Food availability is critical for behavioural immunity under temperature
variability
Abstract
Recent research highlights nature-based solutions to support
biodiversity against climate change, but direct nutritional
interventions need more assessment. We developed an insect model using
fruit flies (Drosophila melanogaster) and the fungus
Metarhizium robertsii and Beauveria bassiana to test if
nutrient supplementation enhances behavioural responses to temperature
change and infection. We examined yeast supplementation and behavioural
thermoregulation in infected insects. Here we show that infected flies
seek cooler temperatures to limit infection costs, effective only with
specific nutrients available post-infection. Without yeast, cooler
temperatures increase survival but decrease reproduction. Yeast
supplementation in cooler environments enhances both lifespan and
fecundity. Mechanistic studies show that fungal virulence decreases with
yeast or tryptophan consumption, especially before infection
intensifies. Tryptophan access is as effective as cold-seeking in
reducing microbe loads. These findings suggest nutrition availability
influences the effectiveness of behavioural thermoregulation in infected
insects, establishing a model for nutrition-based solutions to
human-induced climate change.