Gynodioecy
[2] Gynodioecy occurs as a result of transmission of nuclear (nuclear male sterility) or, more commonly,[3] extra-nuclear (e.g. cytoplasmic male sterility) mutated alleles, which prevents pollen production, while keeping the female reproductive parts intact; other members of the species population don't inherit the mutated alleles, thus remaining hermaphrodites.
Some notable taxa that exhibit a gynodioecious mating system include Beta vulgaris (wild beet), Lobelia siphilitica, Silene, and Lamiaceae.
A high rate of self-pollination in a population facilitates the maintenance of gynodioecy by increasing the inbreeding costs for hermaphrodites.
The first scenario, known as the balancing selection theory, considers the genetic factors that control gynodioecy over long evolutionary time scales.
The second scenario, known as epidemic dynamics, involves the arrival and loss of new cytoplasmic male sterility genes in new populations.
[6] Gynodioecy is determined as a result of a genetic mutation that stops a plant from producing pollen, but still allows normal female reproductive features.
Male sterility genes cause plants to grow anthers that are stunted or withered and as a result, do not produce pollen.
The farmers deliberately make use of the gynodioecy that develops in the maize, resulting in a population of male-sterile and female-fertile individuals.
The reason for this variation in the rarity of gynodioecy stems from certain phenotypic traits or ecological factors that promote and favor the presence of female plants in a population.
For example, a herbaceous growth form is much more highly favored in gynodioecious species of Lamiaceae when compared with woody lineages.
Inbreeding depression was found to be an important factor in the maintenance of gynodioecy in an endemic Hawaiian shrub Schiedea adamantis occurring in a single population in Diamond Head Crater Oahu.
[15] Inbreeding depression, due to selfing in the hermaphrodites, was considered to be caused by the presence of many mutations of small effect.
