In some populations, we allowed parents to help their offspring, but in other populations we removed the parents.
- Benjamin Jarrett
Cooperative behaviour is a key part of animal family life: parents help offspring by supplying them with food, and siblings can also work together to acquire food. The Cambridge study, published in Nature Ecology and Evolution, looked at the burying beetle – unusual in the insect world as the parents feed their offspring.
Larvae in small broods are well supplied with food by their parents and grow large. In the parents’ absence, larvae can also help each other to forage for food. However, in the absence of their parents, small broods of larvae are less effective at helping each other and can never grow as big.
“For our study, we played the role of natural selection. In some experimental beetle populations, we chose only the largest beetles to breed at each generation and in some we chose only the smallest beetles,” said Benjamin Jarrett from the Department of Zoology at the University of Cambridge, who led the study.
“Crucially, we also changed the social conditions within beetle families. In some populations, we allowed parents to help their offspring, but in other populations we removed the parents, and larvae had to help each other. We found that the social conditions made a big difference to how quickly beetle body size evolves over generations.”
Beetles only evolved a larger body size when parents were present to help rear their young. In stark contrast, smaller body size only evolved when beetle parents were removed, and there were too few larvae to help each other.
The experiment helps explain how different species of burying beetle might have evolved their different body sizes. In general, larger species of beetle have more diligent parents than smaller species.
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Reproduced courtesy of the University of Cambridge
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