Behavioral evidence for host transitions in plant, plant parasite, and insect interactions

Authors: Halbritter, Dale; WILLETT, DENIS - University Of Florida; GORDON, JOHNALYN - University Of Florida; STELINSKI, LUKASZ - University Of Florida; DANIELS, JARET - Florida Museum Of Natural History

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2018
Publication Date: 3/31/2018
Citation: Halbritter, D.A., Willett, D., Gordon, J., Stelinski, L., Daniels, J. 2018. Behavioral evidence for host transitions in plant, plant parasite, and insect interactions. Environmental Entomology. 47(3):646-653. https://doi.org/10.1093/ee/nvy033.
DOI: https://doi.org/10.1093/ee/nvy033

Interpretive Summary: We investigated the role of a pine tree parasite, dwarf mistletoe, in influencing interactions between Neophasia butterflies and pine trees, the butterflies' larval hosts. The plant-insect interactions were studied at six sites in pine forest habitats in Arizona, USA: three in N. menapia habitat and three in N. terlooii habitat. Each site contained six stands of trees that varied in mistletoe infection severity. Butterfly behavior was observed at each stand. Airborne odors were collected from trees at each site and analyzed to determine their chemical compositions. Female butterflies interacted more (i.e., landed or patrolled) with pine trees than males, and N. terlooii interacted more with pine trees than N. menapia. Both butterfly species interacted more with tree stands harboring greater mistletoe infection, and N. terlooii interacted more with more severely infected tree stands than did N. menapia. Differences in tree odors resulting from mistletoe infection potentially influence Neophasia behavior. Odors significantly differed between infected and uninfected pine trees. The findings of this research stress the importance of considering the interactions between multiple organisms in a biological system to better understand how changing environments will impact each organism.

Technical Abstract: Plant-insect interactions are a major component of ecosystem processes, and piecing together the mechanisms and evolutionary history behind these interactions is key to understanding them. We investigated the role of a pine tree parasite, dwarf mistletoe (Arceuthobium spp.), in mediating interactions between Neophasia butterflies and pine trees, the butterflies' larval hosts. Mistletoe is considered the butterflies’ ancestral host, and the evolutionary transition to pine may have occurred recently. In Arizona, USA, we studied six sites in pine forest habitats: three in N. menapia (Felder and R. Felder, 1859) habitat and three in N. terlooii Behr, 1869 habitat. Each site contained six stands of trees that varied in mistletoe infection severity. Butterfly behavior was observed at each stand during peak flight periods. Volatile compounds were collected from trees at each site and analyzed using gas chromatography-mass spectroscopy. Female butterflies interacted more (i.e., landed or patrolled) with pine trees than males, and N. terlooii interacted more with pine trees than N. menapia. Both butterfly species interacted more with tree stands harboring greater mistletoe infection, and N. terlooii interacted more with more severely infected tree stands than did N. menapia. The influence of mistletoe on Neophasia behavior may be mediated by differences in tree volatiles resulting from mistletoe infection. Volatile profiles significantly differed between infected and uninfected pine trees. The role of mistletoe in mediating butterfly interactions with their larval host has implications for conservation biology and forest management, and highlights the importance of understanding an organism's niche in an evolutionary context.