Reproduction of a field cricket under high-intensity artificial light at night and a simulated heat wave

Animals are increasingly exposed to both artificial light at night (ALAN; a.k.a., ecological light pollution) and heat waves. Traditionally, the effects of ALAN and heat waves have been investigated in isolation, and results indicate mixed support for their costs to important decisions made at specific stages of reproduction (i.e., before, during, and after mating). Therefore, we used a factorial design to manipulate temperature and light conditions during adulthood in female variable field crickets (Gryllus lineaticeps) to determine (1) whether ALAN has stage-specific effects on reproductive decisions and (2) if ALAN effects on reproduction interact with a simulated heat wave. We found that ALAN simulating bright urban lighting promoted mating success, and a simulated heat wave resulted in even greater benefits to reproduction, including increased reproductive investment (ovary mass prior to mating), the efficiency by which food was converted into reproductive tissue, and reproductive output (number of eggs laid). Heat wave and ALAN did not modulate the effect of one another because we found no evidence of interactive (e.g., synergistic or antagonistic) effects of temperature and light treatments on any reproductive trait. Our study is the first to examine the combined effects of ALAN and heat waves across reproductive stages, and we found that these two increasingly common environmental factors may generally benefit reproduction in an insect. Significance statement Animals are increasingly exposed to artificial light at night (a.k.a., ecological light pollution) and heat waves, but the combined effects of these two potential stressors are unknown. Therefore, we manipulated temperature and light conditions during adulthood in female variable field crickets (Gryllus lineaticeps) to examine effects across three important reproductive stages-before, during, and after mating. We found that ALAN simulating bright urban lighting promoted mating success, and a simulated heat wave resulted in even greater benefits to reproduction, including increased reproductive investment (ovary mass prior to mating) and reproductive output (number of eggs laid after mating). Our results indicate that these two increasingly common environmental factors may generally benefit reproduction in an insect.

Automated summary

The study found that artificial light at night and heat waves have a positive impact on insect reproduction, promoting mating success and increasing reproductive output.