Climate factors, such as temperature and precipitation have a strong effect on the distribution of vegetation, thus influencing the distribution of invertebrates dependent on them for nourishment and nesting.Lupine, a widely distributed herb species along oak savanna and barren habitats in North America, may be influenced by those factors.

Lupine (Lupinus perennis) plays a critical functional role in the oak savanna ecosystem as the host plant for the federally listed Karner Blue butterfly (KBB), Lycaeides melissa samuelis, as well as for other invertebrate species.

The KBB was once widely distributed throughout 12 states along the northern part of the United States and Ontario, Canada. Now it only persists in seven states, and three of them have KBB populations as result of reintroduction programs. Was there a significant change in historical climatic variables at the locations and times the KBB disappeared?

Thirteen ecologically-relevant climatic indices of daily temperature and precipitation from meteorological stations were created and analyzed for patterns and trends in locations where the KBB still has viable numbers and in places where it disappeared.

Results/Conclusions

The results show that different indices have changed differently among the locations. The number of extreme hot days and number of extreme cold days per year have a statistically significant change in the locations where the Karner Blue butterfly disappeared. The precipitation-related indices do not show a statistically significant different trend among the locations. Temperature seems to have more effect on the persistence of the Karner Blue butterfly. Furthermore, butterfly population size and lake effects are also important factors that cannot be neglected. Larger populations seem to have better chances to survive during a dramatic climate change event.

This comparison of historical climatic indices for former and present KBB habitats may allow the exploration of the environmental mechanism of KBB extinction and make the reintroduction efforts more successful.