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The ecology and evolution of cooperative breeding in Lake Tanganyika cichlids

English title The ecology and evolution of cooperative breeding in Lake Tanganyika cichlids
Applicant Heg Dik
Number 108473
Funding scheme Project funding
Research institution Ethologische Station Hasli Institut für Ökologie und Evolution Universität Bern
Institution of higher education University of Berne - BE
Main discipline Zoology
Start/End 01.08.2005 - 30.11.2008
Approved amount 264'903.00
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All Disciplines (2)


Keywords (5)

cooperation and conflict; artifical selection; phylogeny; life history; evolution

Lay Summary (English)

Lay summary
Charles Darwin thought cooperative behaviour was challenging his ideas of natural selection shaping organisms, stating: ‘In social species [natural selection] will adapt the structure of each individual for the benefit of the community, if each in consequence profits by the selected change.’ (Charles Darwin 1859, The Origin of Species). Essentially, Darwin proposes that somehow animals might benefit indirectly, or in the future, from acting altruistically for the community or the group. Understanding the causes and consequences of cooperative behaviour in the animal kingdom remains a very active biological research field nowadays.In this project we work with a model system from Lake Tanganyika: cooperatively breeding cichlid fish from the tribe Lamprologini. These cichlids form a species flock of about 80 species, with about 20 species showing cooperative breeding. Cooperative breeding in groups means that a breeding pair lives together with one or more smaller subordinate fish in a territory, so called ‘helpers’, who assist the pair raising offspring. One major research question we address is whether these cichlid groups are composed of parents with adult related helpers (in which case helping may easily be explained by ‘selfish’ indirect genetic benefits) or whether they are composed of unrelated individuals (in which case reproductive partitioning or future benefits may explain helping behaviour). To do so, we sample fish groups of various species in the field using SCUBA diving, and estimate genetic relatedness using microsatellite DNA markers. We also use these markers in field and laboratory experiments to estimate whether and how much helpers participate in reproduction, or whether they are reproductively suppressed by the dominant breeding pair.Another major research question is whether cichlid groups remain stable because helpers adjust their growth rate to avoid conflict with the breeding pair. We show that growth and body size has major consequences for the reproductive and competitive ability of the helpers, and therefore breeders may evict helpers which are too close in size to themselves.The third major research question targets helping behaviour directly. Why do some helpers show a lot of helping behaviour, whereas others are reluctant to help? May this variation be due to variation in life history strategies young cichlid might follow? We tackle these questions from various angles. First, we conduct breeding and artificial selection experiments to estimate the genetic component of cooperative behaviour (we are worldwide the only group conducting such experiments in a vertebrate). Second, we study the development of helping behaviour and whether it is related to any other behaviours (‘behavioural syndrome’) with potential consequences for the major life history decisions young cichlids face: (1) if, when and where to disperse and (2) If, when and where to reproduce. For instance, helpers may try to reproduce at home, if the breeding pair allows them to do so. Others may only start reproduction after they have dispersed. As before, all these major life history decisions may be size (growth) dependent.
Direct link to Lay Summary Last update: 21.02.2013

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