A wasp's sting might explain it all.
Marty Condon, professor of biology at Cornell College, has been studying flies in the tropics for years, and in a paper published in Science this week, she reports evidence that there is more to a fly's ecological niche than where it lives and what it eats--you have to look at what eats the fly, as well.
In a previous Science paper, Condon and her co-researchers found that there were far more species of flies feeding on tropical flowers than expected. It was counter-intuitive, Condon said, to see so many species of flies filling what appeared to be the same ecological niche.
Her latest research, which included students from Cornell College, showed that the parasitic wasps that attack the flies might help to explain the number of different species. There are 14 species of flies, and 14 species of wasps. The flies live off the plants, and the wasps lay their eggs in the flies. When the wasps' young mature, they emerge from the flies. The flies, unsurprisingly, don't survive that process.
What Condon and her team found was that most of the wasps are extreme specialists--their offspring will only survive in one species of fly. If eggs are laid in other species, the offspring die.
"The prey is lethal to the predator," she said.
The flies--all 14 species--look essentially identical, and so do the wasps. What Condon and the other researchers originally thought was a very strange case of niches overlapping ended up broadening the definition of the niche, once they discovered the interaction between the flies and the wasps.
"It's not just a two-dimensional jigsaw puzzle," Condon said. "There are many dimensions, and we've found two more."
Surprising findings like these are part of the reason Condon and other evolutionary biologists study in the tropics-- the most species-rich zone in the world. Most tropical species haven't even been named, let alone studied in depth. Results like the ones published in Science expand scientists' understanding of that diversity, Condon said, and they also show that much of the ecological diversity in the tropics still remains to be discovered.
Condon was the lead author on the paper, which included co-authors who collaborated on the work. Coauthors included Andrew Forbes at the University of Iowa, Sonja Scheffer and Matt Lewis from the USDA Systematic Entomology Laboratory, Robert Wharton from Texas A&M University, and Dean Adams from Iowa State University.
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