CONTENT - International Society of Zoological Sciences

S16 ICZ2008 - Abstracts
S16 - Genes, individuals, societies: current trends in social insects
Colony relocation in the ant Aphaenogaster senilis: role of
foragers and reminiscence of acquired experience
Aurore Avargues-Weber 1,2 and Thibaud Monnin 1
1 Laboratoire Écologie & Évolution CNRS UMR 7625, Université
Pierre et Marie Curie, 7 quai Saint Bernard, 75005 Paris, France
2 New address: Centre de Recherches sur la Cognition Animale,
CNRS UMR 5169, Université Paul Sabatier, 118 Route de
Narbonne, 31000 Toulouse, France
We studied the pattern of colony emigration of the ant
Aphaenogaster senilis, which reproduces by colony fission, and its
ability to improve at emigrating through acquired experience.
Emigrations were triggered in the laboratory by opening the nest
while providing a new nest 1.6 m away (n=10 colonies). We video
recorded foragers and nurses entering or exiting this arrival nest.
Nest relocation was characterized by a synchronised emigration:
the number of workers present in the arrival nest increased
following a sigmoid curve. The duration of emigration was
relatively constant between colonies, while the delay before
emigrating varied. The queen relocated in the middle of the
emigration, when many workers were on the move. Six to eleven
weeks after the emigration, foragers were removed from the
colonies and a second emigration was triggered. We expected this
emigration to take longer to be completed, yet we found the
opposite. This may stem from experience acquired during the first
emigration, as has been shown in the ant Temnothorax albipennis.
In A. senilis the experience acquired lasted much longer than in T.
albipennis, and this may be because T. albipennis nurses are
passively transported by foragers, while A. senilis nurses actively
walk to the destination nest, so that only the latter gain experience
by emigrating. In T. albipennis experienced individuals are old
foragers, with a short life expectancy, while in A. senilis young
nurses also are experienced.
Choosing an appropriate index to construct dominance
hierarchies in animal societies
Alok Bang 1 , Sujata Deshpande 1 , Annagiri Sumana 1,2 and
Raghavendra Gadagkar 1,3
1
Centre for Ecological Sciences, Indian Institute of Science,
Bangalore, India
2
Indian Institute of Science Education and Research, IIT
Kharagpur Extension Centre, Salt Lake City, Kolkata, India
3
Evolutionary and Organismal Biology Unit, Jawaharlal Nehru
Centre for Advanced Scientific Research, Jakkur, Bangalore, India
There is a vast diversity in methods of computation of dominance
ranks in behavioural literature, but rarely the rationale behind using
a particular index has been explained. In this study, we analyzed
three dominance indices, viz. Frequency-based Index of
Dominance (FDI), Clutton-Brock et al.’s Index (CBI) and David’s
Score (DS). Apart from FDI that is proposed by our group to
calculate dominance ranks in Ropalidia marginata and Ropalidia
cyathiformis, primitively eusocial paper wasps, the other two
indices were chosen based on popularity and recommendations by
other groups. Dominance ranks obtained from the behavioural
data were subjected to correlation analysis and later, the indices
were evaluated based on the number of unique ranks (ranks
without ties) they attributed. We found that the three indices
attributed similar ranks; however, FDI gave significantly more
number of unique ranks. Using artificial data sets, each index was
later tested on two parameters, viz. non-interacting pairs and
reversals. The three indices attributed similar ranks for artificial
data sets with varying percentages of non-interacting pairs or pairs
showing reversals. The numbers of unique ranks given by the
three indices were not significantly different. At high percentage of
non-interacting pairs, FDI emerged as the best index, whereas at
higher reversal rates, DS seemed to be a better index. Our results,
thus, show that the choice of index to be used should be decided
depending on the properties of the index as well as the social
structure and interaction network of the species to which it is
applied.
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A multi-scale study of ant distribution in the Pyrenees
Moutains
Abel Bernadou 1,2 , Xavier Espadaler 2 , Régis Céréghino 3 and
Vincent Fourcassié 1
1 Centre de Recherches sur la Cognition Animale, CNRS UMR
5169, Université de Toulouse, 118 route de Narbonne, F-31062
Toulouse Cedex 4, France; 2 Departament de Biologia Animal, de
Biologia Vegetal i d'Ecologia, Facultat de Ciències, Universitat
Autònoma de Barcelona, E-08193 Bellaterra, Spain; 3 EcoLab,
CNRS UMR 5245, Université de Toulouse, 118 Route de
Narbonne, F-31062 Toulouse Cedex 4, France
As other mountain ranges in the world, the insect fauna of the
Pyrenees (SW France) present interesting cases of endemism
making it an area of great interest for entomologists. Surprisingly
however, relatively few studies have investigated the ant fauna of
these mountains. Here we present a survey of the distribution of
ant species along an altitudinal gradient in two Pyrenean valleys
located in the central part of the ridge and on the opposite sides of
the mountain range. The influence of environmental factors on the
distribution of ant species has traditionally been investigated at two
widely different scales, either the microhabitat or the regional scale.
However, this does not tell much about the key parameters
underlying the distribution of a given species because the factors
intervening at large scale, e.g. altitude, meteorological conditions,
can impinge on the factors intervening at small scale, e.g.
vegetation type. We simultaneously examined the distribution of
ants at three different scales: large (transect - 2000 m 2 ),
intermediate (100m 2 centered on the sample point) and small
(sample point - 1m 2 ). We used a neural network method of
classification to investigate the relationship between the spatial
distribution of ants and the factors considered at the three spatial
scales. The results show that both the factors considered at large
scale (altitude and sun exposure) and those considered at
intermediate and small scales (land cover) contribute to explaining
the differences observed in the distribution of ant species.
The mechanism of queen selection during queen replacement
in a fission-performing ant
Blandine Chéron, Claudie Doums and Thibaud Monnin
Laboratoire d’Ecologie CNRS UMR 7625, Université Pierre et
Marie Curie, 7 Quai St-Bernard, 75005 Paris
Fission is a mode of colony foundation where young queens
(gynes) mate near the nest, and then leave it with a group of
workers to found a new colony. This mode of colony founding
allows for the replacement of the queen by one of her mated
daughters, so that colonies reproducing by fission are potentially
immortal.
The Mediterranean ant Aphaenogaster senilis obligatorily
reproduces by colony fission and is monogynous (a single queen
per colony). When a colony loses its queen, several gynes are
produced, which gives rise to a process of queen selection to
restore the monogyny. This selection could result from competition
between queens, queen choice by workers or a combination of
both. Some characteristics of young queens (e.g. age or weight)
may correlate with the probability that they will inherit the colony.
Additionally, in a polyandrous species workers could favour gynes
which are more related to them (nepotism).
We developed microsatellite markers for A. senilis and showed
that queens mate only once. We investigated queen selection
using orphaned colonies. The mean number of gynes produced
per colony was two (range 1-4) and the mean age difference
between two successive gynes was 12 days (range 1-29). We
observed aggressions from both gynes and workers. The oldest
gyne was more likely to survive and a hierarchy seemed to be
established, with the oldest gyne dominating the others. Thus, we
suggest that during queen replacement in A. senilis,
supernumerary gynes are produced as an insurance, since they
are generally produced with some delay and rarely become the
new queen.