CONTENT - International Society of Zoological Sciences

S16 ICZ2008 - Abstracts
What makes a termite queen – from ecology to genes
Judith Korb
Behavioral Biology, University of Osnabrück, D-49069 Osnabrück,
Germany
Termites are the oldest social insects. Despite their apparent
similarity to ants, they evolved social life independently, probably
from a wood-nesting cockroach ancestor. We studied the ultimate
and proximate factors influencing cooperation in a drywood termite,
Cryptotermes secundus, with an ancestral life type of dwelling in
dead wood. Associated with this life type is a flexible development
in which workers can become sterile soldiers, winged sexuals that
disperse and found a new colony, or replacement reproductives
that inherit the natal breeding position when the same sex
individual of the colony dies. We showed that the ‘decision’ of
individuals to stay in the colony or leave it as winged sexual is
influenced by ecological factors, such as food availability or
parasite pressure, and social factors such as colony size. However,
it is not affected by the number of young present in the nest. These
results together with the finding that the workers do not care for
young, suggest that the workers do not stay to raise siblings.
Rather they seem to stay because they can inherit the colony as
replacement reproductive. Proposing that the opportunity to
become a replacement reproductive builds a major backbone for
the evolution of termite sociality, we investigated genes involved in
reproductive development. In a cross-species comparison we
isolated three genes which were generally highly overexpressed in
female replacement reproductives. These genes are good
candidates to play a crucial role in caste determination and
reproductive division of labor.
Molecular basis of foraging and defense behaviors in the ant
Pheidole pallidula
Christophe Lucas 1,2 and Maria B. Sokolowski 1
1 Department of Biology, University of Toronto, 3359 Mississauga
Rd. Mississauga, Ont. L5L 1C6, Canada
2 present address: Department of Ecology and Evolution,
University of Lausanne, Biophore, CH-1015 Lausanne,
Switzerland
Social insects are spectacular examples of behavioral adaptations
with sterile sisters performing specialized work in the colony.
However, little is known about the molecular basis of their
behavioral specialization and flexibility.
The ant Pheidole pallidula has two sub-castes of workers, majors
and minors, which are specialized in defense and foraging
respectively. However, majors are able to help minors in foraging
activities depending on the needs of the colony. Thus, there is
plasticity in the subcaste behavioral repertoires.
Here we investigate the molecular underpinnings of subcaste
specialization and plasticity in foraging and defense by studying
the foraging (for) gene. The behavioral effects of for which
encodes a cGMP dependent protein kinase (PKG) were first
described in Drosophila melanogaster, where for allelic variation
affects foraging behaviors (Osborne et al. 1997). In Apis melifera,
for expression is different between foragers and nurses (Ben-
Shahar et al. 2002). Here we show that for is involved in
behavioral flexibility and specialization of P. pallidula's sub-caste.
Specifically, majors have higher PKG enzyme activities than
minors, their PKG activities are lower in the presence of a foraging
stimulus and higher in the presence of an alien intruder.
Furthermore, pharmacological activation of PKG decreases
foraging and increases defense behaviors. Finally, both the
number and localization of neuron clusters in which FOR-PKG is
expressed differ between the brains of majors and minors.
Together these results suggest that the foraging gene modulates
responses to task-related stimuli in the ant colony.
Ben-Shahar Y, Robichon A, Sokolowski MB, Robinson GE (2002)
Influence of gene action across different time scales on behavior.
Science 296:741-744.
Osborne K, Robichon A, Burgess E, Butland S, Shaw RA,
Coulthard A, Pereira HS, Greenspan RJ, Sokolowski MB (1997)
Natural behavior polymorphism due to a cGMP-dependant protein
kinase of Drosophila. Science 277:834-836.
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Evolution of queen size polymorphism in the neotropical ants
Ectatomma Smith 1958
Alejandro Nettel 1 , Chantal Poteaux-Leonard 1 , Dominique
Fresneau 1 and Jean-Paul Lachaud 2
1 Laboratoire d‘Ethologie Expérimentale et Comparée (LEEC)
CNRS UMR 7153 - Université Paris 13. 99, avenue J-B. Clément,
93430, Villetaneuse, France
2 Centre de Recherches sur la Cognition Animale (CRCA) UMR
5169 - Université Paul-Sabatier, 118 route de Narbonne, Bât. IVR3,
31062 Toulouse, France
The evolutionary implications of ant queen-size polymorphism, a
phenomenon sparsely present throughout the Formicidae, is a
central question in the study of the reproductive strategies of social
insects. This polymorphism entails the presence of normal sized
queens, macrogynes, and size-reduced queens, microgynes.
Microgynes have been related to different evolutionary trajectories
including parasite queens (inquilinism), alternative dispersal
agents at a lower energetic cost, and dependent colony-founding
specialists. Parasitic forms are thought to originate from queenpolymorphic
populations that undergo sympatric speciation. Two
different instances of microgyny have been described within two
widely distributed species of the neotropical genus Ectatomma.
Microgynes in E. tuberculatum are parasites and have recently
been described as a new species, E. parasiticum. On the other
hand, evidence suggests that E. ruidum microgynes are a
dispersal-related morph. These two cases of queen-size
dimorphism have been described only for colonies from southern
Mexico. The aim of our study is to understand the evolution of
microgyny in Ectatomma by answering the questions: Is there
evidence of a common origin of microgyny in E. ruidum and E.
tuberculatum? If not, is microgyny a recent, derived characteristic
within each species? Our results based on the molecular
phylogeny of the whole Ectatomma genus using mitochondrial and
nuclear sequences show that microgyny has evolved twice
independently and that dissimilar processes were involved in the
origin of mycrogyne-bearing populations in E. ruidum and E.
tuberculatum. We present our results and their implications to our
understanding of the evolution of alternative reproductive
strategies in ants.
Genomic response to sex: A microarray-based study of
queens in the ant Cardiocondyla obscurior
Jan Oettler 1 and John Wang 2
1
Universität Regensburg, Biologie I, Germany
2
University of Lausanne, Department of Ecology and Evolution,
Suisse
Previous research documented a dramatic effect of mating on
aging in the ant C. obscurior: Queens that have been mated with
sterilized males show a similar lifespan compared to queens
mated with fertile males. By contrast, virgin queens have a much
lower life expectancy (50% lower). We were interested in why
those queens that were mated with sterilized males still show
physiological traits of fully functional queens although fecundity is
as low as in virgin queens, i.e. why does aging appear to be
uncoupled from fecundity. To begin investigating the molecular
basis for this uncoupling, we used a cDNA microarray developed
for the closely related Solenopsis invicta to profiled gene
expression differences between virgin queens, queens mated to
normal males and queens mated to sterilized males. We found
many differentially regulated genes among the three different
queen classes, and of particular interest in our preliminary analysis,
some of these genes are involved in metabolism and juvenile
hormone production.