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Summary and Conclusions

Summary and Conclusions

(p.293) Eight Summary and Conclusions
Land Bridges
Alan Graham
University of Chicago Press

This chapter re-emphasizes the complexity of past and present plant and animal distributions, the need for a multiplicity of approaches, interpretations made in the broadest contexts, and the need for data bases of verified plant fossils and of propagules transported by various migratory birds and the survival of these propagules at the target areas. Conceptual issues like geofloras, the madro-tethyan hypothesis, boreotropical vegetation, slightly earlier and more intense glaciation in western than eastern Beringia, initial human migrants following an inland and/or coastal route, and when in different areas they began significantly modifying the biota use for reconstructing paleocommunities and environments need to be monitored. Climate change may be more important than previously thought in island biogeography theory with the implication that continental islands of once-fragmented land bridges, as well as the size and distance of volcanic ones from the mainland, may provide useful information on biological differentiation. Alternative avenues and diverse means of dispersal exist, climates and climatic change is a singularly important factor in regulating migration, especially for regions already in close geographic proximity, and with this perspective an improved understanding of the role of land bridges in biogeography and evolution emerges.

Keywords:   ecosystems, boreotropical, island biogeography, stability, tropics, databases, conservation strategies

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