Taxonomy of Liliaceae Temporal range:68–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N Late Cretaceous - Recent
Lilium candidum
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Monocots
Order:	Liliales
Family:	Liliaceae Juss.[1]
Type genus
Lilium L.
Type species
Lilium candidum L.
Subfamilies and tribes[2]
subfamily:Lilioideae tribe:Medeoleae tribe:Lilieae subfamily:Calochortoideae subfamily:Streptopoideae
Diversity
About 600 species

Thetaxonomy of the plant familyLiliaceae has had a complex history since its first description in the mid-eighteenth century. Originally, the Liliaceae were defined as having a "calix" (perianth) of six equal-coloured parts, sixstamens, a singlestyle, and a superior, three-chambered (trilocular)ovary turning into acapsule fruit at maturity. The taxonomiccircumscription of the family Liliaceae progressively expanded until it became the largest plant family and also extremely diverse, being somewhat arbitrarily defined as all species of plants with sixtepals and a superior ovary. It eventually came to encompass about 300genera and 4,500species, and was thus a "catch-all" and henceparaphyletic. Only since the more modern taxonomic systems developed by theAngiosperm Phylogeny Group (APG) and based onphylogenetic principles, has it been possible to identify the many separate taxonomic groupings within the original family and redistribute them, leaving a relatively small core as the modern family Liliaceae, with fifteen genera and 600 species.

The Liliaceae emerged from theLiliales order, separating from itssister clade around 52 million years ago (mya), anddiversifying around 34 mya. Of the majorclades, the Lilieae arose inEurasia while theMedeoleae arose inNorth America but was subsequently dispersed, as may have theStreptopoideae andCalochortoideae. Liliaceae fossils have been dated to thePaleogene andCretaceous eras in theAntarctic.

The Liliaceae probably arose as shade plants, with subsequent evolution to open areas includingdeciduous forest in the more open autumnal period. This was accompanied by a shift fromrhizomes tobulbs, to more showy flowers, the production of capsular fruit and narrower parallel-veined leaves.

While the suprageneric (above genus level) structure of the family has varied greatly with its ever-changing circumscription, as currently constituted the family consists of threesubfamilies:Lilioideae,Calochortoideae andStreptopoideae. Lilioideae is further divided into twotribes,Medeoleae andLilieae. The three subfamilies contain fifteen genera and approximately 600 species in all.

Thetype genus,Lilium, from which the name of the family was derived, was originally formally described byCarl Linnaeus in 1753, with seven species.^[3] He placedLilium within theHexandria Monogynia (sixstamens, onecarpel) in hissexual classification in theSpecies Plantarum.^[4] Thefamily Liliaceae was first described byMichel Adanson in 1763,^[5][6] but formally named byAntoine Laurent de Jussieu in 1789.^[1][7] Adanson described eight subfamilies with 78 genera, however the subfamily he described asLis (lilies) had seven genera (Uvularia,Mithridatium,Mendoni,Lilium,Fritillaria,Imperialis — now part ofFritillaria — andTulipa) of which four are in the modern genus.^[8] Jussieu placed these into theordo,Lilia in theclassis,Stamina Perigyna of theMonocotyledones (monocots), with eight genera (Tulipa,Erythronioum,Methonica,Uvularia,Fritillaria,Imperialis,Lilium,Yucca) only four of which remain in the family. He definedLilia as "calix" (perianth) of six equal coloured parts, six stamens, a superior ovary, single style, and trilocular capsule. The termordo at that time was closer to what we now understand as family, rather thanorder.^[9][10] Although Jussieu used theLatin "lilia" in hisGenera Plantarum, elsewhere he used the French "liliacées",^[11] as had Adanson. The word "Liliaceae" was soon widely used by botanists such asSamuel Frederick Gray,^[12]John Lindley,^[13] andPierre-Joseph Redouté^[14] in the early nineteenth century.

Gray (1821) provided the first description of Jussieu's scheme in English, identifying two genera occurring in Britain (Tulipa,Fritillaria), distinguished by the absence or presence of basal nectaries. His key used the presence of six equal stamens, a single style, a simplepetaloid (undifferentiatedtepals resembling petals) perianth and a trilocular capsule with flat seeds to identify the family.^[15] AlthoughAugustin De Candolle (1813) had not explicitly described the Liliaceae, his overallclassification scheme influenced many later writers including Gray.^[16] In this scheme,^[17] the Liliaceae were considered a family within thosevascular plants (Vasculares) whose vascular bundles were thought to arise from within (Endogènes,endogenous), a term he preferred toMonocotylédonés. Jussieu'sMonocotyledones became thePhanérogames (Phenogamae in Gray), meaning "visible seed", henceEndogenæ phanerogamæ.^[18] Candolle also instituted the concept ofordered ranks, based on classes, subclasses,familles (Latin:ordines naturales) andtribus (tribes),^[10] subdividing the Liliaceae.

Lindley was the first post-Linnaean Englishsystematist, publishing his work in 1830,^[19] and following the reasoning of Jussieu he used the term tribe to describe the Liliaceae as a division of thehexapetaloid monocots, characterised by a superior ovary, highly developed perianth, inward turning anthers, a trilocular polyspermous capsule and seeds with a soft spongy coat. He offered seven genera as examples (Erythronium,Lilium,Calochortus,Blandfordia,Polianthes,Hemerocallis andFunkia). By 1846, in his final work, he refined and greatly expanded his taxonomy, favouring the termAlliances of Endogens over monocots as a class, of which there were eleven. Of these "alliances", theLiliales consisted of four Orders (families) including Liliaceae, which he referred to aslilyworts in the vernacular, with 133 genera and 1200 species.^[20] In this work he unhappily acknowledged the confusing array of different approaches to the classification of the Liliaceae, the lack of a clear definition, and the great diversity in thecircumscription of the order, which had expanded vastly, with many subdivisions. As he saw it, the Liliaceae had already become a ("catch-all") grouping,^[21] being "everything that does not belong to the other parts of the Lilial Alliance", but expressed hope that the future would reveal some characteristic that would group them better.^[22] In other words, he foresaw that Liliaceae would come to be regarded asparaphyletic. By the time of the next major British classification, that ofBentham and Hooker in 1883 (published in Latin) several of Lindley's other families had been absorbed into the Liliaceae.^[23] This was the last major classification using the "natural" or pre-evolutionary approach to classification, based on characteristics selecteda posteriori in order to group together taxa that have the greatest number of shared characteristics. This approach, also referred to as polythetic was superseded by ones based on an understanding of the acquisition of characteristics through evolution, referred to asphyletic.^[24][25][26]

AlthoughCharles Darwin'sOrigin of Species (1859) preceded Bentham and Hooker's publication, the latter project was commenced much earlier andGeorge Bentham was initially sceptical ofDarwinism.^[24] The newphyletic approach changed the way that taxonomists considered plant classification, incorporatingevolutionary information into their schemata, but this did little to further define the circumscription of Liliaceae.^[27] The major works in the late nineteenth and early twentieth century employing this approach were in theGerman literature, theEichler (1875–1886),Engler and Prantl (1886–1924) andWettstein (1901–1935) systems. These placed the Liliaceae into one of the major subdivisions of themonocotyledons, theLiliiflorae.^{[28][29][30][31][32]} In the English literature,Charles Bessey (1915) followedAdolf Engler in defining Liliaceae as "Pistil mostly 3-celled; stamens 6; perianth of two similar whorls, each of three similar leaves", although placing the Liliales in a novel subclass of monocots, theStrobiloideae,^[33] while fromJohn Hutchinson (1959) onwards the Liliaceae were treated as part of theLiliales (seeTable 1).

Over time the Liliaceae became increasingly broadly, and somewhat arbitrarily, defined as all species of plants with six tepals and a superior ovary. They eventually came to encompass about 300 genera and 4,500 species, within theorderLiliales in thescheme ofArthur Cronquist (1981).^[34] Cronquist was a "lumper" preferring a small number of very large groupings and his classification of the Liliaceae represented the greatest expansion of the family to date. Cronquist placed most floweringpetaloid monocots with six stamens in this very broad (and clearlypolyphyletic) family, hence the alternative name lilioid monocots.^[35] He rejected the importance of ovary position and thus included with the Liliaceae with their superior ovary (hypogynous), theAmaryllidaceae, some species of which had an inferior ovary (epigynous), and which others separated into a distinct family.^[36][37][38] The Liliaceae were one of the major families in the Cronquist system which included 22 families in addition to Liliaceae in the more restricted sense (sensu stricto,s.s.) used by others.^[39][40] Later more conventional schemes include thesystem ofRobert F. Thorne^[38] and that ofArmen Takhtajan^[41] which characterised the family aspetaloid monocots, characterised by showy flowers with tepals and withoutstarch in theendosperm.

Other botanists in the twentieth century echoed Lindley's concerns about the lack of a clearly defined grouping for Liliaceae. The earliest of these wasJohannes Paulus Lotsy (1911),^[42] building on Wettstein's work. Lotsy suggested four separate families, Liliaceae, Alliaceae, Agapanthaceae and Gilliesiaceae, within theLiliifloren. This recognised the major groupings that would later be transferred toAmaryllidaceae as subfamiliesAllioideae andAgapanthoideae, withGilliesieae as a tribe within the Allioideae. This approach was later followed byHerbert Huber in 1969.^[43] These various proposals to separate small groups of genera into more homogeneous families made little impact untilRolf Dahlgren (1985), following Huber's lead,^[44] developed a system incorporating new information, includingsynapomorphic characters (i.e., shared characters believed to have evolved from a common ancestor).^[35] While Cronquist was a "lumper", Dahlgren was a "splitter", preferring a larger number of more homogeneous groupings. Where Cronquist saw one family, Dahlgren saw forty distributed over three orders (predominantlyLiliales andAsparagales), reducing Liliaceae to ten genera (seeTable 3).^[45][46] Over the 1980s, in the context of a more general review of the classification ofangiosperms, the Liliaceae were subjected to more intense scrutiny. By the end of that decade, theRoyal Botanic Gardens at Kew, theBritish Museum of Natural History and theEdinburgh Botanical Gardens formed a committee to examine the possibility of separating the family into smaller taxa, at least for the purpose of organizing theirherbaria. That committee finally recommended that 24 new families be created in the place of the original broad Liliaceae, largely by elevating subfamilies to the rank of separate families.^[40][47]

The 1990s saw considerable progress in plantphylogenetics andcladistic theory, enabling aphylogenetic tree to be constructed for the flowering plants.^[48] The establishment of major newclades necessitated a departure from the older but widely used classifications such as Cronquist and Thorne, based largely on morphology rather than genetic data. These developments complicated discussions on plant evolution and necessitated a major taxonomic restructuring.^[49][50]rbcL gene sequencing and cladistic analysis of monocots in 1995 had redefined the Lilialesorder^[51] out of four original morphological orderssensuDahlgren. The largest clade within this redefined Liliales, christened the "core Liliales" representing a now much reduced Liliaceae, had all previously been included in the Liliales, and included three taxonomic groups: (i) Liliaceaesensu Dahlgren,^[52] but also both the (ii)Calochortaceae as defined byMinoro Tamura (sensu Tamura)^[53] and (iii)Clintonia-Medeola which had been included in Liliaceaesensu Tamura^[53] (seeTable 3).^[54]

This newly, more narrowly (sensu stricto,s.s.) circumscribed Liliaceae, corresponded to the emerging circumscription of the family in theAngiosperm Phylogeny Group system (1998).^[54] While this also corresponded most closely with Dahlgren's circumscription relative to the older much broader (sensu lato,s.l.) constructions, it gave rise to some potentially confusing terminology. Compared to the very broad historicals.l. construction of Liliaceae, the Dahlgren, Tamura and APG constructions were much narrower. These have variously been referred to as "core Liliales" andsensu APG^[54] for the broadest construction, while the intervening schemes of Tamura andTakhtajan (who was also a "splitter")^[55] which are narrower have been referred to as Liliaceaes.s.,sensu Dahlgren, andsensu Tamura. Of these the narrowest circumscription is that of Dahlgren, including onlyLilieaes.l..^[54] In modern terminology, while "core Liliales" represents Liliaceaesensu APG, Liliaceaesensu Tamura corresponds toLilioideaes.l., andsensu Dahlgren withLilieaes.l. or Lilioideaes.s..Calochortoideae andStreptopoideaesensu APG represent andCalochortaceaesensu Tamura, andClintonia plusMedeola (Medeoleae) Medeoloideaesensu Tamura (seeTable 3).^[2]

To meet the need for a thorough revision of the taxonomy of the flowering plants (angiosperms),systematists formed theAngiosperm Phylogeny Group (APG), resulting in a new classification published in 1998.^[55] The scheme was largely based on the work ofKåre Bremer and colleagues atUppsala andStockholm universities in the late 1970s,^[56][57][58] and became universally accessible on the internet in 1996.^[59]It was an ordinal system, concentrating on orders rather than families, prioritisingmonophyly, in which Liliales were recognised as one of ten monocot orders, containing nine families.^[55] However progress was rapid and the modern era of the taxonomy of the family Liliaceae comes fromJudd and colleagues^[37] (2002), theAPG II (2003^[60]) andAPG III (2009^[50][61]), while the Linear APG III assigned it the family number 61.^[62] The original APG did not specifically address the issues of thepolyphyly within Liliaceae, but APG II did so within the two closely morphologically related orders, Liliales and Asparagales^[63] recognising the continued common use of Liliaceae in the broad sense (sensu lato,s.l.).

These studies ofDNA andmorphological data (particularly reproductive morphology) together withphylogenetic analyses, allowed the conclusion that the "petaloid monocots" do not belong to one botanical family but rather are distributed across two separate orders, theAsparagales andLiliales. Themonophyly of these newly defined orders is supported bycladistic analysis based on morphology,18S rDNA, theplastidgenerbcL, and other DNA sequences.^{[64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82]}

These studies, together with other analyses within each of these two orders, allowed the redistribution of the original genera of Liliaceaes.l. into a variety of families across the Liliales and Asparagales, as illustrated inCladogram 1.^[83] This redistribution resulted in considerable changes both in the suprafamilial positioning of Liliaceae within the overall APG classification (as shown in Table 1 below), as well as the subfamilial structure (seeSuprageneric subdivisions).^[84]

The synthesis of molecular data withcladistic analysis suggests eleven orders ofmonocotyledons, one of fourteenclades ofAngiosperms, and forming agrade with six other orders.^[95] Sequencing of therbcL andtrnL-Fplastid genes revealed four main Liliales lineages:^[63]

1. Liliaceae group:Liliaceae (including some formerUvulariaceae andCalochortaceae),Philesiaceae andSmilacaceae;
2. Campynemataceae;
3. Colchicaceae group (Colchicoid lilies):Colchicaceae (includingPetermannia andUvularia),Alstroemeriaceae andLuzuriaga;
4. Melanthiaceae (includingTrilliaceae).

The original family Liliaceae in the broad sense (sensu lato,s.l.), which encompassed a large number of differing groups of genera, was highlypolyphyletic (seeCladogram 1). This led to botanists increasingly adopting a more narrowmonophyletic concept,i.e. strict sense (sensu stricto,s.s.) of the family based onmolecular phylogenetic relationships, as expressed in the 2009 APG III system, rather than the oldersensu lato one. Former members of the Liliaceae are now principally classified in different families and subfamilies of the Liliales and Asparagales as shown in the phylogeny represented in Cladogram I. Other families and orders containing former Liliaceae taxa are theNartheciaceae (Dioscoreales),Tofieldiaceae (Alismatales),Tecophilaeaceae (Asparagales) and the formerUvulariaceae. The achlorophyllous (non-photosynthesising)Corsiaceae were added to Liliales by APG III in 2009.^[50][95]

Sequencing of therbcL andmatKchloroplast genes ofLilium and related genera^[96] confirmed thecircumscription of the family in thesensu stricto usage ofTamura (1998).^[97] ChloroplastndhF gene sequencing also supported Liliaceae monophyly, reuniting the Liliaceaesensu Tamura and Calochortaceaesensu Tamura (seeTable 2 &Table 3 below).

The majordiversification amongst theAngiosperms (flowering plants) can be dated to the end of theEarly Cretaceousperiod which stretched from 146 to 100 million years ago (mya).^{[78][99][100]} The development of a phylogenetic approach to taxonomy, starting withCharles Bessey'sThe phylogenetic taxonomy of flowering plants (1915) suggested the Liliales formed some of the earliestmonocots,^[33] with an estimated date of origin of 124 mya for thestem node (most recent common ancestor of the clade of interest and itssister clade) age^[101] and between 117 mya^[101] to 82 mya^[78] for the crown node (most recent common ancestor of the sampled species of the clade of interest) age. Molecular analysis suggests that the Liliaceaesensu APG ("core Liliales") were part of one of four early clades of Liliales, namelyCampynemataceae,Melanthiaceae,Alstroemeriaceae +Luzuriagaceae +Colchicaceae andSmilacaceae + Liliaceae, dated to 68–65 mya (stem node) with the separation of the Smilaceae and Liliaceaesister clades (crown node) occurring later at around 55–52 mya.^[b]divergence within the Liliaceae appeared at about 36–34 mya, within Liliaceaesensu Tamura (Lilioideaes.l.) at 27 mya, Liliaceaesensu Dahlgren (Lilieaes.s. andTulipeae) at 20 mya (Miocene).

Within the Liliaceaesensu Dahlgren there developed two main evolutionary subclades (seeCladogram II andTable 3). The first of these, characterised as the Lilieae s.s. (Lilium, Fritillaria, Nomocharis), Cardiocrinum), Notholirion) diverged around 12 mya. The second subclade was the Tulipeae (Erythronium, Tulipa), (Gagea). Divergence withinCalochortus is dated to 7 mya. This places the emergence of the Liliaceae at approximately the last (Maastrichtian period) of theLate Cretaceous periods (72 to 66 mya) to early (Paleocene)Paleogene periods (66 to 23 mya), formerly the Cretaceous–Tertiary boundary, 65 mya.^{[78][54][102]}

The southern hemisphere intercontinental distributions of Liliales suggests a connection toGondwana, whose breakup into western (Africa, South America) and eastern (Australia, Antarctica, Madagascar, India) portions occurred at 180–150 mya, and the final separation of the western portion into Africa and South America at 80 mya coinciding with the emergence of the Liliales. Thus the immediate ancestor of the Liliales is likely to have existed during the period of interconnection of the African and South American-Antarctic-Australian portions of Late Cretaceous Gondwana. While the ancestral clade appears to have been distributed in both northern and southern hemispheres, Liliaceaeper se isholarctic, confined to the northern hemisphere with both Eurasian (including some North African representatives) and North American lineages. It is likely that they originated in North America but were able to expand to Eurasia ~30–40 mya viaBeringia that connected the two during the Tertiary period. The presence of genera whIch are restricted to Eurasia suggests avicariance (separation of populations by continental division) split between Medeoleae and Lilieae involving Eurasia and North America (Cladogram II).^[78]

Liliaceaesensu Dahlgren arose inEurasia,^{[54][78][102]} while within Liliaceaesensu Dahlgren theLilieaes.s. subclade arose in theHimalayas (Qinghai-Tibetan Plateau), with laterradiation there inmontane and alpine habitats. Species ofLilium andFritillaria then dispersed into the rest of Eurasia and North America. The second subclade, the Tulipeae arose inEast Asia with subsequent colonisation of North America byErythronium andLloydia. On the other hand,Clintonia-Medeola (Medeoleae) may have appeared in North America but subsequently underwent intercontinental dispersal (although some evidence points to a Eurasian origin). The Calochortaceaesensu Tamura (Streptopoideae andCalochortoideae) appears to have evolved in western North America, with subsequent colonisation of East Asia byStreptopus and the ancestralTricyrtis.^[54]

Liliaceae probably arose asshade plants in closed shaded habitats, with subsequent evolution of Liliaceaesensu Dahlgren andCalochortus to open areas includingdeciduous 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).^[54] In addition such molecular studies show that share characteristics do not necessarily indicate descent from a common ancestor but rather may arise from adaptiveconvergence in similar habitats.^[54]

The fossil record of Liliales is relatively poor,^[103] but Liliaceaefossils have been dated to the Paleogene^[104] and Cretaceous periods in theAntarctic.^{[105][106][107]}

The diversity of characteristics complicates description of Liliaceae morphology, and confused taxonomic classification for centuries. The diversity is also of considerable evolutionary significance (seeEvolution).^[54] The family Liliaceae are characterised as monocotyledonous, perennial, herbaceous, bulbous (orrhizomatous in the case ofMedeoleae)^[97] flowering plants with simpletrichomes (root hairs) and contractileroots.^[108] The flowers may bearranged 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 superior, i.e. placed above the attachment of the other parts. There are three fused carpels (syncarpous) with one to three chambers (locules), a single style and a three-lobed stigma. The embryo sac is of theFritillaria 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.

(SeeTable 3). The ten genera (two genera of Table 3 are subsumed into other genera) of the subfamilyLilioideae are characterised by contractilebulbs and roots and amegagametophyte (embryo-sac) of theFritillaria-type with fourmegaspores. Within the Lilioideae, the eight genera considered as Liliaceae by Dahlgren (sensu Dahlgren), that isLilieaes.l., are characterised byloculicidalcapsules and a basic chromosome number x=12. Within this clade, Lilieaes.s. are characterised by papillosetepals (with the exception ofFritillaria) and numerous fleshy bulb-scales as well as a morphologically distinct karyotype with two longmetacentricchromosomes and 10telocentrics of medium length.^[109] The two genera within Tulipeae are distinguished by pseudo-basifixedanthers and single bulb scales. The two genera ofMedeoleae are distinguished by having rhizomes instead of bulbs andberries instead of capsules, and a very unusual form of vesicular-arbuscularmycorrhizae.^[54]

The five genera constituting theStreptopoideae andCalochortoideae subfamilies form another distinct group, previously characterised under the Calochortoideae alone. These have creepingrhizomes, styles divided at their apices, and an embryo-sac of thePolygonum-type with a simple megaspore and triploidendosperm. At times, these genera were considered as a separate family (Calochortaceae; e.g. Tamura) or even placed in the more heterogeneousUvulariaceaesensu Dahlgren. However most of the latter had low morphological similarity to the Liliaceae, andUvularia andDisporum are now classified in theColchicaceae.Disporum contained both Asian and North American species which had always been distinguishable. Following molecular analysis, the North American species were restored to the genusProsartes and retained in Liliaceae, subfamily Streptopoideae, while the Asian species were moved to Colchicaceae.^{[54][110][111]}

Due to the diversity of the originally broadly defined Liliaceae (s.l.), many attempts have been made to form supageneric classification systems, organizing the genera intosubfamilies,tribes, or other suprageneric taxa (taxonomic groupings between genus and family).^[94] By 1813, Candolle recognised five subdivisions which he called tribes (Asparagées,Trilliacées,Asphodelées,Bromeliées,Tulipacées),^[17] all of which Jussieu had made separate families, with the exception ofTulipa, which was a genus within the Liliaceae. By 1845, John Lindley observed that the family had become extremely diverse, ill-defined and unstable, not only by its overall circumscription, but also by its subdivisions. For the 133 genera he included, he described elevensuborders.^[20] By the 1870s, asBaker describes in his revision of the family, the taxonomy of Liliaceae had become vast and complicated. His approach was to divide the family into eight tribes.^[112][113]

In 1879, a revision of the North American Liliaceae bySereno Watson described sixteen tribes, of which the Lilieae correspond most closely to current concepts of the family,^[114]Bentham and Hooker described twenty tribes in 1883, and Engler and Prantl in theirextensive description of the Liliaceae in 1899 identified 31 tribes distributed over 11 subfamilies, with Tulipeae and Alieae representing the modern family.^[115] In 1936,Franz Buxbaum undertook a major revision of the Liliaceae and among others described the subfamilyLilioideae with three tribes:Lloydieae (Gagea,Lloydia andSzechenya andGiradiella — both now included inLloydia),Tulipeae (Erythronium,Tulipa andEduardoregalia — now part ofTulipa) and Lilieae (Korolkowia,Fritillaria,Notholirion,Cardiocrinum,Nomocharis andLilium).^{[116][117][118]} Hutchinson included most of these genera within the tribe Tulipeae.^[91] The complex rearrangements of the various genera, tribes and subfamilies over a 30-year period from 1985, discussed by Peruzzi and colleagues (2009),^[94] are partly summarised inTable 2 below.

Classifications published since the use ofmolecular phylogenetics have taken a narrower view of the Liliaceae (s.s.). In 1998,Tamura consideredCalochortus sufficiently distinct to elevate the subfamilyCalochortoideae to family status as Calochortaceae,^[97][53] resulting in the term Liliaceaesensu Tamura to indicate Liliaceae without the Calochortoideae. In 2009,Takhtajan used an even narrower definition (seeTable 2 &Table 3 below).^[87]

Despite now having established a taxonomic grouping for the family Liliaceae that is genetically monophyletic, compared to the prior longstandingpolyphyletic assemblages under this name,^[51][119] the morphology remains diverse,^[97] and there exists within the Liliaceae clade a number of subclades. There appeared to be two major clades, the first and largest of these consisted of three subclades:Clintonia—Medeola—Gagea,LiliumFritillaria—Notholirion, andTulipa—Erythronium. The second smaller clade,Streptopus—Tricyrtis contained elements of Dahlgren's Uvulariaceae. The position ofCalochortus remained problematic, being considered a sister clade to Liliaceae, as treated by Tamura, but further analysis suggested it was in fact sister toTricyrtis, although it is now considered separate once again (seeTable 3).^{[63][54][93][120][121]}

Also enigmatic wereClintonia,Medeola,Scoliopus, andTricyrtis.Clintonia, with adisjunct distribution involving East Asia and North America, and the closely relatedMedeola form a subclades and are now considered a separate tribe (Medeoleae) within the Lilioideae, although at different times they have been considered a separate subfamily (Medeoloideae) or family (Medeolaceae). Sequencing of therbcLandmatK chloroplast genes established monophyly forClintonia, but with separate clades corresponding to the two areas of distribution.^[122] TheAngiosperm Phylogeny Website (APWeb)^[2] includes four of Takhtajan's families in Liliaceae, recognizing three subfamilies, one of which is divided into two tribes and referred to as Liliaceaesensu APG III.^[123]

Historically, the inclusion of genera within Liliaceae has been extremely broad. Of the various published systems, one of the best known and also the broadest modern circumscription is theCronquist system (1981),^[34] which included nearly 300 genera in Liliaceae. Most of these have been reassigned to other families, as shown in the following collapsed list, followingITIS, together with their disposition as APG III transfers to other families and subfamilies, withinLiliales and three other orders,Alismatales,Asparagales andDioscoreales. Current members of Liliaceae are shown inbold.^[125]

The more modern phylogenetically based treatment of the genera, including the major systems of the 1980s of Dahlgren and Tamura, are shown in Table 3.

The evolutionary and phylogenetic relationships between the genera currently included in Liliaceae are shown in Cladogram III.

The largest genera areGagea (200),^[132]Fritillaria (130),Lilium (110), andTulipa (75 species), all within the tribe Lilieae. Various authorities (e.g.ITIS 16,^[133]GRIN 27,^[134]WCSP,^[135]NCBI,^[136] DELTA^[137]) differ on the exact number of genera included in Liliaceaes.s., but generally there are about fifteen to sixteen genera, depending on whether or notAmana is included inTulipa andLloydia inGagea. For instanceAmana is still listed separately in WCSP.

The exact subdivision of Liliaceae differs between authors. In 2002 Patterson and Givnish identified two major clades corresponding to Tamura's Calochortaceae and Liliaceae,^[97] but preferred to retain his original division into two separate families rather than the overarching "core Liliales" (Liliaceaesensu APG). Within Liliaceaesensu Tamura they confirmed his decision to include Medeola-Clintonia as a separate subfamily, Medeolioideae, with the remaining genera as subfamily Lilioideae. Liliodeae was then divided into two tribes, Lilieae and Tulipeae (Tulipa,Erythronium,Gagea,Lloydia). Within Calochortaceaesensu Tamura, they proposed erecting a second subfamily, Streptopoideae (Prosartes,Scoliopus,Streptopus), with the remaining genera in subfamily Calochortoideae.^[54] Subsequent work by Rønsted et al. (2005)^[81] and by Fay et al. (2006) confirmed the overall phylogenetic relationships of Patterson and Givnish and their subdivisions, and further elucidated the position ofGagea within the tribe Tulipae, but the latter authors restored the broader circumscription of Liliaceaesensu APG .^[93] In 2013, Kim et al. proposed further subdivision, placing the two genera of Calochortoideae (Calochortus andTricyrtis) into subfamilies of their own and splitting offGagea from the rest of Tulipeae by resurrecting the tribeLloydieae.^[120][121] (seeTable 3)

The best known schema, theAPWeb, lists fifteen genera, arranged as follows, and illustrated in Table 4, with three subfamilies,Lilioideae representing Liliaceaesensu Tamura and the two subfamilies of Calochortaceaesensu Tamura (Streptopoideae andCalochortoideae) as proposed by Patterson and Givnish now included within Lilaceae sensu APG.^[2]

Table 4: APWeb/APG Distribution of Subfamilies, Tribes and Genera of Liliaceae^[2]
with illustration of morphological diversity

Subfamily	Tribe		Genus
LilioideaeEaton	MedeoleaeBenth.		ClintoniaRaf. - bead lilies
			MedeolaGronov. exL. - Indian cucumber-root
	Lilieaes.l.Ritgen		Cardiocrinum(Endl.)Lindl. - giant lilies
			FritillariaTourn. ex L. – fritillary or mission bells
			GageaSalisb. (includingLloydiaSalisb. exRchb.) – yellow star-of-Bethlehem1,2
			LiliumTourn. ex L. – lily
			NomocharisFranch.
			NotholirionWall. exBoiss.
			TulipaL. (includingAmanaHonda) – tulip1
			ErythroniumL. – trout lily1
CalochortoideaeDumort.3			CalochortusPursh - mariposa, globe lilies
			TricyrtisWall. – toad lily
Streptopoideae			ProsartesD.Don – drops of gold
			ScoliopusTorr. – Fetid Adder's Tongue
			StreptopusMichx. – twistedstalk
Some classifications placeTulipa,Erythronium andGagea into a separate tribe,Tulipeae with the remaining genera in Lilieaes.s.[94][120][121] Other authorities placeGagea within its own tribe, Lloydieae[120][121] The situation with respect to Calochortoideae remains uncertain. OriginallyCalochortus andTricyrtis were considered to be sister clades and placed together in subfamily Calochortoideae. Further study has not confirmed this (see Cladogram III, below) and it has been proposed thatTricyrtis be placed in a separate subfamily.[120][121]

The name Liliaceae was coined byMichel Adanson in 1763.^[6] The name was derived fromLilium and thefamily suffix-aceae.Lilium is thetype genus of the family, which is theLatin for Lily, which in turn came from theGreek name for it,λείριον (leírion).^[138][139]

• List of systems of plant taxonomy
• Phylogenetic nomenclature