Knowing how many individuals there are in a population is a fundamental objective in ecology and conservation biology. But estimating abundance is often extremely difficult. It’s particularly difficult in the management of exploited marine, anadromous and freshwater populations. In marine fisheries, abundance estimation traditionally relies on demographic models, costly and time consuming mark recapture (MR) approaches if they are feasible at all, and the relationship between fishery catches and effort (catch per unit effort or CPUE). CPUEs can be subject to bias and uncertainty. This is why they tend to be considered relatively unreliable and contentious.
Close-Kin Mark-Recapture: Reducing Bias and Uncertainty
There is an alternative method though. It’s known as “Close-Kin Mark-Recapture” (CKMR), and is grounded in genomics and was first proposed by Skaug in 2001. The method is based on the principle that an individual’s genotype can be considered a “recapture” of the genotypes of each of its parents. Assuming the sampling of offspring and parents is independent of each other, the number of Parent-Offspring pairs (POP) genetically identified in a large collection of both groups can be used to estimate abundance. Continue reading →
The Struggle is Real: Finding Interesting and Relevant Articles
Where to start? We are awash in data, information, papers, and books. There are hundreds of ecological and environmental journals published regularly around the world; the British Ecological Society alone publishes five journals and is now accepting submissions for a sixth (more information on People and Nature here).
None of us has time even to click on the various articles flagged by alerts, feeds, or keywords, and few even browse tables of contents (which are becoming irrelevant as we move to DOIs and immediate-online publication). Increasingly, we rely on our friends, colleagues, students, and mentors to point us towards papers we might find interesting – further evidence, I suppose, of the importance of good networks for knowledge creation and scientific understanding.
Regular readers of Methods in Ecology and Evolution or this Methods blog may not realise how many methodological papers are published routinely in our BES sister journals. In this inaugural posting of Also of interest…, I highlight three papers recently published in Journal of Applied Ecology that introduce and apply new, model-based methodology to interesting ecological questions. The specific methods are like many seen in the pages of Methods in Ecology and Evolution and suggest general approaches for modelling and studying complex ecological and environmental phenomena. Continue reading →
Sea otters (Enhydra lutris) are an apex predator of the nearshore marine ecosystem – the narrow band between terrestrial and oceanic habitat. During the commercial maritime fur trade in the 18th and 19th centuries, sea otters were nearly hunted to extinction across their range in the North Pacific Ocean. By 1911, only a handful of small isolated populations remained.
But sea otter populations have recovered in many areas due to a few changes. The International Fur Seal Treaty in 1911 and the Marine Mammal Protection Act (1972) protected sea otters from most human harvest. Wildlife agencies helped sea otter colonisation by transferring them to unoccupied areas. Eventually, sea otters began to increase in abundance and distribution, and they made their way to Glacier Bay, a tidewater glacier fjord and National Park in southeastern Alaska. Continue reading →
David Warton (University of New South Wales) interviews interviews Ben Stevenson (University of St Andrews) about his 2015 Methods in Ecology and Evolution paper ‘A general framework for animal density estimation from acoustic detections across a fixed microphone array’. They also discuss what Ben is currently up to, including an interesting new method for dealing with uncertain identification in capture-recapture, published in Statistical Science as ‘Trace-Contrast Models for Capture–Recapture Without Capture Histories’.
Today, on International Owl Awareness Day (August 4), we celebrate the research we have done to better understand owls and their prey. There are over 200 extant species of owls, a handful of which have geographic distributions spanning several continents (i.e., barn owl, snowy owl, short-eared owl, long-eared owl). So no matter where you are in the world you’re probably not too far away from an owl.
This month’s issue contains two Applications articles and two Open Access articles, all of which are freely available.
– piecewiseSEM: A practical implementation of confirmatory path analysis for the R programming language. This package extends the method to all current (generalized) linear, (phylogenetic) least-square, and mixed effects models, relying on familiar R syntax. The article also includes two worked examples.
–RPANDA: An R package that implements model-free and model-based phylogenetic comparative methods for macroevolutionary analyses. It can be used to:
Characterize phylogenetic trees by plotting their spectral density profiles
Compare trees and cluster them according to their similarities
Identify and plot distinct branching patterns within trees
Compare the fit of alternative diversification models to phylogenetic trees
Estimate rates of speciation and extinction
Estimate and plot how these rates have varied with time and environmental variables
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 →
Should scientists make simplifying assumptions in complex models? This is a debate as old as the hills, and one that everyone seems to have strong opinions about. Some argue that because even the most simplistic model based on the best available estimates is objective, it is better than relying solely on “gut feelings”. In such a model, estimates based on expert opinion or simplifying assumptions can at least be included in a transparent fashion. Others argue that such an approach can miss important emergent properties as a result of missed complexity, making any results misleading and potentially even worse than not using a model at all.
Models to Support Management: Invasive Horses, Cats and Deer
Both sides are right in their own way, of course, but perhaps unusually (as an applied mathematics graduate working in ecology), I’ve found myself leaning towards the former view as my career progresses. During my last postdoc, I was confronted with a large, vexing problem: the incursion of wild horses in the Australian Alps. The species was already impacting bogs and wetlands, overpopulated in some places to the point of starvation, and spreading to previously pristine areas of National Park. The issue was (and still is) highly contentious, with activists applying considerable political pressure against lethal forms of control. Knowledge of population densities across the horses’ range was patchy and ability to predict their likely movements equally unreliable. Even predicting their demographics was difficult, with most values for population growth rates conflicting and spatially variable. Continue reading →
As you may know, tomorrow (Saturday 22 August) is National Honey Bee Day in the USA. To mark the day we will be highlighting some of the best papers that have been published on bees and pollinators in Methods in Ecology and Evolution.
You can find out more about National Honey Bee Day (and about bees in general) HERE.
Without further ado though, here are a few of the best Methods papers related to Honey Bees:
Honey Bee Risk Assessment
Our Honey Bee highlights begin with Hendriksma et al.’s article ‘Honey bee risk assessment: new approaches for in vitro larvae rearing and data analyses‘. Robust laboratory methods for assessing adverse effects on honey bee brood are required for research into the issues contributing to global bee losses. To facilitate this, the authors of this article recommend in vitro rearing of larvae and suggest some appropriate statistical tools for the related data analyses. Together these methods can help to improve the quality of environmental risk assessment studies on honey bees and secure honey bee pollination. As this article was published over two years ago, it can be accessed for free by anyone.