Prescribed fire maintains host plants of a rare grassland butterfly

George C Adamidis,Mark T Swartz,Brent J Sewall,Konstantina Zografou

doi:10.1038/s41598-019-53400-1

George C Adamidis, Mark T Swartz + Show 2 more

Open Access

https://doi.org/10.1038/s41598-019-53400-1

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Abstract

As grassland ecosystems transform globally due to anthropogenic pressures, improvements in our understanding of the effect of management on rare and threatened species in such landscapes has become urgent. Although prescribed fire is a very efficient tool for habitat restoration and endangered species management on fire-adapted ecosystems, the specific mechanisms underlying potential effects of burning on population dynamics of butterfly host plants are poorly understood. We analyzed a 12-year dataset (2004–2015), combining violet abundance, habitat physiognomy and fire history data from a fire-managed system, to determine factors influencing the spatiotemporal distribution and abundance of violets (Viola spp.), the host plants of the threatened eastern regal fritillary (Speyeria idalia idalia) butterfly. Our results demonstrate a critical role for fire in driving both presence and abundance of violets, suggesting management with prescribed fires can effectively promote butterfly host plants. In addition, we determined the character of habitats associated with violet presence and abundance, in particular a strong positive association with biocrusts. These results provide a roadmap for efficient site selection to increase the effectiveness of restoration efforts, including assessment of potential reintroduction sites for regal fritillary and other grassland butterflies and actions to promote the re-establishment of host plants in these sites.

Highlights

As grassland ecosystems transform globally due to anthropogenic pressures, improvements in our understanding of the effect of management on rare and threatened species in such landscapes has become urgent
In North American grasslands, for instance, violets serve as the sole host plants for the regal fritillary (Speyeria idalia Drury), a rare North American butterfly that has experienced severe population declines throughout its range[14,31], and is under review for listing under the United States Endangered Species Act[32]
The eastern regal fritillary butterfly, is a distinct subspecies of the regal fritillary[33,34], whose sole population persists in a working landscape in south-central Pennsylvania, wholly within the borders of one of the busiest military training areas in the USA, Fort Indiantown Gap National Guard Training Center

Summary

Introduction

As grassland ecosystems transform globally due to anthropogenic pressures, improvements in our understanding of the effect of management on rare and threatened species in such landscapes has become urgent. We determined the character of habitats associated with violet presence and abundance, in particular a strong positive association with biocrusts These results provide a roadmap for efficient site selection to increase the effectiveness of restoration efforts, including assessment of potential reintroduction sites for regal fritillary and other grassland butterflies and actions to promote the re-establishment of host plants in these sites. Since 2004, land managers at FIG-NGTC have used prescribed fire to maintain grassland habitat and benefit this imperiled butterfly These actions appear to have had beneficial impact, leading to partial recovery in the eastern regal population[15], presumably through an indirect pathway that includes a positive effect of fire on violets, though the specific mechanism remains unclear. Given that regal butterfly populations require sites with sufficient violets[14,36], an understanding of violet ecology is crucial for accurately assessing the suitability of potential recipient habitats and ensuring the success of restoration efforts

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