DNA Maintenance Declines During Sperm Competition in Male Beetles

Researchers from Sweden and Germany reporting in PLOS Biology explore the balance between sperm competition and mutations in the male germline in the Callosobruchus maculatus seed beetle. With sperm competition assays, RNA sequencing-based gene expression profiling, and other experiments on beetles followed over some 50 generations, the team saw signs that DNA damage repair gets dialed down when beetles are exposed to male competitors and sexual selection, while monogamous beetles appeared to father fewer, but higher quality offspring with more resilience in the presence of DNA-damaging radiation — distinct strategies that were accompanied by gene expression shifts affecting at least 18 genes in the male beetle's reproductive tract in response to radiation exposure. "While more work is needed to detail the exact molecular underpinnings of our results, our findings provide rare experimental evidence for a trade-off between male success in sperm competition and germline maintenance," the authors report. "This suggests that sex differences in the relative strengths of sexual and natural selection are causally linked to male mutation bias."