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Copyright © 2003 by the author(s). Published here under license by The Resilience Alliance.

The following is the established format for referencing this article:
Robinson, D. 2003. Step function versus exponential distribution. Conservation Ecology 7(1): r9. [online] URL: http://www.consecol.org/vol7/iss1/resp9/


Response to Keitt et al 2000. "Detecting Critical Scales in Fragmented Landscapes"

Step Function versus Exponential Distribution

Donald Robinson


ESSA Technologies Ltd.

Published: March 28, 2003


An important point in the Discussion section of Keitt et al.'s (2000) article is worded in a misleading way:

"... for an organism to perceive the habitat distribution as a single, large, interconnected cluster, it must, in general, be capable of dispersing a distance of 45 km over inhospitable habitat and must have an average exponential dispersal distance of at least 15 km."

Is it not more accurate to say that the 45-km and 15-km transitions correspond to quite distinct hypotheses about dispersion behavior, rather than being different measures from the same underlying dynamic? The first value results from a step function and the second from an exponential function. The forms are quite different and thus require different analyses (Monte Carlo in the second case) to understand their attributes properly.


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LITERATURE CITED

Keitt, T., D. Urban, and B. T. Milne. 1997. Detecting critical scales in fragmented landscapes. Conservation Ecology 1(1): 4. [online] URL: http://www.consecol.org/Journal/vol1/iss1/art4


Address of Correspondent:
Donald Robinson
ESSA Technologies Ltd.
Third Floor
1765 West 8th Avenue
Vancouver, British Columbia, Canada, V6J 5C6
Phone: 604-535-1997
drobinson@essa.com



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