Insect populations, which play a crucial role in food chains and pollination, have seen a significant decline over the past two decades due to climate change. A study by Northwestern University scientists explores how different fly species have adapted to varying climates, providing insights that could help predict future impacts of climate change on insects.
Researchers studied two fly species from contrasting environments: one from the cool, high-altitude forests of Northern California and another from the hot deserts of the Southwest. Both are related to the common laboratory fly, Drosophila melanogaster. The study revealed that forest flies exhibit increased heat avoidance due to heightened sensitivity in their antennae's molecular heat receptors. In contrast, desert flies are drawn to warmth, a behavior linked to differences in brain wiring related to sensory cue processing.
The scientists suggest these adaptations evolved over 40 million years as each species adjusted to its unique thermal environment. These findings were published in Nature on March 5.
Northwestern neurobiologist Marco Gallio highlighted the importance of this research, stating, "Insects are especially threatened by climate change." He noted that insect behavior is a primary interface with their environment and emphasized that insect population declines could have severe ecological consequences.
Gallio's lab focuses on understanding fruit flies' sensory systems. Despite limited data due to insufficient interest in insects, available figures show dramatic declines in insect populations over recent decades. Gallio warned against dismissing these losses as trivial since insects form the base of most terrestrial food chains and pollinate 70% of crops.
Previous work by Gallio's team examined how small insects respond to temperature changes. The current study used genetic tools like CRISPR to explore differences in temperature preference mechanisms among fly species with distinct thermal habitats.
Lead author Matthew Capek explained that variations in heat-detecting molecules result in different activation temperatures. While these differences explain forest flies' cooler preferences, they do not fully account for desert flies' attraction to warmth.
Capek observed that desert flies favor temperatures around 90 degrees Fahrenheit compared to forest flies' preference below 70 degrees. This suggests their antennae perceive higher temperatures as beneficial rather than threatening.
A field trip provided further insight into desert fly behavior. Research associate professor Alessia Para noted that extreme temperature fluctuations necessitate constant vigilance for ideal conditions—a costly but vital adaptation for survival.
Gallio concluded that this comparative research sheds light on brain programming regarding environmental stimuli and offers clues about evolutionary adaptations to temperature changes. He expressed hope that such studies would enhance appreciation and protection of insects amid ongoing climate change challenges.
The paper titled "Evolution of temperature preference behavior in flies of the genus Drosophila" received funding from the National Institutes of Health and the PEW Scholars Program. Gallio is affiliated with Chicago's Simons National Institute for Theory and Mathematics in Biology under the National Science Foundation.