Landscape-scale response to local habitat restoration in the regal fritillary butterfly (Speyeria idalia) (Lepidoptera: Nymphalidae)

Abstract

The butterfly Speyeria idalia was once a widespread species in the midwestern United States, but declined precipitously during the 1980s. By the early 1990s in NW Indiana and adjacent NE Illinois, it was reduced to a single site where it persisted as a precarious three deme metapopulation managed using prescribed fire. In 1996, a large-scale high diversity restoration was initiated at the site to restore ecological connectivity for grassland and oak barrens communities across the site. Among many restoration goals, we included restoring connectivity for habitat restricted insect communities across the highly fragmented site. In support of that goal, we included over 620 local genotype plant species in the restoration. S. idalia responded positively to the restoration and was the most abundant butterfly across the site in 2014. Ironically, we incorrectly considered the primary hostplant at the site, Viola bicolor, to be non-native when we initiated the restoration and did not include it in our seed mixes. This weedy annual aggressively expanded into the restoration without our assistance. We believe that we transformed the precarious metapopulation into a well-connected patchy population across the restoration. In addition, the butterfly occupied previously unoccupied habitats far beyond the restoration. This suggests that we have created a regional mainland—island metapopulation structure, with the restoration serving as a source of immigrants that sustains colonization rates at or above the rate of local deme extinction across a landscape that currently spans almost 60 km.