Iridaceae
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Iridaceae () is a family of plants in order
Asparagales Asparagales (asparagoid lilies) are a diverse order of flowering plants in the monocots. Under the APG IV system of flowering plant classification, Asparagales are the largest order of monocots with 14 families, 1,122 genera, and about 36,00 ...
, 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 ''Gladiolus'' (from Latin, the diminutive of ''gladius'', a sword) is a genus of perennial cormous flowering plants in the iris family (Iridaceae). It is sometimes called the 'sword lily', but is usually called by its generic name (plural ''g ...
'', and ''
Crocus ''Crocus'' (; plural: crocuses or croci) is a genus of seasonal flowering plants in the family Iridaceae (iris family) comprising about 100 species of perennial plant, perennials growing from corms. They are low growing plants, whose flower stem ...
'', as well as the crop
saffron Saffron () is a spice derived from the flower of '' Crocus sativus'', commonly known as the "saffron crocus". The vivid crimson stigma and styles, called threads, are collected and dried for use mainly as a seasoning and colouring agent ...
. Members of this family are
perennial plant In horticulture, the term perennial (''wikt:per-#Prefix, per-'' + ''wikt:-ennial#Suffix, -ennial'', "through the year") is used to differentiate a plant from shorter-lived annual plant, annuals and biennial plant, biennials. It has thus been d ...
s, with a
bulb In botany, a bulb is a short underground stem with fleshy leaves or leaf basesBell, A.D. 1997. ''Plant form: an illustrated guide to flowering plant morphology''. Oxford University Press, Oxford, U.K. that function as food storage organs duri ...
,
corm Corm, bulbo-tuber, or bulbotuber is a short, vertical, swollen, underground plant stem that serves as a storage organ that some plants use to survive winter or other adverse conditions such as summer drought and heat (perennation). The word ''c ...
or
rhizome In botany and dendrology, a rhizome ( ) is a modified subterranean plant stem that sends out roots and Shoot (botany), shoots from its Node (botany), nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from ...
. 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 Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...
. 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 Asparagales (asparagoid lilies) are a diverse order of flowering plants in the monocots. Under the APG IV system of flowering plant classification, Asparagales are the largest order of monocots with 14 families, 1,122 genera, and about 36,00 ...
order but was traditionally grouped with
Liliales Liliales is an order (biology), order of monocotyledonous flowering plants in the Angiosperm Phylogeny Group and Angiosperm Phylogeny Web List of systems of plant classification, system, within the lilioid monocots. This order of necessity includ ...
. Iridaceae was previously divided into four subfamilies but results from
phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...
analysis suggested an additional three could be recognized. These differences in
circumscription Circumscription may refer to: * Circumscribed circle * Circumscription (logic) *Circumscription (taxonomy) * Circumscription theory, a theory about the origins of the political state in the history of human evolution proposed by the American anthr ...
are a result of homoplastic traits, including asymmetric
corm Corm, bulbo-tuber, or bulbotuber is a short, vertical, swollen, underground plant stem that serves as a storage organ that some plants use to survive winter or other adverse conditions such as summer drought and heat (perennation). The word ''c ...
s, woody corm covering, exclusion of the
vascular Vascular can refer to: * blood vessels, the vascular system in animals * vascular tissue Vascular tissue is a complex transporting tissue, formed of more than one cell type, found in vascular plants. The primary components of vascular tissue ...
trace during
ovule In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the ''integument'', forming its outer layer, the ''nucellus'' (or remnant of the sporangium, megasporangium), ...
development, and
leaf margin A leaf (: leaves) is a principal appendage of the plant stem, stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leav ...
.
Molecular clock The molecular clock is a figurative term for a technique that uses the mutation rate of biomolecules to deduce the time in prehistory when two or more life forms diverged. The biomolecular data used for such calculations are usually nucleot ...
analyses have supported initial
cladogenesis Cladogenesis is an evolutionary splitting of a parent species into two distinct species, forming a clade. This event usually occurs when a few organisms end up in new, often distant areas or when environmental changes cause several extinctions, ...
in
Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...
-
Australasia Australasia is a subregion of Oceania, comprising Australia, New Zealand (overlapping with Polynesia), and sometimes including New Guinea and surrounding islands (overlapping with Melanesia). The term is used in a number of different context ...
82 million years ago (mya) from a
Doryanthaceae ''Doryanthes'' is the sole genus in the flowering plant Family (biology), family Doryanthaceae. The genus consists of two species, ''Doryanthes excelsa, D. excelsa'' (gymea lily) and ''Doryanthes palmeri, D. palmeri'' (giant spear lily), both en ...
ancestor. The distribution of subfamilies in Iridaceae is considered to be phylogenetically structured, with all
neotropical The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone. Definition In biogeogra ...
species belonging to one subfamily, the Irdoideae.


Crocoideae

Subfamily Crocoideae is one of the major subfamilies in the family Iridaceae. It contains many genera, including '' Afrocrocus'', '' Babiana'', '' Chasmanthe'', '' Crocosmia'', ''
Crocus ''Crocus'' (; plural: crocuses or croci) is a genus of seasonal flowering plants in the family Iridaceae (iris family) comprising about 100 species of perennial plant, perennials growing from corms. They are low growing plants, whose flower stem ...
'', '' Cyanixia'', '' Devia'', '' Dierama'', '' Duthiastrum'', '' Freesia'', '' Geissorhiza'', ''
Gladiolus ''Gladiolus'' (from Latin, the diminutive of ''gladius'', a sword) is a genus of perennial cormous flowering plants in the iris family (Iridaceae). It is sometimes called the 'sword lily', but is usually called by its generic name (plural ''g ...
'', '' Hesperantha'', ''
Ixia ''Ixia'' is a genus of cormous plants native to South Africa from the family Iridaceae. Some of them are known as the corn lily. Some distinctive traits include sword-like leaves and long wiry stems with star-shaped flowers. It usually prefers w ...
'', '' Lapeirousia'', '' Melasphaerula'', '' Micranthus'', '' Pillansia'', '' Romulea'', '' Sparaxis'', '' Savannosiphon'', '' Syringodea'', '' Thereianthus'', '' Tritonia'', '' Tritoniopsis'', '' Xenoscapa'' and '' Watsonia''. They are mainly from Africa, but includes members from Europe and Asia. The rootstock is usually a corm, they have blooms which sometimes have scent, are collected in inflorescence and contain six tepals. The nectar is produced mostly in the base of the bloom from the glands of the ovary, which is where the flower forms a tube-like end. In some species there is no such end and the plant only provides pollen to pollinating insects. Members of this subfamily have the sword-shaped leaves typical of Iridaceae.


Isophysidoideae

Subfamily Isophysidoideae is
monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...
, only containing '' Isophysis'' from Tasmania. It is the only member of the family with a superior ovary, and it grows a solitary star-like, yellow to brownish flower. It is also sister to all other extant taxa of Iridaceae, diverging 66mya.


Nivenioideae and allies

Subfamily Nivenioideae contained six genera from South Africa, Australia and Madagascar, including the core genera and only true shrubs in the family ('' Klattia'', '' Nivenia'' and '' Witsenia''). Upon phylogenetic analysis, subfamily Crocoideae is always found nested within Nivenioideae, leading to it not being a
monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...
taxon. A revised description of these groups led to the description of Aristea, Geosiris, and Patersonia each as separate subfamilies, retaining a core, monophyletic Nivenioideae. It is now distinguished as being
evergreen In botany, an evergreen is a plant which has Leaf, foliage that remains green and functional throughout the year. This contrasts with deciduous plants, which lose their foliage completely during the winter or dry season. Consisting of many diffe ...
shrub A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...
s with
monocot Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are flowering plants whose seeds contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. A monocot taxon has been in use for several decades, but ...
-type secondary thickening, shield shaped seeds, and paired rhipidia with only one to two flowers in each cluster.


Iridoideae

Subfamily Iridoideae has the widest geographic distribution and is divided into four tribes and one sister genus: Irideae, Sisyrichieae, Trimezieae, Tigridieae, and Diplarreneae. Iridoideae is differentiated from the other subfamilies by having very short-lived flowers,
nectaries Nectar is a viscous, sugar-rich liquid produced by plants in glands called nectaries, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists, ...
on the
perianth The perianth (perigonium, perigon or perigone in monocots) is the non-reproductive part of the flower. It is a structure that forms an envelope surrounding the sexual organs, consisting of the calyx (sepals) and the corolla (petals) or tepal ...
, and long branching styles. Excluding the Irideae, the evolution of oil-producing
trichome Trichomes (; ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant ...
s, called
elaiophore An elaiophore (from Gr. ''elaion'' -oil and ''phorein'' -carry) is a plant organ that secretes oil. A distinction is made in: * epithelial elaiophors: oil glands * trichome eaiophores: glandular hairs. The oils consist of fatty acids and/or gly ...
s, have been gained and lost in each of the tribes attracting oil bees. The genus Diplarreneae is sister to the rest of the subfamily and is unique to Iridoideae in having
zygomorphic Floral symmetry describes whether, and how, a flower, in particular its perianth, can be divided into two or more identical or mirror-image parts. Uncommonly, flowers may have no axis of symmetry at all, typically because their parts are spir ...
flowers and
stamen The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...
s with unequal height. Irideae represents the
Old World The "Old World" () is a term for Afro-Eurasia coined by Europeans after 1493, when they became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia in the Eastern Hemisphere, previously ...
portion of the subfamily but include several genera that diversified in North America, such as '' Iris''. They are distinguishable with the presence of flattened
anthers The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filamen ...
pressed to the
style Style, or styles may refer to: Film and television * ''Style'' (2001 film), a Hindi film starring Sharman Joshi, Riya Sen, Sahil Khan and Shilpi Mudgal * ''Style'' (2002 film), a Tamil drama film * ''Style'' (2004 film), a Burmese film * '' ...
, petaloid crests, and schlerenchyma tissue along the
margins Margin may refer to: Physical or graphical edges *Margin (typography), the white space that surrounds the content of a page *Continental margin, the zone of the ocean floor that separates the thin oceanic crust from thick continental crust *Leaf ...
of leaves. Sisyrichieae is noted for having long
style Style, or styles may refer to: Film and television * ''Style'' (2001 film), a Hindi film starring Sharman Joshi, Riya Sen, Sahil Khan and Shilpi Mudgal * ''Style'' (2002 film), a Tamil drama film * ''Style'' (2004 film), a Burmese film * '' ...
branches that may interlace with
stamen The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...
s, partially fused filaments, and the lack of oxaloacetate crystals in leaves. Trimezieae is the smallest tribe with two to four genera, noted for the presence of large
rhizome In botany and dendrology, a rhizome ( ) is a modified subterranean plant stem that sends out roots and Shoot (botany), shoots from its Node (botany), nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from ...
s or
corm Corm, bulbo-tuber, or bulbotuber is a short, vertical, swollen, underground plant stem that serves as a storage organ that some plants use to survive winter or other adverse conditions such as summer drought and heat (perennation). The word ''c ...
s rather than
bulb In botany, a bulb is a short underground stem with fleshy leaves or leaf basesBell, A.D. 1997. ''Plant form: an illustrated guide to flowering plant morphology''. Oxford University Press, Oxford, U.K. that function as food storage organs duri ...
s as well as a thickened
midrib A primary vein, also known as the midrib, is the main vascular structure running through the center of a leaf. The primary vein is crucial for the leaf’s efficiency in photosynthesis and overall health, as it ensures the proper flow of material ...
. Several species with ornamented or iris-like flowers also possess a specialized method of forcing pollen onto heavy pollinators with hinged petals. Tigridieae are distinguished for their large bulbous rootstock and plicate, decidious leaves. The number of genera and whether any morphology can distinguish between them has been debated.


Ecology

Members of Iridaceae occur in a great variety of habitats.
Gladiolus ''Gladiolus'' (from Latin, the diminutive of ''gladius'', a sword) is a genus of perennial cormous flowering plants in the iris family (Iridaceae). It is sometimes called the 'sword lily', but is usually called by its generic name (plural ''g ...
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 Fynbos (; , ) is a small belt of natural shrubland or heathland vegetation located in the Western Cape and Eastern Cape provinces of South Africa. The area is predominantly coastal and mountainous, with a Mediterranean climate. The 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 Cladogenesis is an evolutionary splitting of a parent species into two distinct species, forming a clade. This event usually occurs when a few organisms end up in new, often distant areas or when environmental changes cause several extinctions, ...
in arid conditions in Africa, accelerating for Crocoideae as the
Mediterranean climate A Mediterranean climate ( ), also called a dry summer climate, described by Köppen and Trewartha as ''Cs'', is a temperate climate type that occurs in the lower mid-latitudes (normally 30 to 44 north and south latitude). Such climates typic ...
emerged in Southern Africa. 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 Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
. In the tribe Sisyrichieae, the continued formation of the
Andes The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the List of longest mountain chains on Earth, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range ...
supported the movement to lower elevations along the
Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...
. 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 Fynbos (; , ) is a small belt of natural shrubland or heathland vegetation located in the Western Cape and Eastern Cape provinces of South Africa. The area is predominantly coastal and mountainous, with a Mediterranean climate. The 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 Veld ( or , Afrikaans language, Afrikaans and Dutch language, Dutch: ''veld'', field), also spelled veldt, is a type of wide-open, rural landscape in Southern Africa. Particularly, it is a flat area covered in grass or low scrubland, scrub, ...
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 Fynbos (; , ) is a small belt of natural shrubland or heathland vegetation located in the Western Cape and Eastern Cape provinces of South Africa. The area is predominantly coastal and mountainous, with a Mediterranean climate. The fynbos ...
species will only flower in the season after a fire. The majority of Iridaceae are
pollinated Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds. Pollinating agents can be animals such as insects, for example bees, beetles or butterflies; bird ...
by
Hymenoptera Hymenoptera is a large order of insects, comprising the sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are parasitic. Females typi ...
, frequently by single species or a small group of species. These tight relationships found in individual species of Iridaceae, especially in ''
Gladiolus ''Gladiolus'' (from Latin, the diminutive of ''gladius'', a sword) is a genus of perennial cormous flowering plants in the iris family (Iridaceae). It is sometimes called the 'sword lily', but is usually called by its generic name (plural ''g ...
,'' were the inspiration for the description of pollinator syndromes. Pollinators include various species of solitary bees, as well as
sunbird Sunbirds and spiderhunters make up the family Nectariniidae of passerine birds. They are small, slender passerines from the Old World, usually with downward-curved bills. Many are brightly coloured, often with iridescent feathers, particularly i ...
s, long-proboscid flies (such as '' Moegistorhynchus longirostris''),
butterflies Butterflies are winged insects from the lepidopteran superfamily Papilionoidea, characterized by large, often brightly coloured wings that often fold together when at rest, and a conspicuous, fluttering flight. The oldest butterfly fossi ...
, and night
moth Moths are a group of insects that includes all members of the order Lepidoptera that are not Butterfly, butterflies. They were previously classified as suborder Heterocera, but the group is Paraphyly, paraphyletic with respect to butterflies (s ...
s. Ancestrally, flowers were
zygomorphic Floral symmetry describes whether, and how, a flower, in particular its perianth, can be divided into two or more identical or mirror-image parts. Uncommonly, flowers may have no axis of symmetry at all, typically because their parts are spir ...
, as in Crocoideae, with contrasting
nectary Nectar is a viscous, sugar-rich liquid produced by plants in glands called nectaries, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists, ...
locations for pollinators. Flowers may present
nectar Nectar is a viscous, sugar-rich liquid produced by Plant, plants in glands called nectaries, either within the flowers with which it attracts pollination, pollinating animals, or by extrafloral nectaries, which provide a nutrient source to an ...
and
pollen Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm ...
rewards to visitors, but some genera may only offer nectar such as in '' Gladious'' and '' Watsonia''. Species of ''Ferraria'' produce putrid smells, floral cups, and dark mottled perianth in order to attract Diptera. 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.
New World The term "New World" is used to describe the majority of lands of Earth's Western Hemisphere, particularly the Americas, and sometimes Oceania."America." ''The Oxford Companion to the English Language'' (). McArthur, Tom, ed., 1992. New York: ...
Iridoideae represent one of the largest
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
s offering oil to pollinators, ranging from forced pollination using hinged petals to frequent failure to pollinate. Most of the variability in flowers occurs between subfamilies, including
inflorescence In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a mai ...
structure, i.e. rhipidia,
panicle In botany, a panicle is a much-branched inflorescence. (softcover ). Some authors distinguish it from a compound spike inflorescence, by requiring that the flowers (and fruit) be pedicellate (having a single stem per flower). The branches of a p ...
, or spike, and floral longevity, i.e. less than one day to five days. Some members of the
tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...
Irideae have flowers functioning as meranthia, or developing as three separate
zygomorphic Floral symmetry describes whether, and how, a flower, in particular its perianth, can be divided into two or more identical or mirror-image parts. Uncommonly, flowers may have no axis of symmetry at all, typically because their parts are spir ...
units that pollinators visit individually.


List of genera

69 genera have been recognized in the family, with a total of 2597 species described. The
Afrotropical realm The Afrotropical realm is one of the Earth's eight biogeographic realms. It includes Sub-Saharan Africa, the southern Arabian Peninsula, the island of Madagascar, and the islands of the western Indian Ocean. It was formerly known as the Ethiopi ...
, and in particular
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...
, have the greatest diversity of genera.


References

{{Authority control Asparagales families Selandian first appearances Extant Selandian first appearances