Zero tolerance ecology: improving ecological inference by modelling the source of zero observations

Martin, Tara G.; Wintle, Brendan A.; Rhodes, Jonathan R.; Kuhnert, Petra M.; Field, Samuel; Low‐Choy, Samantha; Tyre, Andrew J.; Possingham, Hugh P.

doi:10.1111/j.1461-0248.2005.00826.x

Cited by 753 publications

(703 citation statements)

References 61 publications

(93 reference statements)

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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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“…As with most large food webs, the data display overdispersion with large numbers of zero values (missing interactions), and so a zero-inflated Poisson (ZIP) model is appropriate [29]. In a ZIP model, two generalized linear models are used to explain the data: a logit part for the binary presence-absence of an interaction, and a Poisson part for its magnitude (i.e.…”

Section: Methodsmentioning

confidence: 99%

Warming and nitrogen affect size structuring and density dependence in a host–parasitoid food web

Sassi

Staniczenko

Tylianakis

2012

Phil. Trans. R. Soc. B

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Body size is a major factor constraining the trophic structure and functioning of ecological communities. Food webs are known to respond to changes in basal resource abundance, and climate change can initiate compounding bottom-up effects on food-web structure through altered resource availability and quality. However, the effects of climate and co-occurring global changes, such as nitrogen deposition, on the density and size relationships between resources and consumers are unknown, particularly in host-parasitoid food webs, where size structuring is less apparent. We use a Bayesian modelling approach to explore the role of consumer and resource density and body size on host-parasitoid food webs assembled from a field experiment with factorial warming and nitrogen treatments. We show that the treatments increased resource (host) availability and quality (size), leading to measureable changes in parasitoid feeding behaviour. Parasitoids interacted less evenly within their host range and increasingly focused on abundant and high-quality (i.e. larger) hosts. In summary, we present evidence that climate-mediated bottom-up effects can significantly alter food-web structure through both density-and trait-mediated effects.

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“…A Poisson distribution was used for this analysis because of the large number of zeros in the data set, and because these zeros are likely to represent true low frequency effects rather than missing data (Martin et al, 2005). The interaction between treatment and location was not significant and was not included as there is insufficient replication in this design (only one treatment and one control plot per block).…”

Section: Statistical Analysesmentioning

confidence: 99%

Passive warming reduces stress and shifts reproductive effort in the Antarctic moss,Polytrichastrum alpinum

Shortlidge

Eppley

Köhler

et al. 2016

Ann Bot

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Background and Aims The Western Antarctic Peninsula is one of the most rapidly warming regions on Earth, and many biotic communities inhabiting this dynamic region are responding to these well-documented climatic shifts. Yet some of the most prevalent organisms of terrestrial Antarctica, the mosses, and their responses to warming have been relatively overlooked and understudied. In this research, the impacts of 6 years of passive warming were investigated using open top chambers (OTCs), on moss communities of Fildes Peninsula, King George Island, Antarctica.Methods The effects of experimental passive warming on the morphology, sexual reproductive effort and stress physiology of a common dioicous Antarctic moss, Polytrichastrum alpinum, were tested, gaining the first speciesspecific mechanistic insight into moss responses to warming in the Antarctic. Additionally community analyses were conducted examining the impact of warming on overall moss percentage cover and sporophyte production in intact Antarctic moss communities.Key Results Our results show a generally greater percentage moss cover under warming conditions as well as increased gametangia production in P. alpinum. Distinct morphological and physiological shifts in P. alpinum were found under passive warming compared with those without warming: warmed mosses reduced investment in cellular stress defences, but invested more towards primary productivity and gametangia development.Conclusions Taken together, results from this study of mosses under passive warming imply that in ice-free moss-dominated regions, continued climate warming will probably have profound impacts on moss biology and colonization along the Western Antarctic Peninsula. Such findings highlight the fundamental role that mosses will play in influencing the terrestrialization of a warming Antarctica.

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Zero tolerance ecology: improving ecological inference by modelling the source of zero observations

Cited by 753 publications

References 61 publications

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

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

Warming and nitrogen affect size structuring and density dependence in a host–parasitoid food web

Passive warming reduces stress and shifts reproductive effort in the Antarctic moss,Polytrichastrum alpinum

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