Dim light pollution prevents diapause induction in urban and rural moths

Abstract

Light pollution is increasingly affecting biodiversity and may also disrupt seasonal adaptations. Even dim artificial light, such as skyglow—which can spread far beyond urban areas—can interfere with using photoperiod as a seasonal cue. Here, we test how light pollution impacts diapause induction and whether urban evolution counteracts it, by using common‐garden experiments with a common, widespread geometrid moth (Chiasmia clathrata). We raised offspring from urban and rural populations from North‐ and Mid‐European countries in treatments with and without dim light at night. The dim light treatment strongly increased direct development overall—with no evidence for urban adaptation to it—but distinctly more so in Mid‐ than in North‐European populations. Because diapause induction is critical for surviving winter, these results indicate that dim but widespread light pollution may have detrimental effects on insect populations, especially so at mid‐latitudes, and may hence explain part of the ongoing, large‐scale insect declines globally. Synthesis and applications. Latitudinal variation in sensitivity to light pollution means that its contribution to insect declines—and its conservation importance—should likewise vary among regions. In mid‐latitude regions, where populations seem more sensitive to light pollution, mitigating light pollution should be a high priority for insect conservation. Reducing skyglow from cities should benefit both urban populations—which were just as susceptible as rural populations in our study—and rural populations—because skyglow extends far beyond the geographic boundaries of cities.

Continent‐wide parallel urban evolution of increased heat tolerance in a common moth

“…The data that support the findings of this study are openly available in the Dryad Digital Repository at https://doi.org/10.5061/dryad.6q573n638, Merckx et al., 2024.…”

“…These additional adults were raised under several different light conditions: 20L:4D (166 individuals), 20.5L:3.5D (113 individuals), and 16L:8D (128 individuals; the latter two photoperiods with and without simulated weak light pollution [Merckx et al, 2023]). The temperature was always 21°C (a standard laboratory rearing temperature: see, for example, Merckx et al, 2021Merckx et al, , 2023. Around 5 days after pupation, pupae were excavated from the peat and sexed based on sex-specific genital scars.…”

“…We also used directly developing adults from other experiments to maximize sample size. These additional adults were raised under several different light conditions: 20L:4D (166 individuals), 20.5L:3.5D (113 individuals), and 16L:8D (128 individuals; the latter two photoperiods with and without simulated weak light pollution [Merckx et al, 2023]). The temperature was always 21°C (a standard laboratory rearing temperature: see, for example, Merckx et al, 2021Merckx et al, , 2023.…”

Substantial urbanization‐driven declines of larval and adult moths in a subtropical environment

“…Light pollution, which is strongly associated with urbanization, is one mechanism that may explain the observed declines of moth richness and diversity across urbanization gradients (Straka et al., 2021). Light pollution can potentially lead to population declines and local extirpation by disrupting reproduction (Boyes et al., 2020), larval development (Boyes et al., 2021), and preventing pupal diapause (Merckx et al., 2023). Recent work also indicates that streetlamps with UV emission negatively affect moth species richness on a landscape scale (Straka et al., 2021).…”

Evolutionary change in flight-to-light response in urban moths comes with changes in wing morphology

“…Firstly, it alters day-night cycles, disrupting life cycle regulation (e.g. disrupted diapause induction) [10][11][12] and changing plant-pollinator interactions [13][14][15]. Secondly, many insects experience negative consequences from their innate positive or negative phototaxis, causing them to be attracted [16] or repelled [17] by ALAN.…”