Iridaceae () is a family of plants in order Asparagales, taking its name from the irises. It has a nearly global distribution, with 69 accepted genera with a total of about 2500 species. It includes a number of economically important cultivated plants, such as species of Freesia, Gladiolus, and Crocus, as well as the crop saffron.
Members of this family are perennial plants, with a bulb, corm or rhizome. The plants grow erect, and have leaves that are generally grass-like, with a sharp central fold. Some examples of members of this family are the blue flag and yellow flag.
Etymology
The family name comes from the genus Iris, the family's largest and best-known genus in Europe. This genus dates from 1753, when it was coined by Swedish botanist, Carl Linnaeus. Its name derives from the Greek goddess, Iris, who carried messages from Olympus to earth along a rainbow, whose colors were seen by Linnaeus in the multi-hued petals of many of the species.
Taxonomy
Iridaceae is currently recognized as nested in the Asparagales order but was traditionally grouped with Liliales. Iridaceae was previously divided into four subfamilies but results from phylogenetic analysis suggested an additional three could be recognized. Molecular clock analyses have supported initial cladogenesis in Antarctica-Australasia 82 million years ago (mya) from a Doryanthaceae ancestor. The distribution of subfamilies in Iridaceae is considered to be phylogenetically structured, with all neotropical species belonging to one subfamily, the Irdoideae. The genus Diplarreneae is sister to the rest of the subfamily and is unique to Iridoideae in having zygomorphic flowers and stamens with unequal height. Tigridieae are distinguished for their large bulbous rootstock and plicate, deciduous leaves.
Ecology
Members of Iridaceae occur in a great variety of habitats. Gladiolus gueinzii occurs on the seashore just above the high tide mark within reach of the spray. Most species are adapted to seasonal climates that have a pronounced dry or cold period unfavorable for plant growth and during which the plants are dormant. As a result, most species are deciduous. Evergreen species are restricted to subtropical forests or savanna, temperate grasslands and perennially moist fynbos. A few species grow in marshes or along streams and some even grow only in the spray of seasonal waterfalls.
Members of the subfamilies Crocoideae and Nivenioideae first began cladogenesis in arid conditions in Africa, accelerating for Crocoideae as the Mediterranean climate emerged in Southern Africa.
The aerial portions of deciduous species die back when the bulb or corm enters dormancy. The plants thus survive periods that are unfavorable for growth by retreating underground. This is particularly useful in grasslands and fynbos, which are adapted to regular burning in the dry season. At this time the plants are dormant and their bulbs or corms are able to survive the heat of the fires underground. Veld fires clear the soil surface of competing vegetation, as well as fertilize it with ash. With the arrival of the first rains, the dormant corms are ready to burst into growth, sending up flowers and stems before they can be shaded out by other vegetation. Many grassland and fynbos irids flower best after fires and some fynbos species will only flower in the season after a fire.
The majority of Iridaceae are pollinated by Hymenoptera, frequently by single species or a small group of species. These tight relationships found in individual species of Iridaceae, especially in Gladiolus, were the inspiration for the description of pollinator syndromes. Pollinators include various species of solitary bees, as well as sunbirds, long-proboscid flies (such as Moegistorhynchus longirostris), butterflies, and night moths. Flowers may present nectar and pollen rewards to visitors, but some genera may only offer nectar such as in Gladious and Watsonia. Members of Iridoideae and Nivenioideae have radially symmetric trumpet-like flowers that secrete large amounts of nectar. This novel morphology enabled additional floral complexity and rapid evolution of pollinator relationships, as frequently as a new relationship over 5 speciations.