Trioecy

Trioecy (or subdioecy) is an extremely rare reproductive system characterized by the coexistence of males, females, and hermaphrodites. It has been found in both plants and animals. Trioecy has been estimated to occur in about 3.6% of flowering plants. Although most reports of trioecy are misinterpretions of gynodioecy.
Evolution of trioecy.
Trioecy is usually viewed as evolutionarily unstable. Its exact stability over evolution is unclear, but many speculate it is a transient state. Trioecy is often associated with evolutionary transitioning from Gynodioecy to Dioecy. Other studies support show that trioecious populations originated from gonochoristic ancestors which were invaded by a mutant selfing hermaphrodite, creating a trioecious population.
Species that exhibit trioecy.
The following species have been observed to exhibit a trioecious breeding system.
Plants.
Trioecy, is a relatively common sexual system in plants. The following list gives some examples: