near the trailhead, says Andy Zadnik, WPC’s director of land stewardship. A decade and a half later, there is progress, he says. “We’re now addressing a larger area with the same amount of effort, and I’ve seen West Virginia white there, so it tells me we’re having a positive effect.” Garlic mustard also displaces the butterfly’s host plants and nectar sources. And with the changing climate, Andy notes, plants are coming out of dormancy earlier, which could disrupt the timing for the insects to find food sources. “Everything has to line up. The butterflies require diverse, abundant wildflowers, and they have to be flying when the flowers are in bloom or they won’t have enough nectar.” When controlling invasive species on our preserves, staff begins with a specific part of the site. “Exotic invasives are so widespread everywhere that you have to pick your battles,” Andy says. “If we can have an impact that is sustainable based on our capacity, then we can take on a slightly larger area.” The rare butterfly is just one of Pennsylvania’s many native species threatened by invasive species, which aggressively compete for space and resources, says Brian Daggs, invasive plant ecologist with the Conservancy’s Pennsylvania Natural Heritage Program. “When an invasive plant finds itself in our native habitat, it is set free from its natural competitors, pests, The endangered West Virginia white butterfly often lays its eggs on invasive garlic predators and pathogens,” Brian explains. “So mustard (inset photo), a poisonous decoy plant that kills the caterpillars. now it has the competitive edge to reproduce or grow vigorously, and compete with native species.” Invasive species are one of the leading causes of biodiversity loss worldwide, after habitat loss, and are capable of causing the extinction of native plants, animals, fungi and microorganisms. Sometimes an exotic species resembles a native species so closely that it’s difficult to identify them by sight. Staying up to date on current science and technology is key, Andy says, noting that the Natural Heritage staff takes an active role in assessing threats by invasives. For example, thanks to genetic testing technology unavailable 20-plus years ago, staff recently sent watermilfoil samples from Lake Pleasant to a testing lab in Montana to determine whether they were the exotic species, the native species or a hybrid. “Fantastic news! The samples were native northern watermilfoil,” A delicate, rare butterfly native to Pennsylvania, the West Virginia Andy says. But the concern remains that invasive Eurasian white, flies for just one month each spring. Once ranging through watermilfoil will make its way to the lake. “That’s one reason we’re northern and western Pennsylvania, with some records in southeastern grateful that motorboats are not allowed in the lake. Exotic invasive counties, its populations have decreased, mostly due to the spread of plants can get chopped up and stick to a motor, boat or trailer...a exotic invasive garlic mustard—a toxic decoy to the butterfly’s main major way those species are spread from one waterbody to another.” source of nourishment, the native two-leaved toothwort, also in the Collaboration is extremely important when managing invasive mustard family. When the butterflies become confused and lay their species. For example, Andy explains, “At our Toms Run Nature eggs on garlic mustard, their caterpillars always die. Reserve, we’ll be removing an area of invasive plants to prepare for a At the Conservancy’s Wolf Creek Narrows Natural Area in Butler TreeVitalize spring tree planting. In addition to our regular volunteers, County, dedicated volunteers and staff began controlling garlic we’re partnering with a crew from the Student Conservation mustard 13 years ago in an effort to protect the West Virginia white Association.” and native wildflower populations. The planting and removal are part of a larger project of the Allegheny It has been the Conservancy’s longest and most consistent Bird Conservation Alliance, a partnership between multiple local invasive species control effort, and it began when we removed 10 and national conservation organizations. David Yeany, WPC’s PNHP large bags of garlic mustard from just the small area of floodplain
Controlling Invasive Species that Threaten Biodiversity
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