PS 71-54 - Climate influences the phenology, abundance, and demographic rates of hydaspe fritillary butterflies

Friday, August 16, 2019
Exhibit Hall, Kentucky International Convention Center
Jessica M. Abbott, Brian Hudgens, Melissa Harbert, Kelcy McHarry and Lindsey Gordon, Institute for Wildlife Studies, Arcata, CA
Background/Question/Methods:

Understanding how climate variables influence the life histories of sensitive species is the first step in predicting how climate change might impact their population viability in the future. Insects may be particularly affected by changes in climate because they are short-lived ectotherms that often have complex life cycles that are strongly influenced by temperature. Evaluating the effects of climate change on insect populations is especially important because recent evidence suggests that insect abundances are plummeting globally and that their rate of decline is outpacing that of other taxonomic groups. We studied the life history of hydapse fritillary butterflies (Speyeria hydaspe), which are closely related to the threatened Oregon silverspot butterfly (Speyeria zerene hippolyta), at six sites in Northern California and Oregon that spanned latitudinal and elevational gradients and varied in climate. We evaluated the influence of temperature and precipitation on the phenology, abundance, and demographic rates (fecundity, egg hatch rates, and adult survival) of hydaspe fritillaries over three years.

Results/Conclusions

We found that the best predictor of the timing of the peak of the flight period was growing degree days (GDD), a common measure of heat accumulation, with higher GDD being associated with earlier peaks. The length of the flight period was influenced by both precipitation and temperature, with warmer, drier conditions leading to shorter flight periods. Butterfly abundance was most strongly affected by precipitation and there appeared to be a time lag in its effects. Greater total precipitation in the previous year led to higher hydaspe abundance in the current year. Precipitation and temperature both positively influenced adult survival. The effects of climate on earlier life stages were not as pronounced. The number of eggs laid per female per day decreased slightly with increasing minimum daily temperatures and egg hatch rates also declined with minimum daily temperatures, but only at two of the six sites. The relationships we found in this study can be used to predict how climate change might impact the phenology and population trajectories of hydaspe fritillaries and related species in the future.