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Something unusual has occurred on the Hawaiian island of Oahu, where native birds have been completely replaced by invasive species.
In an unprecedented finding, researchers have discovered that the newcomers are only capable of dispersing seeds in the island, and are thus now playing an essential role in the local ecosystem, according to a study published in the journal. Science Advances.
The authors of the study-representing several U.S. institutions-say that their results demonstrate how ecosystems in which introduced or invasive species dominate can be more prevalent.
"The Hawaiian Islands are known to both" extinction and invasive species capitals of the world, "ecologist Jeferson Vizentin-Bugoni, lead author of the study from the University of Illinois at Urbana-Champaign, told Newsweek. "Nearly all of [Oahu’s] native fruit-eating animals are extinct and seed dispersal-an essential process to maintain ecosystem functioning-is almost entirely dependent on a handful of introduced vertebrate dispersers, nearly all of which are birds.
"Oahu offers an amazing opportunity to understand and anticipate what other ecosystems can cause." said.
It is for this reason that the Hawaiian archipelago studies, which, being the most isolated in the world, is home to many unique plants and animals.
"Hawaii," Corey Tarwater, another author of the study, from the University of Wyoming, said, "We decided to study Oahu because there is no other environment. Newsweek. "You have this isolated archipelago that is more than 1,800 miles from the nearest continental land mass and is home to many endemic species."
"Despite representing only 0.2 percent of the land area of the U.S., almost one-third of the species on the U.S. Endangered and Threatened Species list are in Hawaii," she said. "Then you have introduced species from this continent and this mixture of native species and non-native species from all over the world is becoming more common."
Previous research has shown that interactions between plants and animals in these "ecological communities" are particularly sensitive to invasive species or extinctions. However, this kind of research has been focused on areas dominated by native species, where these interactions have co-evolved over long periods of time.
To address this lack of knowledge in a world where humans are most obviously ubiquitous, the researchers investigated how birds are dispersed on Oahu, in which is the first comprehensive study on species interaction in a novel ecosystem-a place where most species are non-native .
In total, the team identified more than 100,000 seeds that were collected from the island. Their subsequent analysis showed that native plants are almost entirely dependent on invasive bird species to disperse their seeds.
"The first major result is remarkable: There are no native bird species dispersing seeds of native seedlings on Oahu-the interactions are completely novel," Vizentin-Bugoni said. "This island has been greatly improved in the past 700 years, 77 species and subspecies of birds in the Hawaiian archipelago have gone extinct, accounting for 15 percent of bird extinctions worldwide. "
Furthermore, the scientific evidence of the species' interactions on the island bears a striking resemblance to complex and stable ecosystems around the world where flora and fauna dominate. This suggests that new ecological communities can arise in a relatively short time by quickly integrating invasive species.
"This has deep implications for the understanding of how natural is developing, and the emergence of complex and stable networks in such degraded ecosystem challenges that co-evolution is a requirement for the emergence of complexity in interaction networks in nature," Vizentin- Bugoni said.
"Thus, it is a good thing that a highly degraded ecosystem, species can arrange their interactions in a way that stability is increased," he said. "Moreover, the introduced birds can disperse seeds of native plants. However, they are more likely to be more widely dispersed than other plants in the world. . "
According to the researchers, humans have long left their mark on the flora and fauna of the Hawaiian islands -without dramatic changes in the past 200 years because of extensive land use changes and species introductions.
"When Polynesians first settled down on the archipelago," they said, "Jason Gleditsch, another author from Illinois at Urbana-Champaign, told Newsweek. "Later, when Europeans discovered the archipelago and began to trade with the Polynesians there, they introduced new plant species, rats and mongooses, and later settlement on the island of birds, livestock and pets."
"Of those animal introductions, cats, rats, pigs and goats were especially impactful. "The rats and cats became predators of native birds, and the pigs and goats greatly increased herbivory," he said. "Additional, with the introduction of mosquitoes-in with the introduction of infected bird species-came the introduction of avian malaria. The native birds that did not evolve with avian malaria were very susceptible and populations plummeted. "
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