Genetic Applications in Biogeography

The study of the distribution of life, of the biosphere and its respective processes, both past and present, is known as biogeography (see texts by Brown and Lomolino, 1998; Cox and Moore, 2000; MacDonald, 2003). Current biogeographical processes, biotic and abiotic, are often evaluated using ecological research methods. However, there are also historical events and evolutionary processes at play, shaping the biosphere over long time periods. Thus, it is not surprising that biogeographers draw upon methodologies from geography and the Earth sciences, including paleoclimatology, geology, and geomorphology, plus biological approaches such as paleontology and other evolutionary disciplines. A recent additional trend is the recognition that distribution data of organisms and an understanding of biogeographical processes are basic inputs needed to make biodiversity conservation decisions (Young et al., 2004). The apparent simplicity of the definition of biogeography masks the complexity of the discipline (Crisci et al., 2003). Many recent authors (e.g., Avise, 2000; Crisci et al., 2003; Price, 2003) have stressed the need for more interaction and integration among the various biogeographical approaches. This issue of Physical Geography is intended to highlight some of the work being done by biogeographers that integrate traditional methods and genetic analysis. This is particularly timely as the last two decades have seen major advances in the knowledge of how organismal molecular biology functions to create the physiological and reproductive characteristics of species and their respective populations (Stearns and Magwene, 2003; Zhang and Hewitt, 2003). The theme issue begins with several research papers that combine both ecological biogeography and genetic analysis. The first paper by Enright et al. examines the role of climate and geomorphic history in shaping the present pattern of distribution of Banksia hookeriana in southwestern Australia. The paper by Parker and Jorgensen provides an overview of the use of selected molecular markers, utilizing examples from their own genetically based biogeographic research. They stress the importance of studying genetic variation at different spatial scales, drawing on work completed on genetic variation in sand pine (Pinus clausa), an endemic species virtually restricted to Florida. As in the Enright et al. paper, Parker and Jorgensen also show how a combination of genetic analysis and additional evidence of past environments can enrich our understanding of the paleoecology of a region.