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Complementary interactions between indirect and direct fitness in a cooperatively breeding bird
Zhibing Li1, Xinwei Da2, Xin Lu1,2
1Institute for Advanced Studies, Wuhan University, Wuhan, China.
Current Zoology
|March 28, 2023
Summary
Altruism in Tibetan ground tits is explained by a balance of direct and indirect fitness benefits. Helping relatives provides indirect benefits, while helping non-relatives offers direct benefits like territory inheritance, ensuring equal inclusive fitness.
Area of Science:
- Evolutionary biology
- Behavioral ecology
Background:
- Altruism's evolutionary persistence is debated, with kin selection explaining aid to relatives.
- Helping non-relatives suggests direct benefits must compensate for costs to altruists.
Purpose of the Study:
- To investigate the complementary interaction between direct and indirect fitness benefits in altruism.
- To test if altruism towards varying relatedness levels in a population is explained by inclusive fitness.
Main Methods:
- Analysis of 12-year data on lifetime reproductive success in Tibetan ground tits (Pseudopodoces humilis).
- Quantification of indirect (kin selection) and direct fitness benefits for helpers based on relatedness to recipients.
Main Results:
- Helpers assisting distantly related individuals received lower indirect benefits but higher direct benefits compared to those helping close relatives.
- Helping efforts were independent of relatedness, but aiding distant relatives increased the likelihood of territory inheritance.
- Inclusive fitness was equalized across helpers assisting recipients of different relatedness levels.
Conclusions:
- A model is proposed explaining the coexistence of altruists and recipients with varying relatedness within a population.
- Direct and indirect fitness benefits interact to maintain altruistic behaviors in Tibetan ground tits.
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