Symbioses shape feeding niches and diversification across insects

Abstract

For over 300 million years, insects have relied on symbiotic microbes for nutrition and defence. However, it is unclear whether specific ecological conditions have repeatedly favoured the evolution of symbioses, and how this has influenced insect diversification. Here, using data on 1,850 microbe–insect symbioses across 402 insect families, we found that symbionts have allowed insects to specialize on a range of nutrient-imbalanced diets, including phloem, blood and wood. Across diets, the only limiting nutrient consistently associated with the evolution of obligate symbiosis was B vitamins. The shift to new diets, facilitated by symbionts, had mixed consequences for insect diversification. In some cases, such as herbivory, it resulted in spectacular species proliferation. In other niches, such as strict blood feeding, diversification has been severely constrained. Symbioses therefore appear to solve widespread nutrient deficiencies for insects, but the consequences for insect diversification depend on the feeding niche that is invaded.

Paleocene origin of a streamlined digestive symbiosis in leaf beetles

“…Symbioses are key drivers of global biodiversity 63,64 . By facilitating access to new environments, or by allowing organisms to integrate novel metabolic features, mutualistic partnerships can promote diversification by increasing speciation rates, and/or by decreasing the rate of extinction 63,64 .…”

“…Symbioses are key drivers of global biodiversity 63,64 . By facilitating access to new environments, or by allowing organisms to integrate novel metabolic features, mutualistic partnerships can promote diversification by increasing speciation rates, and/or by decreasing the rate of extinction 63,64 . The consequences of beneficial partnerships on species richness are most evident when net diversification rates are compared between symbiotic and nonsymbiotic members of a clade.…”

Complex third-party effects in theDictyostelium-Paraburkholderiasymbiosis: prey bacteria that are eaten, carried, or left behind

“…We speculate that carrying more prey in prey-poor contexts may represent cooperation between hosts and symbionts that allows the symbiosis to persist over repeated harsh environments. Such harsh conditions are potentially an important force shaping cooperation in this (Scott et al ., 2022, 2023b) and other symbioses (Henry et al ., 2021; Veresoglou et al ., 2021; Cornwallis et al ., 2023). These studies in symbiotic systems complement research on the role of harsh environments in the evolution of cooperation that has been focused on interactions between members of the same species (Kennedy et al ., 2018), most commonly in cooperatively breeding birds (Cornwallis et al ., 2017; Griesser et al ., 2017; Capilla-Lasheras et al ., 2021).…”

Microbial Metamorphosis: Symbiotic bacteria and fungi proliferate during diapause and may enhance overwintering survival in a solitary bee

“…The success of a wide range of insect species has hinged on partnerships with microbes (1, 2). The unique metabolic abilities of bacteria and fungi can facilitate novel resource use for insect hosts use via synthesis of limiting nutrients (3), evasion or detoxification of diet defenses (4) or in some cases cultivated as food themselves (5).…”