The Great American Biotic Interchange: Dispersals, Tectonics, Climate, Sea Level and Holding Pens

The biotic and geologic dynamics of the Great American Biotic Interchange are reviewed and revised. Information on the Marine Isotope Stage chronology, sea level changes as well as Pliocene and Pleistocene vegetation changes in Central and northern South America add to a discussion of the role of climate in facilitating trans-isthmian exchanges. Trans-isthmian land mammal exchanges during the Pleistocene glacial intervals appear to have been promoted by the development of diverse non-tropical ecologies

Perceptual Principles for Effective Visualizations

This paper presents a number of perceptual principles for the construction of effective visualizations. Principles are demonstrated in example images. In the example images, value is represented by color, height, position, or opacity. Other representation parameters are certainly possible, but are not covered here. Additional cues which can enhance comprehension are also spotlighted