University of Massachusetts- Amherst, Massachusetts, United States
Abstract: The White Mountain arctic (WMA) butterfly (Oeneis melissa samidea) is a subspecies of the Melissa arctic (Oeneis melissa) that is endemic to a small portion of the alpine zone of Presidential Range of the White Mountain National Forest in New Hampshire. This unique butterfly’s larvae are monophagous, only consuming Bigelow’s sedge (Carex bigelowii) in the wild. With threats of climate change, habitat fragmentation, degradation, and prolonged exposure to trampling due to off-trail hiking, the WMA and Bigelow’s sedge are both at risk of decline or extinction. This preliminary study aimed to provide information on if the WMA larvae will show signs of host plant plasticity to accept alternative food sources should environmental pressures make their host plant less accessible.
Working with New Hampshire Fish and Game we tested the plasticity of host plant acceptance on a captive colony of 110 WMA larvae. Larvae were offered daily clippings of Bigelow’s sedge and three-forked rush (Juncus trifidus), a common rush species found in the area. Larvae were kept in petri dishes that were cleaned daily to monitor feeding behavior. Behaviors that were recorded were active feeding on plants, and resting or searching on plants.
We found that 86 of the larvae fed on Bigelow’s sedge and 21 on the three-forked rush. We performed an unpaired two-sample Wilcoxon test using R software to compare the two independent variables, in our case, the amount of feeding on the three-forked rush and the amount of feeding on Bigelow’s sedge. After performing the Wilcoxon test, the output provided a p-value of 0.01032, which is less than our determined significance level of 0.05. This then allows us to reject the null hypothesis and assume that the two variables are significantly different from one another.
In conclusion, this study suggests that the WMA larvae do not show a significant sign of plasticity when it comes to host plant selection and would likely not switch food sources from Bigelow’s sedge to three-forked rush if pressured due to the loss of their host plant. Considering the limited area and sensitivity in which Bigelow’s sedge inhabits, and the negative impact of climate change and human disturbance, action to protect and preserve the habitat of the WMA is necessary for the persistence of this endemic butterfly, along with the health and biodiversity of the alpine ecosystem in the White Mountain National Forest.
