Cold Nights, City Lights: Artificial Light at Night Reduces Photoperiodically Induced Diapause in Urban and Rural Populations of<i>Aedes albopictus</i>(Diptera: Culicidae)

Urbanization is gaining force globally, which challenges biodiversity, and it has recently also emerged as an agent of evolutionary change. Seasonal phenology and life cycle regulation are essential processes that urbanization is likely to alter through both the urban heat island effect (UHI) and artificial light at night (ALAN). However, how UHI and ALAN affect the evolution of seasonal adaptations has received little attention. Here, we test for the urban evolution of seasonal life-history plasticity, specifically changes in the photoperiodic induction of diapause in two lepidopterans, Pieris napi (Pieridae) and Chiasmia clathrata (Geometridae). We used long-term data from standardized monitoring and citizen science observation schemes to compare yearly phenological flight curves in six cities in Finland and Sweden to those of adjacent rural populations. This analysis showed for both species that flight seasons are longer and end later in most cities, suggesting a difference in the timing of diapause induction. Then, we used common garden experiments to test whether the evolution of the photoperiodic reaction norm for diapause could explain these phenological changes for a subset of these cities. These experiments demonstrated a genetic shift for both species in urban areas toward a lower daylength threshold for direct development, consistent with predictions based on the UHI but not ALAN. The correspondence of this genetic change to the results of our larger-scale observational analysis of in situ flight phenology indicates that it may be widespread. These findings suggest that seasonal life cycle regulation evolves in urban ectotherms and may contribute to ecoevolutionary dynamics in cities.

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“…rural mosquito demes responded similarly (20). In moths, ALAN can disrupt larval development and pupal diapause (e.g., ref.…”

Section: Significancementioning

confidence: 94%

Urbanization extends flight phenology and leads to local adaptation of seasonal plasticity in Lepidoptera

Merckx

Nielsen

Heliölä

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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“…The fly population at the urban OCU site was exposed to light at 0.1 lux or higher during the night but was still able to enter diapause in the autumn in 2 years of the experimental period. Westby & Medley [ 43 ] also found that in a mosquito , populations in urban sites are still able to enter diapause in the autumn [ 43 ]. This may be related to an ability to minimize the effect of light at night at lower temperatures, as observed in our laboratory experiment.…”

Section: Discussionmentioning

confidence: 99%

“…Additionally, such a strong effect on seasonality has been assumed conceptually [13,66] but has been poorly tested empirically. Furthermore, most of the studies in this context used 'simulated' artificial light at night to investigate its effect on seasonality [26,30,31,43,44,[67][68][69]. Field studies with 'natural' artificial light at night are awaited [70,71].…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, only a few studies have focused on the effect of artificial light at night. Westby & Medley [ 43 ] found that simulated urban artificial light at night (illumination at 9–11 lux) reduces diapause incidence by as much as 40% in a species of mosquito [ 43 ]. However, in this experiment, adult mosquitoes had been moved to the laboratory to stimulate mating, feeding and egg-laying at laboratory rearing temperatures; thus, the negative effect of light illumination may have been underestimated.…”

Section: Introductionmentioning

confidence: 99%

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Urban warming and artificial light alter dormancy in the flesh fly

2021

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Seasonal changes in temperature and day length are distinct between rural and urban areas due to urban warming and the presence of artificial light at night. Many studies have focused on the impacts of these ubiquitous signatures on daily biological events, but empirical studies on their impacts on insect seasonality are limited. In the present study, we used the flesh fly Sarcophaga similis as a model insect to determine the impacts of urbanization on the incidence and timing of diapause (dormancy), not only in the laboratory but also in rural and urban conditions. In the laboratory, diapause entry was affected by night-time light levels as low as 0.01 lux. We placed fly cages on outdoor shelves in urban and rural areas to determine the timing of diapause entry; it was retarded by approximately four weeks in urban areas relative to that in rural areas. Moreover, almost all flies in the site facing an urban residential area failed to enter diapause, even by late autumn. Although an autumnal low temperature in the urban area would mitigate the negative effect of artificial light at night, strong light pollution seriously disrupts the flesh fly seasonal adaptation.

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“…albopictus . In urban field sites, although populations showed differences in diapause induction in early September, later on, all populations reached high levels of diapause, suggesting that the effect of artificial light may be minimized due to vegetation or other factors ( Westby and Medley 2020 ).…”

Section: Human-mediated Environmental Influences On Vectorial Capacity and Behaviormentioning

confidence: 99%

Highlights of Medical Entomology, 2020

Stone

2021

Journal of Medical Entomology

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Medical Entomology as a field is inherently global – thriving on international and interdisciplinary collaborations and affected dramatically by arthropod and pathogen invasions and introductions. This past year also will be remembered as the year in which the SARS-CoV-2 COVID-19 pandemic affected every part of our lives and professional activities and impacted (or changed, sometimes in good ways) our ability to collaborate and detect or respond to invasions. This incredible year is the backdrop for the 2020 Highlights in Medical Entomology. This article highlights the broad scope of approaches and disciplines represented in the 2020 published literature, ranging from sensory and chemical ecology, population genetics, impacts of human-mediated environmental change on vector ecology, life history and the evolution of vector behaviors, to the latest developments in vector surveillance and control.

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Cold Nights, City Lights: Artificial Light at Night Reduces Photoperiodically Induced Diapause in Urban and Rural Populations ofAedes albopictus(Diptera: Culicidae)

Cited by 44 publications

References 57 publications

Urbanization extends flight phenology and leads to local adaptation of seasonal plasticity in Lepidoptera

Urbanization extends flight phenology and leads to local adaptation of seasonal plasticity in Lepidoptera

Urban warming and artificial light alter dormancy in the flesh fly

Highlights of Medical Entomology, 2020

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