Dienstag, 11.06.2018, 14ct, U10-146: Mike Steel (Christchurch, New Zealand)
Birth-death models in phylogenetics: symmetries, shapes, and the loss of biodiversity
The role of birth-death processes in modelling speciation and extinction
in macro-evolution has a long history, with a classic paper by Yule in
the 1920s. In this talk, I describe how such models can predict the
‘shape’ of evolutionary trees, as well as the expected loss of
phylogenetic diversity under rapid extinction at the present.I also
describe some recent work revealing certain symmetries in these
processes, which has implications for the inference of speciation and
extinction rates from phylogenies.
Freitag, 24.05.2019, 16ct, V3-204: Elisabeth Georgii (München)
Data-driven plant science: from multi-omics analysis to phenotype modeling
High-throughput omics technologies provide comprehensive measurements of tens of thousands of molecular features at different levels of cellular organization. Integrating such high-dimensional and heterogeneous data to facilitate discovery of biological relationships poses various computational challenges, starting from appropriate data management and automated analysis workflows up to advanced machine learning, data mining and visualization techniques. This talk highlights examples of data-driven hypothesis generation regarding biological mechanisms of combined drought and heat stress responses in plants, which are increasingly important under predicted climate change scenarios. In particular, both correlated and contrasting regulation patterns between the transcriptome and the metabolome are put into biological context. Even after stress relief and during extended recovery periods, plants maintain a molecular memory that increases their tolerance to subsequent stress events. Our data suggest that this memory differs with stress frequency or intensity, exists across tissues, involves specific genes and is consistent with phenotypic observations. Finally, recent developments in plant phenotyping and approaches toward integrative phenotype modeling are presented.
Freitag, 10.05.2019, 16ct, V3-204: Michael Baake (Bielefeld)
The Markov embedding problem revisited - from an algebraic perspective
The Markov embedding problem, namely whether a given
Markov matrix can occur within a continuous time Markov
semigroup, is still unsolved even for 4x4 matrices.
It became quite famous in the 1960s through an influential
paper by Sir John Kingman and led to some interesting
equivalent reformulations, but defied a practically
effective solution already for 3x3 matrices for a long
time, and still does beyond. In this contribution, the
problem will be reviewed and some extensions will be
presented, which were triggered by the recent need in
phylogeny that has put the problem again on the table.
Freitag, 11.01.2019, 16ct, V3-204: Christiane Fuchs (Universität Bielefeld)
Stochastic Modelling and Inference of Cellular Processes
The molecular biology of life seems inaccessibly complex, and gene expression is an essential part of it. It is subject to random variation and not exactly predictable. Still, mathematical models and statistical inference pave the way towards the identification of underlying gene regulatory processes. In contrast to deterministic models, stochastic processes capture the randomness of natural phenomena and result in more reliable predictions of cellular dynamics. Stochastic models and their parameter estimation have to take into account the nature of molecular-biological data, including experimental techniques and measurement error.
This talk presents according modelling and estimation techniques and their applications: the derivation of mRNA contents in single cells; the identification of differently regulated cells from heterogeneous populations using mixed models; and parameter estimation for stochastic differential equations to understand translation kinetics after mRNA transfection.
Freitag, 19.10.2018, 16ct, V3-204: Philip Gerrish, Atlanta/Bielefeld
Is there sex on other planets?
We ask the question: if an alien system of self-replicating
entities were discovered, should we expect sex and/or recombination to
be features of this system? Put differently, is there something about
mutation and natural selection that inherently promotes the evolution of
sex and recombination? Current theory finds many special circumstances
in which sex and recombination might be expected to evolve, but this
“patchwork of special cases” (with many holes) does not seem to fit the
observations: in nature, sex and recombination are everywhere — spanning
all environments and all levels of organismal size and complexity.
Increasingly, even species traditionally thought to be asexual have been
caught “having sex on the sly”. The observations, therefore, seem to
call for an encompassing feature common to living things in general that
promotes the evolution of sex and recombination. And we think we may
have a candidate! We think this general feature might be none other than
natural selection itself. I will show you what we’re thinking and how it
works, will go through the case of structured populations which has a
nice intuitive “visual proof” as well as a presentable “simplest case”
proof, and will show you how far we’ve gotten with the full problem,
with hopes for some nice feedback.
This is joint work with Ben Sprung (Philadelphia), Julien Chevallier
(Grenoble), and Bernard Ycart (Grenoble).