Capturing Dynamics With the Correct Rates: Inverse Problems Using Semiparametric Approaches

Nelson, William A.; McCauley, Edward; Wimbert, Jörg

doi:10.1890/02-8019

Cited by 19 publications

(22 citation statements)

References 69 publications

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“…). This allowed us to model aspects of the system that are known, but allow the empirical patterns to ‘speak for themselves’ with regard to aspects that are unknown (Nelson, McCauley & Wimbert ).…”

Section: Methodsmentioning

confidence: 99%

A complex network of interactions controls coexistence and relative abundances in Patagonian grass‐shrub steppes

et al. 2014

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Summary1. The coexistence of shrubs and grasses has intrigued ecologists for the past century, and the conundrum of shrub-grass coexistence is at the core of debates on the functioning of semi-arid ecosystems. Here, we explored how the interplay of root competition and facilitation between life-forms at different life stages and demographic bottlenecks controls the long-term coexistence of multiple shrub and grass species in semi-arid Patagonian steppes.2. We used the spatially explicit and individual-based simulation model DINVEG that integrates the abundant information on the semi-arid Patagonian grass-shrub steppes to test six competing hypotheses on the mechanisms that govern the coexistence and relative abundances of several grass and shrub species. The structurally realistic model allows for a direct comparison of model outputs with a wide range of previously collected field data.3. We formulate three competing hypotheses on vertical root overlap between grasses and shrubs (no overlap, partial overlap, full overlap) that were crosses with two hypotheses on asymmetric shrub-grass facilitation (with and without). Each of the six variants of DINVEG were tested in their ability to generate dynamics in accordance with detailed field data, and we performed global sensitivity analyses to reveal demographic bottlenecks and controls. The hypothesis combining partial vertical root overlap with no facilitation was the most likely hypothesisgiven the data. It created demographic bottlenecks in recruitment and emergence that controlled grass and shrub abundances, respectively, and only this hypothesis generated a situation where grasses controlled shrub abundances (by limiting shrub recruitment), but where grass abundance was only weakly controlled by shrubs. Internal water dynamics generated reduced competition of shrubs to neighboured grasses that was sufficient to produce the observed ring of grasses around shrubs, and most of the parameterizations that approximated the observed species-specific abundances were able to reproduce the observed equilibrated spatial patterns of the mature community.5. Synthesis. We found a complex network of mechanisms that controlled growth-form coexistence and relative abundances in the Patagonian grass-shrub steppe where both, demographic bottlenecks and species interactions across life-forms, species and life stages were important. Our study points to alternative mechanisms of shrubgrass coexistence that may play an important role in dry grasslands and steppes where fire and herbivory are not key drivers and provide an avenue to detect them.

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Section: Methodsmentioning

confidence: 99%

A complex network of interactions controls coexistence and relative abundances in Patagonian grass‐shrub steppes

et al. 2014

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“…can be used to infer both stage-specific development and stage-specific mortality rates (Nelson et al, 2004). …”

Section: Inferring Stage-specific Development and Mortality Ratesmentioning

confidence: 99%

“…Following Nelson et al (2004), this requires combining likelihood values from both the time series of stage abundances of live animals and the cumulative number of individuals that die from each stage for each pellet quality. In terms of the model, this corresponds to estimating the δ and α parameters for each stage and pellet quality treatment.…”

Section: Inferring Stage-specific Development and Mortality Ratesmentioning

confidence: 99%

“…Importantly, by tracking both the number of live and dead animals on each sampling date, we can estimate both instarspecific development and mortality rates from the observed time series (Nelson, McCauley, & Wimbert, 2004) and show that food quality effects on larval life histories vary significantly across instars. We use the bean weevil Callosobruchus maculatus (Fabricius) (Coleoptera: Bruchidae) because it is an herbaceous pest of seed pulses that is easily maintained in the laboratory on both natural and artificial seed pulses.…”

Section: Introductionmentioning

confidence: 99%

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Food quality effects on instar‐specific life histories of a holometabolous insect

Holmes

Nelson

Lougheed

2020

Ecology and Evolution

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1. It is a long-standing challenge to understand how changes in food resources impact consumer life history traits and, in turn, impact how organisms interact with their environment. To characterize food quality effects on life history, most studies follow organisms throughout their life cycle and quantify major life events, such as age at maturity or fecundity. From these studies, we know that food quality generally impacts body size, juvenile development, and life span. Importantly, throughout juvenile development, many organisms develop through several stages of growth that can have different interactions with their environment. For example, some parasitoids typically attack larger instars, whereas larval insect predators typically attack smaller instars. Interestingly, most studies lump all juvenile stages together, which ignores these ecological changes over juvenile development.2. We combine a cross-sectional experimental approach with a stage-structured population model to estimate instar-specific vital rates in the bean weevil, Callosobruchus maculatus across a food quality gradient. We characterize food quality effects on the bean weevil's life history traits throughout its juvenile ontogeny to test how food quality impacts instar-specific vital rates.3. Vital rates differed across food quality treatments within each instar; however, their effect differed with instar. Weevils consuming low-quality food spent 38%, 37%, and 18% more time, and were 34%, 53%, and 63% smaller than weevils consuming high-quality food in the second, third, and fourth instars, respectively.Overall, our results show that consuming poor food quality means slower growth, but that food quality effects on vital rates, growth and development are not equal across instars. Differences in life history traits over juvenile ontogeny in response to food quality may impact how organisms interact with their environment, including how susceptible they are to predation, parasitism, and their competitive ability. K E Y W O R D Scowpea weevil, juvenile ontogeny, phytophagous consumer, stage-structured population model | 627 HOLMES Et aL.

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“…Certainly, we should be rather careful regarding the model's quantitative predictions-which may be quite inaccurate given the usual uncertainty of model functions and large scattering of points in laboratory experiments [10,[12][13][14]. One possible course of action could be to use data on the experimental population dynamics to reconstruct the unknown underlying model functions [7,25,37,38]. One can try to reconstruct as closely as possible the 'true' model functions that should be used in modelling the given experimental mesocosm or ecosystem.…”

Section: Discussionmentioning

confidence: 99%

When can we trust our model predictions? Unearthing structural sensitivity in biological systems

Adamson

Морозов

2013

Proc. R. Soc. A.

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It is well recognized that models in the life sciences can be sensitive to small variations in their model functions, a phenomenon known as 'structural sensitivity'. Conventionally, modellers test for sensitivity by varying parameters for a specific formulation of the model functions, but models can show structural sensitivity to the choice of functional representations used: a particularly concerning problem when system processes are too complex, or insufficiently understood, to theoretically justify specific parameterizations. Here we propose a rigorous test for the detection of structural sensitivity in a system with respect to the local stability of equilibria, the main idea being to project infinite dimensional function space onto a finite dimensional space by considering the local properties of the model functions. As an illustrative example, we use our test to demonstrate structural sensitivity in the seminal Rosenzweig-MacArthur predator-prey model, and show that the conventional parameterbased approach can fail to do so. We also consider some implications that structural sensitivity has for ecological modelling: we argue that when the model exhibits structural sensitivity but experimental results remain consistent it may indicate that there is a problem with the model construction, and that in some cases trying to find an 'optimal' parameterization of a model function may simply be impossible when the model exhibits structural sensitivity. Finally, we suggest that the phenomenon of structural sensitivity in biological models may help explain the irregular oscillations often observed in real ecosystems.

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Capturing Dynamics With the Correct Rates: Inverse Problems Using Semiparametric Approaches

Cited by 19 publications

References 69 publications

A complex network of interactions controls coexistence and relative abundances in Patagonian grass‐shrub steppes

A complex network of interactions controls coexistence and relative abundances in Patagonian grass‐shrub steppes

Food quality effects on instar‐specific life histories of a holometabolous insect

When can we trust our model predictions? Unearthing structural sensitivity in biological systems

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