Darwin’s Finches: Analysis of Beak Morphological Changes During Evolution

INTRODUCTION

Finches of the Galápagos Islands were first described by Charles Darwin during his voyage on the HMS Beagle in 1835. Since then, through the subsequent work of many biologists, Darwin’s finches have become a classic textbook example of many important processes in evolution. Today, this group of birds continues to be a significant source of information on such processes as speciation, niche partitioning, morphological adaptation, and species ecology. The approximately 14 species of Darwin’s finches are closely related to one another and display a remarkable degree of diversity in bill shapes and sizes that are adapted for different food sources (e.g., seeds, insects, and even young leaves or blood from sea birds) in an otherwise scarce environment. For example, the deep and wide bills of the Ground Finches, one of the subgroups of Darwin’s finches, are used to feed on seeds, whereas the Cactus Finches use their elongated and narrow bills to probe cactus fruit and flowers. These differences in bill shapes are not due to their differential usage or other external factors; rather, the differences are genetically and developmentally regulated and can be observed and studied during embryogenesis. Therefore, Darwin’s finches are becoming a very useful non-model animal and avian system in which to investigate the molecular basis of morphological changes during evolution.