A plant is dioecious if male and female forms exist in separate individuals.
Indeed, the word translates roughly to "two houses", which makes a useful mnemonic
. About 6% of the world's flowering plants (i.e. angiosperms
) are dioecious. Dioecy is believed to convey an evolutionary advantage
to a species
because it helps prevent inbreeding
; a dioecious plant cannot fertilize itself
. Thus, a dioecious population can avoid inbreeding depression
, the exposure of harmful mutations
Despite this hypothesized advantage, dioecy is less frequent than one would be led to believe.
See also: gynodioecious, monoecious.
Reference: Heilbuth JC. 2000. American Naturalist 156: 221-241.