Alismatales

Alismatales is the name of a plant taxon placed in the order taxonomic category, used in modern classification systems such as the 2009 APG III classification system and the APW, systems in which is located in monocots. It includes 13 families and about 165 widely distributed genera. Most of the families are composed of non-succulent herbaceous. The flowers are normally grouped in inflorescences and the mature seeds lack endosperm. Among the Alismatales are many families of aquatic habitats, and all marine angiosperms are delimited within this order.

The group is divided into a considerable number of small families, partly because the adaptations associated with aquatic habitats are so conspicuous that the particular flowers and inflorescences of these families are very different from each other.

Traditionally, the order Alismatales was restricted to only three families (Alismataceae, Butomaceae and Limnocharitaceae), the other families were assigned to different orders. This grouping produced polyphyletic groups, so in the current classification systems the rest of the families were added to this order (see taxobox). In particular, Araceae have recently been considered a sister group to the rest of the Alismatales (sometimes they were included in their own order Arales) and are now included in this order, making them the most important family in the order, with about 4000 species distributed in about 100 genera. The rest of the families of the order contain, in total, about 500 species.

Description

Theoretical Introduction in Descriptive Terminology of Plants

Rhizomatous plants, without mycorrhizae. Starch grains of the pteridophyte type, amylophilic. The extrorse anthers. The amoeboid tapetum. Uninucleate cells. Carpels with channels ("canals") completely unfused. With styles. Commonly with dry stigma. helobial endosperm. Large embryo, probably always chlorophyllic. Development from seed with well developed hypocotyl and root.

The root stele is often tri to pentarch.

When the leaves are petiolate, the vascular bundles are arranged in an arc, inverted bundles are also common.

In some Alismatales there seems to be a fusion between the bract underlying the flower and the abaxial tepal (Buzgo 2001).

It is not yet known whether the endexin in pollen is lamellar, as it is in Acorus.

Riley and Stockey (2004) describe the venation of a number of reticulate-venation members of this order in considerable detail, those leaves usually having tertiary veins.

The Alismatales, including Araceae, have been said to be the only monocots in which embryos have been reported to be green, and therefore chlorophyllous (Seubert 1993), but they are also known in the Amaryllidaceae-Amaryllidae.

There have been suggestions that the flowers on Alismatales are actually pseudantial, that is, if they are actually a reduced, flower-like inflorescence (Soltis et al. 2005 for references). Many authors have suggested that the "flowers" of Alismatales, except those of Araceae and Tofieldiaceae, are several types of modified inflorescences (Buzgo 2001, Rudall 2003), which could explain the wide variety of flower types found in these families.

Ecology

Alismatales contains many families adapted to marine habitats. Plants in marine habitats apparently evolved independently many times in the order, once within the Hydrocharitaceae, and more than twice in the seagrass families Zosteraceae, Cymodoceaceae, Ruppiaceae, and Posidoniaceae (Les et al. 1997a). Until a genus-level phylogenetic analysis is complete, it is not possible to know how many times adaptation to marine conditions occurred. However, marine angiosperms are confined to this order.

Green and Short (2003) provide a general discussion of the ecology of marine angiosperms, along with distribution maps, etc.

The apparent absence of mycorrhizae in this group may be connected to the prevalence of preferred aquatic habitats by its members, since mycorrhizae are usually absent in such situations.

Caterpillars of Pyralidae-Schoenobiinae are found in aquatic monocots, as well as Chrysomelidae-Donaciinae larvae (Powell et al. 1999, Jolivet 1988), the latter at least, are found in aquatic plants in general.

Les et al. (2003) discuss the distribution of a number of the hydrophytic taxa of this clade, many of them quite young.

For a relatively small clade, floral diversity is exceptionally high in Alismatales, and their pollination mechanisms are among the most extravagant to be found among angiosperms (Cox and Humphries 1993, Les et al. 1997a also discuss the pollination mechanisms of marine and freshwater AliSmatales).

Diversity

The taxonomic diversity of monocots is presented in detail by Kubitzki (1998, 2006).

The following is a list of the diversity of Alismatales. The descriptions are deliberately incomplete. For more information follow the links.

Inflorescence (yellow) and spat (white) of a cove. Araceae Main article: Araceae Rings and coves belong to the family of the sprigs. What seems to be the flower of the araceas, is actually the inflorescence, being the tiny and distributed flowers all along a thick spike called spadice; while what seems to be the great petal of the flower, is actually the bract that is born under the inflorescence, called spate. Inflorescences and spats are of different colors. In the espadice ripen the fruits that are small berries.

Water lentils (general aspect). Water lenses Main article: Lemnoideae Water lentils are in stagnant waters around the world. They are very small plants, with undifferentiated stem and leaves, in a lenticular way, sometimes with small roots under the surface of the water. Because of its shift to aquatic habit, both the raft and inflorescence have been very small, having to go to molecular DNA analysis to know its phylogenetic location. In this way it has been shown that they are a subfamily of the arace family (formerly they were located within their own family, Lemnaceae).

Habits of Tofieldia calyculata. Tofield Main article: Tofieldiaceae Distributed in cold regions of the Northern Hemisphere, they can be recognized by its isobifatal equitant leaves, its racemose inflorescences, in which there is usually a calcle (a simulated chalice of bracts or bracteolas) from 1 to 3 pieces below the flower, and monocotyleon flowers, with the teapals usually free and each tip of the carpals. The fruit is usually a septic capsule.

Habits of Elodea. Hydrocaritaceae Main article: Hydrocharitaceae La Elodea (also known as "yana"), as well as other genera of the Hydrocharitaceae family, is known in aquariums around the world. All hydrocaritaceae are aquatic, most fresh water although there are some salt water genres. Its leaves are fished or usually indifferentiated. Inflorescence often has two fused bracts (sometimes free) at the base. The ovary is inferous, often with laminar or parietal pleasing more or less intrusive. The lobes of stigma are bifids.

Habits of Butomus umbellatus. Butomaceae Main article: Butomaceae Butomus umbellatus It's the only species of the butomaceae family. It is a native herb of temperate Eurasia, naturalized in North American NE. It is an aquatic herb that can be recognized by its long, triangular leaves, and its umbelled inflorescence at the end of a escapo, axilar, bracteada. The flowers are perfect and there are clearly two separate verticils of perianto petaloides. The fruit is a follicle.

Habits of Sagittaria montevidensis. Alismataceae Main article: Alismataceae Alismataceae are herbs with laticulous, aquatic. Its floating or aerial leaves are sinned and have a prominent medium vein, parallel veins and also cross veins. Its petals are wrinkled in the pympoline and its masculine flowers usually have many extruded antennas and their female flowers have many free flaps. At a glance at the seed it is observed that the embryo is heavily curved. Inflorescences often consist of branches or flowers more or less verticilated at the end of a escapo. Widely distributed.

Flower of Hydrocleys nymphoides. Limnocaritaceae Main article: Limnocharitaceae They are aquatic herbaceous plants, floating or fixed by roots, present in tropical or subtropical regions. They're latent. Its floating or aerial leaves are sinned and have a prominent average vein and parallel and cross veins as well. Their flowers have sepals, petals small to large but evanescent, many stamens (and also staminods), and carpals with many eggs and laminar placentation. At a glance at the seed it is observed that the embryo is heavily curved. In APG III and APWeb this family was included in Alismataceae so that the latter is monophyllic and has apomorphies.

Habits of Scheuchzeria palustris. Scheuchzeriaceae Main article: Scheuchzeriaceae Scheuchzeria palustris is the only species of the Scheuchzeriaceae family. It is a perennial herbaceous plant, of pantanous places, native to cold regions of the Northern Hemisphere. It reaches 10-40 cm high, with narrow linear, basal, distic leaves, the open pods have atriums at the tip and there is a small pore at the tip of the foil. Cluster inflorescence has large folious bracts and all parts of the flowers (except the bases of the carpals) are free of each other and other floral pieces. The greenish yellow flowers have 4-6 mm in diameter with six petals.

Flowers and leaves Aponogeton distachyos. Aponogetonaceae Main article: Aponogetonaceae Aponogeton is the only genus of the family Aponogetonaceae. They are aquatic plants with pacified leaves, the foils sometimes fenestradas have a medium vein, parallel veins, and large cross veins, the finest veins are reticulated. Inflorescence is a spike at the end of a long escapo and flowers, rather small, have more or less conspicuous teapals. They are of tropical and subtropical regions, common in aquariums.

Flowers and leaves Triglochin maritima. Juncaginaceae Main article: Juncaginaceae Juncaginaceae are perennial, aquatic or pale herbs. They have more or less uniacable leaves and an inflorescence that is a spike or a cluster at the end of a escapo, all the floral parts are free from each other and from the other pieces. It consists of only about 10 species in 4 genera, distributed in temperate areas.

Habits of Posidonia. Seafood The so-called "sea ducks" evolved into a series of families closely related to each other: Zosteraceae, Cymodoceaceae, Ruppiaceae and Posidoniaceae. Due to their more or less linear leaves they have a look similar to land pastures but are not closely related to these. A family closely related to seagrass is Potamogetonaceae, which consists of freshwater plants.

Habits of Posidonia oceanica. Posidoniaceae Main article: Posidoniaceae Posidonia is the only genus of posidoniaceae. They are "sea ducks" recognizable by their fibrous strips without liigning persisnts along the monopodial rhizome, and branched cluster inflorescences. Distributed in the Mediterranean and southern Australia.

Habits of Ruppia cirrhosa. Rupiaceae Main article: Ruppiaceae Ruppia It's the only kind of rupiaceae. They are "sea ducks" but they are also in fresh water. They can be recognized by their serrulada, distic leaves, with an obvious medium vein and a wrapping base, the internals are well developed. Ruppiaceae is characterized by flowers with two stamens that have tiny appendices, slightly elongate pollen, and carpals with long stems. Distributed all over the world.

Habits of Cymodocea nodosa. Cymodoceaceae Main article: Cymodoceaceae They are more or less tropical to temperate-cálidos. It is a difficult family to distinguish from rupiaceae and needs more research.

Habits of Marine zoos. Zosteraceae Main article: Zosteraceae They are "sea ducks" with branches opposed to the leaves and axis of flat inflorescence (spadices) with flowers on the adaxial surface, inflorescences are enclosed by a spata. Many of them have "retinacles", perhaps they are either tepalos or bracts, opposed to stamens.

Sheets Potamogeton. Potamogetonaceae Main article: Potamogetonaceae They are perennial freshwater herbs. Most of them have more or less pecioladas with medium veins and cross veins, usually there is a conspicuous basal leg. The inflorescence is densely spiced and the flowers have small teapals that seem to be born in the back of the stambers. Carpets are besieged, as is particularly clear in Zannichellia, although that genus does not have a spurious inflorescence. Distributed more or less all over the world.

Phylogeny and description of clades

Theoretical Introduction in Philogenia

The order has often been divided into two, Arales (which includes only Araceae) and Alismatales sensu stricto (long equivalent to Alismatidae sensu Cronquist 1981 and Takhtajan 1997), with Arales possibly related to Arecales (for example in Cronquist 1981), but recent molecular DNA analyzes support the union of these two groups.

Cladistic analyzes of nuclear and chloroplastid DNA sequences (Chase et al. 1993, 1995b, 2000, 2006, Duvall et al. 1993, Hilu et al. 2003, Källersjö et al. 1998, Soltis et al. 2000) support the monophyly of Alismatales, as so does the possible morphological synapomorphy of stems with small scales of glandular hairs within the sheathing bases of the leaves at the nodes, the extrorse anthers, and the large, green embryo (Dahlgren and Rasmussen 1983, Dahlgren et al).. 1985, Stevenson and Loconte 1995). The trichomes found in the axils of the sheathing leaves, also known as intravaginal scales, are common in many Alismatales but also in Acorales. The evolution of raphidian crystals may constitute an apomorphy of monocots after the Acorales clade diverged, although they must have been lost secondarily in a number of monocot lineages, such as in many Poales, Zingiberales, and most of the monocots themselves. Alismatales (except Araceae).

Araceae are sister to the rest of the families of the order, they are different from the rest of the families by the inflorescence, the structure of the flowers, and the habit (in general they are not aquatic and do not have "gaps" 34; ("lacunae") in its stems, etc.), but Tofieldiaceae (family that diverges a little later) has been poorly studied regarding its relationship with the rest of the families of the order. The flowers of Tofieldiaceae are not described and are generally typical of monocots, except for some species that have up to 12 stamens, and the fruit is a septicidal capsule. In most species a calculus (a simulated calyx of bracts or bracteoles) is present below the flowers.

Araceae is by far the largest family of the order (106 genera with about 4000 species, cosmopolitan). The family is particularly diversified in the humid tropics, but there are some temperate genera (such as Arisaema) that are also species-rich. Araceae are typically herbs with a defined petiole and an expanded leaf blade. Their most distinctive character is the inflorescence, which has a often petaloidal spathe and a spadix of sessile flowers with an expanded sterile portion that emits odors. Many genera have separate male and female flower zones on the spadix. Duckweed, five genera formerly placed in Lemnaceae (Les et al. 1997b, Rothwell et al.2003) are embedded in Araceae, so they were included in family, are the smallest angiosperms. Molecular phylogenetic analyzes have indicated that Araceae is sister to the rest of the members of Alismatales, the monophyly of the clade being supported by DNA sequence data and by non-molecular characters.

Tofieldiaceae is located within the Alismatales with only moderate support from molecular analyzes (Källersjö et al. 1998, Chase et al. 2000, Graham et al. 2006 -which ranks it as a sister to the rest of the order, but sampling is limited). The family is quite different from the rest of the Alismatales, as can be seen by its numerous potential apomorphies. However, Tamura et al. (2004), Janssen and Bremer (2004), Givnish et al. (2006b), and Chase et al.. (2006, with strong support) all rank Araceae as sister to the rest of the order, and Tofieldiaceae as sister to the rest of the taxa, so that is the topology presented here.

The rest of the families of the order (all except Araceae and Tofieldiaceae) share seeds without endosperm and cell hairs on the roots that are shorter than other epidermal cells (Judd et al. 2007). All members of this subclade are present in wetland or aquatic habitats, and Judd et al call this subclade the "aquatic clade", while Stevens at the Angiosperm Phylogeny Website he calls it "nucleus of the Alismatales" ("core Alismatales"). This subclade probably diverged very early in the evolution of the monocots.

Alismatales.

For relationships within the aquatic clade, see Les et al. (1997a), on which this part of the tree is largely based. Also see Kato et al. (2003), Chen et al. (2004b) and G. Petersen et al. (2006c) that uses 2 mitochondrial genes and 1 chloroplastid. A number of uncertainties about the relationships remain and G. Petersen et al. (2006c) cannot even recover a monophyletic (Hydrocharitaceae + Alismataceae sensu lato + Butomaceae). Janssen and Bremer's (2004) tree is largely similar to the one presented here, but the positions of Aponogetonaceae and Scheuchzeriaceae are reversed, and Ruppiaceae is ranked sister to (Zosteraceae + Potamogetonaceae).

Two large clades are recognized within this aquatic clade. The first clade is the smallest and contains the Alismataceae, Hydrocharitaceae, Butomaceae and Limnocharitaceae, and is supported by the apomorphies of the perianth differentiated into sepals and petals, the stamens being more than 6 or the carpels more than 3 (a secondary increase), and the ovules scattered on the inner surface of the locules. It has a scapous inflorescence and seeds with exotesta.

Alismataceae sensu stricto and Limnocharitaceae are closely related and phylogenetic analyzes indicated that they should be considered a single family (Soros and Les 2002), as APG III (2009) finally does. and the APWeb. They are united by the presence of latex, leaves with a pseudopetiole with a midvein and crossing veins, spiny-pantoporate pollen, and a follicular fruit.

Butomaceae is monopodial with distichous, triangular leaves, and an umbel-like inflorescence. Like Araceae and Alismataceae, members of the Butomaceae have a distinct perianth and a follicular fruit.

Hydrocharitaceae is the largest family in this subclade (18 genera with 116 species). They are submerged aquatic, some of which are marine (such as Halophila, Enhalus, and Thalassia), with stalked leaves, usually undifferentiated, and an inflorescence with two underlying bracts, and an inferior ovary (the rest of this subclade has a superior ovary).

The largest families constituting the second clade within the aquatic Alismatales clade are Potamogetonaceae, Ruppiaceae, Zosteraceae, Posidoniaceae, and Cymodoceaceae. The smallest are Aponogetonaceae, Juncaginaceae and Scheuchzeriaceae. This group is diagnosed on the basis of a pollen that usually has no apertures and more or less lacks the exine (Dahlgren and Rasmussen 1983, Cox and Humphries 1993).

Scheuchzeriaceae is highly apomorphic and is not clearly related in its morphological characters to the rest of the second subclade. This family is monospecific, and has auriculate and couplet leaves, and a racemose inflorescence with many bracts, as in the other subclade the fruit is a follicle.

The rest of the subclade (the entire subclade except Scheuchzeriaceae) shares more or less linear leaves and, except for Aponogetonaceae, united carpels. In addition, they present an unusual condition in which the perianth appears to be a "growth" of the stamens.

Aponogetonaceae is monogeneric with 43 species. It presents petiolate leaves, parallel venation and crossed veins, and small spiked flowers with tepals.

Juncaginaceae (with 4 genera and 15 species) are emergent aquatic to terrestrial from humid sites, and have imperfect flowers often without perianth or with the perianth internal to the stamens.

The rest of the families are all rhizomatous, aquatic, pollinated by water, with ascidian carpels.

Posidoniaceae (monogeneric, 5 species), Ruppiaceae (perhaps monospecific) and Cymodoceaceae (5 genera, 16 species) are predominantly marine, with couplet leaves and threadlike pollen. Ruppiaceae should perhaps be included in Posidoniaceae, as these families are highly similar in many ways (but APWeb has not yet done so as of January 2009).

Zosteraceae (2 genera, 14 species) and Potamogetonaceae (7 genera, 122 species) share a leaf with an apical pore (its sheaths are closed), although the former is marine and the latter is found in freshwater. Zosteraceae are seagrasses with linear leaves and opposite-leaf branches, and spadic-enclosed inflorescences (see recent reviews by Les et al. 2002). Potamogetonaceae has stalked leaves with a median vein and a spiked inflorescence densely packed with flowers in which there is a tepal opposite each stamen. Pollination is commonly by wind or on the water surface or in the water.

Taxonomy

Theoretical Introduction in Taxonomy

The group is always divided into a number of small families, partly because the adaptations associated with aquatic habitats are so conspicuous that the particular flowers and inflorescences of these families are very different from each other.

Alismatales sensu APG III (2009) contains 13 families and about 3,320 species, the largest families being Araceae, Alismataceae, Hydrocharitaceae, Butomaceae, Potamogetonaceae, Ruppiaceae, Zosteraceae, Posidoniaceae, Cymodoceaceae, and Tofieldiaceae. Also present Aponogetonaceae, Juncaginaceae, Scheuchzeriaceae.

The APG III (2009) and the APWeb introduced a change with respect to the APG II (2003): they include Limnocharitaceae in an Alismataceae sensu lato, since apparently otherwise Alismataceae it would be paraphyletic. In this way the number of families in the order was reduced from 14 to 13.

The APWeb also suggests, but has not yet done so as of January 2009, merging Ruppiaceae with Cymodoceaceae because they are difficult to distinguish from each other.

The list of families, sensu APG III (2009, with the family numbers according to Linear APG III (LAPG III 2009)

• Araceae (family n.o. 30)
• Tofieldiaceae (family No. 31)
• Alismataceae (family No. 32)
• Butomaceae (family No. 33)
• Hydrocharitaceae (family No. 34)
• Scheuchzeriaceae (family No. 35)
• Aponogetonaceae (family No. 36)
• Juncaginaceae (family n.o 37)
• Zosteraceae (family No. 38)
• Potamogetonaceae (family No. 39)
• Posidoniaceae (family n.o 40)
• Ruppiaceae (family No. 41)
• Cymodoceaceae (family No. 42)
• Limnocharitaceae was in APG II but in APG III it is included in Alismataceae (family 32)

Synonyms (APW): Alismatales Dumortier, Aponogetonales Hutchinson, Arales Dumortier, Butomales Hutchinson, Cymodoceales Nakai, Elodeales Nakai, Hydrocharitales Dumortier, Juncaginales Hutchinson, Najadales Dumortier, Posidoniales Nakai, Potamogetonales Dumortier, Ruppiales Nakai, Scheuchzeriales B. Boivin, Tofieldiales Reveal and Zomlefer, Vallisneriales Nakai, Zosterales Nakai - Alismatanae Takhtajan, Aranae Reveal, Butomanae Reveal, Najadanae Reveal, Zosteranae Doweld - Alismatidae Takhtajan, Aridae Takhtajan - Aropsida Bartling, Hydrocharitopsida Bartling, Najadiopsida Hoffmannsegg and Link

Evolution

The Alismatales stem group dates from about 131 million years to the present, the Alismatales crown group from about 128 million years to the present (Janssen and Bremer 2004, instead in Bremer 2000b about 133 and 103 million years of years to the present).

The oldest fossils assigned to this clade were recently discovered in the early Cretaceous, about 110-120 million years old (Araceae-Pothoideae-Monstereae: Friis et al. 2004, see Stockey 2006 for a review of the fossils that have been located in Alismatales).

Chen et al. (2004b) discuss the evolution of various life forms in the group: parallels are common.

Sulphated phenolics are common in seagrasses and Hydrocharitaceae (McMillan et al. 1980), and was probably a parallel. Their function is not clear, they are probably involved in adapting to life in the marine habitat.