AimUnderstanding the evolution of altruism is a fundamental question in biology.
Typically, a single group of altruists can be readily invaded by cheaters,
making the evolution and maintenance of altruism extremely difficult.
However, many social organisms form multiple dynamic groups with a high degree of merging
and splitting. In this talk, we ask the question, can altruism evolve and be
sustained in such grouping organisms?
MethodsWe built an individual based model capable of displaying a wide range of
movement types including solitary movement, swarming groups,
large polarized groups, and groups with merge-split dynamics.
We assigned two kinds of behaviours to each individual, namely local flocking
interactions and cooperation-defection behaviour, and let both of them evolve.
We also derived analytically, the conditions required for altruism to be
maintained in such a population.
ResultsFor low costs of cooperation, we find that the frequency of altruists is
substantially larger in the presence of local flocking interactions than in
the case of solitary movement. As cost increases the frequency of
altruists decreases. Analytically, we find that altruism can evolve only
when the group sizes satisfy a certain criteria.
ConservationOur study shows that even in the absence of kin-selection or limited dispersal,altruism can not only co-evolve with collective movement, but is also resistant to invasion by cheaters. Since group size distributions necessary for evolution of altruism may occur only in some highly specific niches, it is crucial to understand and conservethem.