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Research Area's : Spatio temporal dynamics
Whole Heart modeling
Evolution
Lymphocyte dynamics
Development
Publications:
PhD theses (D1-8)
1993 (1-13)
1994 (14-25)
1995 (26-41)
1996 (42-51)
1997 (52-70)
1998 (71-97)
Eco-evolutionary dynamics
Evolutionary models have long neglected to look explicitly to
the evolution of complexity.
Examining what did happen in evolution Maynard Smith and Sathmary
postulated that the occurrence of multiple levels of selection is
crucial. From the early nineties we pioneered studying the
evolutionary consequences of
space in simple, individual based ecological
interaction models,
and studied what does happen. We
have shown that new levels of selection automatically
arise, in the form of generic spatio-temporal patterns
which enslave the
dynamics of the self-replicating entities (D4,D7,5,27,28,65,66).
The direction of evolution of the replicators
tends to be such as to stabilize the patterns
in which they find themselves.
This leads to many
counterintuitive results, because the spatio-temporal dynamics leads
to long term information integration, e.g. variants
which are less fit over each
time-slice of many generations, can nevertheless persist or
take over in the long run. Thus, selection at multiple levels
provides counterexamples for the general held
'taboo', that only immediate benefits should be considered in
evolution. Within such multilevel systems processes as division of labor,
and conflicts between levels of selection occur and we have shown
that pattern formation is a a prerequisite for exploitation
of long term information storage
(19,20). The latter work was the first to use as modeling
strategy the focus on side-effect of evolutionary optimization towards
a 'trivial' target.
see review paper
Three mechanisms of sympatric speciation were
elucidated: (a.) in coevolving predator/prey or host parasitoid
systems sympatric speciation happens due to oscillatory dynamics and
interlocking ecological and evolutionary time scales (D5,36),
(b.) the long standing
question of the stability of the sexual continuum was finally
solved analytically in terms of Turing and resonance type
pattern formation in phenotype space (61), and (c.) sexual selection can lead to speciation
provided the trade preference mapping has certain properties. These
properties are realized in below water color perception, and the
model nicely explains speciation and the current
loss of species in cychlid fishes.
Molecular Evolution
Evolution is often portrayed as an optimization process in a
rugged fitness landscape, with many local peaks.
Our work (with Schuster's group, Vienna) on RNA evolution, incorporating
the (computable)
non-linear mapping between RNA primary and RNA secondary structure,
has led to a modification of this (spin-glass like) picture: RNA forms
a rugged fitness
landscape with long neutral paths connecting the peaks. In collaboration
with Santa Fe Institute we characterize the dynamics on these landscapes
analytically. The resulting evolution reconciles
adaptionist and neutralists views on evolution. Evolutionary
trajectories on these neutral paths lead in a stationary landscape to
flatter parts (i.e. relative insensitive to mutations) while in
coevolution
they lead to more rugged parts (D2,6,21) In other coevolutionary models
this effect occurs as well and we have shown that
robustness to mutations and robustness to
environmental differences are inversely correlated (p).
Evolution of Immune repertoire
We have shown in several models that the diversity of vertebrate immune
repertoires does not seem to reflect primarily the diversity
of pathogens. It can be explained as evolutionary enhanced
side-effect of somatic recombination (p) or in terms of constraints on
self-tolerance avoiding
auto-immunity (3,p).
Next: Lymphocyte dynamics
Up: Overview of research 1993-1998
Previous: Whole Heart modeling
Paulien Hogeweg
1999-03-05