Kin effects on energy allocation in group-living ground squirrels
Résumé
1. The social environment has potent effects on individual phenotype and fitness in group-living
species.
2. We asked whether the presence of kin might act on energy allocation, a central aspect of
life-history variation.
3. Using a 22-year data set on reproductive and somatic allocations in Columbian ground
squirrels (Urocitellus columbianus), we tested the effects of co-breeding and non-breeding kin
on the fitness and energy allocation balance between reproduction and personal body condition
of individual females.
4. Greater numbers of co-breeding kin had a positive effect on the number of offspring
weaned, through the mechanism of altering energy allocation patterns. On average, females
with higher numbers of co-breeding kin did not increase energy income but biased energy
allocation towards reproduction.
5. Co-breeding female kin ground squirrels maintain close nest burrows, likely providing a
social buffer against territorial invasions from non-kin ground squirrels. Lower aggressiveness,
lower risks of infanticide from female kin and greater protection of territorial boundaries
may allow individual females to derive net fitness benefits via their energy allocation
strategies.
6. We demonstrated the importance of kin effects on a fundamental life-history trade-off.