Trait-mediated phenological shifts in moths under climate change: evidence for alternative response strategies

Abstract

Introduction: Climate warming has shifted the timing of many insect life-history events; yet, the links between these shifts, ambient temperature exposure, and species’ traits remain unclear. Aims and methods: We quantified seasonal and trait-mediated changes in moth phenology and temperature exposure by comparing nightly light trap data for 15,451 individuals representing 96 univoltine species collected in central Sweden in 1975 and 2019. Across the community, 35 species advanced their activity periods, while 23 delayed them. Spring species advanced consistently (median = − 5.2 days), while summer species showed heterogeneous responses. Autumn species either delayed activity into cooler intervals or advanced into warmer ones. Phenological advancement was greater in species overwintering as pupae than in those overwintering as eggs or larvae (Δ = 4.7 days) and in adult-feeding species relative to non-feeding species (Δ = 3.9 days). Advancement was also correlated with larger body size and lower intraspecific variation in colour patterns. Shifts in timing were closely mirrored by corresponding changes in median temperature exposure, indicating that phenological responses rather than plastic adjustments in activity temperature underpin most observed thermal shifts. Discussion: The heterogeneous, trait-linked responses observed here counter the notion of uniform phenological advancement across taxa. The overwintering stage, adult feeding, body size, and colour pattern variability appear to mediate the capacity of species to track or avoid warming temperatures through phenological change. Implications for insect conservation: Incorporating life-history traits into phenological assessments can identify species most at risk of climate-driven mismatches, thereby improving prioritisation in conservation planning.