PALEOBIOGEOGRAPHY : TRACKING THE COEVOLUTION OF THE EARTH AND ITS BIOTA

1 BIOGEOGRAPHY is a scientific discipline with a rich intellectual heritage extending back at least to the 18th century, and the discipline figured prominently in the development of ideas on evolution (see review in Lieberman, 2000). During the development of ideas on evolution, an important analogy was recognized between patterns of change in organisms across geographic space and patterns of change in organisms through geological time. For instance, Alfred Russel Wallace argued that, “If we now consider the geographical distribution of animals and plants upon the Earth, we shall find all the facts beautifully in accordance with, and readily explained by, the present hypothesis (Evolution). A country having species, genera, and whole families peculiar to it, will be the necessary result of its having been isolated for a long period.The phenomena of geological distribution are exactly analogous to those of geography. Closely related species are found associated in the same beds, and the change from species to species appears to have been as gradual in time as in space. ” (Wallace, 1855 in Brooks, 1984, p. 75). Charles Darwin felt it was important enough to remark in the very introduction to his On the Origin of Species that, “. when on board H.M.S. ‘Beagle,’ as naturalist, I was much struck with certain facts in the distribution of the organic beings inhabiting South America, and in the geological relations of the present to the past inhabitants of that continent. These facts, as will be seen in the latter chapters of this volume, seemed to throw some light on the origin of species-that mystery of mysteries” (Darwin, 1859, p. 1). The fact that Wallace and Darwin recognized the connection between geographic differentiation and macroevolutionary divergence probably ultimately derives from their understanding of the work of Charles Lyell (1832) and his famous dictum, “As in space, so in time”. It also ties together, in an important way, the sciences of biogeography and paleontology, and it is clear that there is a long-lasting connection between these two fields, realized in the discipline of paleobiogeography. This long history, however, is not an impediment and does not prevent paleobiogeography or biogeography (and of course paleontology) from remaining relevant and topical to this day. Results from biogeographic and paleobiogeographic research still continue to make important contributions to the fields of evolutionary biology, geology, and conservation biology (Brooks and McLennan, 2002). This continued relevance is partly due to the development of new techniques including phylogenetic methods, molecular approaches to investigate systematic relationships, and Geographic Information Systems. The continued relevance also stems from the recognition that some of the topics early biogeographers debated are still debated today and have implications for core research paradigms. As a useful example, we note that Charles Lyell (1832) lamented the loss of biodiversity caused by the human introduction of exotic species and considered it partly a problem of biogeography. Today, the biodiversity crisis continues unabated, and it is recognized that it is caused at least in part by invasive species; it is also currently recognized that the impact of invasive species is a topic that can usefully be approached as a biogeographic and paleobiogeographic phenomenon (Rode and Lieberman, 2004). Paleobiogeography (and its closely allied intellectual cousin biogeography) is an intriguing PALEOBIOGEOGRAPHY: TRACKING THE COEVOLUTION OF THE EARTH AND ITS BIOTA