I am interested in evolutionary ecology and behaviour in general.
First I focused on sexual selection. I worked with Nico Michiels at
the Max-Planck Institute in Seewiesen on a project where we
observed earth worms (Lumbricus terrestris) to find out how
they choose their partners (or what they actually do on a golf
course in the middle of the night...).
I also did my oral exams in Ecology and Zoology and my Diploma
thesis on sexual selection. For my Diploma thesis I worked with
Bart Kempenaers' group at the Max-Planck Institute for Ornithology
in Seewiesen on 'Blood parasites of blue tits: abundance and
fitness effects'. I wanted to find out if blood parasites in this population
are costly for their hosts and could therefore play a role in partner
choice. For this study I correlated individual data about blood
parasites (species, abundance) with breeding data from a long term
study of blue tits in the Viennese Forest.
For my PhD thesis I was working on the evolution of cooperation.
Cooperation in larger group is often more difficult to explain then
cooperation in pairs. For humans it has been proposed that punishment
plays a major role in stabilising individual contributions to group success
(‘public goods’) but that claim remains contentious. The aim of my thesis
was to gain understanding of a system in which both punishment and
public goods may exist, and which can be studied both in nature and with
an experimental setup in the laboratory. The interactions between victim
reef fishes and parasitic sabre-tooth blennies (Plagiotremus rhinorhynchus,
P. tapeinosoma) that bite mucus and scales off other fishes provided
a suitable study system.
In the first part of my thesis I describd the natural history of this peculiar
host-parasite complex. The blennies occupy small territories. Resident
victim species that are constantly under threat of being bitten reacted
aggressively to blenny attacks, while visiting species used their potential
to escape further interactions by swimming off. Among residents, the probability
of aggressive reactions to blenny attacks was negatively correlated to group
size without dropping to zero. The latter results fitted a public goods scenario
where benefits of acting decrease with increasing group size.
In the second part I could demonstrate that aggression by victims functions
as punishment as it reduced the probability of future attacks by a blenny.
Furthermore, field observations revealed that punishment creates a public good
in locally abundant species as it increased the probability that blennies switched
to a different victim species. Nevertheless, punishment appeared to be
self-serving rather than altruistic because lab experiments suggested that blenny
preferentially target non-punishing individuals.
The third part focussed more specifically on the blennies’ foraging
decision rules. Overall, I documented that blennies may attack at preferred
locations,that they may prefer abundant hosts, and that they may focus on
specific non-punishing individuals. However, there was huge variation
between individuals with respect to the relative importance of these factors,
including the probability of switching victim species between subsequent
attacks irrespective of victim responses. This variation may locally undermine
the effectiveness of punishment, and may also sometimes create
competition between conspecifics instead of a public good.
In conclusion, the study demonstrates the existence of self-serving punishment in
a parasite-host system. Public goods may emerge as a by-product of self-serving
punishment due to the parasite’s foraging decision rules, which typically select
against non punishing ‘free-riders’. How the observed variation in blenny decision
rules may evolve and how victims should evolve their optimal responses in return
would ideally be addressed in evolutionary game theoretic modelling, amenable to
further empirical testing
All field data were collected at Marsa Bareika, Ras Mohammed
National Park, Egypt. All lab experiments were conducted at
Lizard Island Research Station, Australia.