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Research interests
I am interested in the evolutionary biology and chemical ecology
of social insects. In particular, I have been investigating the
communication strategies of social parasites (the slave making
ant Polyergus) and, more recently, the dynamics of reproductive
conflict in ponerine ants (Pachycondyla).
My favourite slave-maker
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The ponerine ant Pachycondyla
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Chemical strategies in Polyergus rufescens
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The obligatory slave making ant Polyergus rufescens cannot
survive without its hosts (genus Formica). To found a new
colony, a newly mated Polyergus queen must find and usurp
a host colony and kill the resident queen. Which are the successful
strategies to integrate into the host society?
| The parasitic queen relies on a double chemical
strategy: a repellent from the Dufour's gland, and the lack
of chemical labels on the cuticle to penetrate the host nest
and to easily acquire the host chemical pattern. After usurpation,
the P. rufescens queen exhibits the chemical signature
typical of the host queen and she succeeds to be accepted
by the host workers. |
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To establish a functional mixed colony, the P. rufescens
queen starts to lay eggs. How can the slave-making brood be cared
for by the heterospecific slaves? Young parasitic workers integrate
into host colonies thanks to a specialised chemical mimicry characterised
by a high level of plasticity. There is also evidence for a host-specificity,
since the slave-making callows reared without any contact with
adult workers, develop a chemical profile similar to that of the
host present in their natal nest. Besides their interest for the
evolutionary biology and chemical ecology of social parasites,
these results contribute to the understanding of the chemical
basis of nestmate recognition in ants in general.
Reproductive conflicts in primitive social system
The genus Pachycondyla is a good model system for the comparative
study of key social traits. Pachycondyla inversa queens associate
during colony foundation and form a hierarchy with the dominant
taking care of the brood and the others being engaged in foraging
activities.
I am trying to identify the active chemical compounds responsible
for the discrimination of caste and social status; to investigate
whether substances correlated to the reproductive status are detected
and recognised; to clarify the Linksrmation processing of biological
active compounds starting from the antennal level; to understand
whether these active compounds are reliable signals reflecting
the quality of the sender.
Detection of cuticular hydrocarbon signals by the ants' antennae.
In the same colony, slight differences among individual odours
can be the basis to discriminate among different castes, classes
of age, and social status. The challenge is to identify the active
chemicals involved in this signalling system and their mechanism
of action.
In collaboration with Professor Manfred Ayasse
(Ulm, Germany), I used electrophysiological techniques (EAG,
GC-EAD) to study the chemoreception of signals. After Heinze
et al. (2001) observed that the quantity of the unsaturated
alkane 3,11-dimethylheptacosane on an individual's cuticula
is correlated with its reproductive status, we tested whether
this substance is detected by P. inversa workers. Workers
indeed detect and react to this key compound (which was synthesised
by the laboratory of Professor W. Franke, Hamburg). It appears
that 3,11-diMeC27 is correlated with the ovarian activity
and, thus, can assume the role of a fertility signal reflecting
the quality of the sender.
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Worker policing by egg eating.
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| In collaboration with Professor Francis Ratnieks
(Sheffield, UK) I investigated the occurrence of worker policing
by egg-eating in P. nversa. Worker policing (workers
preventing other workers from reproducing), is a mechanism
to solve conflicts over reproduction (Ratnieks F.L.W. 1988
Am. Nat. 132, 217-236). We showed for the first time in ants
that worker-laid eggs are differentially eaten in comparison
to queen-laid eggs. Chemical analyses of the egg surface revealed
that queen-laid eggs and worker-laid eggs have different chemical
signatures due to different relative proportions of several
compounds. This could be the basis for the differential treatment
of eggs. Interestingly, queen-laid eggs are characterized
by a high proportion of 3,11-diMeC27 on their surface. This
is likely to be an example of the widespread pheromonal parsimony,
with 3,11-diMeC27 serving both as a fertility signal and for
protecting queen-laid eggs from policing. |
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· (INSECTS
EU - Network)
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