Evolution – an interviewer’s favourite talking point

Interviews will soon be upon us! But fear not, as you are well prepared having done several practice interviews, refreshed yourself on all your summer reading, and stayed up to date with all the interesting science developments that have occurred this autumn? Right?

If not, let me share one fascinating nugget that should be easy to bring into the discussion. It concerns a recent development in the field of evolution, which is always a likely topic in any biological or natural sciences interview process. Furthermore it concerns research relating to Darwin’s own Galapagos finches…

The story starts with the arrival 36 years ago of a strange bird to a remote island in the Galápagos archipelago and has since provided direct genetic evidence of a novel way in which new species arise.

Last week in the journal Science, researchers from Princeton University and Uppsala University in Sweden report that the newcomer belonging to one species mated with a member of another species resident on the island, giving rise to a new species that today consists of roughly 30 individuals. The study comes from work conducted on Darwin’s finches, which live on the Galápagos Islands in the Pacific Ocean. This remote location has enabled researchers to study the evolution of biodiversity due to natural selection under pristine conditions.

In 1981, a graduate student working on Daphne Major (one of the Galápagos Islands) noticed the newcomer, a male that sang an unusual song and was much larger in body and beak size than the three resident species of birds on the island. The researchers took a blood sample and released the bird, which later bred with a resident medium ground finch of the species Geospiz fortis, initiating a new lineage. The research team followed the new “Big Bird lineage” for six generations, taking blood samples for use in genetic analysis.

In the current study, researchers analyzed DNA collected from the parent birds and their offspring over the years. The investigators discovered that the original male parent was a large cactus finch of the species Geospiza conirostris from Española island, which is more than 100 kilometers to the southeast in the archipelago. The remarkable distance meant that the male finch was not able to return home to mate with a member of his own species and so chose a mate from among the three species already on Daphne Major. This reproductive isolation is considered a critical step in the development of a new species when two separate species interbreed.

The offspring were also reproductively isolated because their song, which is used to attract mates, was unusual and failed to attract females from the resident species. The offspring also differed from the resident species in beak size and shape, which is a major cue for mate choice. As a result, the offspring mated with members of their own lineage, strengthening the development of the new species. Researchers previously assumed that the formation of a new species takes a very long time, but in the Big Bird lineage it happened in just two generations.

Such new developments as these are very important to know about – not only are they fascinating pieces of research building the foundation of an already monumental theory, but the impressiveness and scope of the research is amazing in itself (36 years in the making!). Perhaps one day one of you readers will be writing the next paper on Darwin’s finches.