Family of flowering plants in order Liliales, including lilies
General floral formula of the Liliacaeae: Flowers actinomorphic or slightly zygomorphic and hermaphrodite with 6 undifferentiated tepals in two whorls of three, the same number and arrangement of stamens, and a superior ovary with 3 fused carpels. Individual species and genera may have more or less derived formulas.
The lily family, Liliaceae, consists of about 15 genera and 610 species of flowering plants within the order Liliales. They are monocotyledonous, perennial, herbaceous, often bulbous geophytes. Plants in this family have evolved with a fair amount of morphological diversity despite genetic similarity. Common characteristics include large flowers with parts arranged in threes: with six colored or patterned petaloid tepals (undifferentiated petals and sepals) arranged in two whorls, six stamens and a superior ovary. The leaves are linear in shape, with their veins usually arranged parallel to the edges, single and arranged alternating on the stem, or in a rosette at the base. Most species are grown from bulbs, although some have rhizomes. First described in 1789, the lily family became a paraphyletic "catch-all" (wastebasket) group of lilioid monocots that did not fit into other families and included a great number of genera now included in other families and in some cases in other orders. Consequently, many sources and descriptions labelled "Liliaceae" deal with the broader sense of the family.
The family evolved approximately 68 million years ago during the Late Cretaceous to Early Paleogene epochs. Liliaceae are widely distributed, mainly in temperate regions of the Northern Hemisphere and the flowers are insect pollinated. Many Liliaceae are important ornamental plants, widely grown for their attractive flowers and involved in a major floriculture of cut flowers and dry bulbs. Some species are poisonous if eaten and can have adverse health effects in humans and household pets.
A number of Liliaceae genera are popular cultivated plants in private and public spaces. Lilies and tulips in particular have had considerable symbolic and decorative value, and appear frequently in paintings and the decorative arts. They are also an economically important product. Most of their genera, "Lilium" in particular, face considerable herbivory pressure from deer in some areas, both wild and domestic.
Description.
The diversity of characteristics complicates any description of the Liliaceae morphology, and confused taxonomic classification for centuries. The diversity is also of considerable evolutionary significance, as some members emerged from shaded areas and adapted to a more open environment (see Evolution).
General.
The Liliaceae are characterised as monocotyledonous, perennial, herbaceous, bulbous (or rhizomatous in the case of Medeoleae) flowering plants with simple trichomes (root hairs) and contractile roots. The flowers may be arranged (inflorescence) along the stem, developing from the base, or as a single flower at the tip of the stem, or as a cluster of flowers. They contain both male (androecium) and female (gynoecium) characteristics and are symmetric radially, but sometimes as a mirror image. Most flowers are large and colourful, except for Medeoleae. Both the petals and sepals are usually similar and appear as two concentric groups (whorls) of 'petals', that are often striped or multi-coloured, and produce nectar at their bases. The stamens are usually in two groups of three (trimerous) and the pollen has a single groove (monosulcate). The ovary is placed above the attachment of the other parts (superior). There are three fused carpels (syncarpus) with one to three chambers (locules), a single style and a three-lobed stigma. The embryo sac is of the "Fritillaria" type. The fruit is generally a wind dispersed capsule, but occasionally a berry (Medeoleae) which is dispersed by animals. The leaves are generally simple and elongated with veins parallel to the edges, arranged singly and alternating on the stem, but may form a rosette at the base of the stem.
Specific.
Characteristics often vary by habitat, between shade-dwelling genera (such as "Prosartes", "Tricyrtis", "Cardiocrinum", "Clintonia", "Medeola", "Prosartes", and "Scoliopus") and sun loving genera. Shade-dwelling genera usually have broader leaves with smooth edges and net venation, and fleshy fruits (berries) with animal-dispersed seeds, rhizomes, and small, inconspicuous flowers while genera native to sunny habitats usually have narrow, parallel-veined leaves, capsular fruits with wind-dispersed seeds, bulbs, and large, visually conspicuous flowers. (See also "Evolution").
Taxonomy.
The taxonomy of the Liliaceae has a very complex history. The family was first described in the eighteenth century, and over time many other genera were added until it became one of the largest of the monocotyledon families, and also extremely diverse. Modern taxonomic systems, such as the APG which is based on phylogenetic principles using molecular biology, have redistributed many of these genera resulting in the relatively small family that is currently recognised. Consequently, there are many different accounts of the Liliaceae in the literature and older uses of the term occur commonly. To distinguish between them, the Latin terms "sensu lato" and "sensu stricto" are frequently used (together with their abbreviations, "s.l." and "s.s.") to denote the broader or stricter sense of the circumscription respectively, e.g. Liliaceae "s.s.".
History.
The family Liliaceae was described by Michel Adanson in 1763 and formally named by Antoine Laurent de Jussieu in 1789. Jussieu defined this grouping as having a calyx of six equal colored parts, six stamens, a superior ovary, single style, and a trilocular (three-chambered) capsule. By 1845, John Lindley, the first English systematist, unhappily acknowledged the great diversity in the circumscription of the family, and that it had expanded vastly, with many subdivisions. As he saw it, the Liliaceae were already paraphyletic ("catch-all"), being all Liliales not included in the other orders, but hoped that the future would reveal some characteristic that would group them better. He recognized 133 genera and 1200 species. By the time of the next major British classification – that of Bentham and Hooker in 1883 (published in Latin) – several of Lindley's other families had already been absorbed into the Liliaceae. Over time the family became increasingly broad and somewhat arbitrarily defined as all species of plants with six tepals and a superior ovary, eventually coming to encompass about 300 genera and 4,500 species within the order Liliales under the Cronquist system (1981). Cronquist merged the Liliaceae with the Amaryllidaceae, making this one of the largest monocotyledon families.
Many other botanists echoed Lindley's earlier concerns about the phylogeny of the Liliaceae, but various schemes to divide the family gained little traction. Dahlgren (1985) suggested there were in fact forty – not one – families distributed over three orders (predominantly Liliales and Asparagales). In the context of a general review of the classification of angiosperms, the Liliaceae were subjected to more intense scrutiny. Considerable progress in plant phylogeny and phylogenetic theory enabled a phylogenetic tree to be constructed for all of the flowering plants, as elaborated by the Angiosperm Phylogeny Group (1998).
Modern APG classification and phylogeny.
The Angiosperm Phylogeny Group (APG) made rapid progress in establishing a modern monophyletic classification of the flowering plants by 2009. Despite establishing this relative degree of monophyly (genetic homogeneity) for the family Liliaceae, their morphology remains diverse and there exists within the Liliaceae clade or grouping, a number of subclades (subgroups). Particularly enigmatic were "Clintonia", "Medeola", "Scoliopus", and "Tricyrtis".
Of the fifteen genera within the Liliaceae, the ten genera of the Lilioideae subfamily form one morphological group that is characterised by contractile bulbs and roots, and a Fritillaria-type embryo-sac (megagametophyte with four megaspores). Within the Lilioideae, "Clintonia" and the closely related "Medeola" form a subclade, and are now considered a separate tribe (Medeoleae). The other major grouping consists of the five genera constituting the Streptopoideae (including "Scoliopus") and Calochortoideae (including "Tricyrtis") subfamilies characterised by creeping rhizomes, styles which are divided at their apices, and by megagametophyte development of the "Polygonum"-type (a simple megaspore and triploid endosperm) embryo-sac.
Evolution and biogeography.
The development of a phylogenetic approach to taxonomy suggested the Liliales formed some of the earliest monocots. Molecular analysis indicates that divergence amongst the Liliales probably occurred around 82 million years ago. The closest sister family to the Liliaceae are the Smilacaceae with the Liliaceae separating 52 million years ago. Liliaceae thus arose during the late (Maastrichtian) Cretaceous to early (Paleocene) Paleogene periods. Major evolutionary clades include the Lilieae ("Lilium, Fritillaria, Nomocharis, Cardiocrinum, Notholirion") from the Himalayas about 12 mya and the Tulipeae ("Erythronium", "Tulipa", "Gagea") from East Asia at about the same time. The Medeoleae ("Clintonia" and "Medeola") may have appeared in North America but were subsequently dispersed, as may have the Streptopoideae and Calochortoideae. Liliaceae fossils have been dated to the Paleogene and Cretaceous eras in the Antarctic.
The Liliaceae probably arose as shade plants, with subsequent evolution to open areas including deciduous forest in the more open autumnal period, but then a return of some species (e.g. "Cardiocrinum"). This was accompanied by a shift from rhizomes to bulbs, to more showy flowers, the production of capsular fruit and narrower parallel-veined leaves. Again, some reversal to the broader reticulate-veined leaves occurred (e.g. "Cardiocrinum").
Subdivisions and genera.
Suprageneric subdivisions.
Due to the diversity of the originally broadly defined Liliaceae "s.l.", many attempts have been made to form suprageneric classifications, e.g. subfamilies and tribes. Classifications published since the use of molecular methods in phylogenetics have taken a narrower view of the Liliaceae (Liliaceae "s.s."). The Angiosperm Phylogeny Website (APweb) recognizes three subfamilies, one of which is divided into two tribes.
Genera.
Various authorities (e.g. ITIS 16, GRIN 27, WCSP, NCBI, DELTA ) differ on the exact number of genera included in Liliaceae "s.s.", but generally there are about fifteen to sixteen genera, depending on whether or not "Amana" is included in "Tulipa" and "Lloydia" in "Gagea".
Currently the APWeb lists fifteen genera, arranged as shown in this table:
The largest genera are "Gagea" (200), "Fritillaria" (130), "Lilium" (110), and "Tulipa" (75 species), all within the tribe Lilieae.
Etymology and pronunciation.
The name "Liliaceae" () comes to international scientific vocabulary from Neo-Latin, from "Lilium", the type genus, + "-aceae", a standardized suffix for plant family names in modern taxonomy. The genus name comes from the Classical Latin word "lilium", "lily", which in turn came from the Greek "" ().
Distribution and habitat.
The Liliaceae are widely distributed, but mainly in the temperate regions of the Northern Hemisphere. The centre of diversity is from southwest Asia to China. Their distribution is diverse, mainly in plains, steppes, and alpine meadows, but also in deciduous forests, Mediterranean scrub and arctic tundra. "Tulipa" and "Gagea" provide examples of ornamental geophyte biomorphological types representing continental thermoperiodic zones (Irano-Turanian region), characterised by cessation of underground growth at high temperatures in early summer and requiring low winter temperatures for spring flowering. While some genera are shade-dwelling, such as the Medeoleae, and Streptopoideae, "Tricyrtis", and "Cardiocrinum", others prefer a more open habitat.
Ecology.
The Liliaceae are ecologically diverse. Species of Liliaceae bloom at various times from spring to late summer. The colorful flowers produce large amounts of nectar and pollen that attract insects which pollinate them (entomophily), particularly bees and wasps (hymenopterophily), butterflies (psychophily) and moths (phalaenophily). The seeds are dispersed by wind and water. Some species (e.g. "Scoliopus", "Erythronium and Gagea") have seeds with an aril structure that are dispersed by ants (myrmecochory).
The proliferation of deer populations in many areas, due to human factors such as the elimination of their animal predators and introduction to alien environments, is placing considerable herbivory pressure on many of the family's species. Fences as high as 8 feet may be required to prevent them from consuming the plants, an impractical solution for most wild areas. Those of the genus "Lilium" are particularly palatable, while species in "Fritillaria" are repellant.
Pests and predators.
Liliaceae are subject to a wide variety of diseases and pests, including insects, such as thrips, aphids, beetles and flies. Also fungi, viruses and vertebrate animals such as mice and deer. An important horticultural and garden pest is the scarlet lily beetle (Japanese red lily beetle, "Lilioceris lilii") and other Lilioceris species which attack "Fritillaria" and "Lilium". "Lilium" species may be food plants for the Cosmia trapezina moth. A major pest of Tulips is the fungus, "Botrytis tulipae".
Both "Lilium" and "Tulipa" are susceptible to a group of five viruses of the family "Potyviridae", specifically the potyvirus (named for "potato virus Y)" group, which includes the "tulip-breaking virus" ("TBV") and the "lily streak virus" (lily mottle virus, "LMoV") resulting in 'breaking' of the color of the flowers. The viruses are transmitted by aphids. This breaking effect was of economic importance during the tulip mania of the seventeenth century, because it appeared to be producing new varieties. In