An Examination of Reproductive Phenology with Implications for Understanding Climate Change Effects

Abstract

Climate change has impacted ecological systems in a variety of ways, leading to advancement in spring events, shifts in species distributions, and changes in phenology (the timing of life history events) for many plants and animals. Earlier spring temperatures have been correlated with earlier emergence of a number of butterfly species in Europe. It is possible that changes in the spring could also influence the timing of events throughout the season. The Clodius Parnassian (Parnassius clodius) butterfly has one flight per year that averages 3 weeks in length. The males emerge first, followed shortly by the females. Reproductive success of these butterflies depends on the timing of emergence and mating events. A disturbance in the timing of emergence between males and females could cause an incomplete temporal overlap between the sexes, leading to reproductive asynchrony. Reproductive asynchrony occurs when males and females within a population do not overlap completely in time, and it can significantly affect population dynamics of species with narrowly defined breeding periods, such as univoltine butterflies. Our research examined how climate change may influence flight time and mating success in Parnassius clodius butterflies. A mark-recapture study to assess timing of emergence and mating success was performed in Grand Teton National Park. Six plots were surveyed daily for Parnassius clodius butterflies using mark recapture techniques during the annual flight period from late June until mid-July 2009. Each captured butterfly was marked with a permanent marker on both of its hindwings prior to release. The sex and wing condition of each butterfly was determined and recorded at time of capture. A total of 838 butterflies were marked during the 2009 flight period, with a recapture rate of 26%. Preliminary examination of the data reveals the expected pattern of male emergence prior to female emergence. The emergence times appear consistent with other survey years. We also observed a small number of unmated females at the end of the season. Further data analysis needs to be performed before any additional conclusions can be made. This study provides a baseline understanding of climatic and phenological trends in an effort to understand how gender-specific emergence times and mating status of a common species of butterfly (Parnassius clodius) may be affected by climatic changes.