Coastal Butterfly and Moth Species at Risk
We have worked on a group of rare butterflies and moths in coastal BC including Sand-verbena Moth, Dun Skipper, Vancouver Island Ringlet, and Edward’s Beach Moth. Most of our recent work (2007 to present) has focused on a population of Taylor’s Checkerspot on Denman Island, BC. Taylor’s Checkerspot was thought to be extirpated from Canada after remnant populations on Hornby Island and near Shawnigan Lake collapsed in the late 1990s. In 2005, a small population was discovered on Denman Island in a regenerating logged area. Several years of surveys focusing on adult and larval use have been undertaken to better understand the ecology of this novel population (see map above showing 2007 to 2011 distribution records).
The Taylor’s Checkerspot population on Denman Island is unusual for two reasons. First, it has rapidly expanded into early-successional habitats created by forest harvesting in the late 1990s. Conservation strategies for Taylor’s Checkerspot often focus on maintaining or restoring the structure and composition of existing habitat patches, particularly dry meadows. The success of the Denman Island checkerspot population indicates that anthropogenic habitat disturbance may sometimes increase host plant resources that are associated with early-successional habitats. The map above shows sightings of adult checkerspots in 2007 and 2008. It has recently undergone a substantial decline that may be related to cooler and wetter spring conditions or vegetation succession. Second, the Denman Island checkerspot population uses a previously unrecorded suite of host plants. While this is not unexpected given the variability of host plant use in checkerspot taxa, it substantiates the view that Taylor’s Checkerspot host plant use is both plastic and opportunistic. Our research also suggests that native Veronica species may be the archetypal host plant from which populations switched once ribwort plantain was introduced.
Location: Denman Island, BC; other areas of southeastern Vancouver Island