Effects of street lighting technologies on the success and quality of pollination in a nocturnally pollinated plant

Artificial light at night (ALAN) is an increasingly important driver of global change. Lighting directly affects plants, but few studies have investigated indirect effects mediated by interacting organisms. Nocturnal Lepidoptera are globally important pollinators, and pollen transport by moths is disrupted by lighting. Many street lighting systems are being replaced with novel, energy‐efficient lighting, with unknown ecological consequences. Using the wildflower Silene latifolia, we compared pollination success and quality at experimentally lit and unlit plots, testing two major changes to street lighting technology: in lamp type, from high‐pressure sodium lamps to light‐emitting diodes, and in lighting regime, from full‐night (FN) to part‐night (PN) lighting. We predicted that lighting would reduce pollination. S. latifolia was pollinated both diurnally and nocturnally. Contrary to our predictions, flowers under FN lighting had higher pollination success than flowers under either PN lighting or unlit controls, which did not significantly differ from each other. Lamp type, lighting regime, and distance from the light all significantly affected aspects of pollination quality. These results confirm that street lighting could affect plant reproduction through indirect effects mediated by nocturnal insects, and further highlight the possibility for novel lighting technologies to mitigate the effects of ALAN on ecosystems. Artificial light at night (ALAN) represents one of the fastest growing anthropogenic environmental changes globally, with background sky brightness increasing by 6%/yr (H？lker et al. 2010). Although often associated with urbanization, artificial light also affects natural and semi‐natural ecosystems, with temperate ecosystems experiencing some of the fastest increases in exposure (Bennie et al. 2015). The nature of artificial lighting is also changing rapidly. An increasing drive for energy efficiency, cost reduction, and improved visibility has led to the widespread implementation of novel lighting technologies for street lighting. Most notably, part‐night (PN) lighting regimes are being introduced; whereby, lights may be switched off or dimmed at certain times of night (Stone et al. 2015). Also, the incumbent lamp types, especially high‐pressure sodium (HPS) lights, are being replaced by arrays of light‐emitting diodes (LEDs; Gaston et al. 2015). The uptake of LED lighting can alter assemblages of nocturnal invertebrates (Davies et al. 2017) and is recognized as a key emerging threat to biodiversity in urban ecosystems due to the greater