Zero‐Altered and other Regression Models for Count Data with Added Zeros

Heilbron, David C.

doi:10.1002/bimj.4710360505

Cited by 294 publications

(219 citation statements)

References 8 publications

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“…Because of a zero-inflated distribution [28], a two-part approach [29,30] was taken to analysing seed set data. First, we used a logistic regression to model the probability of setting seeds (yes or no), with the same predictors as for stigma closure, followed by a LR test.…”

Section: Methods (A) Study Organismsmentioning

confidence: 99%

Nectar bacteria, but not yeast, weaken a plant–pollinator mutualism

2013

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Mutualistic interactions are often subject to exploitation by species that are not directly involved in the mutualism. Understanding which organisms act as such 'third-party' species and how they do so is a major challenge in the current study of mutualistic interactions. Here, we show that even species that appear ecologically similar can have contrasting effects as third-party species. We experimentally compared the effects of nectar-inhabiting bacteria and yeasts on the strength of a mutualism between a hummingbird-pollinated shrub, Mimulus aurantiacus, and its pollinators. We found that the common bacterium Gluconobacter sp., but not the common yeast Metschnikowia reukaufii, reduced pollination success, seed set and nectar consumption by pollinators, thereby weakening the plant-pollinator mutualism. We also found that the bacteria reduced nectar pH and total sugar concentration more greatly than the yeasts did and that the bacteria decreased glucose concentration and increased fructose concentration whereas the yeasts affected neither. These distinct changes to nectar chemistry may underlie the microbes' contrasting effects on the mutualism. Our results suggest that it is necessary to understand the determinants of microbial species composition in nectar and their differential modification of floral rewards to explain the mutual benefits that plants and pollinators gain from each other.

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Section: Methods (A) Study Organismsmentioning

confidence: 99%

Nectar bacteria, but not yeast, weaken a plant–pollinator mutualism

2013

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“…The explanatory covariates selection was carried out by first independently fitting a binomial regression model for the dichotomized data for fruiting occurrence and, after, fitting a log-normal model using only the non-null intensity data (weight of pods), as proposed by Heilbron (1994) and Woollons (1998). The independent fitting of these generalized linear models can be accomplished using maximum likelihood estimation methods.…”

Section: Modeling Approachmentioning

confidence: 99%

Inter-annual variability in Prosopis caldenia pod production in the Argentinean semiarid pampas: A modelling approach

Risio

Calama

Bogino

et al. 2016

Journal of Arid Environments

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The driest part of the Argentinean pampas is occupied by semiarid woodlands dominates by Prosopis caldenia Burkart (Calden). Calden pods are a highly valuable fodder supplement for livestock but its production is highly variable. Our objective was to analyze and model the temporal pattern in inter-annual variability of Calden pod production. Our key hypothesis is that weather conditions are the main determinant of the pod masting behavior. Tree size and climatic variables were evaluated as explanatory covariates using a zero-inflated log-normal modelling approach. The proposed final model structure incorporated 25 parameters, including four variance components, two intercepts for both the logistic and the log-normal parts of the model, and nineteen parameters associated with fixed effects. Climate had a strong influence on the flowering-fruiting Calden process and on the inter-annual variability of the final pod production at the tree level. Temperatures during bud breaking, flowering and fruit shedding, together with the precipitation from the final month of fruit shedding and the total amount of the prior vegetative cycle, were the main weather covariates that affect the processes. KeywordsZero-inflated, fruit, non-wood forest product, calden.Abbreviation list g per crown area square metre grams per square metre of crown area; ZILN zero inflated log normal

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“…The works of White and Bennetts (1996) give an example of fitting the negative binomial distribution to point count data for orange-crowned warblers (Vermivora celata) when comparing their relative abundance among forest sites. Zero-inflated Poisson (ZIP) models and negative binomial regression models are recommended for analysis of count data with frequent 0 values (e.g., rare species studies) in which data transformations are not feasible ( Heilbron 1994, Welsh et al 1996, Ridout et al 1998, Agarwal et al 2002, Hall and Berenhaut 2002.…”

Section: Generalised Least Squares (Gls) Apporachmentioning

confidence: 99%