Eric
Klopfer
Advisor: Tony Ives
PhD Abstract: Ecological and evolutionary consequences of
explicit spatial structure in exploitervictim systems
A large and diverse literature
on spatial models in ecology exists.
Yet, in many ways the science
of spatial ecology remains "the
final frontier for ecological
theory," with many of the
fundamental principles of the
science still developing.
One class of spatial model which
has been widely used in ecology
has been termed "pseudospatial
models" and classically employs
various types of aggregation in
studying the coexistence of competing
parasitoids. Yet, little is known
about the relative effects of
each of these aggregation behaviors.
Thus, in Chapter 1 I choose to
examine three types of aggregation
and explore their relative strengths
in promoting coexistence of two
competing parasitoids. While it
is difficult, or impossible, to
state a priori which of the three
mechanisms has the strongest tendency
to promote coexistence, I provided
various tools for examining the
common statistical properties
of these mechanisms that promote
coexistence. Providing these tools
to examine different mechanisms
in a common light serves to unify
this class of spatial models.
A striking shortcoming of spatial
models in ecology to date is that
there is a relative lack of use
of spatial models to investigate
problems on the evolutionary as
opposed to ecological time scale.
Consequently, in Chapter 2 I chose
to start with a classic problem
of evolutionary time scale  the
evolution of virulence and predation
rates. Debate about this problem
has continued through several
decades, yet many instances are
not adequately explained by current
models. In this study I explored
the effect of explicit spatial
structure on exploitation rates
by comparing a cellular automatia
(CA) exploitervictim model which
incorporates local dynamics to
a metapopulation model which does
not include such dynamics. These
models showed that in the absence
of the model which does not include
such dynamics. These models showed
that in the absence of the spatial
localization, selection always
favors higher rates of exploitation,
but in the presence of spatial
localization, intermediate rates
of exploitation may be the evolutionary
stable strategy.
One advantage of CA models is
that they are defined by simple
rules rather than the often complex
equations of other types of spatial
models. This is an extremely useful
attribute when one wants to convey
results of models to an audience
with an applied bent that is often
uncomfortable with hardtounderstand
equations. Thus in Chapter 3 I
chose to use CA models to investigate
some potential problems with biocontrol.
Through the use of CA models,
I showed that there are spatial
phenomena which alter the impact
of introduced predators and that
these phenomena are potentially
important in the implementation
of biocontrol programs.
The relatively recent incorporation
of spatial models into the ecological
literature has left most ecologists
and evolutionary biologists without
the ability to understand, let
alone employ, spatial models in
evolutionary problems. In order
to give the next generation of
potential ecologists a better
understanding of these modesl,
in Chapter 4 I developed an interactive
tutorial in which students are
able to explore the most well
studied of these models (the evolution
of cooperation in a spatial environment).
