Cane Toad: “Evolution” in Action?

BBC News reports on a “runaway evolutionary effect” that is helping invasive cane toads take over an ecological niche in Australia. James Cook University scientist Ben Phillips made the discovery by tracking cane toads with radio tags, letting his team determine which toads headed away from the release site most quickly.

Phillips had collected the toads from several locations in Australia: some close to the center of where cane toads had spread, and others from near the edge of cane toad territory. As it turns out, those collected from the edge traveled farthest and fastest from a release point, indicating that they carried a gene allowing them to travel quickly. Moreover, since the toads mate with toads nearby, the fast-traveling toads on the frontier perpetuate their quickness, while the slow-moving toads near the center of toad territory maintain their slower speed.

To confirm this hypothesis, Phillips bred the toads he had previously collected, then set up the same experiment with the new generation, again using radio tags. Unsurprisingly, toads whose parents were fast movers won the race.

The research is an interesting demonstration of the workings of genetics and heredity, but does it show that “evolution” is at work? The fast-moving toads have larger and stronger legs, enabling them to jump farther and faster, and hence invade the continent more quickly. But they remain cane toads; even if, at some point, these fast-moving cane toads are unable to breed with the slow-moving toads and they become separate species, the toads are not evolving into a “higher” species with increased genetic information. Rather, each population would have lost genetic information (e.g., the genes for big, strong legs in the slow-moving population and for disease and parasite resistance, as postulated in the article, for the fast-moving toads). Far from a case of evolution in action, the great toad race shows how selective forces run the opposite direction from the speculations of molecules-to-man evolution.