Price 9806692 The number of species on earth depends on a balance between the production of new species and their loss through extinction. While great attention is being paid to extinction, many questions about the way in which species form remain unresolved. Ernst Mayr drew attention to the value of studying so-called ring species. Ring species consist of a chain of populations encircling a geographical barrier. At one point in the ring two populations meet but do not interbreed. Because the reproductively isolated populations are very closely related, they offer a model system in which to examine the process of speciation. Ring species are rare, requiring a special arrangement of geography and history. Dr. Price has identified a probable ring species and will conduct research to investigate its formation. The species being studied is a small passerine bird for which song appears to be the main trait used in species recognition. Song variation and recognition of songs are being studied around the ring in order to understand how reproductive isolation has arisen at its ends. Studies of DNA variation across the populations are being used to ask to what extent they are still connected by levels of gene flow, and to trace historical patterns of range expansion and fragmentation. This approach should enable Dr. Price to trace a complete continuum from within-population variation up to reproductively isolated sympatric species. A thorough understanding of that continuum is crucial to understanding speciation, and ultimately what controls species number.
