Altruism and natural selection in a variable environment

• 成果类型: Article
• 署名作者: dos Santos, Miguel; Downing, Philip A.; Griffin, Ashleigh S.; Cornwallis, Charlie K.; West, Stuart A.
• 署名单位: University of Oxford; Lund University; University of Oulu
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-10210
• DOI: 10.1073/pnas.2402974121
• 发表日期: 2024-09-17
• 关键词: kin selection; inclusive fitness; formal darwinism; EVOLUTION; variances

摘要

Hamilton's rule provides the cornerstone for our understanding of the evolution of all forms of social behavior, from altruism to spite, across all organisms, from viruses to humans. In contrast to the standard prediction from Hamilton's rule, recent studies have suggested that altruistic helping can be favored even if it does not benefit relatives, as long as it decreases the environmentally induced variance of their reproductive success (altruistic bet- hedging). However, previous predictions both rely on an approximation and focus on variance- reducing helping behaviors. We derived a version of Hamilton's rule that fully captures environmental variability. This shows that decreasing (or increasing) the variance in the absolute reproductive success of relatives does not have a consistent effect-it can either favor or disfavor the evolution of helping. We then empirically quantified the effect of helping on the variance in reproductive success across 15 species of cooperatively breeding birds. We found that a) helping did not consistently decrease the variance of reproductive success and often increased it, and b) the mean benefits of helping across environments consistently outweighed other variability components of reproductive success. Altogether, our theoretical and empirical results suggest that the effects of helping on the variability components of reproductive success have not played a consistent or strong role in favoring helping.