The ‘species concept’ – the definition of what constitutes a distinct species – has been a headache for biologists for at least 70 years. Recent genetic studies in natural populations have led to a revolution in the understanding of biodiversity and speciation. Species are demonstrably continuous with subspecies and varieties in nature, and intermediates in the speciation process are all around us. I will illustrate my talk with examples such as butterflies, birds and even whales.

Lecture given on 30 November 2006.