High selfing can result in high levels of homozygosity. Hybrids are not always sterile. Black oak found in moist bottm lands, and Scarlet oak found in dry upland lands are ecolologically-isolated but not incapable of introgressive hybridization. Iris fulva found in shaded dry areas found in Louisiana up along edges of the Mississippi river to Arkansas and I. hexagona found in marshes from Louisiana to South Carolina are capable of introgressive hybridization in regions where these two species overlap. These two species appear to have been distinct up to 12 million years ago.
Hybrids are widespread, fertile and ancient.
Even when plants hybridize and hybrid offspring are sterile, these organism have the potential to restore their fertility through a process called polyploidy. Remaining Topics Allopatric, Sympatric, and Parapatric Speciation Refer to handouts and discussions from lecture.