Evolution of The Number of Sexes
Most diploid organisms have two sexes, but some have three or more. For instance, among ciliates in which mating occurs by the contact of two diploid cells and the subsequent exchange of haploid genome, cells are grouped into several mating types (or sexes) so that mating occurs only between cells of different sexes (sonneborn, 1939). Stylonychia spp. have as many as 48 sexes (Ammermann, 1965). Other organisms with three or more sexes are fungi, in which mating occurs by the fusion of isogamous haploid gametes (Raper, 1966).
KeywordsDiploid Cell Mating Period Central Equilibrium Dominant Eigenvalue Random Drift
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