Sex ratio biases in termites provide evidence forkin selection

摘要

Inclusive fitness theory, also known as kin selection theory, is the most general expansion ofDarwin’s natural selection theory. It is supported by female-biased investment by workers inthe social Hymenoptera where relatedness to sisters is higher than to brothers because ofhaplodiploidy. However, a strong test of the theory has proven difficult in diploid social insectsbecause they lack such relatedness asymmetry. Here we show that kin selection can result insex ratio bias in eusocial diploids. Our model predicts that allocation will be biased towardsthe sex that contributes more of its genes to the next generation when sex-asymmetricinbreeding occurs. The prediction matches well with the empirical sex allocation ofReticulitermes termites where the colony king can be replaced by a queen’s son. Our findingsopen broad new avenues to test inclusive fitness theory beyond the well-studied eusocialHymenoptera.