Beyond the host plant: Environmental factors that predict habitat suitability for a northern peripheral population of a threatened butterfly (Apodemia mormo) at two spatial scales

Background/Question/Methods

The Mormon metalmark (Apodemia mormo) butterfly in the primarily neotropical family Riodinidae has a range that extends across western North America and northward into Saskatchewan and British Columbia, Canada. This butterfly was listed as threatened in Saskatchewan in 2002, where all known colonies reside in and around Grasslands National Park. This metalmark’s habitat was previously identified as areas where the larval host plant (Eriogonum pauciflorum) occurs, however, the butterfly is not found in many areas of seemingly suitable host plant habitat. 

Results/Conclusions

We analyzed habitat data using a series of models for both microhabitat and landscape scales to test the influence of environmental factors on suitability of host plant sites as butterfly habitat. Results from the microhabitat (25 m² plots, n=104) analyses suggest that slope and host plant cover are the strongest predictors of butterfly presence. Landscape models using spatial data (~500 m² study area at 20 m resolution) suggest that slope, CTI, amount of solar radiation and NDVI are also important. A blended approach using both scales is best suited to define Mormon metalmark habitat and identify appropriate conservation measures for the species in its northern range.