dioicas

Dioicas is a botanical term used to describe plants in which individuals are exclusively male or exclusively female, i.e., species that are dioecious. In such populations there are separate male and female plants; males produce pollen, females produce ovules that develop into seeds after fertilization. This contrasts with monoecious species, where a single plant bears both male and female flowers, and with hermaphroditic species, where flowers contain both sex organs.

In dioicas, reproduction requires cross-pollination between individuals; self-fertilization is not possible within a single plant. Pollination is typically via wind or animals, depending on the species. The male-to-female ratio can vary, but many populations are close to equal.

Dioecy has evolved multiple times across angiosperms and some gymnosperms; dioecious species are a minority of flowering plants. Advantages include avoidance of selfing and maintenance of genetic diversity; costs include the need for two sexes, and skewed sex ratios can limit population growth. Environmental conditions and genetics influence sex expression in some taxa.

Examples include Ginkgo biloba, willows (Salix), poplars (Populus), asparagus (Asparagus officinalis), and Cannabis sativa. In agriculture and horticulture, dioecy affects crop management; many crops require planting both sexes or selecting male and female cultivars for fruit or seed production. In bryophytes, a related term, dioicous, describes mosses and liverworts with separate male and female gametophytes.

The form dioicas is found in some languages or older botanical texts; in English, the standard terms are dioecious species or plants are dioecious.