A plant on British Columbia’s Gulf Islands has genetically evolved to avoid being eaten by herds of hungry deer, according to research from the University of British Columbia.
Researchers discovered seablush, a flowering plant native to the endangered Garry oak ecosystem of the Pacific Northwest, grows differently depending on the presence or absence of deer.
On islands free of deer, seablush grows 70 to 120 centimetres tall with branches high off the ground. On islands where deer are present, seablush grows 10 to 20 cm tall with branches low to the ground, making it less visible to herbivores. The plant also remains smaller for a longer period of time and increases its height only later in spring.
When researchers grew both kinds of seablush together in a habitat with deer, the plants that originated from islands with deer produced more seeds and were three times more likely to survive than their counterparts from islands without deer.
“In order to restore this endangered ecosystem, seeds from seablush that have genetically adapted to withstand or resist being eaten need to be collected and replanted on the islands that have deer,” said researcher Cora Skaien, a PhD candidate in the department of forest and conservation sciences, whose work is supervised by professor Peter Arcese.
The large number of deer on the Gulf Islands, located off the coast of southwestern B.C., has contributed to the devastation of the Garry oak ecosystem. A joint study from UBC and the University of Victoria in 2004 found the ecosystem had been reduced to roughly five per cent of its original extent since European settlement in the 1800s.
According to Skaien, deer populations on the islands can be as high as 170 animals per square-kilometer. She said that’s bad for both business and the deer.
“Deer can cause hundreds of thousands of dollars in damage for farmers, gardeners and insurance companies from trampling, browsing and grazing,” she said. “The deer also suffer from overcrowded herds where they’re forced to compete for food. Many of the deer are sickly, or starve, and their offspring are not carried to full-term.”
Skaien said culling or hunting deer is crucial to protect both the plant and deer community. She pointed to the benefits of annual culls on Sidney Island, which she said has now seen a resurgence of camas and Oregon grape, culturally significant plants for First Nations, in addition to seablush. The plants also serve as habitat for songbirds whose numbers decline in a reduced ecosystem.
“Deer are beautiful creatures,” said Skaien. “But we’ve eliminated predators from their natural habitat. Without culling, we’re reducing biodiversity of plants and birds and hurting deer in the process.”
Skaien and Arcese used exclosures on Sidney Island to conduct the research. They planted seeds of seablush native to islands with and without deer inside and outside the exclosures. Studying the plants’ survival and health based on their genetic differences, they were able to make the correlation between genetic adaptation and deer density.
The research is part of Skaien’s doctoral work.