Natural ecosystems are vibrant and dynamic, filled with countless species that coexist and interact in intricate ways. However, some species in these ecosystems are not native to the area; they have been introduced by humans from different environments. Once they become abundant and widespread, some non-native species can disrupt the local balance of the ecosystem. Even though not all non-native species have negative impacts, many people still consider all non-native species to be harmful to native ecosystems. However, research conducted by PhD graduate Stephanie Rivest from Professor Heather Kharouba’s lab challenges this preconceived notion. Stephanie discovered that some non-native species in an endangered ecosystem could be harmless and may even help this native ecosystem thrive.
Stephanie’s research focused on understanding the role of non-native plants in the nectar diets of native butterflies. During the summer of 2019, she conducted field surveys in the Garry oak savannas on Vancouver Island, British Columbia, an ecosystem with magnificent biodiversity that is home to over 100 species at risk, including seven endangered butterflies. Armed with her notebook and camera, Stephanie traversed the hills, observing adult butterflies as they foraged for nectar.
By the end of the season, she documented 1143 nectar-foraging visits by 14 native butterfly species. Her results were astonishing: 83% of the nectar foraging visits were to non-native flowers and 64% of butterfly species chose non-native flowers over native ones. Even more intriguing was the fact that butterflies seemed to favour non-native nectar, choosing these flowers even when other nectar sources were more abundant. “Now we know that non-native flowers can be important components of native butterflies’ nectar diets, particularly at key times of the season. But why would they prefer those flowers? Is there something about the nectar? Is it more nutritious? Are the flowers more attractive? These are all important questions that myself and other graduate students from the Kharouba lab are now exploring,” Stephanie explains.
Traditionally, invasion biology research has focused on the negative impacts of non-native species. However, Stephanie’s findings suggest that the role of non-native species in ecological systems is multifaceted. While some non-native species contribute to the decline of native species, others may enhance regional biodiversity or fulfill crucial roles in food provision and habitat restoration. While monitoring and managing non-native species is essential, this process can be resource-intensive.
Therefore, studying their range of impacts on native ecosystems before taking action is advisable. Stephanie’s research can improve our current management strategies for non-native plants in seasonal ecosystems, aiding in prioritizing which species should be removed, and which can be left undisturbed. After all, many species that are now beloved were once considered invasive. Are they villains or heroes? The answer remains to be discovered.
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