Catching Evolution Red-Handed
(Nathan Bailey 9/3/2012)
Hermaphroditic worms. Human intelligence. Insect societies. Carnivorous plants. Evolutionary biologists are obsessed with understanding why there is such a bewildering diversity of species, forms and behaviours in the natural world.
One of the challenges we face is that evolution tends to proceed at a glacially slow pace. Changes in the genetic code that affect an organism's appearance or behaviour are not everyday events, and when they do happen they usually only cause subtle variations that are difficult to detect and might not persist across generations. So even though evolution continually putters along right under our noses, we are unlikely to witness in our lifetimes the types of dramatic transitions that generate new forms or species in the wild.
However, an unassuming field cricket from Hawaii recently defied all the odds.
Biologists at St. Andrews are studying the genetics of a wild population of the cricket Teleogryllus oceanicus that recently experienced an extraordinary evolutionary event. Male crickets chirp to attract females, but over the course of about 20-30 generations a mutant variety of silent male crickets has arisen and spread in a population on Hawaii. Being silent protects them from attack by deadly parasitoid flies that are attracted to their song. The shift from singing to silent male crickets on Hawaii represents one of the fastest rates of evolution ever documented in the wild, but the genetic mutation responsible for this rapid change remains elusive.
Why is it important to understand what genetic changes alter the appearance or behavior of animals?
When a mutation does become established in a population, it can trigger a cascade of changes that affect how genes are regulated, how the physical features of an organism develop, and how individuals behave. Understanding what parts of the genome those mutations occur in and how they propagate gives us a clearer picture of how evolution by natural selection changes the way organisms develop, look and behave, and ultimately how new biological diversity is generated.
Audio: listen to male crickets calling