Resiliency of the Butterfly Fauna (Papilionoidea and Hesperioidea) at Roxborough State Park, Colorado: Long-Term and Short-Term Alterations in Phenology and Species Presence

Abstract

The butterfly assemblage at Roxborough State Park, Douglas County, Colorado was examined for long-term and short-term changes over 41 years. Seven surveys occurred between 1979–1995 (=historic) with more recent surveys in 2018 and 2019. We compared flight phenology and species assemblages between these periods. Increased monthly species richness in 2018-2019 may have been related to decreased grazing and/or climate change. Additional species were noted in 2018 and 2019, however, some species from 1979 to 1995 went undetected. In most cases, species detected on a very common (VC) basis (calculated from interquartile ranges) between 1979 and 1995 were still VC in 2018–2019. Long-term temperature data (1979-2019) indicated a significant increase over time in winter temperatures. VC species mostly had earlier dates of first flight (DFF) in 2018 compared to historic. However, 2019 DFF's were later. Temperatures differed significantly between 2018 and 2019, with lower winter and spring temperatures in 2019. Eight species were newly detected in 2018-2019. Three of these: Erynnis horatius, Speyeria coronis, and Polites themistocles, were found in both years suggesting they are persistent members of the Roxborough assemblage. Including historical surveys, the Roxborough species list stands at 102. Perhaps surprisingly during times that suggest a decline of insects, including butterflies, Roxborough State Park has shown a degree of resiliency. We will suggest reasons for this apparent persistence.