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Why species evolved to recognise their kin

EU researchers have helped to solve an evolutionary puzzle by revealing why recognising and associating with relatives helps social spiders to feed better.
Why species evolved to recognise their kin
Species that live at least part of their lives in mixed social groups have two reasons to recognise kin in their group. One is to avoid inbreeding, and the other is to cooperate preferentially with related individuals.

The EU-funded PROKIN (Proteomic explanations for the adaptive significance of kin recognition in subsocial spiders) initiative used social spiders as a model to understand how kin recognition evolved.

Studies have shown that spiders in groups containing only siblings grow faster and bigger than those in mixed-kin groups. To see why cooperating with relatives appears to increase their fitness and survival, PROKIN studied a mixed-kin species called Stegodyphus lineatus.

Researchers suspected that it may have something to do with how the spiders feed together. Several or all spiders in a group release digestive fluids onto the body of captured prey to dissolve its tissues before consuming it together. It is possible that digestion of the prey is less efficient when the spiders are not related.

The researchers found nothing, however, in the digestive fluids of related and unrelated spiders that could explain differences in digestion efficiency. They therefore decided to see whether spiders changed their behaviour depending on whether they were feeding with relatives or non-relatives.

To do this, they carried out 200 feeding trials on kin-only and mixed-kin groups of another spider species, Stegodyphus africanus. The results confirmed that mixed-kin groups feed less efficiently, and that this is due to competition between unrelated spiders in the group.

Intriguingly, unrelated spiders cooperated until they were given prey. Once a tasty meal was involved, individuals in mixed groups tried to monopolise the prey and chased off co-foragers.

Researchers concluded that foreign individuals are tolerated in a group as they help to forage for food and ward off predators. Associating with kin, however, is advantageous as it frees up more time to feed by reducing competition between individuals. This would explain why the ability to recognise kin evolved in these species.

Related information

Keywords

Social spiders, PROKIN, kin recognition, mixed-kin groups, digestion efficiency
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