Theoretical
Ecology Lab Tea
The Theoretical Ecology lab teas are
designed to be informal meetings for members of the research groups of Simon Levin, Steve
Pacala, and Andy
Dobson to give talks on their current research and receive feedback
from their audience. The talks are usually 30 minutes, including the
question and answer sessions, scheduled on Wednesdays at 12:00 PM.
Additionally, other members of the Princeton University community and
visitors are welcome to attend and to give presentations.
Talk schedules and email lists are
maintained by Marissa Baskett and Jeremy Lichstein. Please contact mbaskett@princeton.edu
or jwl@princeton.edu
to have your name added to the labtea email list so that you can
receive reminders about upcoming lab teas.
To view previous schedules and
summaries, go to:
Fall
2000 Spring
2001
Fall
2001 Spring
2002
Fall
2002 Spring
2003
Fall 2003
Wednesday, September 24, at 12:30 PM
|
Marissa Baskett |
Wednesday, October 1, at 12:30 PM
|
Anping Chen
|
Wednesday, October 8, at 12:30 PM
|
Adi Livnat
|
Wednesday, October 15, at 12:30 PM
|
Meredith Root-Bernstein
|
Wednesday, October 22, at 12:30 PM
|
Ricardo Holdo
|
Wednesday, October 29
|
(Fall break)
|
Wednesday, November 5, at 12:00 PM
|
Ben Strauss
|
Wednesday, November 12, at 12:00 PM
|
Kelly Caylor
|
Wednesday, November 19, at 12:00 PM
|
Kiona Ogle
|
Wednesday, November 25, at 12:00 PM
|
(Thanksgiving)
|
Tuesday,
December 2, at 12:00 PM
|
Joshua Weitz |
Wednesday, December 10, at 12:00 PM
|
Georgii Bazykin
|
Titles and
abstracts most recent first (posted approximately one week
before the talk):
Wednesday December 10 @ 12:00 PM
Georgii Bazykin
Detection of
positive selection in codons with multiple substitutions
When multiple replacement mutations occur in a single codon between a
pair of species, these mutations tend to occur in the same lineage. In
every codon, this can only be explained by positive Darwinian selection
on the level of DNA sequence acting in one lineage but not the other.
This potentially provides us with a method for detecting positive
selection. Surprisingly, intensity of selection can differ strongly
between lineages. When we have the available data to look at
orthologous codons in multiple sister lineages (e.g., in HIV), the
resolution of the method can be increased and we can analyse selection
in individual codons as opposed to general statistical trends.
[back to schedule]
Tuesday, December 2 @ 12:00 PM
Joshua Weitz
Phage Attacks!
Co-evolutionary Arms Races Between E. coli and Lambda Phage
Bacteriophage lambda is a temperate phage that infects E. coli and then
either kills the bacteria and releases a burst of phage progeny or
inserts its viral DNA into the bacterial genome leading to a stable
virus-host association known as a lysogen. My aim is to
demonstrate the suitability of this model system for analyzing how
ecological dynamics influence/control the co-evolution of invasion and
defense mechanisms in microbial systems. In so doing I am
motivated by the following questions:
(1) Is it possible to develop chemostat experiments to probe for
co-evolution in targeted loci of lambda phage and E. coli?
(2) How does the temperate nature of lambda phage modify its ability to
adapt to its host?
(3) Can spatial models of phage-bacteria interactions explain the
behavior of wild type lambda with regards to its lysogenic
pathway? I will discuss preliminary results from simulations and
theory.
[back to schedule]
Wednesday,
November 12 @ 12:00 PM
Kinoa Ogle
A potpourri of
plant ecophysiology: linking root, shoot, whole-plant, and population
responses
I will spend the first part of my talk highlighting my dissertation
work, which examined the physiological and growth responses of a desert
shrub to annual, seasonal, and pulse precipitation. I developed a
comprehensive framework for elucidating whole-plant responses to
rainfall by coupling field experiments and mathematical and statistical
models. I will give an overview of my work including: 1) above-ground
responses (e.g., stomatal control, photosynthesis) to seasonal drought
and temperature regimes, 2) below-ground responses (e.g., root
activity, water uptake) to soil water availability, and 3) whole-plant
responses (e.g., growth, allocation) to storms of different sizes,
duration, and timing. In the last part of my talk, I will present some
current postdoctoral research ideas. In my doctoral work, I focused on
the individual plant; for my postdoc, I am developing theoretical and
empirical approaches for linking variation in physiological traits of
individual plants to short- and long-term population and dynamics.
[back to schedule]
Wednesday,
November 19 @ 12:00 PM
Kelly Caylor
Tree Canopy
Effects on Simulated Water Stress in Southern African Savannas
A coupled energy and water balance model is used to simulate the
effects of large tree canopies on soil moisture and water stress across
a series of sites spanning a regional moisture gradient in southern
Africa. The model tracks evapotranspiration from five components of the
land surface at each site - the tree canopy, grass under and between
tree canopies, and bare soil under and between tree canopies. The soil
moisture dynamics are simulated at daily time steps and driven by a
stochastic model of storm arrivals and storm depth. Evapotranspiration
is modeled using the Priestley-Taylor approach, with potential
evapotranspiration scaled by soil moisture availability. The soil
moisture under tree canopies is compared to the soil moisture between
tree canopies, and differences in average annual soil moisture stress
conditions are analyzed at each site. The spatial distribution of large
trees has important consequences on the small-scale soil moisture
dynamics across the rainfall gradient. Results from the model regarding
the distribution of water stress under and between large tree canopies
are in general agreement with the observed pattern of small tree
distribution across the sites. The application of the model for
understanding the interaction between pattern and process in governing
the dynamics of Kalahari savanna communities will be discussed.
[back to schedule]
Wednesday,
November 5 @ 12:00 PM
Ben Strauss
Life in the slow
lane: dispersal and distribution of a stream-dwelling snail
I will report preliminary results from my research on the influence of
hydrology on the distribution of the snail Elimia proxima in southern
Appalachian mountain streams. I aim to use one model of snail
diffusion, directed movement, and dislodgement by flooding to explain
observations of snail presence and absence from a wide geographic
survey, and also observations of snail dispersal from a
mark-release-resurvey experiment I am conducting at several
sites. The model exploits known empirical relationships which
allow fair predictions of many features of stream geometry and flow
from knowledge of area drained and slope. These in turn can be
calculated from publicly available digital elevation models, offering
some promise of a general method for making rough predictions of the
distributions of benthic stream organisms strongly influenced by flow.
[back to schedule]
Wednesday,
October 22 @ 12:30 PM
Ricardo Holdo
Modelling the
impact of elephant herbivory, fire, and frost on woodland structure and
species composition in Zimbabwe
I will present the first results of a simulation of Kalahari sand
woodland dynamics as a function of elephant herbivory, fire, and frost.
The simulation model is a stochastic, discrete-time model that tracks
the fate of individual trees on a one-hectare torus. The model
consists of a number of components that track growth, mortality (of
both ramets and genets), effects of disturbance (death or resprouting),
and recruitment from seed for 10 dominant tree species. All model
parameters were derived from data collected from tagged trees followed
over a three-year period in a semi-arid woodland in Zimbabwe.
Preliminary results suggest a marked effect of elephants on woodland
biomass and structure, the impact varying greatly across tree species,
with less pronounced effects of fire and frost.
[back to schedule]
Wednesday,
October
15 @ 12:30 PM
Meredith Root-Bernstein
The origins of
communication in animal populations
I will be discussing some ongoing research on the evolution of
communication
which I started this summer at the Santa Fe Institute. Most
models
of the evolution of communication assume that some communication
already
exists, and ask questions about its dyanamics. However, I am
interested
in how communication originates in a non-communicating
population.
In my model individuals meet objects in the environment which put them
into
states (but they are not finite state automata). The states give
the
individuals certain perceptible properties which they attempt to
coordinate
with other individuals' perceptual and cognitive abilities, in order to
indicate
the existence of the object which was met. This system is highly
redundant
and degenerate, which constrains the possible solutions to
communication.
Dialects appear to develop in both spatial and non-spatial
conditions.
One also finds that evolution of the state repetoire of the species
must
occur simultaneously to the communication in order to achieve full
coordination.
Further, because in this model communication is linked to perception of
the
biotic and abiotic environment, the evolution of communication in any
one
species is necessarily a case of interspecific co-evolution. I
will
also discuss how this model could in future be linked to other models
of
the evolution of communication.
[back to schedule]
Wednesday,
October 8 @ 12:30 PM
Adi Livnat
The Evolution of
Intergenerational Discounting
Although the importance of intergenerational effects has been
recognized, they have not yet been incorporated fully into life history
theory. When intergenerational
effects and evolutionary change are combined in theoretical models, a
new
result emerges: Mutation and segregation affect the distribution of
life
history strategies at equilibrium above and beyond disrupting selection
pressure.
Higher rates of mutation and of sexual as opposed to parthenogenic
reproduction
favor lower parental investment per offspring and lower total
reproductive
effort. It follows that in general, the relatedness between the
generations
of a lineage corresponds to the level of investment of ancestors in
descendants.
I will discuss how this result differs from inclusive fitness and
interpret
it as a biological form of intergenerational discounting that evolves
independently
of environmental uncertainty.
[back to schedule]
Wednesday, October 1 @ 12:30 PM
Anping Chen
Environmental Interpretations for
the Geographical Patterns of China's Spermatophyte Richness
In this study, I try to interpret the geographical patterns of
China’s spermatophyte richness at a spatial resolution of
1°latitude_1°longitude, and at both generic and species levels
(tree species only), with the contemporary environmental factors. The
preliminary results reveal that at both levels, the contemporary
environmental factors can explain the seed plants’ geographical
patterns excellently, reaching 93% and 87% respectively. The climatic
factors dominate the distributions of China’s seed plants, while
topographic factors have little correlation with seed plant richness at
such a spatial scale. Both generic richness and tree species richness
showed positive linear correlation with NDVI, with coefficients of
correlation of 0.76 and 0.66, respectively. However, the
richness-environment relationships may change with the study objectives
or scale, which was usually ignored.
[back to schedule]
Wednesday,
September 24 @ 12:30 PM
Marissa Baskett
Predation, competition, and the
recovery of overfished rockfish
Rockfish, a diverse group of species, comprise many important
commercial fisheries in the northeastern Pacific. In response to
the recent overfishing of some rockfish species, fishery closures are
being established to promote their recovery. However, overfishing
may have shifted rockfish communities to a new stable state, and
trophic interactions with unfished populations of smaller species may
prevent or delay the recovery of the overfished species. I will
present a simple model of a rockfish community to assess how the
potential for the overfished species to recover depends on trophic
interactions and the size of fishery closures. Preliminary
results from the model indicate the importance of different parameters,
assumptions, and interactions for rockfish recovery.
[back to
schedule]
Last updated 12/13/03
mbaskett@princeton.edu