WICOMICO'S WILD LUPINE
Climate change is likely to wipe out populations of eastern Wild Lupine, and consequently result in the disappearance of the Frosted Elfin butterfly which depends on the plant for survival. Wicomico County hosts two of the few remaining stands of Wild Lupine on the Eastern Shore, but as temperatures become more variable, the life cycles of these plants and their pollinators could be thrown out of sync, reducing the biodiversity of the county.
Climate change is likely to wipe out populations of eastern Wild Lupine, and consequently result in the disappearance of the Frosted Elfin butterfly which depends on the plant for survival. Wicomico County hosts two of the few remaining stands of Wild Lupine on the Eastern Shore, but as temperatures become more variable, the life cycles of these plants and their pollinators could be thrown out of sync, reducing the biodiversity of the county.
INTRODUCTION
In Wicomico County, the Nanticoke watershed is home to many species of plants and animals. However, it is special in that it hosts more rare plants than any other landscape in Delmarva. The Nanticoke river itself is one of the Chesapeake Bay's most productive tributaries as it supports various aquatic species across its gradient of brackish to freshwater tidal habitat. Rare Atlantic Cedar Swamps are protected here. However, the Nanticoke watershed presents unique topographic features inland as well, such as the Delmarva bays, which are concave indentations in the land created by glacial retreat after the last ice age. Because their soils are so rich, many of these bays have been historically drained for agricultural purposes. Yet, some still remain filled in by non-tidal wetlands that support rare species such as the carpenter frog and eastern tiger salamander. Glacier retreat 13,000 - 30,000 years ago also resulted in the upland formation of sand dunes that support globally rare plant species like the Wild Lupine [1].
WILD LUPINE AND FROSTED ELFIN
Wild Lupine (Lupinus perennis) is a rare, threatened perennial plant from the pea family native to Wicomico County. As an upland species, it prefers the sunny spots in cool, dry, forested habitats with sandy, well-drained soils. It is an early successional species that is often the first to appear after disturbances such as wildfires. Its purple-blue flowers attract various pollinators; however, one specific pollinator, the globally rare Frosted Elfin butterfly (Callophrys irus), has a life cycle unconditionally tied to that of the Wild Lupine and depends on it as its primary larval host plant. Although the Blue False Indigo (Baptisia australis) may serve as a secondary host, it is also threatened in the state of Maryland [6]. Adult Frosted Elfin lay eggs individually on the leaves of the Wild Lupine in May when the lupines begin to flower. When the caterpillars hatch a few weeks later, they feed on their flowers and fruits. Afterward, the caterpillars bury themselves in the soil and overwinter in their chrysalis cocoons. They reemerge in the spring as adults, ready to lay their eggs on the lupines and restart their life cycle. Adult Frosted Elfins are not strong fliers and cannot flee too far from their host plant. Therefore, the loss of a stand of Wild Lupine also tends to eliminate entire populations of Frosted Elfins [2].
In Wicomico County, many of the Wild Lupine's sandy ridges have been lost to land development, sand and gravel mining, forest degradation, roadside mowing, and fire suppression (which allows shrubs to overtake early successional species) [1]. There are only three known stands of Wild Lupine remaining on the Eastern Shore, four in the entire state of Maryland, and two of those places are located in Wicomico County [3,8]. When I asked Jill Parisi, from Delmarva Native Plants, where these patches of lupine could be found, she kindly stated that she could not release that information because the location is classified for the preservation of these species [3]. Due to the greatly reduced ranges of the Wild Lupine, the Frosted Elfin is also rarely encountered. According to the Maryland Biodiversity Project, the Frosted Elfin is endangered and vulnerable and holds a state rank of S1 (highly-state-rare), and a global rank of G3 (globally rare and local) [4].
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According to Jill Parisi from Delmarva Native Plants, there are only a few places left on the eastern shore where wild lupines exist naturally - and two of those places are located in Wicomico County. |
WILD LUPINE AND CLIMATE
As the climate warms, Wild Lupine will attempt to migrate north because they require cold temperatures to incubate their seeds over winter. A study done in southern Ontario found that seeds stored in a freezer for a month and a half had significantly (p<0.05) higher germination rates (nearly 100% germination), than those that were stored at room temperature (62% germination) [5]. However, seed dispersal only travels short distances, rendering it unlikely for the lupines to cross fragmented ecosystems for northward migration. Meanwhile, butterflies like the Frosted Elfin tend to stay in warmer areas, causing the lupines to lose their pollinators. Even though the Frosted Elfin are not the only pollinators of the Wild Lupine, variable temperatures are likely to put the life cycles of all types of insect pollinators out of sync with the flowering of the Wild Lupine [3].
As the climate warms, Wild Lupine will attempt to migrate north because they require cold temperatures to incubate their seeds over winter. A study done in southern Ontario found that seeds stored in a freezer for a month and a half had significantly (p<0.05) higher germination rates (nearly 100% germination), than those that were stored at room temperature (62% germination) [5]. However, seed dispersal only travels short distances, rendering it unlikely for the lupines to cross fragmented ecosystems for northward migration. Meanwhile, butterflies like the Frosted Elfin tend to stay in warmer areas, causing the lupines to lose their pollinators. Even though the Frosted Elfin are not the only pollinators of the Wild Lupine, variable temperatures are likely to put the life cycles of all types of insect pollinators out of sync with the flowering of the Wild Lupine [3].
Delmarva Native Plants is currently growing lupine seed (left) to help the Maryland DNR with their mission to increase the population of Wild Lupines and Frosted Elfin butterflies. DNR will be planting 2,000 plugs of Wild Lupine in a few locations throughout the region. Unfortunately, because the species is threatened, excess seed is unavailable to the public for planting. However, if Delmarva Native Plants has extra plugs after the DNR completes their planting, the nursery is allowed to give away the seeds for for free, but this year it doesn't look as though they will have extra. The seeds cannot be sold for profit due to their status. So, while some retail plant stores claim they sell the native lupines, they actually do not [3].
In addition, the Maryland Natural Heritage Program has started deploying temporary electric fencing in effort to protect large stands of Wild Lupine from deer. Deer also like to eat the same flowers and seed pods as the Frosted Elfin caterpillars, and it is even possible that while they forage through the lupine, they are consuming Frosted Elfin larvae. This fencing is installed and maintained by volunteers and has helped elevate populations of both the Wild Lupines and the Frosted Elfins. Prescribed fire is also being used to maintain early successional areas where both species can colonize [7].
The Nature Conservancy is currently working to protect the integrity of the region's remaining sandy dunes in effort to allow the reestablishment of the eastern Wild Lupine, and hopefully encourage the return of butterfly pollinators [1].
In addition, the Maryland Natural Heritage Program has started deploying temporary electric fencing in effort to protect large stands of Wild Lupine from deer. Deer also like to eat the same flowers and seed pods as the Frosted Elfin caterpillars, and it is even possible that while they forage through the lupine, they are consuming Frosted Elfin larvae. This fencing is installed and maintained by volunteers and has helped elevate populations of both the Wild Lupines and the Frosted Elfins. Prescribed fire is also being used to maintain early successional areas where both species can colonize [7].
The Nature Conservancy is currently working to protect the integrity of the region's remaining sandy dunes in effort to allow the reestablishment of the eastern Wild Lupine, and hopefully encourage the return of butterfly pollinators [1].
Disturbance and the Frosted Elfin Butterfly
Prescribed burns can maintain an open canopy that encourages the growth of Wild Lupines and consequently supports populations of endangered Frosted Elfin butterflies [2]
Click to return to Forests or learn more about its species!
References
- The Nature Conservancy (n.d.). Nanticoke River Watershed, Dorchester and Wicomico Counties. Retrieved from https://www.nature.org/ourinitiatives/regions/northamerica/unitedstates/maryland_dc/placesweprotect/preserve-visitors-guide-nanticoke-river-watershed.pdf
- Maryland Department of Natural Resources. (n.d.). Rare, Threatened and Endangered Plant Fact Sheets: Sundial Lupine. Retrieved from http://dnr.maryland.gov/wildlife/Pages/plants_wildlife/rte/rteplantfacts.aspx?PID=Sundial Lupine
- Personal communication, Jill Parisi, Delmarva Native Plants, 9 April 2018, phone interview.
- Maryland Biodiversity Project (n.d.). Frosted Elfin. Retrieved from https://www.marylandbiodiversity.com/viewSpecies.php?species=524
- Fire Effects Information System (n.d.). Lupinus perennis. Retrieved from https://www.fs.fed.us/database/feis/plants/forb/lupper/all.html
- Maryland Department of Natural Resources. (n.d.). Rare, Threatened and Endangered Plant Fact Sheets: Blue Wild Indigo. Retrieved from http://dnr.maryland.gov/wildlife/Pages/plants_wildlife/rte/rteplantfacts.aspx?PID=Blue%20Wild%20Indigo
- Maryland Department of Natural Resources – Wildlife & Heritage Service (2017). Retrieved from https://www.facebook.com/mddnrwildlife/posts/932110683594689%E2%80%8B
- Personal communication, Dr. Tami Ransom, Environmental Studies professor at Salisbury University, 16 May 2018, Salisbury University.