Fixed-effect variable selection in linear mixed models using statistics

Orelien, Jean G.; Edwards, Lloyd J.

doi:10.1016/j.csda.2007.06.006

Cited by 84 publications

(70 citation statements)

References 23 publications

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“…We evaluated the significance of each of the parameters retained in the best models for snowshoe hares and redbacked voles based on whether their 95% confidence intervals excluded 0. The fit of the best isodar models for each species was evaluated using marginal R 2 values (Orelien and Edwards 2008).…”

Section: Isodar Analysismentioning

confidence: 99%

An appraisal of the fitness consequences of forest disturbance for wildlife using habitat selection theory

et al. 2010

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Isodar theory can help to unveil the fitness consequences of habitat disturbance for wildlife through an evaluation of adaptive habitat selection using patterns of animal abundance in adjacent habitats. By incorporating measures of disturbance intensity or variations in resource availability into fitness-density functions, we can evaluate the functional form of isodars expected under different disturbance-fitness relationships. Using this framework, we investigated how a gradient of forest harvesting disturbance and differences in resource availability influenced habitat quality for snowshoe hares (Lepus americanus) and red-backed voles (Myodes gapperi) using pairs of logged and uncut boreal forest. Isodars for both species had positive intercepts, indicating reductions to maximum potential fitness in logged stands. Habitat selection by hares depended on both conspecific density and differences in canopy cover between harvested and uncut stands. Fitness-density curves for hares in logged stands were predicted to shift from diverging to converging with those in uncut forest across a gradient of high to low disturbance intensity. Selection for uncut forests thus became less pronounced with increasing population size at low levels of logging disturbance. Voles responded to differences in moss cover between habitats which reflected moisture availability. Lower moss cover in harvested stands either reduced maximum potential fitness or increased the relative rate of decline in fitness with density. Differences in vole densities between harvested and uncut stands were predicted, however, to diminish as populations increased. Our findings underscore the importance of accounting for density-dependent behaviors when evaluating how changing habitat conditions influence animal distribution.

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Section: Isodar Analysismentioning

confidence: 99%

An appraisal of the fitness consequences of forest disturbance for wildlife using habitat selection theory

et al. 2010

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“…We used AIC corrected for small sample size (AIC c ) to rank candidate models and multimodel inference to calculate coefficients for variables with 90% and 95% CIs. To evaluate the accuracy of top ranking models (DAIC c 2.0) we calculated marginal R 2 -values for each model (Orelien and Edwards 2008). General linear mixed models were run using the MIXED procedure in SAS 9.1 (SAS Institute Inc. 2003).…”

Section: Methodsmentioning

confidence: 99%

Changes in spatial pattern of trees and snags during structural development in Picea mariana boreal forests

et al. 2006

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“…The goodnessof-fit of the regressions was quantified using a coefficient of determination for mixed models (r 2 ) (Vonesh and Chinchilli, 1997), which has been shown to perform well in simulation studies (Orelien and Edwards, 2008). Gait-specific effects on COM mechanics were tested using a mixed-model analysis of covariance (ANCOVA), where speed, gait and speed ϫ gait were set as fixed factors and individual lemur was set as a random factor.…”

Section: Statisticsmentioning

confidence: 99%

The gaits of primates: center of mass mechanics in walking, cantering and galloping ring-tailed lemurs,Lemur catta

O’Neill

Schmitt

2012

Journal of Experimental Biology

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SUMMARY Most primates, including lemurs, have a broad range of locomotor capabilities, yet much of the time, they walk at slow speeds and amble, canter or gallop at intermediate and fast speeds. Although numerous studies have investigated limb function during primate quadrupedalism, how the center of mass (COM) moves is not well understood. Here, we examined COM energy, work and power during walking, cantering and galloping in ring-tailed lemurs, Lemur catta (N=5), over a broad speed range (0.43–2.91 m s–1). COM energy recoveries were substantial during walking (35–71%) but lower during canters and gallops (10–51%). COM work, power and collisional losses increased with speed. The positive COM works were 0.625 J kg–1 m–1 for walks and 1.661 J kg–1 m–1 for canters and gallops, which are in the middle range of published values for terrestrial animals. Although some discontinuities in COM mechanics were evident between walking and cantering, there was no apparent analog to the trot–gallop transition across the intermediate and fast speed range (dimensionless v>0.75, Fr>0.5). A phenomenological model of a lemur cantering and trotting at the same speed shows that canters ensure continuous contact of the body with the substrate while reducing peak vertical COM forces, COM stiffness and COM collisions. We suggest that cantering, rather than trotting, at intermediate speeds may be tied to the arboreal origins of the Order Primates. These data allow us to better understand the mechanics of primate gaits and shed new light on primate locomotor evolution.

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Fixed-effect variable selection in linear mixed models using statistics

Cited by 84 publications

References 23 publications

An appraisal of the fitness consequences of forest disturbance for wildlife using habitat selection theory

An appraisal of the fitness consequences of forest disturbance for wildlife using habitat selection theory

Changes in spatial pattern of trees and snags during structural development in Picea mariana boreal forests

The gaits of primates: center of mass mechanics in walking, cantering and galloping ring-tailed lemurs,Lemur catta

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