Effects of temporal variation on ambient light in Northwest Arkansas

An animal’s life success is determined solely by its fitness, which makes choosing a mate one of its most important life decisions. Natural selection plays a big part in an animal’s phenotype, but so does sexual selection. Even though females are usually thought to be the choosier sex, in many species or seasons males are also choosy. Male mate preference is an understudied topic compared to female mate preference and therefore, even less is known about the outcomes of a male’s prior mating experience’s influence on future mating experiences. Therefore, I dove deeper into this topic with the highly studied species of butterfly, Bicyclus anynana. Bicyclus anynana males have shown a predisposed preference for females with no UV-reflective spots as opposed to two UV-reflective spots on their hindwings. Given this preference, I designed a full factorial experiment to test how males allocate spermatophore to the preferred (0 spot) and unpreferred (2 spot) female phenotypes in a second mating. Male B. anynana have a cryptic preference, meaning they give a more attractive female a higher quality spermatophore, which she uses to lay more eggs. Therefore, male preference was to be assessed by the number of eggs laid by the second mated female. However, COVID-19 interrupted these plans. Due to the restrictions and shutdowns, I discontinued this project and switched to analyzing the variation in ambient light observed when butterflies make mate choice decisions in field conditions. Light measurements were collected at three sites in Northwest Arkansas over three years (2018-2020), from May to November in the morning, noon, and evening. These data were tested to assess whether time of day, site, season, and year had an effect on the total amount of light available, wavelength of peak intensity, total amount of UV light available, UV peak intensity, and wavelength of UV peak intensity. I found an effect of time of day on amount of light, with noon light environments receiving the greatest amount light and morning light environments receiving greater amounts of light than evening light environments. I also found an effect of season, as there was a decrease in amount and variation of light as the year went on. Lastly, I found an interactive effect of time of day and month, as noon light environments decreased in brightness and morning light environments increased in brightness as the year progressed. These findings suggest daily and seasonal changes in light could serve as drivers of animal behavior change.