A new studyby the Institute of Food and Agricultural Sciences at the University of Florida (UF/IFAS) sheds light on the role native species play in preventing the establishment of invasive species.
Once a species is introduced into a new environment, it can ‘establish' itself by forming a self-sustaining population, but most invaders do not survive.
While this is a good thing, scientists want to know why. If they are able to understand why an invasive species fails to establish, it helps them understand how to prevent other invaders from surviving.
UF/IFAS researchers decided to examine guppies and mosquito fish to find out.
Quenton Tuckett is an assistant research scientist at the UF/IFAS Tropical Aquaculture Lab (TAL) in Ruskin, Florida. He said scientists spend considerable effort studying successful invaders.
Tuckett and his team led research into the guppy (Poecilia reticulata), a widespread invasive species native to northern South America. He said they're a highly successful, non-native species.
“We picked the guppy because it's a worldwide invader,” Tuckett said. “It's on just about every continent, and usually highly successful, because it's what's called a livebearer; that means it gives birth to live young. So sometimes these fish can remain pregnant without a male around and just keep giving birth to babies.”
The scientists recreated typical habitats where guppies could be found, and then followed them. They put the fish into outdoor containers and checked on them again months later to see what had happened.
Scientists found mosquitofish killed the guppies, even if only a few mosquitofish were involved.
The results confirmed the suspicions of many: that the native mosquitofish (Gambusia holbrooki) provides what scientists call “biotic resistance,” or the ability of a collection of species to resist an invasion.
Tuckett said to think about the theory of biotic resistance as an idea of higher diversity.
“So if you have more species in a habitat, they occupy all different kinds of space and niches, and that prevents species from coming in. What's interesting about this work here, is that we're showing it's not exactly you know, how many species you have. It's those species that are called strongly interacting,” Tuckett said.
He added that mosquitofish are strongly interacting fish, and super-aggressive too.
“It's one of the reasons why they've been also introduced, like the guppy, for mosquito control and just all over the world,” Tuckett said. “What they do is they actually chew the fins off of fish and eat the babies of all these fish too.”
Tuckett added that this kind of research opens the door to a better understanding of failed invasions. Rather than being unique, the “guppy-mosquito fish” system may be one of many where strongly interacting species lead to population extinction and invasion failure.
“As part of that, too, we try to find out why a lot of the fish don't survive in the wild,” Tuckett said. “If we can figure some of that out, maybe we can be more predictive about what fish might become established, and correctly assign the risks, the appropriate risk to those species. At the end of the day that's kind of what it's about.”
