Host species' extinction could make parasites jump onto alternative hosts

Washington, June 2 (ANI): In a new study, scientists have determined that when host species go extinct, their parasites could switch onto alternative hosts which in turn could increase the rate of emerging pathogens for humans, domesticated animals and plants.

The study was carried out by North Carolina State University biologist Rob Dunn and colleagues.

They examine the concept of coextinction, or the domino effect of extinctions caused by species loss.

For example, each fig species tends to be pollinated by a single fig wasp such that the loss of one should result in the loss of the other.

Mathematical models suggest that coextinctions due to the actions of humans are very common. Yet, counter intuitively, there have been few reported cases of coextinction in the scientific literature.

"What we know about coextinctions presents a kind of paradox. The models suggest thousands of coextinctions have already occurred and that hundreds of thousands may be on the horizon. Yet we have observed few such events," Dunn said.

"So, we're not sure if all of these coextinctions are happening and not being tracked, or if parasites and mutualist species are better able to switch partners than we give them credit for, or something in between. Maybe some of the specialized relationships like between the figs and fig wasps - aren't so specialized," he added.

There is something even scarier about the consequences of coextinction.

"There is a distinct possibility that declines in host species could drive parasite species to switch onto alternative hosts, which in turn could escalate the rate of emerging pathogens and parasites both for humans and our domesticated animals and plants," Dunn said.

"Put simply, when a host becomes rare, its parasites and mutualists have two choices: jump ship to another host or go extinct. Either situation is a problem," he added.

Dunn noted that the regions where new human diseases, such as bird flu, are emerging coincide with the regions where the most mammal and bird species are endangered.

"We have long talked about the negative consequences of the endangerment of the species we love, but getting left with their parasites is a consequence no one bargained for," he said. (ANI)