Fruit flies diversify their offspring in response to parasite infection

The evolution of sexual reproduction is often explained by Red Queen dynamics: Organisms must continually evolve to maintain fitness relative to interacting organisms, such as parasites. Recombination accompanies sexual reproduction and helps diversify an organism’s offspring, so that parasites cannot exploit static host genotypes. Here we show that Drosophila melanogaster plastically increases the production of recombinant offspring after infection. The response is consistent across genetic backgrounds, developmental stages, and parasite types but is not induced after sterile wounding. Furthermore, the response appears to be driven by transmission distortion rather than increased recombination. Our study extends the Red Queen model to include the increased production of recombinant offspring and uncovers a remarkable ability of hosts to actively distort their recombination fraction in rapid response to environmental cues.

有性生殖的演化通常可通过红皇后动力学（Red Queen dynamics）解释：生物体必须持续演化，以相对于寄生虫等互作生物维持自身的适合度。重组伴随有性生殖发生，可帮助生物体的后代实现基因型多样化，从而使寄生虫无法利用固定的宿主基因型。本研究发现，黑腹果蝇（Drosophila melanogaster）在被感染后，会通过表型可塑性提升重组型后代的产生比例。该响应在不同遗传背景、发育阶段以及寄生虫类型下均保持一致，但在仅施加无菌创伤时不会被诱导产生。此外，该响应似乎由传递扭曲（transmission distortion）驱动，而非重组率提升本身。本研究将红皇后动力学模型拓展至包含重组型后代产生比例提升的情形，并揭示了宿主能够主动调整自身重组率以快速响应环境信号的非凡能力。