Oviposition substrate preferences of two endangered prairie butterflies in an ex situ conservation environment

The Dakota skipper Hesperia dacotae and the Poweshiek skipperling Oarisma poweshiek (Hesperiidae) are imperiled univoltine prairie obligate butterflies native to the north-central USA and southern Canada, and ex situ conservation strategies have been identified as important tools for their recovery. Understanding the reproductive behaviors of these taxa is crucial for maximizing their reproductive potential and the efficacy of these conservation activities. It is generally assumed that, within Lepidoptera, females preferentially oviposit on substrates that are most suitable for the development of their offspring, but this has been shown to not always be true. Here, we examined whether Dakota skipper and Poweshiek skipperling females exhibited oviposition substrate preferences for 3 potential larval host graminoids: prairie dropseed Sporobolus heterolepis, tussock sedge Carex stricta, and smooth brome Bromus inermis. Our results suggest that, at least in an ex situ setting, Dakota skippers and Poweshiek skipperlings preferentially oviposit on graminoids over abiotic substrates, and both taxa demonstrate a stronger preference for prairie dropseed over tussock sedge and smooth brome. These results will better inform continued ex situ management and have important in situ implications, as these skippers may oviposit on invasive grasses (i.e. smooth brome in our experiment) despite the presence of more suitable host plants.