The evolution of adult light emission color in North American fireflies

Abstract

Firefly species (Lampyridae) vary in the color of their adult bioluminescence. It has been hypothesized that color is selected to enhance detection by conspecifics. One mechanism to improve visibility of the signal is to increase contrast against ambient light. High contrast implies that fireflies active early in the evening will emit yellower luminescence to contrast against ambient light reflected from green vegetation, especially in habitats with high vegetation cover. Another mechanism to improve visibility is to use reflection off the background to enhance the light signal. Reflectance predicts that sedentary females will produce greener light to maximize reflection off the green vegetation on which they signal. To test these predictions, we recorded over 7500 light emission spectra and determined peak emission wavelength for 675 males, representing 24 species, at 57 field sites across the Eastern United States. We found support for both hypotheses: males active early in more vegetated habitats produced yellower flashes in comparison to later-active males with greener flashes. Further, in 2 of the 8 species with female data, female light emissions were significantly greener as compared to males.

The impact of artificial light at night on nocturnal insects: A review and synthesis

“…The color of firefly bioluminescence varies as follows: Among crepuscular species, flashes are generally yellower compared to the greener flashes emitted by nocturnal fireflies (Seliger, Lall, Lloyd, & Biggley, 1982); this is thought to maximize signal contrast against the green foliage dominating the background at dusk. However, signal color also shows intraspecific variation, perhaps related to differences in habitat type (Hall, Sander, Pallansch, & Stanger-Hall, 2016).…”

Molecular variation across populations of a widespread North American firefly, Photinus pyralis, reveals that coding changes do not underlie flash color variation or associated visual sensitivity

“…These populations differed in their mean peak emission color (558 to 568 nm) and habitat type (6 open field populations and 6 closed forest populations) ( [16]; Fig. 1; Additional File 1, Note 1).…”

“…[4–16]. Generally, in nocturnal species, flying males direct species-specific flash patterns to sedentary females in the vegetation [17].…”

Diversity in warning coloration is easily recognized by avian predators

“…Thus, colour signals should be interpreted in line with the specific contexts they are used in (Endler & Day, 2006). For example, male fireflies signalling early in the evening produce yellower bioluminescence that contrasts with high grasses, whereas later in the evening they produce greener lights that contrast more with the environmental light (Hall et al, 2016). In addition, Endler and Day (2006) found that bowerbirds tend to use ornaments in their bowers that have more contrasting colours than those of the surrounding area, giving them an advantage in female mate choice.…”

“…This is because visibility will be affected by characteristics such as the contrast of the signal against the background, the environmental light conditions, and the place and substrate where the signal is being displayed (e.g. Arenas et al, 2014;Hall et al, 2016). Furthermore, physiological properties of the predator's visual system can influence how a signal is perceived and interpreted (Endler, 1978;Guilford & Dawkins, 1991;Endler & Mielke, 2005;Stevens, 2011Stevens, , 2013.…”