The paper Removal models accounting for temporary emigration by Ming Shou, Rachel McCrea, Eleni Matechou , Diana Cole and Richard Griffiths has just been published online early in Biometrics.

Open access link to paper.

Summary:

Removal of protected species from sites scheduled for development is often a legal requirement in order to minimize the loss of biodiversity. The assumption of closure in the classic removal model will be violated if individuals become temporarily undetectable, a phenomenon commonly exhibited by reptiles and amphibians. Temporary emigration can be modeled using a multievent framework with a partial hidden process, where the underlying state process describes the movement pattern of animals between the survey area and an area outside of the study. We present a multievent removal model within a robust design framework which allows for individuals becoming temporarily unavailable for detection. We demonstrate how to investigate parameter redundancy in the model. Results suggest the use of the robust design and certain forms of constraints overcome issues of parameter redundancy. We show which combinations of parameters are estimable when the robust design reduces to a single secondary capture occasion within each primary sampling period. Additionally, we explore the benefit of the robust design on the precision of parameters using simulation. We demonstrate that the use of the robust design is highly recommended when sampling removal data. We apply our model to removal data of common lizards, Zootoca vivipara, and for this application precision of parameter estimates is further improved using an integrated model.

From 8th-13th July Byron and Marina attended the International Biometric Conference in Barcelona.

Marina gave a talk on Integrated Population Modelling Incorporating Spatial Information.

Byron gave a talk on Hidden Markov modelling for a multi-species index.

Daniel Bearup with Dylan Childs and Robert Freckleton have written the paper Funder Restrictions on Application Numbers Lead to Chaos, which has been published by Trends in Ecology and Evolution.

Paper abstract: Restricting application rates is an attractive way for funders to reduce time and money wasted evaluating uncompetitive applications. However, mathematical models show that this could induce chaotic cycles in total application numbers, increasing uncertainty in the funding process. One emergent property is that smaller institutions spend disproportionally more time unfunded.

Rachel, Byron, Diana and Marina attended the International Statistical Ecology Conference in St Andrews from 2nd to 6th July.

Rachel was chair of the scientific committee.

On 2nd July Marina gave a talk on Integrated Population Modelling Incorporating Spatial Information.

On 3rd July Diana gave a talk entitled Is Bayesian Identifiability Really a Problem?

On 6th July Byron talked about Integrated population modelling of fuliginator beetle data with two temporal dynamic scales.

On 25th April Diana gave a talk on Parameter Redundancy and Identifiability at the University of Nottingham as a joint seminar of the  Algebra and Analysis group and the Statistics and Probability group.

The abstract for the talk was:

Mathematical and statistical models can be used to describe different systems or provide a representation of a process, which are defined by parameters that describe different characteristics that underlie the model. For example, a dynamic system could be used to describe a pharmacokinetic system with a parameter representing the infusion rate of a drug or a statistical model could be used to describe an ecological population, with a parameter describing the survival probability of an animal.  Determining or estimating these parameters will provide key information about the underlying process, though it is not always possible to estimate every parameter.  Such a problem stems from the inherent structure of a model; for example two parameters could be confounded and only ever appear as a product. This is known as parameter redundancy or the parameters are termed unidentifiable.

It may not be obvious whether parameters in a model are identifiable. A general method for checking identifiability involves forming a matrix of derivatives and calculating its rank, which can be executed in symbolic algebra packages such as Maple. However for more structurally complex models Maple can run out of memory trying to calculate the rank. This talk discusses two methods to solve this problem. The first uses reparameterisation to simplify the derivative matrix and allow the calculation of the rank, and the second involves calculating the rank numerically.

Congratulations to Daniel whose paper, Diverse responses of species to landscape fragmentation in a simple food chain (Jinbao Liao, Daniel Bearup, Bernd Blasius, 2017, Journal of Animal Ecology), was highly commended for the Elton prize – see https://besjournals.onlinelibrary.wiley.com/hub/early-career-researcher-awards-2017.html

Congratulation to Marina for receiving a £500 BIR-FMT bursary to attend the International Biometrics Conference in Barcelona in July. She will present a talk on Integrated Population Modelling incorporating Spatial Information.

In April Daniel gave a talk on The emergence of mutualistic relationships in communities of competing ecosystem engineers at Models in Population Dynamics, Ecology, and Evolution in Leicester.

Talk Abstract:

Ecosystem engineers, species which significantly modify their habitats, play a disproportionate role in shaping the composition, and character, of the ecological communities of which they are a part. In particular, by creating and maintaining an atypical habitat (e.g. a coral reef), they support communities that are uniquely adapted to that habitat. Studies of these species have focused either on capturing the effect of ecosystem engineering activity on its own survival (or invasion) chances, or on interactions between ecosystem engineers with antithetical preferred habitats. Far less is known about how these species interact when they engineer compatible habitats.

In this study, we use a simple mathematical model, inspired by the classical competitive Lotka-Volterra system and the more recent work of Hastings and Cuddington, to investigate such interactions. While a species is always able to attain a higher population in a single species community, greater habitat improvements (and indeed higher total populations) can be attained in multi-species communities. Furthermore, species spread is often fastest in such communities. Thus ecosystem engineering facilitates a form of mutualism.

On 13th November 2017 Diana gave a talk on

Inference with Non-Identifiable Models: Reparameterisation, Constraints and Integrated Models

at the MIR@W Day on Identifiability and Inference at the University of Warwick.