Artificial light at night and temperature as combined stressors on the development, life-history, and mating behaviour of the Pacific field cricket, Teleogryllus oceanicus

Abstract

Unprecedented rates of urbanisation cause detrimental impacts on the natural environment. Two of the most prominent and ubiquitous urban stressors are artificial light at night (ALAN) and the urban heat island (UHI) effect. Individually, these two stressors have a wide array of effects on physiological, behavioural, and life-history traits of organisms. However, stressors rarely work in isolation, and the potential interactions of ALAN and elevated temperatures on organismal life-history traits, particularly with respect to sexual signalling and reproduction, are not well understood. Here, in a fully factorial design, we manipulated intensities of ALAN exposure (simulating urban light pollution) and temperatures (simulating UHI effects) during development to explore the consequences for juvenile development, survival, sexual signalling, and mating behaviour of the Pacific field cricket, Teleogryllus oceanicus. Our data revealed significant effects of temperature on key life-history traits. Crickets reared under elevated temperatures had higher mortality; reduced adult longevity, altered sexual signalling and male attractiveness. In isolation, ALAN had very limited impacts; it reduced male juvenile development time. Similarly, both stressors acting in concert also had little impact; ALAN reduced female developmental duration when reared at control temperatures, but not elevated temperatures. These data suggest very limited effects of combined stressors in this species, while elevated temperatures, consistent with urban heat island effects, had equivocal effects on life-history traits, reducing survival, but potentially increasing male fitness. Our data highlight the complexity of urban stressors on wildlife behaviour and fitness. Understanding these processes is essential as both ALAN and temperature are predicted to intensify.