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Symbiont-driven niche expansion shaped the adaptive radiation of insects


 For over 300 million years, insects have relied on symbiotic microbes for nutrition and defence1,2. However, it is unclear whether specific ecological conditions have repeatedly favoured the evolution of symbioses, and how this has influenced insect diversification1,3,4. Using data on 1844 microbe-insect symbioses across 400 insect families, we found that symbionts have allowed insects to radiate into a range of feeding niches deficient in B vitamins, including phloem, blood and wood. In some cases, such as herbivorous insects, the shift to a new niche has resulted in spectacular species proliferation. In other niches, such as strict blood feeding, diversification has been severely constrained. Symbioses therefore appear to solve universal nutrient deficiencies for insects, but the consequences for insect diversification depend on the feeding niche invaded.