James Mallet: Why Species are Fuzzy: Hybridization and the Nature of Biodiversity
Professor James Mallet, University College London
The evolution of new species, or 'speciation', is often regarded by biologists as a difficult problem. This seems to me largely an artefact of a rigid and highly non-Darwinian concept of what species are. Species are regarded by many biologists even today as 'real', distinct units of biodiversity in nature, and indeed as the only real taxonomic level in nature (for instance, the genus, the population, and the subspecies are not held in such high regard). This idea was proposed along with theories of 'reproductive isolation' and the 'biological species concept' 65 years ago, around the time that Stalin, Hitler, Franco, and Mussolini ruled much of Europe. I argue that recent genetic data from natural populations tell us that 'species reality' and the concomitant difficulty of speciation have both been overstated. I will illustrate my talk with examples from butterflies, birds, and even whales. Species are demonstrably continuous with subspecies and 'varieties' in nature, and the evidence of continuous speciation processes is all around us. A return by biologists to a more pragmatic view of species and speciation, closer to Darwin's own ideas, seems now to be taking place, although there is still considerable resistance.
James Mallet is Professor of Biological Diversity, University College London. His research group investigates the evolution of Lepidoptera, chiefly the butterflies from the Amazon and Andes of South America, where the world's highest diversity of terrestrial organisms is found.