This is my full dissertation, available to anyone who wants it. Of note, there's really only two chapters that are unpublished: the introduction, which was my research proposal heavily modified; and one article that we just couldn't get published on greenhouse experiments. Everything else is in its more final form in the journals where we published.
Humans have caused drastic changes in ecosystems and communities through their modification of the natural landscape. Rare species, often highly specialized, are more impacted by these changes. Pieris virginiensis is a rare butterfly native to eastern North America that is a species of concern due to negative influences from habitat loss and plant invasion. This thesis discusses several threats to P. virginiensis, including habitat loss, climate change, competition, and the cascading effects of a novel European invasive plant, Alliaria petiolata, that attracts oviposition but does not allow for larval survival.
First, I examined a local extinction event and attributed it primarily to several seasons of poor weather and extreme climatic events, but with contributions by an increasing deer population and the introduction of A. petiolata. Second, I found that A. petiolata attracts approximately two-thirds of total eggs, but no larvae survive on the novel host. I tested several chemical causes of larval death and identified two potential contributors: sinigrin, which delays growth, and alliarinoside, which reduces survival.
I also examined competition between P. virginiensis, its host plants, and novel competitors in the habitats. First, I looked at shared habitat use between P. virginiensis and another, exotic Pierid butterfly P. rapae. Although habitats are occasionally shared, P. rapae is most likely not a large influence on the success or failure of P. virginiensis. Second, I examined the influence of A. petiolata when it competes with two native host plants of P. virginiensis, and found differential effects of each life stage of A. petiolata on the native host plants.
Finally, I used a combination of species distribution modeling and genetic sequencing to determine the current and future states of P. virginiensis given the changing climate and other stressors on P. virginiensis populations. Although secure currently, future stressors will most likely cause a range contraction and local extinctions