There's More Than One Way to Silence a Cricket: Co-evolution of Crickets Who Lost Their Chirp

Source: Cell Press
Date: May 29, 2014
http://www.sciencedaily.com/releases/2014/05/140529142442.htm

Summary

Crickets, usually most recognizable from their distinct chirping sounds males make with their wings to attract females, have gone silent on the islands of Hawaii. The silence is an adaptation for the quiet males to use to avoid parasitoid flies, which are attracted the the cricket song. The fly larvae burrow into the cricket, and kill the cricket within a week or so. These quiet crickets are able to avoid the flies, and still manage to mate with female crickets by positioning themselves near male crickets that are able to produce the cricket song and attract female mates.

At first, scientists had thought that a group of these silent crickets had traveled or migrated from one island in Hawaii to another. After further research, scientists have noticed obvious differences in the wings of the silent crickets from the different islands Oahu and Kauai. The silent wing mutation was traced back to a sex-linked gene. Another scientist performed a genome-wide scan which showed that the genes responsible for the traits were linked to different genetic markers for the two silent cricket populations. This has led scientists to believe that the trait for the silent crickets rose in two different islands independently, but at the same time. This is an example of convergent evolution.

Relevance

This relates to our topic about evolution. If the flies were not present, the normal chirping crickets would possess traits that would be more favorable to the environment, as the crickets would be able to find mates more easily than the silent ones.With the presence of the flies, the silent crickets are more likely to survive, so they will be able to reproduce and pass on the gene. But, since the silent crickets depend on the song-producing crickets, each new generation of crickets must have a few chirping crickets for both different types of crickets to survive.

This also relates to our study of genetics. Crickets do not have Y chromosomes to determine sex. Two X chromosomes (XX) would be a female, and one X chromosome would be a male. Because this mutation is sex-linked, it would explain why the trait for silent-wings spread rapidly. It would only require one copy of the silent wing gene to be displayed in the cricket's phenotype.