Tag: community ecology

Conservation and management, Methods papers

Demography and Big Data

Post provided by BRITTANY TELLER, KRISTIN HULVEY and ELISE GORNISH

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To understand how species survive in nature, demographers pair field-collected life history data on survival, growth and reproduction with statistical inference. Demographic approaches have significantly contributed to our understanding of population biology, invasive species dynamics, community ecology, evolutionary biology and much more.

As ecologists begin to ask questions about demography at broader spatial and temporal scales and collect data at higher resolutions, demographic analyses and new statistical methods are likely to shed even more light on important ecological mechanisms.

Population Processes

Midsummer Opuntia cactus in eastern Idaho, USA. © B. Teller.
Midsummer Opuntia cactus in eastern Idaho, USA. © B. Teller.

Traditionally, demographers collect life history data on species in the field under one or more environmental conditions. This approach has significantly improved our understanding of basic biological processes. For example, rosette size is a significant predictor of survival for plants like wild teasel (Werner 1975 – links to all articles are at the end of the post), and desert annual plants hedge their bets against poor years by optimizing germination strategies (Gremer & Venable 2014).

Demographers also include temporal and spatial variability in their models to help make realistic predictions of population dynamics. We now know that temporal variability in carrying capacity dramatically improves population growth rates for perennial grasses and provides a better fit to data than models with varying growth rates because of this (Fowler & Pease 2010). Moreover, spatial heterogeneity and environmental stochasticity have similar consequences for plant populations (Crone 2016). Continue reading “Demography and Big Data”

Unknown's avatarIndia Stephenson3 Comments
Methods papers, Statistical methods

My Entropy ‘Pearl’: Using Turing’s Insight to Find an Optimal Estimator for Shannon Entropy

Post provided by Anne Chao (National Tsing Hua University, Taiwan)

Shannon Entropy

Not quite as precious as my entropy pearl
Not quite as precious as my entropy pearl ©Amboo Who

Ludwig Boltzmann (1844-1906) introduced the modern formula for entropy in statistical mechanics in 1870s. Since its generalization by Claude E. Shannon in his pioneering 1948 paper A Mathematical Theory of Communication, this entropy became known as ‘Shannon entropy’.

Shannon entropy and its exponential have been extensively used to characterize uncertainty, diversity and information-related quantities in ecology, genetics, information theory, computer science and many other fields. Its mathematical expression is given in the figure below.

In the 1950s Shannon entropy was adopted by ecologists as a diversity measure. It’s interpreted as a measure of the uncertainty in the species identity of an individual randomly selected from a community. A higher degree of uncertainty means greater diversity in the community.

Unlike species richness which gives equal weight to all species, or the Gini-Simpson index that gives more weight to individuals of abundant species, Shannon entropy and its exponential (“the effective number of common species” or diversity of order one) are the only standard frequency-sensitive complexity measures that weigh species in proportion to their population abundances. To put it simply: it treats all individuals equally. This is the most natural weighing for many applications. Continue reading “My Entropy ‘Pearl’: Using Turing’s Insight to Find an Optimal Estimator for Shannon Entropy”

Unknown's avatarIndia Stephenson2 Comments
Journal updates, Methods papers

Issue 7.1

Issue 7.1 is now online!

The January issue of Methods is now online!

As always, the first issue of the year is our sample issue. You can access all of the articles online free of charge. No subscription or membership is required!

We have two Open Access articles and two Applications papers in our January issue.

– Recognizing False Positives: Environmental DNA (eDNA) is increasingly used for surveillance and detection of species of interest in aquatic and soil samples. A significant risk associated with eDNA methods is potential false-positive results due to laboratory contamination. To minimize and quantify this risk, Chris Wilson et al. designed and validated a set of synthetic oligonucleotides for use as species-specific positive PCR controls for several high-profile aquatic invasive species.

– BiMat: An open-source MATLAB package for the study of the structure of bipartite ecological networks. BiMat enables both multiscale analysis of the structure of a bipartite ecological network – spanning global (i.e. entire network) to local (i.e. module-level) scales – and meta-analyses of many bipartite networks simultaneously. The authors have chosen to make this Applications article Open Access.

Gemma Murray et al. provide this month’s second Open Access article. In ‘The effect of genetic structure on molecular dating and tests for temporal signal‘ the authors use simulated data to investigate the performance of several tests of temporal signal, including some recently suggested modifications. The article shows that all of the standard tests of temporal signal are seriously misleading for data where temporal and genetic structures are confounded (i.e. where closely related sequences are more likely to have been sampled at similar times). This is not an artifact of genetic structure or tree shape per se, and can arise even when sequences have measurably evolved during the sampling period.

Our January issue also features articles on Monitoring, Population Ecology, Genetics, Evolution, Community Ecology, Diversity and more. Continue reading “Issue 7.1”

Unknown's avatarIndia StephensonLeave a comment
Methods papers

Joint Species Distribution Models to Study Species and their Interactions

David Warton (University of New South Wales) interviews Otso Ovaskainen (University of Helsinki) about his two recent articles in Methods in Ecology and Evolution. David and Otso talk about studying communities of species and their interactions via joint species distribution models, the advances made by Otso’s papers and future developments in this field.

Continue reading “Joint Species Distribution Models to Study Species and their Interactions”

Unknown's avatarIndia StephensonLeave a comment
Editor Profiles, Journal updates

New Associate Editors

Over the next few weeks we will be welcoming three new Associate Editors to Methods in Ecology and Evolution. Susan Johnston (University of Edinburgh, UK) became a member of the Associate Editor Board on Monday 5 October. She will be joined on 19 October by Natalie Cooper (Natural History Museum, London, UK) and finally by Luísa Carvalheiro (University of Brasília, Brazil) on 2 November. You can find out … Continue reading New Associate Editors

Unknown's avatarIndia Stephenson1 Comment
Journal updates, Methods papers

Issue 6.6

Issue 6.6 is now online!

The June issue of Methods is now online!

This month’s issue contains one Applications article and one Open Access article.

– VirtualCom: A simple and readily usable tool that will help to resolve theoretical and methodological issues in community ecology. VirtualCom simulates the evolution of the pool of regionally occurring species, the process-based assembly of native communities and the invasion of novel species into native communities. One of the authors of this Application is the 2014 Robert May Young Investigator Prize Winner, Laure Gallien.

Calibrating animal-borne proximity loggers, this month’s only Open Access article, comes from Christian Rutz et al. The authors calibrated a recently developed digital proximity-logging system (‘Encounternet’) for deployment on a wild population of New Caledonian crows. They show that, using signal-strength information only, it is possible to assign crow encounters reliably to predefined distance classes, enabling powerful analyses of social dynamics. Their study demonstrates that well-calibrated proximity-logging systems can be used to chart social associations of free-ranging animals over a range of biologically meaningful distances.

Our June issue also features articles on Phylogenetic Methods, Physiological Ecology, Biomonitoring and Conservation, Species Distribution Monitoring and Bioinformatics. Continue reading “Issue 6.6”

Unknown's avatarIndia StephensonLeave a comment
Methods papers, Statistical methods

Traits, community ecology and demented accountants

McGill et al. (2006) argued that community ecology had lost its way. Shipley (2010) accused community ecologists of acting like a bunch of demented accountants. Strong words – so what’s the issue exactly?  And what can we do about it?

Dannymanic Image
Doing some end-of-financial-year field work? © Dannymanic

Their beef was that when studying groups of species and their environmental association, ecologists often were not thinking enough about the reasons for variation across species. (In this post we’ll focus on variation in abundance or in environmental response of abundance across species. We’re interpreting “abundance” loosely – counts, biomass, 1-0, whatever.)  While alternative methods are more readily available nowadays, “accountancy” is still common.

Continue reading “Traits, community ecology and demented accountants”

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General, Journal updates, Methods papers, Robert May Prize, Society, Virtual Issues

2014 Robert May Prize Winner: Laure Gallien

The Robert May Prize is awarded annually for the best paper published in Methods by a young author at the start of their research career. We’re delighted to announce that the 2014 winner is Laure Gallien, for her article ‘Identifying the signal of environmental filtering and competition in invasion patterns – a contest of approaches from community ecology‘.

Today, biological invasions are of major concern for maintaining biodiversity. However, understanding what drives the success of invasive species at the scale of the community remains a challenge. Two processes have been described as main drivers of the coexistence between invasive and native species: environmental filtering and competitive interactions. However, recent reviews have shown that competitive interactions are rarely detected, and thus their importance as drivers of invasion success placed under question. But can this be due to pure methodological issues? Using a simulation model of community assembly, Laure and co-authors (Marta Carboni and Tamara Münkemüller) show that the infrequent detection of competition can arise from three important methodological shortcomings, and provide guidelines for future studies of invasion drivers at the scale of the community.

Continue reading “2014 Robert May Prize Winner: Laure Gallien”

Unknown's avatarIndia Stephenson3 Comments
Journal updates

2011 top cited papers – part 2

Today we look at part 2 of our most cited papers in Methods in Ecology and Evolution in 2011. Plant monitoring and modelling Comparison of seedling emergence and seed extraction techniques for estimating the composition of soil seed banks Jodi N. Price, Boyd R. Wright, Caroline L. Gross, Wal R. D. B. Whalley Stable isotope ecology Sensitivity of stable isotope mixing models to variation in … Continue reading 2011 top cited papers – part 2

Unknown's avatarHarriet RhodesLeave a comment