Iridaceae

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.

Iradaceae is currently recognized as nested in the Asparagales order but was traditionally grouped with Liliales.[5][6] Iradaceae was previously divided into four subfamilies but results from phylogenetic analysis suggested an additional three could be recognized.[7][5][6] These differences in circumscription are a result of homoplastic traits, including asymmetric corms, woody corm covering, exclusion of the vascular trace during ovule development, and leaf margin.[5][8] Molecular clock analyses have supported initial cladogenesis in Antarctica-Australasia 82mya from a Doryanthaceae ancestor.[5][9] The distribution of subfamilies in Iradaceae is considered to be phylogenetically structured, with all neotropical species belonging to one subfamily, the Irdoideae.[8]

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.[5] A similar process occurred for the tribe Tigridieae in Iridoideae following long-distance dispersal from South to North America, resulting in high levels of endemism.[18][5] In the tribe Sisyrichieae, the continued formation of the Andes supported the movement to lower elevations along the Atlantic.[19]

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.[20] These tight relationships found in individual species of Iridaceae, especially in Gladiolus, were the inspiration for the description of pollinator syndromes.[21] Pollinators include various species of solitary bees, as well as sunbirds, long-proboscid flies (such as Moegistorhynchus longirostris),[22] butterflies, and night moths.[23] Ancestrally, flowers were zygomorphic, as in Crocoideae, with contrasting nectary locations for pollinators.[24] Flowers may present nectar and pollen rewards to visitors, but some genera may only offer nectar such as in Gladious and Watsonia.[4] Species of Ferraria produce putrid smells, floral cups, and dark mottled perianth in order to attract Diptera.[25] 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.[20] New World Iridoideae represent one of the largest clades offering oil to pollinators, ranging from forced pollination using hinged petals to frequent failure to pollinate.[12] Most of the variability in flowers occurs between subfamilies, including infloresence structure, i.e. rhipidia, panicle, or spike, and floral longevity, i.e. less than one day to five days.[20][26] Some members of the tribe Irideae have flowers functioning as meranthia, or developing as three separate zygomorphic units that pollinators visit individually.[4]

69 genera have been recognized in the family, with a total of 2597 species described.[3] The Afrotropical realm, and in particular South Africa, have the greatest diversity of genera.[27]