Abstract
BackgroundSocial insects (ants, bees, wasps and termites) are considered as prime examples of altruism in which individuals (workers) forego their own reproduction to help other individuals reproduce. Such a behaviour is favoured by natural selection because the workers rear close kin and in doing so enhance their inclusive fitness.ResultsHere I show, however, that this does not generally apply to termite workers which are scarcely investigated. In the basal drywood termite Cryptotermes secundus the 'workers', which form the large majority of a colony, did not stay to raise relatives. There is no brood caring behaviour and they do not engage in costly help. They are large immature offspring that develop into either winged (dispersing) or unwinged (replacement) reproductives and the probability that they did so was unaffected by the number of brood in the nest as a brood addition experiment showed.ConclusionThus, in contrast to general perception where termite workers are considered equivalent to workers in Hymenoptera, the 'large immatures' of C. secundus did not behave as workers that help in raising younger siblings. This apparently is not necessary as the colony lives inside its food. These results, which are likely to be typical for wood-dwelling termites, open the possibility that large complex group living can evolve without altruistic helping and that costly altruistic helping by workers in termites evolved only as a second step.
Highlights
Social insects are considered as prime examples of altruism in which individuals forego their own reproduction to help other individuals reproduce
The results showed that contrary to current perceptions, these supposed termite workers neither seem to stay in the colony to gain indirect benefits by helping to raise young offspring nor did they help in raising young at all
The effect size f was 0.20 and the partial eta2 showed that trial accounted for only 4 % of the total variability in number of 'large immatures' leaving the colony, while 62 % of the variability was explained by colony size
Summary
Social insects (ants, bees, wasps and termites) are considered as prime examples of altruism in which individuals (workers) forego their own reproduction to help other individuals reproduce Such a behaviour is favoured by natural selection because the workers rear close kin and in doing so enhance their inclusive fitness. Worker behaviour is generally associated with costs in direct reproduction [1,2] Even in species such as paper wasps, in which workers and queens are not morphologically different, workers have lower direct reproduction because they probably cannot do both carry out the risky tasks of foraging and laying eggs These conclusions are mainly based on social Hymenoptera (ants, some bees, and wasps), while few studies exist on the oldest social insects, the termites, that independently evolved sociality [7,8]
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