Thursday, December 9, 2010

Paper: Heritable Social Attributes

A recent paper by Lea et al. from Dan Blumstein's lab in UCLA states that while many morphological and behavioral traits of animals were shown to be heritable, the role of genetics in social interactions is not yet understood. The researchers constructed positive and negative networks based on different types of interactions between yellow-bellied marmots (Marmota flaviventris). The social traits of each individual were classified as agonistic or affiliative; direct (i.e., measure based only on interactions including the individual) or indirect; and initiated or received.

Surprisingly, agonistic in-degree and attractiveness, and affiliative in-degree were somewhat heritable, but not initiated properties. Measures based on direct interactions were more heritable than measures based on indirect ones.

The authors suggest that the lack of heritability in initiated agonistic traits may be due to the fact that these traits are already fixed in the population, i.e. that sociality caused the need to be aggressive in order to survive in a competitive social unit.

It was also found that marmots attacking more individuals lived longer. Individuals receiving more agonistic interactions had lower fitness in terms of reproductive success over lifetime. As receiving agonistic interactions is heritable, it shows that there are genes that lead to low social rank. Interestingly, marmots that are more central in the agonistic network have higher fitness and longevity. The authors state that "It is possible that a central and integrated position in the social group (which presumably results in more affiliative and agonistic partners and interactions) produces more benefits than the costs associated with the aggressive interactions themselves".

Personally, I believe that no one "wants" to receive agonistic interactions, and that the shown benefits of it in this paper actually point at the benefits of sociality, as negative and positive interactions were found to be highly correlated here. The results of this study surely call for further examination.

To summarize, the methodic highlights are:
1. First comparison of genetic vs. social attributes of animals.
2. The analysis of affiliative vs. agonistic networks.

Again, the importance of long-term studies on individually-identified animals proves its advantages.

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