154 research outputs found
Robust information from phylogenetic trees?
Traditional information criteria approaches can lead to misleading model choice in comparative phylogenetics. I present both these weaknesses and a more robust comparison by likelihood ratio. I then discuss a new class of models to capture the transition process between evolutionary regimes
Reading the Secrets of Biological Fluctuations
I explore tools and applications of the van Kampen expansion of the stochastic master equation in several areas of population biology. I highlight fluctuation-dissipation and fluctuation-enhancement regimes, using information from noise to help model choice, and examples where noise changes the macroscopic dynamics of a system
Early warning signals: The charted and uncharted territories
The realization that complex systems such as ecological communities can
collapse or shift regimes suddenly and without rapid external forcing poses a
serious challenge to our understanding and management of the natural world. The
potential to identify early warning signals that would allow researchers and
managers to predict such events before they happen has therefore been an
invaluable discovery that offers a way forward in spite of such seemingly
unpredictable behavior. Research into early warning signals has demonstrated
that it is possible to define and detect such early warning signals in advance
of a transition in certain contexts. Here we describe the pattern emerging as
research continues to explore just how far we can generalize these results. A
core of examples emerges that shares three properties: the phenomenon of rapid
regime shifts, a pattern of 'critical slowing down' that can be used to detect
the approaching shift, and a mechanism of bifurcation driving the sudden
change. As research has expanded beyond these core examples, it is becoming
clear that not all systems that show regime shifts exhibit critical slowing
down, or vice versa. Even when systems exhibit critical slowing down,
statistical detection is a challenge. We review the literature that explores
these edge cases and highlight the need for (a) new early warning behaviors
that can be used in cases where rapid shifts do not exhibit critical slowing
down, (b) the development of methods to identify which behavior might be an
appropriate signal when encountering a novel system; bearing in mind that a
positive indication for some systems is a negative indication in others, and
(c) statistical methods that can distinguish between signatures of early
warning behaviors and noise
A new phylogenetic comparative method: detecting niches and transitions with continuous characters
Traditional information criteria approaches can lead to misleading model choice in comparative phylogenetics. I present examples of these weaknesses using a classic data set on Anoles lizards. I describe a more robust comparison by likelihood ratio. I then discuss a new class of models to capture the transition process between evolutionary regimes
Using TreeBASE from R
I introduce an R package allowing programmatic access to the phylogenetic data in the TreeBASE archive and highlight why this is important
An introduction to Docker for reproducible research, with examples from the R environment
As computational work becomes more and more integral to many aspects of
scientific research, computational reproducibility has become an issue of
increasing importance to computer systems researchers and domain scientists
alike. Though computational reproducibility seems more straight forward than
replicating physical experiments, the complex and rapidly changing nature of
computer environments makes being able to reproduce and extend such work a
serious challenge. In this paper, I explore common reasons that code developed
for one research project cannot be successfully executed or extended by
subsequent researchers. I review current approaches to these issues, including
virtual machines and workflow systems, and their limitations. I then examine
how the popular emerging technology Docker combines several areas from systems
research - such as operating system virtualization, cross-platform portability,
modular re-usable elements, versioning, and a `DevOps' philosophy, to address
these challenges. I illustrate this with several examples of Docker use with a
focus on the R statistical environment
After the games are over: life-history trade-offs drive dispersal attenuation following range expansion.
Increased dispersal propensity often evolves on expanding range edges due to the Olympic Village effect, which involves the fastest and fittest finding themselves together in the same place at the same time, mating, and giving rise to like individuals. But what happens after the ranges leading edge has passed and the games are over? Although empirical studies indicate that dispersal propensity attenuates following range expansion, hypotheses about the mechanisms driving this attenuation have not been clearly articulated or tested. Here, we used a simple model of the spatiotemporal dynamics of two phenotypes, one fast and the other slow, to propose that dispersal attenuation beyond preexpansion levels is only possible in the presence of trade-offs between dispersal and life-history traits. The Olympic Village effect ensures that fast dispersers preempt locations far from the ranges previous limits. When trade-offs are absent, this preemptive spatial advantage has a lasting impact, with highly dispersive individuals attaining equilibrium frequencies that are strictly higher than their introduction frequencies. When trade-offs are present, dispersal propensity decays rapidly at all locations. Our models results about the postcolonization trajectory of dispersal evolution are clear and, in principle, should be observable in field studies. We conclude that empirical observations of postcolonization dispersal attenuation offer a novel way to detect the existence of otherwise elusive trade-offs between dispersal and life-history traits
A general model of continuous character evolution
I present a general model for continuous character evolution, review some of the common challenges that emerge in such complex methods and review strategies for handling them
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