Invasive species may help ecosystems
The study demonstrates that once-malignant invasive species outcompete many of the native species in a particular ecosystem, these non-native animals assume the new role of primary pollinators for plants.
“If you go ahead and eradicate the invasive species, you could have a real problem,” said co-author and ecology and evolutionary biology professor David Wilcove.
In 2009, Wilcove traveled to New Zealand with the study’s lead author and New Zealand native David Pattemore, wanting to understand the impact of both native and invasive animal species on plant life in New Zealand. Pattemore noted that the ecosystem on the reserve of Little Barrier Island consisted mostly of native animals, while on the mainland North Island, invasive species were the dominant vertebrates.
When Pattemore put samples of Pohutukawa evergreen trees, New Zealand honeysuckle trees and Veronica macrocarpas in wire-mesh cages, he discovered that plants on both islands suffered equally from a lack of pollination. Pattemore also positioned miniature video cameras near plants that were not put into cages. These cameras recorded all diurnal and nocturnal visitors to the plants for several days, providing the researchers with 1,200 hours of footage to use as data.
As expected, native birds and bats on Little Barrier Island played a major role in the pollination of the reserve’s plants. However, on the mainland, the researchers discovered that certain invasive species, such as the ship rat and the silvereye, were some of the plants’ only pollinators.
“The ship rat is the major culprit behind the extinction of native birds and bats,” explained Wilcove. “The goal of conservation is to get rid of these invasive species. We were quite surprised that these species did a reasonably good job at pollinating the plants.”
The two researchers hope that their findings will help conservationists develop effective strategies when trying to conserve biodiversity.
“Invasive species are one of the biggest threats to biodiversity,” Wilcove stated. “But I suggest that conservationists think carefully about their helpful roles and contributions to the ecosystem as well. They can’t focus exclusively on the excavation of native species.”
As a solution to the problem, Wilcove suggested that conservationists remove invasive species while reintroducing native species to the ecosystem.
Pattemore is now conducting research at the New Zealand Institute for Plant and Food Research, while Wilcove is continuing his studies on how human activities affect biodiversity. On Monday, Wilcove delivered a keynote address on the decline in migratory species at the Convention on Migratory Species in Bergen, Norway.
“I’m driven by the desire to find solutions to biodiversity,” Wilcove stated. “One of the implications of this study is that it’s not a simple picture.”
The report was published in the journal Proceedings of the Royal Society B on Nov. 16.
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