Anthropogenic light impacts life-history traits and induces a trade-off in female field crickets

Abstract

Human-induced rapid environmental changes introduce animals to novel selection pressures that may impact how individuals allocate resources into life-history traits. One pervasive anthropogenic stressor, artificial light at night (ALAN), extends into remote areas and masks the day:night cycles to which animals are attuned. Here we ask how animals use this environmental input to dictate their investment in survival and reproductive traits and whether they must trade off investment in these traits in female Gryllus veletis field crickets. Using the second generation of field-collected individuals from a location absent from ALAN, we reared females from the antepenultimate instar through adulthood in either a control environment or one with ALAN. We then measured their investment in survival through two aspects of immunity, encapsulation and lysozyme activity, and their reproductive investment as the number of eggs within a female. We found that ALAN reduced one aspect of immunity, lysozyme activity, and reproductive investment. Further, there was a negative trade-off in investment in encapsulation and reproduction, an investment cost that was not present in females reared without ALAN. Our results suggest a two-fold cost of ALAN on females: one on investment in individual traits and another on a trade-off between them. These maladaptive responses to ALAN could substantially impact natural populations in the short term, and whether populations could respond in the long term remains an open question.