Butterfly community temporal trends and responses to resource availability along a hydrologic gradient of montane meadows

Butterfly species have proven to be useful indicators of environmental change in many ecosystems. Their tight association with plant communities and their sensitivity to microclimates can provide insight regarding changes in landscape or vegetative composition. Here we report on a study within two regions of the Greater Yellowstone Ecosystem where butterflies have been surveyed in montane meadows along a hydrological gradient since 1997. We have studied this system to better understand butterfly community ecology within one of the most pristine meadow systems in the lower 48 of the United States. This research examined the temporal and spatial patterns of montane meadow butterfly communities in relation to meadow moisture availability and quantity of floral and larval host plant resources. This information is a valuable tool for conservation of montane meadows, and could be useful in monitoring meadow changes due to climatic, anthropogenic, or other natural changes in the landscape

Montane meadow change during drought varies with background hydrologic regime and plant functional group

Climate change models for many ecosystems predict more extreme climatic events in the future, including exacerbated drought conditions. Here we assess the effects of drought by quantifying temporal variation in community composition of a complex montane meadow landscape characterized by a hydrological gradient. The meadows occur in two regions of the Greater Yellowstone Ecosystem (Gallatin and Teton) and were classified into six categories (M1–M6, designating hydric to xeric) based upon Satellite pour l’Observation de la Terre (SPOT) satellite imagery. Both regions have similar plant communities, but patch sizes of meadows are much smaller in the Gallatin region. We measured changes in the percent cover of bare ground and plants by species and functional groups during five years between 1997 and 2007. We hypothesized that drought effects would not be manifested evenly across the hydrological gradient, but rather would be observed as hotspots of change in some areas and minimally evident in others. We also expected varying responses by plant functional groups (forbs vs. woody plants). Forbs, which typically use water from relatively shallow soils compared to woody plants, were expected to decrease in cover in mesic meadows, but increase in hydric meadows. Woody plants, such as Artemisia, were expected to increase, especially in mesic meadows. We identified several important trends in our meadow plant communities during this period of drought: (1) bare ground increased significantly in xeric meadows of both regions (Gallatin M6 and Teton M5) and in mesic (M3) meadows of the Teton, (2) forbs decreased significantly in the mesic and xeric meadows in both regions, (3) forbs increased in hydric (M1) meadows of the Gallatin region, and (4) woody species showed increases in M2 and M5 meadows of the Teton region and in M3 meadows of the Gallatin region. The woody response was dominated by changes in Artemisia spp. and Chrysothamnus viscidiflorus. Thus, our results supported our expectations that community change was not uniform across the landscape, but instead could be predicted based upon functional group responses to the spatial and temporal patterns of water availability, which are largely a function of plant water use and the hydrological gradient.This material is based upon research supported by the National Science Foundation under Grants 0518150 and EPS0814387, the Environmental Protection Agency under STAR Grant R825155, the University of Wyoming National Park Service Research Station, and the Grand Teton Natural History Association. We thank the University of Wyoming National Park Service Research Station (particularly Henry Harlow and Sue Consolo-Murphy) and the U.S. Forest Service for providing support and housing. Philip Dixon provided statistical consulting, and Mark Jakubauskas collaborated in setting up our initial field campaigns. Edward Cook assisted in selection and assessment of PDSI data; and Lisa Graumlich, Andy Bunn, Steve Gray, and Jeremy Littel advised us on climate reconstruction options for the GYE. Scott Creel, Sue Fairbanks, and Matt Kaufmann provided information on elk population trends in the region. Jill Sherwood designed the map. William Clark and two anonomous reviewers provided important suggestions that helped improve the manuscript. Finally, we thank the many research technicians and field assistants who helped in the fieldwork

Appendix A. Butterfly species categorized by habitat affinity.

Butterfly species categorized by habitat affinity

Appendix C. Single-species model summary.

Single-species model summary

Appendix B. Mixed-effects model incorporating habitat affinity.

Mixed-effects model incorporating habitat affinity