Factors affecting ant tending in Fender’s blue butterfly (Plebejus icarioides fenderi): implications for habitat restoration and species recovery

Fender’s blue butterfly, Plebejus icarioides fenderi (Macy), is a federally endangered species which survives in remnant native prairie habitat in Oregon’s Willamette Valley. Less than 1% of historic Fender’s habitat remains and much of that has been degraded by invasive grasses and forbs. To date, research involving habitat restoration for Fender's blue has focused primarily on how invasive vegetation affects the adult stage, but recent work suggests ant tending may significantly increase survivorship in Fender's blue larvae, resulting in a higher population growth rate. Fender's blue, like ~45% of all lycaenids, maintains a facultatively mutualistic relationship with ants.  Our work indicates that Fender's blue larvae are tended by at least five ant species in as many genera. Here, we systematically document ant tending in post-diapause Fender's blue larvae by its native ant mutualists. We also examine biotic and abiotic factors associated with ant tending in the West Eugene population with a specific focus on the vegetation gradient among nine sites. Our results aim to inform restoration efforts relative to the potential influence of invasive species on vegetation structure during the Fender’s blue larval phase, a stage that may be more significant than previously documented.