Seasonality of forest insects: why diapause matters.

Diapause is a strategy in insects to mitigate seasonal stress and synchronize lifecycles with favorable times. Forests are 3D, dynamic ecosystems with contrasting microhabitats where numerous insects enter diapause and the duration of diapause affects their phenology. Ecologically important forest insects, like defoliators, bark breeders, or soil/litter-dwelling species have diverse diapause strategies. Anthropogenic change, like climate change and urbanization, has and will have substantial impacts on forest insects. Some species may increase their impact on ecosystems, while that of others may be reduced. Understanding how climate change or urbanization factors, like artificial light at night and the urban-heat-island effect, affect diapause may help develop generalizable rules to predict which species will show population expansion and which are likely to contract. Insects have major impacts on forest ecosystems, from herbivory and soil-nutrient cycling to killing trees at a large scale. Forest insects from temperate, tropical, and subtropical regions have evolved strategies to respond to seasonality; for example, by entering diapause, to mitigate adversity and to synchronize lifecycles with favorable periods. Here, we show that distinct functional groups of forest insects; that is, canopy dwellers, trunk-associated species, and soil/litter-inhabiting insects, express a variety of diapause strategies, but do not show systematic differences in diapause strategy depending on functional group. Due to the overall similarities in diapause strategies, we can better estimate the impacts of anthropogenic change on forest insect populations and, consequently, on key ecosystems. [ABSTRACT FROM AUTHOR]