Abstract
The timing of events in the life history of temperate insects is most typically primarily cued by one of two drivers: photoperiod or temperature accumulation over the growing season. However, an insect's phenology can also be moderated by other drivers like rainfall or the phenology of its host plants. When multiple drivers of phenology interact, there is greater potential for phenological asynchronies to arise between an organism and those with which it interacts. We examined the phenological patterns of a highly seasonal group of fireflies (Photinus spp., predominantly P. pyralis) over a 12-year period (2004–2015) across 10 plant communities to determine whether interacting drivers could explain the variability observed in the adult flight activity density (i.e. mating season) of this species. We found that temperature accumulation was the primary driver of phenology, with activity peaks usually occurring at a temperature accumulation of approximately 800 degree days (base 10°C); however, our model found this peak varied by nearly 180 degree-day units among years. This variation could be explained by a quadratic relationship with the accumulation of precipitation in the growing season; in years with either high or low precipitation extremes at our study site, flight activity was delayed. More fireflies were captured in general in herbaceous plant communities with minimal soil disturbance (alfalfa and no-till field crop rotations), but only weak interactions occurred between within-season responses to climatic variables and plant community. The interaction we observed between temperature and precipitation accumulation suggests that, although climate warming has the potential to disrupt phenology of many organisms, changes to regional precipitation patterns can magnify these disruptions.
Highlights
Much can be learned about biological systems by observation alone [1], and observational data are often captured incidentally as a result of human activity [2]
We found that temperature accumulation was the primary driver of phenology, with activity peaks usually occurring at a temperature accumulation of approximately 800 degree days; our model found this peak varied by nearly 180 degree-day units among years
Few studies have been conducted on firefly conservation and broader-scale ecology in relation to changing environments and land uses, and little is known about how environmental parameters drive firefly life history
Summary
Much can be learned about biological systems by observation alone [1], and observational data are often captured incidentally as a result of human activity [2]. Research activities can produce systemic observational data of very high quality; for instance, insect trapping systems seldom only capture target taxa. This ‘by-catch’ can provide data that support investigations into entirely uninvestigated phenomena. Species within the family Lampyridae spend much of their time living underground feeding on earthworms, molluscs and other subterranean invertebrates [4]. It has been demonstrated that the life history of at least one species of firefly is temperature-dependent; researchers found that P. pennsylvanica adult emergence could be artificially accelerated by exposing larvae to increased soil temperature [8]. Much of the primary research on fireflies has focused on the bioluminescent properties of the firefly [9,10,11,12,13,14], while research describing basic population and community ecology of this important family is lacking
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