CONTENT - International Society of Zoological Sciences

ICZ2008 – Abstracts S17
Does early sibling aggression in Lynx fit facultative siblicide
theories?
Anastasia Antonevich 1 and Sergey Naidenko 2
A.N. Severtsov Institute of Ecology and Evolution, Leninsky pr.33,
Moscow, 119071, Russia
One spontaneous and sometimes lethal sibling fight occurs in
more than 50% of European lynx twins and triplets during 6-7
week of cubs life (Sokolov et al., 1994). The same siblicidal fights
were described in zoos and found in Iberian lynx litters (Vargas et
al., 2005). Facultative siblicide can evolve when the fitness benefit
gained by a dominant offspring, exceeds the cost of reduced
inclusive fitness. The main environmental component expected to
control sibling aggression is food, fights can lead to individual
advantages in feeding and growth as well as deaths of broodmates
(Drummond, 2001). According to the Challenge Hypothesis the
androgens level is up-regulated during social challenges (Wingfield
et al., 1990) including sibling aggression period (Ferree et al.,
2004). We tested these hypotheses for facultative in Eurasian lynx.
Fights were recorded both in twins and triplets. Contrary to
expectation aggression in lynx litters was not directly dependent on
food supply and intralitter competition for food. None the less,
fights occurred mostly in the litters with lower growth rate and led
to weight gain advantages for winners. Winners also got priority in
food access. Although predictions of the resource-tracking
hypothesis were not supported, growth rate differences reveal the
resource competition role in sibling aggression. No enhancement
of androgens or cortisole levels were found during the fighting
period but plasma androstendione was elevated 3 weeks before
fighting period in aggressive comparing to non-aggressive cubs.
Spontaneous fights in lynx appear to be unique phenomenon that
nevertheless fits main siblicide patterns.
Diversity of the baltic clam Macoma balthica L. at local and
geographical scales (Barents Sea)
Larisa Basova, Mikhail Gantsevich, Eugene Genelt-Yanovsky and
Petr Strelkov
Leninskie Gory 1, build.12, 119991, Moscow, Russia
The bivalve mollusc Macoma balthica is common and often
dominant member of littoral soft-bottom communities along the
North European coasts. Macoma demonstrates considerably high
inter- and intra-population variability in size, growth and
morphological characters such as shell shape, colour and hinge
structure. Spatial variation of some of these parameters was early
studied at local and (or) geographical scales! . However there is no
common opinion about the level of variation and factors causing
the variability. The goal of our study was to analyze spatial
variation of M. balthica growth and morphology at the scale of Kola
Bay, the biggest fjord in the Russian sector of the West Barents
Sea. Results of our study show that the southern segment of the
Kola Bay and open shore localities represents two the most
different marine environments. Top of the Bay is a typical estuary
while oceanic conditions predominate in open shore localities.
Central and northern segments of the Bay can be described as
transitory area. Populations of M. balthica are in fact the most
different between the top of the Bay and open coast in respect of
shell shape and color, hinge plate abnormalities, and longevity. At
the same time growth rate is similarly high in two regions, and is
depressed in the transitory area. Latitudinal clines in growth rate,
longevity, size and shell shape of M. balthica were early revealed
in Europe. The result of our investigation shows that variation of all
listed parameters in the Kola Bay is comparable to that in the
whole Europe.
S17 - Phenotypical plasticity and behavior
- 57 -
A theoretical study of alternative female mating strategies
Josefa Bleu, Carmen Bessa-Gomes and David Laloi
Laboratoire Écologie & Évolution (UMR 7625), Université Pierre et
Marie Curie, 7 quai St Bernard, 75 252 Paris Cedex 05, France
Alternative mating strategies are increasingly recognized as being
common in many species. Although alternative female mating
strategies have been less studied than male ones, they may also
be frequent. For example, both monandrous and polyandrous
females of Lacerta vivipara are observed simultaneously. The aim
of this study is to unravel the behavioural mechanisms that can
lead to the coexistence of singly and multiply-mated females in the
same population. We focused on the role of female mate choice
(either by trade-up or by selection given a threshold of mating
acceptance). We explored the role of external factors (density,
sex-ratio and cost of multiple mating). This analysis was conducted
with an evolutionary individual based model. Trade-up alone
allows the coexistence of monandrous and polyandrous females at
the beginning of a reproductive season, but if the season is long
enough, all females become polyandrous. When adding a
threshold to first mate acceptance, the evolutionary simulations
show that populations converge towards coexisting strategies with
a high percentage of monandrous females, while the acceptance
threshold evolves towards similar values among females. The
selected threshold is very sensitive to the demographic factors
whereas the monandrous / polyandrous females' ratio is relatively
stable. An increase of the cost of multiple mating selects for higher
threshold and consequently for more monandrous females despite
the risk of remaining unmated at the end of the season.
Sex-specific flexibility of parental care allows for the sexual
conflict to be resolved in King penguins, Aptenodytes
patagonicus
Hélène Corbel, Sylvie Geiger and René Groscolas
Institut Pluridisciplinaire Hubert Curien, UMR 7178 CNRS,
Département Ecologie, Physiologie et Ethologie, 23, rue Becquerel,
67087 Strasbourg Cedex 2, France
In biparental species, sex differences in reproductive costs and
mate availability entail a conflict over parental investment between
sexual partners. In King penguins, breeding cycles last more than
one year and are just separated by moult, resulting in high
availability of mates for a extended period. On the other hand,
breeding success depends on the hatching date so that
reproduction is highly time-constrained. Because of size
dimorphism and male-biased sex-ratio, sexual conflict would be
resolved through female-initiated divorce resulting in 50% of brood
being deserted by mother during rearing. Aiming at determining
the mechanisms underlying the resolution of sexual conflict, we
investigated sex-specific correlates of the transition from
reproduction to moult. We focused on prolactin (Prl) and T4 levels,
involved in care and the initiation of moult, respectively, together
with offspring signals. In females, care was inflexible and required
elevated Prl to be maintained. The termination of care was
characterized by a concerted decrease of Prl and body condition
and by antagonism between Prl and T4, possibly to prevent from
the initiation of energy-demanding moult while feeding the chick. In
males, the intensity of care was linked to Prl and chick solicitation.
Accordingly, males partially compensated for the desertion of
females. Both body condition and T4 tended to increase at the end
of rearing, indicating that males were able to initiate moult and
associated energy storage while feeding the chick. Therefore,
flexibility of paternal care together with overlapping of male
reproduction and moult allow for energy-restrained females to
desert.