Research at the Institute of Biology I
Evolution, Behaviour and Genetics
Main research topics at the Institute of Biology I
Living organisms are characterized by an enormous diversity
of "bauplans" and life histories. Mean body size, longevity, number
and size of offspring, etc. differ between species in the order
of several magnitudes: while some mites already mate in their
mother's body and are born themselves being pregnant, a number
of vertebrates start reproduction only after several years or
decades of costly growth. The factors causing and sustaining such
a wide variety of life histories remain insufficiently understood.
One of the main aims of evolutionary biology is to explain these
differences and the underlying evolutionary forces.
At the Institute of Biology I of Regensburg University we try
to analyse the evolution of different features and behavioural
traits in various model organisms and to understand their respective
adaptive values and how environmental factors influence the formation
of alternative life histories. Predictions based on evolutionary
biology models (game theory, kin selection theory, etc.) are tested
by comparative analyses and experimental manipulations between
and within species. These questions simultaneously touch diverse
fields of biological sciences: evolutionary biology, ecology and
ecophysiology, behavioural biology and chemical ecology, phylogeography,
population and social genetics.
Correspondingly, we are applying diverse methods in our investigations.
Next to classical field work (in Europe, Africa, North and South
America, Southeast Asia and Australia), video and computer-supported
behavioural documentation, histology, and electron microscopy,
we use molecular methods for the analysis of relatedness and phylogeny
(allozyme electrophoresis, PCR, microsatellite analysis, sequencing
of nuclear and mitochondrial DNA) and gas chromatography / mass
spectrometry to reveal the chemical composition of signals. Other
approaches of our work are statistical and population genetic
evaluation procedures, model constructions and simulations. Our
interest is devoted to the entire animal kingdom. However, the
groups on which we predominantly work are:
Evolution and Structure of Animal Communities
Main topics in evolutionary biology are questions related to the
formation of social communities. Why do individuals cooperate, given
that cooperative, altruistic behaviour is associated with costs
to the single individual? Social insects represent one extreme along
a continuum of social organization. Here, some individuals refrain
from reproducing to support other individuals in raising their offspring.
We study those factors that favour such cooperative behaviour.
Ants are
in the focus of attention, one animal groups, which appear to be
strikingly similar in their social organization, though different
because of different ecology and phylogeny.
Crustaceans stand on the other extreme of the sociality continuum, even though
some species show brood care and in few cases even advanced sociality.
This allows studying the transitions between different degrees of
social behaviour. Special emphasis is given to the study of conflicts
between members of a group. Since these are normally genetically
non-identical, different reproductive interests arise. We investigate
how the resulting conflicts are expressed and how they can be solved
without destroying group living.
Collective anti-parasite defence
Colonies of social insects offer a valuable resource for parasites, as many host individuals live together in close density, typically within nicely thermoregulated nests. Moreover, colony members are often highly related and thus susceptible to the same types of parasites. To be able to exploit this resource, parasites need to enter the nest, establish there, and spread between group members. To prevent this from happening, social insects have evolved a great number of highly sophisticated collective defence mechanisms, both being of prophylactic nature and being induced upon parasite attack. For example, group members regularly groom infectious particles from each others bodies, they warn each other about hazardous sites, and they have highly elaborate waste management. In collective anti-parasite defence, hygienic behaviours play together with the physiological immune systems of the individuals and the regulation of their contact rates to prevent disease outbreak in the colony.
.
Reproductive Strategies and Tactics
Individuals within a species often differ in the strategies they
apply to ensure and maximize reproductive success. On one hand there
are differences between the sexes. Males generally compete for females,
which represent the limiting sex. This leads to sexual selection,
in which females can choose the males, whereas males compete for
the females. However, also within sexes individuals can differ in
their reproductive strategies. These differences can be based on
genetic polymorphism (for example in the case of evolutionary stabile
strategies) or caused by the environment (different tactics of an
individual). Questions on sexual selection (e.g. female choice and
male fights in ants), evolutionary stabile strategies (e.g. associated
with queen or male polymorphism) and tactics based on phenotypic
plasticity (e.g. worker versus sexual in lower termites) are being
studied in
ants.
Since the colony of social insects as a whole must be considered
an enlarged selection unit, results from our studies can be used
to contribute to and broaden concepts of evolution (e.g. multi-level
selection) and to show the significance of alternative reproductive
tactics in animals.
Population Genetics
Population genetics is the study of changes of allele frequencies
within the gene pool of a species as a whole and its constituent
populations. The addressed questions can be diverse. In
ants the
analysis of the frequency of molecular markers (allozymes, microsatellites,
AFLP) allows quantifying the degree of relatedness within and among
colonies. In addition, these methods can be applied to test whether
mating occurs randomly within a population, whether there is inbreeding,
and if populations are
geographically or
ecologically structured, which eventually can lead to speciation. This is investigated
in
ants, and
crustaceans.
Phylogeny and Zoogeography
The goal of phylogeny or the history of lineages is to clarify evolutionary
relationships (common ancestry, order of speciation) between taxa.
In addition, ecological, ethological and physiological peculiarities
of selected groups can be plotted onto a phylogenetic tree to determine
whether they have evolved convergently or only once in monophyly.
Next to the classical methods of phylogenetic reconstruction (comparative
morphology), we use molecular methods, such as DNA-sequencing in
ants and
crustaceans, to establish phylogenetic relationships. We also carry out intraspecific
phylogenetic studies of geographically separated populations (phylogeography)
to determine if and for how long populations have been isolated
and if allopatric differentiation, incipient speciation, or hybridisation
is taking place. These methods can also be used to reveal the existence
of cryptic species
Chemical Ecology
Our surroundings are full of animal signals that
cannot be perceived by humans. Chemical signals (pheromones) play
a crucial role in social insects to ensure the functioning of
the colony. Cuticular hydrocarbons apparently provide Linksrmation
about the colony to which an individual belongs, the tasks it
carries out within the colony, and its reproductive status. With
the aid of gas chromatography and mass spectrometry we identify
the relevant substances for communication in ants.
By using electrophysiological
techniques (EAG, GC-EAD) we study the chemoreception of biologically
active compounds. Of special interest is, whether communication
exclusively consists of "honest signals" or whether cheating and
manipulation are possible in evolution.
