population projection matrices are commonly used by ecologists and managers to analyze the dynamics of stage-structured populations. Building projection matrices from data requires estimating transition rates among stages, a task that often entails estimating many parameters with few data. Consequently, large sampling variability in the estimated transition rates increases the uncertainty in the estimated matrix and quantities derived from it, such as the population multiplication rate and sensitivities of matrix elements. Here, we propose a strategy to avoid overparameterized matrix models. This strategy involves fitting models to the vital rates that determine matrix elements, evaluating both these models and ones that estimate matrix elements individually with model selection via information criteria, and averaging competing models with multimodel averaging. We illustrate this idea with data from a population of Silene acaulis (Caryophyllaceae), and conduct a simulation to investigate the statistical properties of the matrices estimated in this way. The simulation shows that compared with estimating matrix elements individually, building population projection matrices by fitting and averaging models of vital-rate estimates can reduce the statistical error in the population projection matrix and quantities derived from it. 相似文献