BioMaths Colloquium - 17/03/2016

BioMaths Colloquium Series - 2015/16

18 March 2016 - 3pm Maths Seminar Room 

(room 224 Talbot Building 2nd floor)

Playing Colourful Games: 

Evolutionary Game Theory in Stochastic Environments

Dr Mike Fowler

(University of Swansea, UK)

Abstract

Game theory has a rich history across diverse academic fields, from economics to psychology. It has arguably been applied most successfully in Evolutionary Biology, explaining phenomena across multiple taxa, ranging from mating systems to boldness behaviours, with particular focus on the evolution and maintenance of co-operation in social systems. 

Here, I explore the effect of spatial and temporal coloured environmental variability – so called in analogy with the dominant frequencies in visible light – on the spatially iterated Prisoner’s dilemma. Building on classic work by Nowak & May (1992), I introduced coloured temporal and spatial variability into the payoff defectors receive when meeting a co-operator, to investigate how this variability altered the proportion (and variability in this proportion) of co-operators found in a population. 

Results show that introducing coloured environmental variability has an intriguing array of context-dependent effects on the maintenance of co-operation in a population, from promotion of co-operaton to its complete loss. This talk is deliberately aimed at a general audience and includes at least one analogy with a pop music video.

The discussions will continue over biscuits and tea/coffee after the seminar. 

Hope to see many of you!

Biosciences Seminar Speaker 17 March 2016

Biosciences Seminar Series - Winter 2016
17 March 2016 - 1pm - Zoology Museum

          Reputation: 

a driving force in the evolution of cooperation and punishment

Dr Nicola Raihani

(University College London, UK)

Abstract

Evolution is a strict accountant. Costly actions must be ultimately repaid if they are to come under positive selection. In this talk, I will consider the role of reputation in explaining the evolution of costly helping and costly punishing. I will explore when helping might improve an individual's reputation and - conversely - when reputation costs might lead individuals to hide their helpful actions from others. 

Although harming others is typically expected to result in reputation costs, there might nevertheless be scenarios where harming others actually improves an individual's reputation. I will present a conceptual framework and empirical evidence to describe when harmful actions result in reputation gains to the actor - and offer an evolutionary explanation as to why. 

Ultimately I will argue that reputation offers a powerful incentive for both helping and punishing in nature.

Hope to see many of you - everyone most welcome to attend!

Biosciences Seminar Speaker 25 February 2016

Biosciences Seminar Series - Winter 2016
25 February 2016 - 1pm - Zoology Museum

          Diel colour changes in male Sapphirina 

nigromaculata (Cyclopoida, Copepoda)

Prof Kazutaka Takahashi

(The University of Tokyo, Japan)

We are delighted to welcome to our Biosciences seminar series a visitor from The University of Tokyo, Prof Kazutaka Takahashi. Kazutaka is based at the Department of Aquatic Bioscience at the Graduate School of Agricultural and Life Sciences. Kazutaka has a keen interest in zooplankton dynamics, especially the ecology, behaviour and physiology of copepods.

Abstract

Males of the pelagic copepod genus Sapphirina are known to exhibit brilliant iridescence, presumably to attract mates. However, the males of some species have been described as not being able to produce iridescence. To resolve this 
apparent contradiction, we conducted detailed observations of colouration patterns in Sapphirina nigromaculata, which has been previously described as both iridescent and non-iridescent. 

from: www.whoi.edu

The colouration of male S. nigromaculata ranges from intensely iridescent to transparent with pigmented spots. These two phases appear to have a circadian rhythm, with males turning iridescent at midnight and remaining in that state until several hours after sunrise, then becoming transparent again towards the afternoon. Adult S. nigromaculata occurrence in surface waters shows temporal changes, in that they occasionally occur in higher densities than their average in the water column, particularly from midnight to around noon. 

The synchronization of iridescence in concert with upward migration is considered to be an adaptation for increasing the likelihood of encountering a mate. Observations using a video plankton recorder revealed that the transparent phase is an adaptation for decreasing predation risk by making the copepods more difficult to distinguish while they are associated with doliolids.

Hope to see many of you - everyone most welcome to attend!

Biosciences Seminar Speaker 18 February 2016

Biosciences Seminar Series - Winter 2016
18 February 2016 - 1pm - Wallace Lecture Theatre

Note Change of Room!

          Spatial cognition in wide-ranging birds

Prof Tim Guilford

(Oxford University, UK)

Our Biosciences seminar series continues with an exciting talk by Prof Tim Guilford, from the Department of Zoology at the University of Oxford (UK) and member of the Oxford Navigation Group. Tim is fascinated about animal behaviour and understanding what drives their decisions. Initially Tim focussed his research on understanding the evolution of animal signals, such as warning signals. More recently Tim has been working hard on unravelling the mysteries of how animals map the environments and find their ways, from more localised movement of pigeons to long-distance travels of seabirds. To achieve these goals Tim uses a wide combination of new technological developments, such as on-board cameras and miniatures GPS loggers, experiments and new analytical approaches borrowed from other fields, such as computational engineering. In short - expect a fascinating talk!

Abstract

Birds are amongst the greatest long-distance navigators on earth, but what do we know about the spatial cognition that underlies their wide-ranging movements? Using miniature tracking technology to follow movements in a variety of field-experimental and naturally free-ranging paradigms, I will explore what we have learnt about the nature of the bird’s large-scale familiar area map. From route-following behaviour in homing pigeons to migratory navigation in pelagic seabirds, I will concentrate especially on the perhaps neglected role of individual learning and memory in the control of long-distance movements in birds.

Hope to see many of you - everyone most welcome to attend!

BioMaths Colloquium - -05/02/2016

BioMaths Colloquium Series - 2015/16

05 February 2016 - 3pm Maths Seminar Room 

(room 224 Talbot Building 2nd floor)

Mathematical modelling of Ca2+ influx and calmodulin activation in dendritic spines: implications for synaptic plasticity

Prof Krasimira Tsaneva-Atanasova

(University of Exeter, UK)

from: www.wun.ac.uk

Our BioMaths Colloquium seminars resume for the winter term, with a great programme! We kick it off with a talk by Prof Krasimira Tsaneva-Atanasova from the College of Engineering, Mathematics and Physical Sciences at the University of Exeter. Krasimira is a Professor of Mathematics for Healthcare and her research is focussed on biomathematics. Her ultimate goals are to develop novel applications of mathematics for improved quantitative healthcare methods. 

Abstract

The rise of intracellular calcium concentration [Ca2+] is believed to play a critical role in triggering synaptic plasticity. This is supported by experimental evidence demonstrating that both, synaptic long-term potentiation (LTP) and depression (LTD), are blocked by pharmacological buffering of Ca2+. The importance of intracellular Ca2+ is reflected in the fact that the dynamics of [Ca2+], acting as intermediate signals for induction of plasticity, are a common feature of most biophysical models of STDP.

Calcium-based biophysical models of STDP include a description of the changes in [Ca2+] due to pre- and post-synaptic spiking. Ca2+ sources may depend on the particular synapse to be modelled, but most frequently include: influx via NMDA receptors (NMDARs); influx via Ca2+-permeable AMPA receptors (AMPARs); influx via voltage-gated Ca2+ channels, or Ca2+ release from intracellular stores. Entry of extracellular Ca2+ via postsynaptic membrane ion channels can be dependent on both the postsynaptic membrane-potential and the action of neurotransmitters in the synaptic cleft, therefore biophysical models of STDP often contain descriptions of electrophysiological cell membrane phenomena and AMPAR/NMDAR ligand-gating in response to neuron pair-spiking.

It is an open question how the multiple special and temporal scales involved in intracellular Ca2+ handling within the STDP models affect the plasticity outcomes predicted by these models. Hebbian or associative plasticity is triggered by postsynaptic Ca2+ influx which activates calmodulin and CaMKII. The influx of Ca2+ through voltage-dependent NMDA receptors and Ca2+ channels is regulated by Ca2+ -activated K+ channels (SK-channels) providing negative feedback regulation of postsynaptic [Ca2+]. Using 3-dimensional modelling of Ca2+ and calmodulin dynamics within dendritic spines we show that the non-linear relationship between Ca2+ influx and calmodulin activation endows SK-channels with the ability to “gate” calmodulin activation and therefore the induction of Hebbian synaptic plasticity. Since SK-channels are inhibited by several neuro-modulator receptors including acetylcholine and noradrenaline, the gating of synaptic plasticity by SK-channels could represent a common mechanism by which neuro-modulators control the induction of synaptic plasticity.  

The discussions will continue over biscuits and tea/coffee after the seminar. 

Hope to see many of you!

Biosciences Seminar Speaker 28 January 2016

Biosciences Seminar Series - Winter 2016
28 January 2016 - 1pm - Zoology Museum (Wallace 129)

          Structure and Stability of Ecological Networks -

The role of dynamic dimensionality and species variability in resource use

Dr David Gilljam

(Linköping University, SE)

Our Biosciences seminar series resumes this winter term with a talk by  Dr David Gilljam, from Linköping University (Sweden). David has a keen interest in ecology and in computer programming, so maybe not surprisingly he ended up becoming a theoretical ecologist! And, David will join us soon at Biosciences Swansea as post-doctoral fellow, in the group of Dr Mike Fowler - who tweets under the handle '@theorecol'. So, theoretically ... this sounds like a perfect combination :-)

Abstract

In this talk, I will present the major research results and implications of my work on the response of ecological communities to environmental variability and species loss. A central and much discussed question in ecology is what properties of ecosystems promote the long-term coexistence of numerous interacting species, that is, properties conferring a ‘balance of nature’. Especially, understanding the ecological processes and mechanisms that links diversity and stability in natural ecosystems has been at the heart of community ecology for more than half a century. 

My approach is theoretical; I use mathematical models of networks where species population dynamics are described by ordinary differential equations. A common theme of the papers in the thesis is variation – variable link structure and within-species variation in resource use. To explore how such variation affect the stability of ecological communities in variable environments, I use numerical methods evaluating for example community persistence (the proportion of species surviving over time). I also develop a new method for quantifying the dynamical dimensionality of an ecological community based on eigenvalue analysis and investigate its effect on community persistence in stochastic environments. 

Moreover, if we are to gain trustworthy model output, it is of course of major importance to create study systems that reflect the structure of natural systems. To this end, I also study highly resolved, individual based empirical food web data sets. 

Hope to see many of you - everyone most welcome to attend!

BioMaths Colloquium - 11/12/2015

BioMaths Colloquium Series - 2015/16

11 December 2015 - 3pm Maths Seminar Room 

(room 224 Talbot Building 2nd floor)

Effects of spatial structure on a cyclic herbivore populations

Dr Christina Cobbold

(University of Glasgow, UK)

From: Hughes, Cobbold et al. (2015) Am. Nat. 185(5): E130-E152

Our final BioMaths Colloquium seminar of this term will be by Dr Christina Cobbold from the School of Maths & Stats at the University of Glasgow. Christina is Senior Lecturer in Applied Mathematics and member of the Boyd Orr Centre for Population and Ecosystem Health.  Her keen interest in Mathematical Biology concerns especially the mathematics of biological interactions, such as host-parasitoid interactions, the evolution of developmental timing, and modelling dynamics of rapid evolutionary processes. Examples of the latter include antigenic variation in trypanosomes and mutation leading to myotonic dystrophy. 




Abstract

Understanding how cycles of forest-defoliating insects (herbivores) are affected by forest  structure is of major importance for forest management. Achieving such an understanding with data alone is difficult. We therefore constructed mathematical models to investigate the effects of forest structure on herbivore cycles, focusing on herbivore cycles driven by parasitoids.  

Forest tent caterpillar moth
Pic from Wikipedia

Typically when we think of spatially structured habitat we think of a habitat fragmentation and a mosaic of suitable and unsuitable habitat. However, suitable habitat can be uniformly distributed, but still show spatial structure  via spatial variation in the  plant genotype. It has been shown the plant genotype can strongly affect not only individual herbivore performance, but also community composition and ecosystem function. In this talk I will examine the impact of two these types of spatial heterogeneity (fragmentation and genotype variation) on the population cycles of forest-defoliating insects.

Forest tent caterpillar.
Pic from Wikipedia

Our integrodifference equation model shows that forest destruction can increase herbivore density when parasitoids disperse much farther than the herbivores because the benefits of reduced herbivore mortality due to increased parasitoid dispersal mortality exceed the costs of increased herbivore dispersal mortality. This novel result can explain observations of increased outbreak duration with increasing forest fragmentation in forest tent caterpillar populations.

A Tachinidae parasitoid, genus Leschenaultia.
Pic from bugguide.net

I will also show how plant genotype, the relative size of genotypic patches, and the rate of herbivore dispersal between them, affect the frequency, amplitude, and duration of herbivore outbreaks. We found that coupling two different genotypes does not necessarily result in an averaging of herbivore dynamics. Instead, depending on the ratio of patch sizes, when dispersal rates are moderate, outbreaks in the two- genotype case may be more or less severe than in forests of either genotype alone.

The discussions will continue over biscuits and tea/coffee after the seminar. 

Hope to see many of you!