Theoretical Ecology Lab Tea




The Theoretical Ecology Lab Teas are informal meetings where members of affiliated lab groups give talks on their current research and receive feedback from their audience.  The talks are 30 minutes and are scheduled on Wednesdays at 12.30pm in Eno Hall 209.

Talk schedules and email lists are maintained by Andrew Berdahl, Allison Shaw, and Carla Staver. Please contact, or to have your name added to the labtea email list so that you can receive reminders about upcoming lab teas.



Autumn 2010

Wednesday September 15th at 12.30pm Simon DeDeo
Wednesday September 22nd at 12.30pm Eili Klein
Wednesday September 29th at 12.30pm Ann Thomas
Wednesday October 6th at 12.30pm Christine Taylor
Wednesday October 13th at 12.30pm Charles Yackulic
Thursday October 21st at 12.30pm Sally Archibald
Wednesday October 27th at 12.30pm Liliana Salvador
Wednesday November 3rd at 12.30pm Fall Break: No LabTea
Wednesday November 10th at 12.30pm Ashley Crump
Wednesday November 17th at 12.30pm Allison Shaw
Wednesday November 24th at 12.30pm Yoel Greenberg
Wednesday December 1st at 12.30pm Eili Klein
Wednesday December 8th at 12.30pm cancelled
Wednesday December 15th at 12.30pm Guy Ziv

Titles and abstracts

Wednesday September 15th at 12.30pm

The Statistical Physics of Animal Behavior
Simon DeDeo
We'll look at three ways analogies from the physical sciences have provided provocative insights into a detailed study of animal behavior: spectral analysis in the Fourier domain, the "spin glasses" of condensed matter, and (time permitting) random boolean networks.

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Wednesday September 22nd at 12.30pm

Cross-reactivity of Antigenic Variants Can Generate Malaria Infection Dynamics
Eili Klein
The within-host dynamics of an infection with the apicomplexan parasite Plasmodium falciparum are the result of a complex dance between the parasite and the host’s immune system. While the immune system is capable of recognizing and developing a specific response to the variant surface antigens (VSAs) displayed on the surface of infected RBCs, the continual shifting of displayed antigens mediates recrudescence of infection, and is the presumed mechanism by which the parasite lengthens the duration of an infection. Despite the importance of antigenic variation in prolonging infection, our understanding of the mechanisms by which antigenic variation generates long term infections is still limited. In this paper, we examine the role of cross-reactivity in generating infection dynamics that are comparable to the measured infections in individuals. Using a simple hybrid model, we explain how the multiple infectious peaks of the parasite can be dominated by single VSAs and how this leads to infections that are significant in length.

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Wednesday September 29th at 12.30pm

Immune priming across life stages and generations: implications for infectious disease dynamics in insects
Ann Thomas
Despite the lack of mechanisms associated with adaptive immunity, many invertebrates can mount immune responses against previously encountered pathogens. A burgeoning body of evidence suggests that these responses can be pathogen-specific, maintained over long periods of time, and can even be transferred from one generation to the next. Most experiments, however, have focused on detecting immune priming at the individual level, and the implications of immune priming for population scale patterns and processes remain unexplored on both theoretical and empirical fronts. Here we develop a stage-structured SIRS model to explore the relative and combined impact of priming across life stages (ontogenetic priming) and generations (trans-generational priming) on infection prevalence, host population size, and population age structure. Our model predicts that both types of immune priming can dramatically reduce disease prevalence at equilibrium, but their individual and combined effects on population size and age structure depend on the magnitude of trade-offs between resistance and reproduction as well as on the symmetry of infection parameters between life stages. This model underscores the potential importance of invertebrate immune priming for disease dynamics and highlights the need for wide-spread empirical estimation of parameters that represent the maintenance of immune priming in insects.

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Wednesday October 6th at 12.30pm

Punishment and the Evolution of Cooperation: some analytic results on effects and costs
Christine Taylor
The emergence and maintenance of cooperation is a central theme in evolutionary biology. Cooperators provide benefit to others at a cost to themselves, while defectors reap the benefit and forgo the costs. Darwinian selection favors defectors; yet groups of cooperators outperform groups of defectors. There have been several recent experimental and theoretical studies on the effects of reward and punishment on cooperative behavior of players in repeated Prisoner's Dilemma and Public Goods games. I will discuss the effect of institutional and individual punishment on the evolution of continuous strategy space in repeated cooperative dilemma games under replicator dynamics with mutation. In addition, I will derive the optimal institutional punishment with cost as a function of cooperation level, which boosts cooperation in a community without unduly draining its resources.

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Wednesday October 13th at 12.30pm

Can Northern Spotted Owls coexist with Barred Owls?
Charles Yackulic
Few species are as well studied or have had as large an impact on land-use planning as the Spotted Owl. The Northern Spotted Owl (NSO), one of 3 subspecies of the spotted owl, is found in Northern California, Oregon, Washington and British Columbia. NSO numbers have been declining for decades, primarily in response to large-scale clearing of their preferred habitat, old growth forest. NSO is unique amongst federally listed (sub)-species in that it is still fairly numerous and most of the population is found on public lands. For the greater part of the last 25-years, 14+ sites comprising ~12% of the range of the subspecies have been intensively monitored. Despite changes in forest management practices, following the Northwest Forest Plan (1994), NSO continue to show negative growth rates across most of their range. Continuing declines were predicted by many of the models developed to describe population dynamics in NSO and aid in reserve design; however, the strength of these declines, particularly in the northern parts of the subspecies' range has been much greater than predicted. Many biologists believe that competition with the invading barred owl is at least partially responsible for continuing declines in the NSO. Here I review the models that have been developed to describe population dynamics in the NSO, as well as the evidence for and against competition. I conclude by discussing future approaches that may shed more light on the mechanisms driving observed patterns of decline.

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Thursday October 21st at 12.30pm

Where there is a spark is there a fire? Reconstructing human impacts on fire regimes
Sally Archibald
There is much speculation about how humans altered fire regimes once they learned to control fire. Before this, lightning was the main source of ignition on the globe, and lightning is highly variable both spatially and temporally. The general consensus seems to be that humans have artificially increased ignition sources, and increased fire frequency, and that most systems are therefore experiencing more frequent fire regimes than they might have evolved under. Some of the assumptions about the importance of humans might be misguided, however, in systems where ignitions are not an important factor limiting fire. Here I present some modeling approaches I am exploring to get a more mechanistic understanding of the degree to which humans might have altered fire regimes from when they first learned to control fire (circa 300 000 years ago) to today. The aim is to provide better information to fire mangers and to global modelers about what sorts of fire regimes they should be imposing in their conservation areas and Dynamic Global Vegetation Models.

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Wednesday October 27th at 12.30pm

Quantitative behavioral analysis of C.elegans foraging movement
Liliana Salvador
The study of animal foraging behavior has extreme importance in the field of ecology and exemplifies the wider scientific problem of optimizing search strategies. There is empirical evidence that the type of searching strategies employed by animals while foraging depends on the amount of information that is involved in the search process. When information is lacking, the random search is a possible strategy. To characterize this strategy, it is important to know which are the behavioral mechanisms that animals use while they search and how to link these behaviors to their movement. Recent studies show that the notion of intermittent locomotion is important to link animal behavior to large-scale statistical properties of movement. C. elegans present a very interesting set of behaviors and during labtea, I will present a behavioral analysis of the movement of C. elegans while it is foraging in a cueless environment and how these behaviors change through the search process.

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Wednesday November 10th at 12.30pm

A Mathematical Analysis of Hookworm Infection on Malaria Population Dynamics
Ashley Crump
Despite their commonly observed coinfection, control and treatment for Malaria and Hookworm are typically studied separately. However, recent studies of the within-host interactions of this coinfection system describe an ecological framework that suggests coinfection can increase malaria transmission rates and even protect against severe malaria infection at low worm burdens. It is not obvious how coinfection will impact the population level malaria dynamics since the within-host interactions of the parasites may be both beneficial and detrimental. We explore the complexity of this coinfection system by developing a nonlinear differential equations model to understand how within-host interactions affect population-level Malaria dynamics.

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Wednesday November 17th at 12.30pm

Migration or Residency? Evolution of Movement Behavior & Information Usage in Seasonal Environments
Allison Shaw
Migration is a widespread phenomenon in the animal kingdom that has attracted a lot of attention, both public and scientific alike. However, most discussion of migration occur at the species level and little work has been done to understand migration as a general phenomenon. Additionally, the type of questions that would be most interesting to answer at a cross-taxa level, such as 'What are the ultimate factors that drive migration?', are rarely studied. Here I present a spatially-explicit, individual based model to address this question. I show that certain ecological conditions (in terms of seasonality and patchiness of resources and survival) select for migration, whereas other conditions select for residency (non-migratory behavior). When selected for, migration evolves as both a movement behavior and an information-usage strategy. I also find that different types of migration can evolve, depending on the ecological conditions and availability and cost of information. Finally, I discuss these results in the context of patterns of animal migration that have been observed in different groups of species.

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Wednesday November 24th at 12.30pm

Decomposing Sonata Form: from selfish sonatas to blind music-makers
Yoel Greenberg
Sonata form is by far the predominant musical form of the last 250 years. It appears in instrumental works and vocal works, in symphonies and concertos, in chamber music and orchestral music. Yet defining the form proves a remarkably elusive task (there is no agreement among musicologists even on the parameters involved!), as does the construction of a convincing genealogy. This research shows how questions, concepts and modes of thought from modern evolutionary theory can shed light on such problems. While evolutionary modes of thought are no strangers to music theory, this rarely goes any further than a rather crude and frequently problematic parallel with natural selection. More specific questions and concepts are rarely invoked, Here, a number of questions and ideas which are standard fare in evolutionary thought are introduced to assist in understanding the development of complex creative norms, in particular sonata form. Examples of these are questions such as "what are the units of selection?" and concepts such as convergent evolution and mutualism, which are shown to provide straightforward answers to problems that have heretofore been considered difficult.

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Wednesday December 1st at 12.30pm

Prereferral rectal artesunate for treatment of severe childhood malaria: a cost-effectiveness analysis
Eili Klein
Severely ill patients with malaria with vomiting, prostration, and altered consciousness cannot be treated orally and need injections. In rural areas, access to health facilities that provide parenteral antimalarial treatment is poor. Safe and effective treatment of most severe malaria cases is delayed or not achieved. Rectal artesunate interrupts disease progression by rapidly reducing parasite density, but should be followed by further antimalarial treatment. We estimated the cost-effectiveness of community-based prereferral artesunate treatment of children suspected to have severe malaria in areas with poor access to formal health care. We assessed the cost-effectiveness (in international dollars) of the intervention from the provider perspective. We studied a cohort of 1000 newborn babies until 5 years of age. The analysis assessed how the cost-effectiveness results changed with low (25%), moderate (50%), high (75%), and full (100%) referral compliance and intervention uptake. At low intervention uptake and referral compliance (25%), the intervention was estimated to avert 19 disability adjusted life-years (DALYs) (95% CI 16-21) and to cost I$1173 (95% CI 1050-1297) per DALY averted. Under the full uptake and compliance scenario (100%), the intervention could avert 967 DALYs (884-1050) at a cost of I$77 (73-81) per DALY averted. Prereferral artesunate treatment is a cost-effective, life-saving intervention, which can substantially improve the management of severe childhood malaria in rural African settings in which programmes for community health workers are in place.

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Wednesday December 8th at 12.30pm


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Wednesday December 15th at 12.30pm

Trading off hydropower, biodiversity and food security in the Mekong river basin
Guy Ziv
The Mekong river basin is home to about 73 million people, most of them rely on inland fisheries as a major part of their diet. To date 860 freshwater fish species have been recorded in the river, of which 90 species migrate seasonally along its 4,600 km long basin. Both species diversity and food security are threatened by hydropower plans of the six riparian counties – China, Myanmar, Laos, Thailand, Cambodia and Vietnam. These plans include the construction of 11 mainstream dams which will obstruct fish migration along the river. In this talk I will present an analytic model of fish migration and determine under which biotic and abiotic conditions migration establishes and maintains. The model predicts significant changes of migratory species distribution, abundance and annual catch variability due to anthropogenic drivers including dam construction and over-harvesting. Such changes will have critical impact on the livelihood of people residing far downstream from the potential beneficiaries. This general theory is applied to the Mekong basin using an extensive presence/absence dataset of all fish species in 20 sub-basins. I consider five possible scenarios of Mekong basin development for the years 2015 and 2030, and elucidate the expected impact on species richness and fish catch in each of them. Finally, these impacts are compared with the designed hydropower production for each scenario. This trade-off analysis highlights the international conflicts which will shape the future of this important river in the next decades.

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Links to previous schedules

    Fall 2000    Spring 2001
    Fall 2001    Spring 2002
    Fall 2002    Spring 2003
    Fall 2003    Spring 2004
    Fall 2004    Spring 2005
    Fall 2005    Spring 2007
    Fall 2007    Spring 2008
    Fall 2008    Spring 2009
    Fall 2009    Spring 2010
    Fall 2010   

Last update: September 14th 2010
Allison Shaw