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Autumn 2010
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
cancelled
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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
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