Mollie E. Brooks

Technical University of Denmark

13Publications

7H-index

4,786Citations

Publications 13

Newest

#1Mollie E. Brooks (DTU: Technical University of Denmark)H-Index: 7

#2Kasper Kristensen (DTU: Technical University of Denmark)H-Index: 14

Last.Benjamin M. Bolker (McMaster University)H-Index: 46

view all 7 authors...

Reproduction by individuals is typically recorded as count data (e.g., number of fledglings from a nest or inflorescences on a plant) and commonly modeled using Poisson or negative binomial distributions, which assume that variance is greater than or equal to the mean. However, distributions of reproductive effort are often underdispersed (i.e., variance < mean). When used in hypothesis tests, models that ignore underdispersion will be overly conservative and may fail to detect significant patte...

#1Mollie E. Brooks (UZH: University of Zurich)H-Index: 7

#2Christopher F. Clements (UoB: University of Bristol)H-Index: 14

Last.Arpat Ozgul (UZH: University of Zurich)H-Index: 22

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AbstractIndividuals in a population vary in their growth due to hidden and observed factors such as age, genetics, environment, disease, and carryover effects from past environments. Because size affects fitness, growth trajectories scale up to affect population dynamics. However, it can be difficult to estimate growth in data from wild populations with missing observations and observation error. Previous work has shown that linear mixed models (LMMs) underestimate hidden individual heterogeneit...

#1Mollie E. Brooks (DTU: Technical University of Denmark)H-Index: 7

#2Kasper Kristensen (DTU: Technical University of Denmark)H-Index: 14

Last.Benjamin M. Bolker (McMaster University)H-Index: 46

view all 9 authors...

Ecological phenomena are often measured in the form of count data. These data can be analyzed using generalized linear mixed models (GLMMs) when observations are correlated in ways that require random effects. However, count data are often zero-inflated, containing more zeros than would be expected from the standard error distributions used in GLMMs, e.g., parasite counts may be exactly zero for hosts with effective immune defenses but vary according to a negative binomial distribution for non-r...

glmmTMB Balances Speed and Flexibility Among Packages for Zero-inflated Generalized Linear Mixed Modeling

#1Mollie E. BrooksH-Index: 7

#2Kasper KristensenH-Index: 14

Last.Benjamin M. Bolker (McMaster University)H-Index: 46

view all 9 authors...

Count data can be analyzed using generalized linear mixed models when observations are correlated in ways that require random effects. However, count data are often zero-inflated, containing more zeros than would be expected from the typical error distributions. We present a new package, glmmTMB, and compare it to other R packages that fit zero-inflated mixed models. The glmmTMB package fits many types of GLMMs and extensions, including models with continuously distributed responses, but here we...

How well can body size represent effects of the environment on demographic rates? Disentangling correlated explanatory variables

#1Mollie E. Brooks (UZH: University of Zurich)H-Index: 7

#2Marianne Mugabo (University of Leeds)H-Index: 7

Last.Arpat Ozgul (UZH: University of Zurich)H-Index: 22

view all 5 authors...

1. Demographic rates are shaped by the interaction of past and current environments that individuals in a population experience. Past environments shape individual states via selection and plasticity, and fitness-related traits (e.g. individual size) are commonly used in demographic analyses to represent the effect of past environments on demographic rates. 2. We quantified how well the size of individuals captures the effects of a population's past and current environments on demographic rates ...

Stable nitrogen isotope patterns of trees and soils altered by long-term nitrogen and phosphorus addition to a lowland tropical rainforest

#1Jordan R. Mayor (STRI: Smithsonian Tropical Research Institute)H-Index: 14

#2S. Joseph Wright (STRI: Smithsonian Tropical Research Institute)H-Index: 76

Last.Benjamin L. Turner (STRI: Smithsonian Tropical Research Institute)H-Index: 67

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Foliar nitrogen (N) isotope ratios (δ15N) are used as a proxy for N-cycling processes, including the “openness” of the N cycle and the use of distinct N sources, but there is little experimental support for such proxies in lowland tropical forest. To address this, we examined the δ15N values of soluble soil N and canopy foliage of four tree species after 13 years of factorial N and P addition to a mature lowland rainforest. We hypothesized that N addition would lead to 15N-enriched soil N forms ...

#1Mollie E. Brooks (UF: University of Florida)H-Index: 7

#2Michael W. McCoy (UF: University of Florida)H-Index: 18

Last.Benjamin M. Bolker (UF: University of Florida)H-Index: 46

view all 3 authors...

In most ecological studies, within-group variation is a nuisance that obscures patterns of interest and reduces statistical power. However, patterns of within-group variability often contain information about ecological processes. In particular, such patterns can be used to detect positive growth autocorrelation (consistent variation in growth rates among individuals in a cohort across time), even in samples of unmarked individuals. Previous methods for detecting autocorrelated growth required d...

A direct test of nitrogen and phosphorus limitation to net primary productivity in a lowland tropical wet forest

#1Silvia Alvarez-Clare (UF: University of Florida)H-Index: 9

#2Michelle C. Mack (UF: University of Florida)H-Index: 45

Last.Mollie E. Brooks (UF: University of Florida)H-Index: 7

view all 3 authors...

Experimental evidence for limitation of net primary productivity (NPP) by nitrogen (N) or phosphorus (P) in lowland tropical forests is rare, and the results from the few existing studies have been inconclusive. To directly test if N or P limit NPP in a lowland tropical wet forest in Costa Rica, we conducted a full factorial fertilization experiment (4 treatments × 6 replicates in 30 × 30 m plots). We focused on the influence of tree size and taxa on nutrient limitation, because in these forests...

#1Benjamin M. Bolker (McMaster University)H-Index: 46

#2Beth Gardner (Patuxent Wildlife Research Center)H-Index: 26

Last.Elise F. Zipkin (Patuxent Wildlife Research Center)H-Index: 22

view all 22 authors...

1. Ecologists often use nonlinear fitting techniques to estimate the parameters of complex ecological models, with attendant frustration. This paper compares three open-source model fitting tools and discusses general strategies for defining and fitting models. 2. R is convenient and (relatively) easy to learn, AD Model Builder is fast and robust but comes with a steep learning curve, while BUGS provides the greatest flexibility at the price of speed. 3. Our model-fitting suggestions range from ...

The prevalence and persistence of sigma virus, a biparentally transmitted parasite of Drosophila melanogaster

#1Marta L. Wayne (UF: University of Florida)H-Index: 20

#2Gabriela M. BlohmH-Index: 1

Last.Benjamin M. BolkerH-Index: 46

view all 8 authors...

Question: How do vertically transmitted parasites persist? Organisms: Drosophila melanogaster (host) and sigma virus (parasite). Field site: Peach stands in northern Georgia, USA, on a transect between Macon and Athens. Empirical methods: We estimated prevalence in the field. We also estimated male and female transmission in the laboratory, using field-collected animals as parents. We further quantified patrilineal (father to son) transmission in the laboratory, and estimated cost of infection (...

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