Product Code Database
Asparagales ( asparagoid lilies) are a diverse order of in the monocots. Under the APG IV system of flowering plant classification, Asparagales are the largest order of monocots with 14 families, 1,122 Genus, and about 36,000 species, with members as varied as asparagus, , , irises, onions, garlic, , and other , daffodils, Galanthus, Hippeastrum, , Ruscus, Agapanthus, Polygonatum, , Hyacinthoides, spider plants, Xanthorrhoea, aloe, , Gladiolus, , and saffron.
Most species of Asparagales are herbaceous , although some are vines and some are trees or shrubs. The order also contains many (bulbs, corms, and various kinds of tuber). The Leaf of almost all species form a tight rosette, either at the base of the plant or at the end of the plant stem, but occasionally along the stem. The are not particularly distinctive, being 'lily type', with six and up to six stamen. One of the defining characteristics (Synapomorphy) of the order is the presence of phytomelanin, a black pigment present in the seed coat, creating a dark crust. Phytomelanin is found in most families of the Asparagales (although not in Orchidaceae, thought to be the sister-group of the rest of the order).
The order Asparagales takes its name from the type family Asparagaceae and has only recently been recognized in classification systems. The order is clearly circumscribed on the basis of molecular phylogenetics, but it is difficult to define plant morphology since its members are structurally diverse. The order was first put forward by Huber in 1977 and later taken up in the Dahlgren system of 1985 and then the Angiosperm Phylogeny Group systems. Before this, many of its families were assigned to the old order Liliales, which was redistributed over three orders, Liliales, Asparagales, and Dioscoreales, based on molecular phylogenetics. The boundaries of the Asparagales and of its families have undergone a series of changes in recent years; future research may lead to further changes and ultimately greater stability.
The order is thought to have first diverged from other related monocots some 120–130 million years ago (early in the Cretaceous period), although given the difficulty in classifying the families involved, estimates are likely to be uncertain.
From an economic point of view, the order Asparagales is second in importance within the monocots only to the order Poales (which includes and ). Species are used as food and flavourings (e.g. onion, garlic, leek, asparagus, vanilla, saffron), in medicinal or cosmetic applications ( Aloe), as cut flowers (e.g. freesia, gladiolus, iris, ), and as garden Ornamental plant (e.g. Hemerocallis, Convallaria, Agapanthus).
Almost all species have a tight cluster of Leaf (a rosette), either at the base of the plant or at the end of a more-or-less woody plant stem as with Yucca. In some cases, the leaves are produced along the stem. The are in the main not particularly distinctive, being of a general 'lily type', with six , either free or fused from the base and up to six stamen. They are frequently clustered at the end of the plant stem.
The Asparagales are generally distinguished from the Liliales by the lack of markings on the tepals, the presence of septal nectaries in the ovaries, rather than the bases of the tepals or stamen filaments, and the presence of secondary growth. They are generally geophytes, but with linear leaves, and a lack of fine reticular venation.
The characteristically have the external epidermis either obliterated (in most species bearing fleshy fruit), or if present, have a layer of black carbonaceous phytomelanin in species with dry fruits (nuts). The inner part of the seed coat is generally collapsed, in contrast to Liliales whose seeds have a well developed outer epidermis, lack phytomelanin, and usually display a cellular inner layer.
The orders which have been separated from the old Liliales are difficult to characterize. No single morphological character appears to be diagnostic of the order Asparagales.
According to Telomere, at least two evolutionary switch-points happened within the order. The basal sequence is formed by TTTAGGG like in the majority of higher plants. Basal motif was changed to vertebrate-like TTAGGG and finally, the most divergent motif CTCGGTTATGGG appears in Allium.
The literature on the organisation of genera into families and higher ranks became available in the English language with Samuel Frederick Gray's A natural arrangement of British plants (1821). Gray used a combination of Linnaeus' sexual classification and Jussieu's natural classification to group together a number of families having in common six equal stamens, a single style and a perianth that was simple and petaloid, but did not use formal names for these higher ranks. Within the grouping he separated families by the characteristics of their fruit and seed. He treated groups of genera with these characteristics as separate families, such as Amaryllideae, Liliaceae, Asphodeleae and Asparageae.
The circumscription of Asparagales has been a source of difficulty for many botanists from the time of John Lindley (1846), the other important British taxonomist of the early nineteenth century. In his Lindley system, An Introduction to the Natural System of Botany (1830) he partly followed Jussieu by describing a subclass he called Endogenae, or Monocotyledonous Plants (preserving de Candolle's Endogenæ phanerogamæ) divided into two tribes, the Petaloidea and Glumaceae. He divided the former, often referred to as petaloid monocots, into 32 orders, including the Liliaceae (defined narrowly), but also most of the families considered to make up the Asparagales today, including the Amaryllideae.
By 1846, in his final scheme Lindley had greatly expanded and refined the treatment of the monocots, introducing both an intermediate ranking (Alliances) and tribes within orders ( i.e. families). Lindley placed the Liliaceae within the Liliales, but saw it as a Paraphyly ("catch-all") family, being all Liliales not included in the other orders, but hoped that the future would reveal some characteristic that would group them better. The order Liliales was very large and included almost all monocotyledons with colourful tepals and without starch in their endosperm (the ). The Liliales was difficult to divide into families because morphological characters were not present in patterns that clearly demarcated groups. This kept the Liliaceae separate from the Amaryllidaceae (Narcissales). Of these, Liliaceae was divided into eleven tribes (with 133 genera) and Amaryllidaceae into four tribes (with 68 genera), yet both contained many genera that would eventually segregate to each other's contemporary orders (Liliales and Asparagales respectively). The Liliaceae would be reduced to a small 'core' represented by the tribe Tulipae, while large groups such Scilleae and Asparagaceae would become part of Asparagales either as part of the Amaryllidaceae or as separate families. While of the Amaryllidaceae, the Agavaceae would be part of Asparagaceae but the Alstroemeriaceae would become a family within the Liliales.
The number of known genera (and species) continued to grow and by the time of the next major British classification, that of the Bentham & Hooker system in 1883 (published in Latin) several of Lindley's other families had been absorbed into the Liliaceae. They used the term 'series' to indicate suprafamilial rank, with seven series of monocotyledons (including Glumaceae), but did not use Lindley's terms for these. However, they did place the Liliaceous and Amaryllidaceous genera into separate series. The Liliaceae were placed in series Coronariae, while the Amaryllideae were placed in series Epigynae. The Liliaceae now consisted of twenty tribes (including Tulipeae, Scilleae and Asparageae), and the Amaryllideae of five (including Agaveae and Alstroemerieae). An important addition to the treatment of the Liliaceae was the recognition of the Allieae as a distinct tribe that would eventually find its way to the Asparagales as the subfamily Allioideae of the Amaryllidaceae.
Adolf Engler, in his Engler system developed Eichler's ideas into a much more elaborate scheme which he treated in a number of works including Die Natürlichen Pflanzenfamilien (Engler and Prantl 1888) and Syllabus der Pflanzenfamilien (1892–1924). In his treatment of Liliiflorae the Liliineae were a suborder which included both families Liliaceae and Amaryllidaceae. The Liliaceae had eight subfamilies and the Amaryllidaceae four. In this rearrangement of Liliaceae, with fewer subdivisions, the core Liliales were represented as subfamily Lilioideae (with Tulipae and Scilleae as tribes), the Asparagae were represented as Asparagoideae and the Allioideae was preserved, representing the alliaceous genera. Allieae, Agapantheae and Gilliesieae were the three tribes within this subfamily. In the Amaryllidaceae, there was little change from the Bentham & Hooker. A similar approach was adopted by Wettstein.
These various proposals to separate small groups of genera into more homogeneous families made little impact till that of Dahlgren system (1985) incorporating new information including synapomorphy. Dahlgren developed Huber's ideas further and popularised them, with a major deconstruction of existing families into smaller units. They created a new order, calling it Asparagales. This was one of five orders within the superorder Liliiflorae. Where Cronquist saw one family, Dahlgren saw forty distributed over three orders (predominantly Liliales and Asparagales). Over the 1980s, in the context of a more general review of the classification of angiosperms, the Liliaceae were subjected to more intense scrutiny. By the end of that decade, the Royal Botanic Gardens at Kew, the British Museum of Natural History and the Edinburgh Botanical Gardens formed a committee to examine the possibility of separating the family at least for the organization of their herbaria. 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.
From the Dahlgren system of 1985 onwards, studies based mainly on morphology had identified the Asparagales as a distinct group, but had also included groups now located in Liliales, Pandanales and Zingiberales. Research in the 21st century has supported the monophyly of Asparagales, based on morphology, 18S rDNA, and other DNA sequences, although some phylogenetic reconstructions based on molecular data have suggested that Asparagales may be paraphyletic, with Orchidaceae separated from the rest. Within the monocots, Asparagales is the sister group of the commelinid clade.
This cladogram shows the placement of Asparagales within the orders of Lilianae sensu Chase & Reveal (monocots) based on molecular phylogenetic evidence. The lilioid monocot orders are bracketed, namely Petrosaviales, Dioscoreales, Pandanales, Liliales and Asparagales. These constitute a Paraphyly assemblage, that is groups with a common ancestor that do not include all direct descendants (in this case commelinids as the sister group to Asparagales); to form a clade, all the groups joined by thick lines would need to be included. While Acorales and Alismatales have been collectively referred to as "alismatid monocots" (basal or early branching monocots), the remaining clades (lilioid and commelinid monocots) have been referred to as the "core monocots". The relationship between the orders (with the exception of the two sister orders) is , that is diverging in succession from the line that leads to the commelinids. Numbers indicate crown group (most recent common ancestor of the sampled species of the clade of interest) divergence times in mya (million years ago).
The tree shown above can be divided into a basal paraphyletic group, the 'lower Asparagales (asparagoids)', from Orchidaceae to Asphodelaceae, and a well-supported monophyletic group of 'core Asparagales' (higher asparagoids), comprising the two largest families, Amaryllidaceae sensu lato and Asparagaceae sensu lato.
Two differences between these two groups (although with exceptions) are: the mode of microsporogenesis and the position of the ovary. The 'lower Asparagales' typically have simultaneous microsporogenesis (i.e. cell walls develop only after both meiosis divisions), which appears to be an apomorphy within the monocots, whereas the 'core Asparagales' have reverted to successive microsporogenesis (i.e. cell walls develop after each division). The 'lower Asparagales' typically have an inferior ovary, whereas the 'core Asparagales' have reverted to a superior ovary. A 2002 morphological study by Rudall treated possessing an inferior ovary as a synapomorphy of the Asparagales, stating that reversions to a superior ovary in the 'core Asparagales' could be associated with the presence of nectaries below the ovaries. However, Stevens notes that superior ovaries are distributed among the 'lower Asparagales' in such a way that it is not clear where to place the evolution of different ovary morphologies. The position of the ovary seems a much more flexible character (here and in other ) than previously thought.
|
|
|
Orchids have simultaneous microsporogenesis and inferior ovaries, two characters that are typical of the 'lower Asparagales'. However, their nectaries are rarely in the septa of the ovaries, and most orchids have dust-like seeds, atypical of the rest of the order. (Some members of Vanilloideae and Cypripedioideae have crustose seeds, probably associated with dispersal by birds and mammals that are attracted by fermenting fleshy fruit releasing fragrant compounds, e.g. vanilla.)
In terms of the number of species, Orchidaceae diversification is remarkable, with recent estimations suggesting that despite the old origin of the family dating back to the late cretaceous, modern orchid diversity originated mostly during the last 5 million years. However, although the other Asparagales may be less rich in species, they are more variable morphologically, including tree-like forms.
The clade from Iridaceae upwards appears to have stronger support. All have some genetic characteristics in common, having lost Arabidopsis-type . Iridaceae is distinctive among the Asparagales in the unique structure of the inflorescence (a rhipidium), the combination of an inferior ovary and three stamens, and the common occurrence of unifacial leaves whereas bifacial leaves are the norm in other Asparagales.
Members of the clade from Iridaceae upwards have infra-locular septal nectaries, which Rudall interpreted as a driver towards secondarily superior ovaries.
The 'core Asparagales', comprising Amaryllidaceae sensu lato and Asparagaceae sensu lato, are a strongly supported clade, as are clades for each of the families. Relationships within these broadly defined families appear less clear, particularly within the Asparagaceae sensu lato. Stevens notes that most of its subfamilies are difficult to recognize, and that significantly different divisions have been used in the past, so that the use of a broadly defined family to refer to the entire clade is justified. Thus the relationships among subfamilies shown above, based on APWeb , is somewhat uncertain.
| +
! Approx. date in Millions of Years Ago !! Event |
| Origin of Asparagales, i.e. first divergence from other monocots |
| Split between Asphodelaceae and the 'core group' Asparagales |
| Origin of Alliodeae and Asparagoideae |
| Divergence of Agavoideae and Nolinoideae |
A 2009 study suggests that the Asparagales have the highest diversification rate in the monocots, about the same as the order Poales, although in both orders the rate is little over half that of the eudicot order Lamiales, the clade with the highest rate.
The APG III system's family circumscriptions are being used as the basis of the Kew-hosted World Checklist of Selected Plant Families. With this circumscription, the order consists of 14 families (Dahlgren had 31) with approximately 1120 genera and 26000 species.
Order Asparagales Link
The earlier 2003 version, APG II, allowed 'bracketed' families, i.e. families which could either be segregated from more comprehensive families or could be included in them. These are the families given under "including" in the list above. APG III does not allow bracketed families, requiring the use of the more comprehensive family; otherwise the circumscription of the Asparagales is unchanged. A separate paper accompanying the publication of the 2009 APG III system provided subfamilies to accommodate the families which were discontinued. The first APG system of APG system contained some extra families, included in square brackets in the list above.
Two older systems which use the order Asparagales are the Dahlgren system and the Kubitzki system. The families included in the circumscriptions of the order in these two systems are shown in the first and second columns of the table below. The equivalent family in the modern APG III system (see below) is shown in the third column. Note that although these systems may use the same name for a family, the genera which it includes may be different, so the equivalence between systems is only approximate in some cases.
| + Families included in Asparagales in three systems which use this order ! Dahlgren system !! Kubitzki system !! APG III system |
| Amaryllidaceae: Agapanthoideae |
| Asparagaceae: Agavoideae |
| Amaryllidaceae: Allioideae |
| Amaryllidaceae: Amaryllidoideae |
| Asparagaceae: Agavoideae |
| Asparagaceae: Agavoideae |
| Asparagaceae: Aphyllanthoideae |
| Asparagaceae: Asparagoideae |
| Asphodelaceae: Asphodeloideae |
| Asteliaceae |
| Asparagaceae: Agavoideae |
| Blandfordiaceae |
| Boryaceae |
| Not in Asparagales (family Dasypogonaceae, unplaced as to order, clade commelinids) |
| Asparagaceae: Nolinoideae |
| Tecophilaeaceae |
| Not in Asparagales (family Dasypogonaceae, unplaced as to order, clade commelinids) |
| Doryanthaceae |
| Asparagaceae: Nolinoideae |
| Asparagaceae: Nolinoideae |
| Asphodelaceae: Hemerocallidoideae |
| Asparagaceae: Agavoideae |
| Asparagaceae: Agavoideae |
| Asparagaceae: Scilloideae |
| Hypoxidaceae |
| Iridaceae |
| Ixioliriaceae |
| Asphodelaceae: Hemerocallidoideae |
| Lanariaceae |
| Not in Asparagales (family Alstroemeriaceae, order Liliales) |
| Asparagaceae: Lomandroideae |
| Asparagaceae: Nolinoideae |
| Orchidaceae |
| Not in Asparagales (family Philesiaceae, order Liliales) |
| Asphodelaceae: Hemerocallidoideae |
| Asparagaceae: Nolinoideae |
| Tecophilaeaceae |
| Asparagaceae: Brodiaeoideae |
| Asphodelaceae: Xanthorrhoeoideae |
|
|
