Box 000, Washington D.C. 00000
March 8, 2012
Role of ecological and environmental differences in natural selection of Geospiza difficilis in Darwin and Santiago Islands Introduction
Few places are better suited for the study of biodiversity and evolution than the Galapagos Islands, home to Darwin’s finches. Free of most anthropogenic influences, these islands provide researchers with a natural, undisturbed environment in which to study the functions of natural selection as Darwin did 177 years ago (Grant, 2003). Since then, Darwin’s finches have been studied extensively for the insight they provide into the evolutionary questions of adaptation and speciation. However, the complex role of ecological and environmental factors (including competitive exclusion, cultural/behavioral differences, disturbances, reproductive barriers, etc.) in the process of divergence is still not well understood. Using the finch species Geospiza difficilis and the islands Darwin and Santiago as the subjects of our study, we will address these questions, simultaneously filling in the gaps left in previous studies of these islands and species. We are using the BIRDD database (Price, 1998) as the basis for our analysis of previously collected data concerning Geospiza difficilis on Darwin and Santiago. Analysis of the data indicated a significant correlation between beak size and island habitat (see table 1) suggesting island dissimilarity as a major influence in natural selection. Character displacement (i.e. divergence in body structure in allopatric populations as a result of niche competition) is one possible explanation for this variation (Campbell, 2010). Gaps in the data provided and collection dates limited our ability to analyze specific characteristics (body length and beak width in particular). Information concerning beak height and length for Darwin and Santiago Islands separately is found on tables 2 and 3. Collecting...