Tag: R package

Evolution, Meetings, Methods papers, Phylogenetic analysis

RPANDA: A Time Machine for Evolutionary Biologists

Post provided by HÉLÈNE MORLON

Yesterday saw the start of this year’s annual Evolution meeting and to celebrate Hélène Morlon has written a blog post discussing the amazingly versatile RPANDA package that she is developing with her research group. A description of RPANDA was published in the journal earlier this year and, like all our Applications papers, is freely available to read in full.

If you are attending Evolution, as well as attending the fabulous talks mentioned by Hélène below, do stop by booth 125 to see our BES colleague Simon Hoggart. Simon is the Assistant Editor of Journal of Animal Ecology and would be happy to answer your questions about any of our journals or any of the other work we do here at the BES.

RPANDA: a time machine for evolutionary biologists

Imagine “Doc”, Marty’s friend in Back to the Future, trying to travel back millions of years in an attempt to understand the history of life. Instead of building a time machine from a DeLorean sports car powered by plutonium, he could dig fossils, or more likely, he would use molecular phylogenies.

Molecular phylogenies are family trees of species that can be built from data collected today: the genes (molecules) of present-day species (Fig 1). They are often thought of as trees, in reference to Darwin’s tree of life. The leaves represent the present: species that can be found on Earth today. The branches represent the past: ancestral species, which from time to time split, giving rise to two independent species. The structure of the tree tells us which species descend from which ancestors, and when their divergence happened.

birds_phylog
Fig 1: The phylogenetic tree of all birds (adapted from Jetz et al. 2012). Each bird order is represented by a single bird silloutter and a specific colour (the most abundant order of Passeriformes, for example is represented in dark orange). Each terminal leaf represents a present-day bird species, while internal branches represent the evolutionary relationships among these species.

Continue reading “RPANDA: A Time Machine for Evolutionary Biologists”

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Editor Profiles, Journal updates

New Associate Editor: Will Pearse

Today, we are pleased to be welcoming a new member of the Methods in Ecology and Evolution Associate Editor Board. Will Pearse joins us from McGill University in Canada and you can find out a little more about him below. Will Pearse “I am an evolutionary ecologist and use phylogeny to link the evolution of species’ traits with their ecological community assembly. I’m interested in phylogenetic methods, macro-evolution of species’ traits, community assembly … Continue reading New Associate Editor: Will Pearse

Unknown's avatarIndia StephensonLeave a comment
Conservation and management, Methods papers

Spatially-explicit Power Analysis: A First Step for Occupancy-Based Monitoring

Post provided by Martha Ellis and Jody Tucker

Where’s Waldo? Trying to find this fisher somewhere in a giant landscape is going to be tricky! ©Mike Schwartz
Where’s Waldo? Trying to find this little guy somewhere in a giant landscape is going to be tricky! © Mike Schwartz

The seemingly basic question of whether a population is increasing, decreasing, or stable can be one of the most difficult to answer. Collecting data on rare and elusive species is hard. Imagine trying to detect a handful of fisher or wolverine across hundreds of thousands of acres – it is physically demanding, time consuming and logistically complicated. And that’s just to do it once! To monitor a population for changes, you have to repeat these surveys regularly over many years. The long-term monitoring that is necessary for conservation requires careful planning and a substantial commitment of resources and funding. So before we spend these valuable resources, it’s critical to know whether the data we are collecting can help us to answer our questions. Continue reading “Spatially-explicit Power Analysis: A First Step for Occupancy-Based Monitoring”

Unknown's avatarIndia StephensonLeave a comment
Methods papers

Stage-dependent Demographic Modelling at Your Finger Tips

Post provided by EELKE JONGEJANS and ROB SALGUERO- GÓMEZ

Soay sheep: an organism that can be modelled with two-sex dynamics. ©Julian Paren
Soay sheep: an organism that can be modelled with two-sex dynamics. ©Julian Paren

Typically, ecology courses contain at least a day of matrix population models. So most ecologists are somewhat familiar with how simple life cycles (and complex ones) can be depicted and analysed using matrix models. Briefly, these models represent what happens to individuals over a certain time interval (do they die? do they reproduce? if so, how much?). What individuals do in the context of these models can then be used to study the dynamics of a population.

Often, individuals are classified by size in matrix models, as small individuals tend to have different survival, growth and reproduction rates than large ones. But how many classes do you need to model the dynamics of a size-structured population properly? Instead of choosing arbitrary size class boundaries, Easterling, Ellner and Dixon (2000) came up with the idea of using continuous size variables and integrals to define a population model… and that’s how the first Integral Projection Model (‘IPM’ for us friends) came to be.

Naturally, for the development of a new demographic tool to prove useful to the scientific community, it must be flexible enough to be ‘one-size-fits-all’… and the needs of ecologists, evolutionary biologists and conservation biologists – who have to date used extensively size-based matrix models – are rather variable in size, colour and shape. Continue reading “Stage-dependent Demographic Modelling at Your Finger Tips”

Unknown's avatarIndia StephensonLeave a comment
Journal updates, Methods papers

Issue 7.2: Demography Beyond the Population

Issue 7.2 is now online!

Sagebrush steppe in eastern Idaho, USA
© Brittany J. Teller

The February issue of Methods is now online! As you may have seen already, it includes the BES cross-journal Special Feature: “Demography Beyond the Population“. There are also eight other wonderful articles to read.

We have four articles in the Demography Beyond the Symposium Special Feature. You can read an overview of them by two of the Feature’s Guest Editor Sean McMahon and Jessica Metcalf here (Sean and Jessica are also Associate Editors of Methods).

If you’d like to find out more about each of the individual papers before downloading them, we have blog posts about each one. Daniel Falster and Rich Fitzjohn discuss the development of plant and provide some advice on creating simulation models in Key Technologies Used to Build the plant Package (and Maybe Soon Some Other Big Simulation Models in R). There is a look back at the evolution of Integral Projection Models from Mark Rees and Steve Ellner in How Did We Get Here From There? A Brief History of Evolving Integral Projection Models. In Inverse Modelling and IPMs: Estimating Processes from Incomplete Information Edgar González explains how you can estimate process that you can’t observe. And keep an eye out for Brittany Teller’s blog post coming next week!

Don’t wait too long to get the Demography Beyond the Population Special Feature papers though, they’re freely available for a limited time only

Continue reading “Issue 7.2: Demography Beyond the Population”

Unknown's avatarIndia StephensonLeave a comment
Methods papers

Inverse Modelling and IPMs: Estimating Processes from Incomplete Information

Post provided by Edgar J. González

In demography, a set of processes (survival, growth, fecundity, etc.) interacts to produce observable patterns (population size, structure, growth rate, etc.) that change over time. With traditional approaches you follow the individuals of a population over some timespan and track all of these processes.

Demographic patterns and processes (Click to expand)
Demographic patterns and processes (Click to expand)

However, depending on the organism, some processes may be very hard to quantify (e.g. mortality or recruitment in animals or plants with long lifespans). You may have observed the patterns for the organism that you’re studying and, even better, measured some, but not all, of the processes. The question is: can we use this limited information to estimate the processes we couldn’t measure? Continue reading “Inverse Modelling and IPMs: Estimating Processes from Incomplete Information”

Unknown's avatarIndia Stephenson1 Comment
Methods papers

Key Technologies Used to Build the plant Package (and Maybe Soon Some Other Big Simulation Models in R)

Post provided by RICH FITZJOHN and DANIEL FALSTER

Our paper in Methods in Ecology and Evolution describes a new software package, plant. plant is an individual-based simulation model that simulates the growth of individual trees, stands of competing plants, or entire metacommunities under a disturbance regime, using common physiological rules and trait-based functional trade-offs to capture differences among species.

Non-Linear Processes and Thousands of Plants

Since the development of gap models in the 1970s (e.g. Botkin 1972), researchers have been using computer simulations to investigate how elements of plant biology interact with competition and disturbance regimes to influence vegetation demography, structure and diversity. Simulating the competitive interactions among many thousands of plants, however, is no easy task.

Despite widespread recognition of the importance of key non-linear processes — such as size-structured competition, disturbance, and trait-based trade-offs — for vegetation dynamics, relatively few researchers have been brave (or daft) enough to try and incorporate such processes into their models. The situation is most extreme in theoretical ecology, where much contemporary theory (e.g. coexistence theory, neutral theory) is still built around completely unstructured populations.

Features of plant

Key processes modelled within the plant package.
Key processes modelled within the plant package.

The plant package attempts to change that by providing an extensible, open source framework for studying trait-, size- and patch-structured dynamics. One thing that makes the plant model significant is the focus on traits. plant is one of several attempts seeking to integrate current understanding about trait based trade-offs into a model of individual plant function (see also Moorcroft et al 2001, Sakschewski et al 2015).

A second feature that makes the plant software significant, is it that is perhaps the first example where a computationally intensive model has been packaged up in a way that enables widespread usage, makes the model more usable and doesn’t  sacrifice speed.

In this post we will describe the key technologies used to build the plant software. Continue reading “Key Technologies Used to Build the plant Package (and Maybe Soon Some Other Big Simulation Models in R)”

Unknown's avatarIndia Stephenson2 Comments
Journal updates, Methods papers

Methods Beyond the Population

Post Provided by SEAN MCMAHON and JESSICA METCALF

“Demography Beyond the Population” is a unique Special Feature being published across the journals of the British Ecological Society.  The effort evolved from a symposium of the same name hosted in Sheffield, UK last March. Both the meeting and the Special Feature were designed to challenge ecologists from a range of fields whose research focuses on populations.

The participants were charged with sharing how they are pushing the work they do beyond the stage where the population is the focus into research where the population is just the beginning and the focus spans scales, systems and tools. This encompasses a broad suite of biological research, including range modelling, disease impacts on communities, biogeochemistry, evolutionary theory, and conservation biology. The meeting was a great success, and this Special Feature should be equally valuable to the broad readership of the BES journals.

Methods in Ecology and Evolution has a special place in the Special Feature, hosting four papers. These papers not only introduce new efforts in population biology, they provide the methods that other scientists can use to implement them. With the tools provided by these four papers, researchers will be able to advance forest modelling, evolutionary theory, climate change biology and statistical inference of hidden population parameters.  Seriously good stuff! Continue reading “Methods Beyond the Population”

Unknown's avatarIndia Stephenson2 Comments
Evolution, Methods papers

Measuring Survival Selection in Natural Populations: How important is recapture probability?

Post Provided by John Waller

The “Lande-Arnold” Approach

Damselflies marked in the field, which will hopefully be recaptured later. This small insect at our field site had only about 10% recapture probability.
Damselflies marked in the field, which will hopefully be recaptured later. This small insect at our field site had only about 10% recapture probability.

The quantification of survival selection in the field has a long history in evolutionary biology. A considerable milestone in this field was the highly influential publication by Russel Lande and Steve Arnold in the early 1980s.

The practical implementation of Lande and Arnold’s method involved simply fitting a linear model with standardized response (survival) and explanatory (trait) variables values with quadratic terms (multiplied by two). This straightforward method allowed evolutionary biologists to measure selection coefficients using commonly available statistical software and these estimates could be used directly within a quantitative genetic framework.  Continue reading “Measuring Survival Selection in Natural Populations: How important is recapture probability?”

Unknown's avatarIndia StephensonLeave a comment
Journal updates, Methods papers

Issue 6.12

Issue 6.12 is now online!

The December issue of Methods is now online! 

Our final issue of 2015 contains one Applications article and two Open Access articles, all of which are freely available.

– stagePOP: A tool for predicting the deterministic dynamics and interactions of stage-structured populations (i.e. where the life cycle consists of distinct stages, for example eggs, juveniles and reproductive adults). The continuous-time formulation enables stagePop to easily simulate time-varying stage durations, overlapping generations and density-dependent vital rates.

Julia Cherry et al. provide one of this month’s Open Access articles. In ‘Testing sea-level rise impacts in tidal wetlands: a novel in situ approach‘ the authors describe the use of experimental weirs that manipulate water levels to test sea-level rise impacts in situ and at larger spatial scales. This new method can provide more robust estimates of sea-level rise impacts on tidal wetland processes. This article was accompanied by a press release when it was published in Early View. You can read more about this article here.

Our September issue also features articles on Biodiversity, Demography, Predator-Prey Interactions, Animal Communication and much more. Continue reading “Issue 6.12”

Unknown's avatarIndia Stephenson4 Comments