Among all animals, say Mendelson and Shaw, only the African cichlid fish spawns new species more quickly.
While early biologists based their estimates of speciation rates on morphological, or structural characteristics, Mendelson says, scientists today are more likely to use genetic data to come up with estimates.
Closely related species of Laupala have no clear morphological differences, Mendelson says. They are similar in appearance, they have similar diets, and they live in similar habitats. Members of closely related species possess no physiological differences that would prevent them from interbreeding.
But closely related species are distinguished by subtle differences in the pulse rates of male crickets' simple courtship songs, a secondary sexual trait that plays a large role in mate attraction.
Among all species of Laupala, pulse rates of male courtship songs range from .5 to 4.2 pulses per second. Female crickets can detect these differences, says Mendelson, and they tend to hop towards the pulse rate of their own species and to reject songs sung at a different tempo.
The Laupala mating ritual lasts up to eight hours and consists of eight to 15 transfers of spermatophores between male and female, says Mendelson. The final spermatophore, or capsule, to be transferred contains the actual sperm cells that impregnate the female.
As a species begins to split into two separate species, says Mendelson, "the songs appear to be the first characteristic that changes."
During the early part of the speciation process, says Mendelson, crickets of the two emerging lines interbreed. After a point, however, members of the two distinct species no longer mate with each other.
This discovery led Mendelson to name one of her graduate-school papers after the pop song "Will You Still Love Me Tomorrow?" The Nature article was given the more conserv