New species evolves, according to a report in BBC News, 9 June 2004. Scientists at the University of Arizona have been studying breeding patterns in fruit flies and believe they are witnessing the birth of a new species. In the Arizona desert there are two groups of fruit flies, named Drosophila mojavensis and Drosophila arizonae, which don’t interbreed even though their geographical ranges overlap. Biologists were able to get them to crossbreed in the laboratory but found male offspring from a cross between D. Arizonae females and D. Mojavensis males were sterile. The scientists who carried out the breeding experiments claim that the limited capacity for interbreeding is a sign that the two groups of flies are about to become completely different species. They also claim genetic change involved must be recent, because the male hybrid sterility depends on the mother’s genes. BBC News Science Editor David Whitehouse commented: “In fruit flies there are several examples of mutant genes that prevent different species from breeding but scientists do not know if they are the cause or the consequence of speciation.”


Editorial Comment: Species are generally defined as groups of organisms that reproduce with one another but don’t breed with other organisms. Therefore, if these flies do split up into two separate groups that don’t interbreed, technically they will have formed new species. However, they will not have evolved. All that is happening here is a large and varied group of flies is splitting into two smaller less varied groups of flies, because of a mutant gene. This is degeneration, not evolution. It’s a good reminder that speciation is not evolution. (Ref. species, flies, mutations)