Alien Bird Species Aiding Native Plants: A Surprising Discovery
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Chapter 1: The Unique Ecosystem of Oʻahu
The Hawaiian island of Oʻahu has witnessed a dramatic shift in its avian population, leading to the near extinction of native bird species. These have been replaced by a diverse array of non-native birds from various regions, fundamentally altering the local ecosystem. Recent research indicates that these introduced bird species are now crucial for seed dispersal, a role once fulfilled by extinct native birds.
"This is remarkable because it demonstrates that non-native species can effectively fill essential ecosystem roles, such as seed dispersal," commented Jeferson Vizentin-Bugoni, the lead author and community ecologist at the University of Illinois at Urbana-Champaign.
"In my initial visits to the island, I was struck by the realization that many areas resembling tropical forests contained no native species at all," Dr. Vizentin-Bugoni shared in an email.
Section 1.1: The Extinction Crisis in Hawaii
Hawai'i is often referred to as the "extinction capital of the world." Since human arrival, 95 of the 142 bird species in the Hawaiian archipelago have gone extinct. Currently, 33 out of the remaining 44 endemic birds are listed as endangered, with many having not been observed for years.
"Despite making up just 0.2% of the U.S. land area, Hawaii is home to nearly one-third of the species listed as endangered or threatened in the U.S.," noted Corey Tarwater, co-author of the study and assistant professor of zoology at the University of Wyoming.
Section 1.2: Interactions in a Novel Ecosystem
The study explored how introduced bird species are integrated into the local seed dispersal networks. This research is critical for understanding the ecological dynamics of communities heavily influenced by non-native species.
"We aimed to investigate how these new bird species interact with the local flora, particularly given the dramatic loss of native species," Dr. Vizentin-Bugoni stated.
Chapter 2: Understanding Seed Dispersal Networks
By examining over 100,000 seeds found in bird feces from various locations across Oʻahu, researchers uncovered that 86.7% of the birds involved in seed dispersal were non-native. Surprisingly, no interactions between native birds and plants were recorded during the study.
"Given that all native fruit-eating birds are extinct on Oʻahu, we expected few native interactions," said Jinelle Sperry, a wildlife biologist involved in the research. "To not find a single native interaction over three years is quite astonishing."
Non-native birds show a strong preference for non-native fruits, raising concerns about the future of native plants.
"While these invasive birds are aiding native plants by dispersing their seeds, they are also promoting the spread of invasive plant species," Professor Tarwater explained.
In light of these findings, it is clear that restoring native ecosystems will require strategic efforts to encourage non-native birds to consume native fruits, ensuring the survival of native plant species.
"The dynamics we observed challenge long-held beliefs about how invasive species interact within new environments," Dr. Vizentin-Bugoni remarked, highlighting the intricate balance of these novel ecosystems.
"The loss of native species not only diminishes biodiversity but also erases potential benefits to humanity, such as the discovery of new medicinal plants," he concluded.
Source:
Jeferson Vizentin-Bugoni, Corey E. Tarwater, Jeffrey T. Foster, Donald R. Drake, Jason M. Gleditsch, Amy M. Hruska, J. Patrick Kelley, and Jinelle H. Sperry (2019). Structure, spatial dynamics, and stability of novel seed dispersal mutualistic networks in Hawai'i, Science, 364(6435):78–82 | doi:10.1126/science.aau8751
Originally published at Forbes on 7 April 2019.