Wednesday, 6 April 2016

Predators drive social complexity

Date: March 29, 2016
Source: University of Bern

Variation in social organization and behavior of highly social animals like cichlids is primarily explained by predation risk and related ecological factors. This stresses the significance of predation for social evolution.

Sociality is a ubiquitous feature of life, but the reasons why animals cluster together can vary. In nature, there is great diversity in social organization and in the complexity of interactions among group members. It is widely accepted that high predation risk may select for group living, but predation is not regarded as an important driver of social complexity.
This view neglects the important effect of predation on dispersal and offspring survival, which may require cooperation among group members. The significance of predation for the evolution of social complexity can be well illustrated by behavioural and morphological adaptations of highly social animals showing division of labour, such as ants and cooperatively breeding fishes like cichlids.

Long-time study of eight fish populations
In several species of cichlids in Lake Tanganyika, for example, groups consist of many individuals differing in size, age, dominance rank and relatedness. Group members typically cooperate in brood care, territory maintenance and defence, and they decide about their cooperative effort in dependence of relatedness to beneficiaries and the outcome of negotiations with other group members. Importantly, the form and function of social organization varies considerably among different populations of the same species, which enables to study the significance of ecological factors for social organization.




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