This was one of my favorite peer-reviewed articles that came out of my dissertation work. Plus, Don, my advisor and coauthor, absolutely loved the first part of the title (full credit to him!). In this research, we investigated egg-laying in Pieris virginiensis, the West Virginia White butterfly through a combination of field observation and lab oviposition experiments. We even tracked our lab-raised caterpillars' success via feeding assays. In essence, this article told the whole observatory story about these butterflies and their mismatched egg-laying preferences on an invasive species instead of their usual native host.
Work like this is critical in light of climate change. As invasive species continue to push forward into new habitats, they may drastically shift ecological relationships between other existing species. If native species are suddenly exposed to something bigger and flashier, they may start making the wrong choice. Sometimes it can result in success, but in the case of P. virginiensis, we never had a single caterpillar survive on the invasive garlic mustard. That's some strong evolutionary pressure, right there!
Alliaria petiolata is a European biennial herb that invades North American forests and has direct negative effects on associated flora and fauna. In some places, A. petiolata has invaded the habitat of Pieris virginiensis, a rare, univoltine butterfly that normally uses native spring ephemeral crucifer hosts. There are occasional observations of P. virginiensis laying eggs on A. petiolata, but the frequency and effects of these “mistake oviposition events” are not yet known.
We investigated P. virginiensis oviposition preference through field observations in three locations (NY, OH, PA), and also through laboratory experiments measuring egg deposition of adult females on either a native or invasive crucifer. In addition, we examined neonate larval performance through no-choice feeding assays on both A. petiolata leaves and cabbage leaves painted with A. petiolata leaf extracts.
We found that P. virginiensis lays significantly more eggs on the exotic A. petiolata than on its native host Cardamine diphylla in both field and laboratory experiments. Caterpillars fed either A. petiolata leaf tissue or its ethanol extract did not survive to pupation, and most died after only a few days. Continual invasion and persistence of in P. virginiensis habitats may lead to genetic bottlenecking and possibly local extinctions without human intervention.