Return of the species



1. Wolves. Endangered?
2. Wolves on the rebound
3. History of extermination
4. Midwestern wolves

5. Causes of extinction
6. Trumpeter swan sings
Wisdom of reintroductions
8. Helping the plants
9. Moving the plants

10. Genetics movement
11.House flies!



  But will it really work?

Potential prey of a mosquitofish.
Photo by John VanDyk, Department of Entomology, Iowa State University

Craig Stockwell and Margaret Mulvey, ecologists at the University of Georgia's Savannah River Ecological Laboratory, looked at the issue by examining populations of mosquito fish that had been moved 60 years before to control whining arthropods. According to records, 900 young fish hit the road in that move (far more animals than are involved in the reintroduction of larger species). "We expected that most rare alleles would be retained," Stockwell says. "But a good portion of them were lost in the newly-founded population."

This was all the more surprising because the female fish retain some sperm in their reproductive tracts, meaning some males that didn't make the trip were probably represented among the new population.

What are the implications of this research for species reintroductions? Stockwell notes that "if you grab a handful of animals, by chance, you are not going to sample all the genetic variability in the parent population." He recommends the use of screening and surveys to monitor genetic diversity when fish are moved to reestablish populations. How do we know that reintroductions will work?To survive for long, reintroduced species must have enough geneticvariability so they can adaptand survive as conditions change.

But such monitoring would be much easier with relatively numerous fish than with, say, whooping cranes, whose wild population, after decades of preservation and reintroduction work, totals all of about 150. Stockwell acknowledges the sampling he recommends would be difficult, dangerous and expensive in many cases.

What can go wrong?
These are some of the key dangers of moving small numbers of organisms to a new location for purposes of reintroduction:

  • Inbreeding
  • Hybridization, or interbreeding, with local species
  • Failure to survive
Theoretically, there's also the danger that the newly-established population may carve its own evolutionary path -- form a new species or subspecies. (Remember, it's the isolation of small groups that often precedes the creation of a new species in nature.) "Evolution can occur very rapidly in a new population," Stockwell says. But he adds that "nobody has documented a speciation event [the formation of a new species] due to translocation" (moving a population to a new place).

Want to know what house flies are good for? Yes, a thousand times, Yes!


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