NATR 320 Lecture Notes - Lecture 28: Defaunation, Insular Biogeography, Biogeography
6 Oct 2020
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Island"s species richness is determined by 3 distinct processes: immigration, extinction, evolution. Every species found on an island either immigrated to it from elsewhere, or evolved in place. They can be lost when all individuals of the species die or leave local extinction. Simply the # of insect species that disappear from the island per unit time. Simulation p = 20 (insect species) Extinction rates increase as the number of species on the island approaches the number of species in the mainland pool (upward curve) Intersection of the 2 curves (when immigration rate = extinction rate) predicts the equilibrium number of species s* The intersection of the 2 curves also predicts the rate at which new species replace extinct species, reflecting the dynamic nature of equilibrium on the island. There is one theoretical value of s*, but composition of s* is always changing. Changes bc of equilibrium turnover rate t*
