What are the characteristics of an island?

Just off Iceland in 1963, a brand new island formed, Surtsey, and the arrival of new life on this volcanic land has been well documented.

On the more general front, when a new population arrives on a land, then the main source of genetic information is restricted to those few individuals.

So the arrival of new varieties or the development of a new species is a normal circumstance.

Had those same individuals arrived on a land where many of their species already existed, then their diversity, if any, would be swamped by the existing population.

Indeed, if the new arrivals were different from the existing population, then they may well be shunned or isolated.

Once these populations adapt to the environment, however, speciation rapidly occurs.