Evol Ecol Res 6: 115-124 (2004)     Full PDF if your library subscribes.

New theory of insular evolution: unifying the loss of dispersability and body-mass change

Ido Filin* and Yaron Ziv

Department of Life Sciences, Ben-Gurion University, Beer Sheva 84105, Israel

Author to whom all correspondence should be addressed.
e-mail: filin@bgumail.bgu.ac.il

ABSTRACT

Loss of dispersability and body-mass change (dwarfism and gigantism) are two common phenomena on islands. Based on Skellam’s (1951) theory of dispersal, we suggest a new theory of insular evolution that connects isolation and island size to dispersability and body mass. Using optimal body mass considerations and allometric scaling laws, our new theory predicts: (1) expected direction of body-mass change depends on the relationship between body mass and dispersability; (2) rate of body-mass change (i.e. evolution rate) is inversely proportional to the island’s area; (3) the magnitude of the shift in optimal body mass, either towards gigantism or dwarfism, is also inversely proportional to the island’s area. Available empirical data support our predictions. Our theory provides new, consistent and testable predictions that connect several known observations on islands.

Keywords: allometry, dispersability, dwarfism, gigantism, insular evolution, island size, optimal body mass.

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