Data from: Skyglow and especially direct streetlight pollution alter moth communities

Light pollution caused by artificial light at night (ALAN) affects
biodiversity worldwide and is still increasing. Species vary in their
response to ALAN, but the impact on communities remains poorly understood.
Effects of indirect light pollution by skyglow and direct streetlight
pollution on communities have usually been addressed separately, and in
most studies so far, urbanisation levels are a confounding factor for ALAN
effects per se. Here, we sampled garden moth communities according to a
study design that integrated two levels of direct streetlight pollution
and two regional skyglow levels to test for additive effects of both types
of ALAN. We also tested whether ALAN conditions related to community
changes in species’ morphological, behavioural and life-history traits.
Both skyglow and streetlights negatively affected moth abundance. Species
richness and diversity decreased under direct streetlight, independent of
skyglow levels. Both types of ALAN affected moth community composition,
and we identified several relationships with species traits in the local
moth communities. Skyglow filtered for hibernating stage and larval
habitation, while streetlight pollution filtered for voltinism, larval
food specificity, habitat openness, and hibernating stage. Our study
provides evidence that both skyglow and, more strongly, streetlight
pollution affect moth communities. A significant decline in moth abundance
will have consequences for ecosystem functioning through reduced food
availability for predators and diminished pollinator services. At the
community level, ALAN operates as a filter for species and species traits,
and based on our results, we argue that future studies should consider
both skyglow and direct light pollution.