A research team is studying frogs in the Southeastern United…
A research team is studying frogs in the Southeastern United States. They find that in one area, male frogs produce either a low-pitched call or a high-pitched call. Females use the calls to identify mates, and show strong preferences for a particular type of call. A female who prefers a low-pitched call will mate only with males who produce that call, and will not respond to high-pitched calls. Females who prefer high-pitched calls will only mate with males who produce high-pitched calls. This is an example of . If the researchers classify the two groups as separate species, they are applying the species definition.