Monday, November 2, 2015

Watching species evolve, one after another

apple maggot (Rhagoletis pomonella) by Joseph Berger,

The apple maggot (Rhagoletis pomonella), a fruit fly native to the U.S., is curious, as apples are not native to the U.S. Before the apple maggot started feeding on the apple in the 1850s, they would feed on native hawthorns and their life cycle was tied to the life cycle of the hawthorn.  Interestingly, there are wasp parasitoids which will infest larval apple maggot,s and so their life cycle is also tied into the same time frame.  As some of the apple maggots have displayed a preference for the apple trees over the hawthorns, very slowly, their life cycle has shifted to match the fruiting cycle of the apples.  Scientists have been watching the apple maggot and have seen how the feeding and mating habits have changed in the apple tree feeders, thus splitting the apple maggots into two different species based on their apple or hawthorn preferences.  As the life cycle of the maggots is changing, the parasitoid wasps are also splitting based on their hosts' preferences.  This supports the "sequential speciation" evolutionary process, stating that adaption and speciation doesn't occur independently and is more of a cascade of new species that arise as new niche opportunities are introduced.

apple maggot (Rhagoletis pomonella) by Whitney Cranshaw,

Source Article: Caught in the act: New wasp species emerging
Apple Maggot Images: Rhagoletis pomonella