No single rescue recipe: genome complexities modulate insect response to climate change.

Declines in insect populations have gained formidable attention. Given their crucial role in the ecosystem, the causes of declining insect populations must be investigated. However, the insect clade has been associated with low extinction and high diversification rates. It is unlikely that insects underwent mass extinctions in the past. However, the pace of current climate change could make insect populations vulnerable to extinction. We propose genome size (GS) and transposable elements (TEs) to be rough estimates to assess extinction risk. Larger GS and/or proliferating TEs have been associated with adaptation in rapid climate change scenarios. We speculate that unstable, stressful environmental conditions are strongly associated with GS and TE expansion, which could be further correlated with adaptations. Alternately, stressful conditions trigger TE bursts that are not purged in smaller populations. GS and TE loads could be indicators of small effective populations in the wild, likely experiencing bottlenecks or drastic climatic perturbations, which calls for an urgent assessment of extinction risk.