On the number of stable equilibria and the simultaneous stability of fixation and polymorphism in two-locus models.

It is shown that in simple symmetric two-locus, two-allele constant fitness models the bound of four simultaneously stable equilibria previously accepted for general two-locus, two-allele models is exceeded. Situations with five and six stable equilibria are exhibited. These involve four chromosomal fixations and either one or two polymorphic stable equilibria.