Faculty advisor Western Colorado University, United States
Background/Question/Methods
The Uncompahgre fritillary butterfly (Boloria improba acrocnema) was listed as a federally endangered species in 1991. They are exclusively found on patches of their larval host plant, snow willow (Salix nivalis) in isolated, alpine habitats of the San Juan Mountains, Colorado, USA, a region predicted to be very sensitive to climate change. B. improba acrocnema are considered habitat indicators of alpine ecosystem health, yet limited research focuses on species interactions. This study asks: What additional microhabitat factors impact adult B. improba acrocnema abundance, and how can we improve monitoring efforts to observe climate change impacts? First, we estimated historical B. improba acrocnema abundance from annual distance sampling (2003-2020) at seven sub-colonies to define sampling sites along permanent transects with significantly high and low abundance estimates. We sampled 700 sites for current (July 2021) measurements of herbaceous coverage, soil moisture content, and terrain variability (slope, aspect, elevation) to describe the additional habitat requirements of this species. We used Generalized Linear Models in R Statistical Package to test for significant effects between these fine-scaled habitat characteristics and historical B. improba acrocnema abundance.
Results/Conclusions
Results showed significant interactions on historical B. improba acrocnema abundance with 14 out of 42 field measurements, including positive relationships between increased percent coverage of Salix nivalis, Salix reticulata, Geum rossii, Phacelia sericea, Noccaea fendleri, and Lewisia pygmaea. Additionally, our model indicated that increases in slope grade and soil moisture content positively affect historical B. improba acrocnema abundance, while increased elevation had consistent negative effects. These results suggest that this species might be at risk of extirpation or extinction due to an upper elevation limit in their limited geographic range and prolonged drought conditions in the San Juan Mountains. Our surveys of host plant coverage and herbaceous diversity express that there could be areas optimal for nutrient sources and ovipositional sites within these habitats. By defining which ecological factors impact historical B. improba acrocnema abundance, we can target conservation efforts to observe adult behavior and functionality of flowering plants from our results and implement continuous local climate monitoring. In summary, the mechanisms underlying population dynamics and behaviors of pollinators in alpine ecosystems can inform researchers and land managers of the factors impacting global species decline, especially under climate change conditions.
