Can butterflies evade fire? Pupa location and heat tolerance in fire prone habitats of Florida

Authors: Thom, Matthew; DANIELS, JARET - University Of Florida; KOBZIAR, LEDA - University Of Florida; COLBURN, JONATHAN - University Of Florida

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2015
Publication Date: 5/27/2015
Publication URL: http://handle.nal.usda.gov/10113/60943
Citation: Thom, M.D., Daniels, J.C., Kobziar, L.N., Colburn, J.R. 2015. Can butterflies evade fire? Pupa location and heat tolerance in fire prone habitats of Florida. PLoS One. 10(5):e0126755.

Interpretive Summary: The imperiled frosted elfin butterfly is restricted to frequently disturbed habitats where its larval host plants occur. Pupae are noted to reside in both leaf litter and soil. This may allow them to escape direct mortality by fire, a prominent disturbance in many areas they inhabit. The capacity of pupae to cope with fire is a critical consideration for land management and conservation strategies in the few remaining locations where this species is found. Frosted elfin butterfly pupa locations were sampled from a well-known population in the Southern Coastal Plain of North Florida, USA. This area is characterized by an active history of intentional prescribed fire. Survival of butterfly pupae in relation to temperature and duration of heat pulse was tested using controlled water bath experiments and a series of prescribed fire field experiments. Fifty percent of frosted elfin butterfly pupae survived the heat generated by prescribed fire when at depths greater than or equal to 1.75 cm. This suggests that pupation in the soil at depth can protect from fatal temperatures caused by fire. If applied to depths observed for butterfly pupae, approximately 25% of pupae would survive a typical spring season burn. A reduction of 75% of pupae of a given population from a burn event is a significant loss. Therefore, decreasing the impact of prescribed fire on a population is critical. Management suggestions follow those from previous studies on rare insects. Divide the inhabited area into smaller units that are burned on a multi-year rotational schedule. This provides an undisturbed refuge and supports organisms across all life stages. This research benefits public and private land managers who are involved in active restoration, conservation, and other environmental activities. The general public who visit lands such as national and state forests and park will also benefit from this research.

Technical Abstract: The imperiled frosted elfin butterfly, Callophrys irus Godart, is restricted to frequently disturbed habitats where its larval host plants, Lupinus perennis L. and Baptisia tinctoria (L.) R. Br. occur. C. irus pupae are noted to reside in both leaf litter and soil, which may allow them to escape direct mortality by fire, a prominent disturbance in many areas they inhabit. The capacity of C. irus to cope with fire is a critical consideration for land management and conservation strategies in the few remaining locations where this species is found. C. irus pupa locations were sampled from a well-known population in the Southern Coastal Plain of North Florida, USA, characterized by an active history of prescribed fire. Survival of a surrogate butterfly pupae (Eumaeus atala Poey) in relation to temperature and duration of heat pulse was tested using controlled water bath experiments and a series of prescribed fire field experiments. Twelve C. irus pupae were excavated from 2010 to 2012: eight were located at the soil surface, with the remaining four found in the soil between 0.5-3.0cm depths. Survival of E. atala pupae was correlated to peak temperature and heat exposure in both laboratory and field trials. In addition, E. atala survival following field trials was correlated to depth of burial; complete mortality was observed for pupae at the soil surface. Fifty percent of experimental surrogate E. atala survived the heat generated by prescribed fire when at depths greater than or equal to 1.75cm, suggesting that pupation in the soil at depth can protect from fatal temperatures caused by fire. If applied to depths observed for C. irus, approximately 25% of pupae would survive in a typical spring season burn. A reduction of 75% of pupae of a given C. irus population from a burn event is a significant loss, and so decreasing the impact of prescribed fire on a population is critical.