2000 The Society for the Study of Evolution. All rights reserved.
Evolution, 54(2), 2000, pp. 387396
GENETIC AND PHYLOGENETIC CONSEQUENCES OF ISLAND BIOGEOGRAPHY
KEVIN P. JOHNSON,1 FREDERICK R. ADLER, AND JOSHUA L. CHERRY
Department of Biology, University of Utah, Salt Lake City, Utah 84112-0840
Abstract. Island biogeography theory predicts that the number of species on an island should increase with island
size and decrease with island distance to the mainland. These predictions are generally well supported in comparative
and experimental studies. These ecological, equilibrium predictions arise as a result of colonization and extinction
processes. Because colonization and extinction are also important processes in evolution, we develop methods to test
evolutionary predictions of island biogeography. We derive a population genetic model of island biogeography that
incorporates island colonization, migration of individuals from the mainland, and extinction of island populations.
The model provides a means of estimating the rates of migration and extinction from population genetic data. This
model predicts that within an island population the distribution of genetic divergences with respect to the mainland
source population should be bimodal, with much of the divergence dating to the colonization event. Across islands,
this model predicts that populations on large islands should be on average more genetically divergent from mainland
source populations than those on small islands. Likewise, populations on distant islands should be more divergent
than those on close islands. Published observations of a larger proportion of endemic species on large and distant
islands support these predictions.