Alismatids

(Tree TSAR early-diverging monocot grade)

1. Supertaxonomy Overview

The Alismatids are Tree TSAR’s explanatory grouping for the two earliest-diverging living monocot lineages, Acorales and Alismatales. Together they include sweet flags, aroids, duckweeds, water-plantains, flowering rush, frogbit and waterweeds, pondweeds, arrow-grasses, and every living seagrass lineage. The group contains about fifteen extant families and roughly 4,500 species, the great majority belonging to Alismatales and especially Araceae. It is one of the most important parts of the flowering-plant tree for understanding how the distinctive monocot body plan emerged and how flowering plants repeatedly adapted to wetlands, freshwater, and eventually the sea (Givnish et al. 2018; Chen et al. 2022; Angiosperm Phylogeny Group 2026).

Alismatids in this Tree TSAR sense do not form a monophyletic clade. Acorales is sister to all other living Monocots, whereas Alismatales is sister to the remaining Monocots after Acorales diverges. Acorales plus Alismatales therefore form a paraphyletic evolutionary grade: a useful sequence of early branches rather than a crown clade containing all descendants of a single exclusive common ancestor. Tree TSAR uses the name deliberately in the same explanatory spirit as other operational grades, because it gives readers a memorable landmark for the first stages of monocot diversification without implying that the two orders are one exclusive natural group (Timilsena et al. 2022; Angiosperm Phylogeny Group 2026).

The ecological association with water is conspicuous but must be described carefully. Acorus is primarily a wetland plant, and most non-aroid Alismatales are aquatic, amphibious, or marsh-dwelling. Alismatales contains the largest radiation of aquatic angiosperms and all fully marine flowering plants. Yet Araceae contributes several thousand species of terrestrial herbs, climbers, epiphytes, and hemiepiphytes, particularly in tropical forests. The Alismatid story is therefore not simply a story of aquatic plants; it is a story of an ancient monocot radiation in which wetland ancestry, terrestrial diversification, and repeated transitions into fresh and salt water became intertwined (Chen et al. 2022).

Several of the most dramatic angiosperm life forms occur here. Duckweeds reduce the flowering-plant body to tiny floating thalli only millimeters across. Seagrasses live completely submerged in marine sediments and complete pollination underwater. Aroids range from minute floaters to giant tropical herbs and canopy climbers. Water-plantains, pondweeds, eelgrasses, and tape-grasses occupy freshwater and coastal habitats worldwide, while Acorus retains an unusual combination of features that has made it central to research on the earliest monocot condition.

For Tree TSAR, Alismatids is useful precisely because it marks a transition rather than a rigid rank. The Monocots page introduces the full radiation; the Alismatids page focuses on the earliest two surviving branches and the evolutionary problem of life in water; Acorales and Alismatales can then receive their own order-level treatments without forcing the reader through a series of obscure historical subclasses. This produces a compact handoff from broad monocot identity to the specialized biology of the earliest-diverging lineages.

2. Placement in Tree TSAR

Within Tree TSAR, the broad pathway is:

Seed Plants → Angiosperms → Monocots → Alismatids

The Alismatids page gathers Acorales and Alismatales as an explanatory early-diverging grade. APG V continues to place Acorales as sister to all other living Monocots and Alismatales as the next branch, before Petrosaviales and the later lilioid and commelinid radiations. That ordering agrees with the broad pattern recovered repeatedly by plastid and large nuclear datasets, even though relationships within Alismatales and among some later monocot orders remain more contentious (Givnish et al. 2018; Timilsena et al. 2022; Angiosperm Phylogeny Group 2026).

Acorales contains only Acoraceae and the genus Acorus. Its small living diversity contrasts sharply with its phylogenetic importance. The position of Acorus at the base of the living monocot tree means that comparisons between Acorus, Alismatales, and later Monocots are repeatedly used to test hypotheses about ancestral leaf development, roots, vascular anatomy, genome organization, and ecology.

Alismatales is much larger, with fourteen families in the APG framework. Araceae accounts for most of its species richness, while Tofieldiaceae and the twelve-family core alismatid radiation contribute a smaller number of species but an extraordinary share of the world’s aquatic angiosperm diversity. APG V does not fragment this assemblage into the multiple orders favored by some alternative classifications; Tree TSAR follows the APG V ordinal scaffold and therefore treats those lineages beneath Alismatales rather than recognizing Arales, Tofieldiales, or Potamogetonales as parallel primary orders (Angiosperm Phylogeny Group 2026; Les & Tippery 2026).

No formally ranked name is presented beneath the Tree TSAR page title as an exact synonym. The historical subclass name Alismatidae has been applied to several different circumscriptions, usually focused on the aquatic core of Alismatales and not to the specific Acorales + Alismatales grade used here. Treating Alismatidae as though it were a one-to-one formal equivalent would therefore create more confusion than clarity. The relationship among these terms is explained explicitly in the classification and nomenclature sections below.

3. Evolutionary History and Fossil Context

The Alismatid grade reaches back to the initial radiation of Monocots in the Early Cretaceous. Molecular-clock estimates vary, but modern analyses commonly place the monocot crown well over 120 million years ago. Because Acorales and Alismatales are the first two living branches, their stems must have separated very early in that history. The living plants should not be mistaken for unchanged relics, however: both lineages have had more than 100 million years to evolve independently, and their modern traits are mixtures of retained ancestral states and substantial specialization (Givnish et al. 2018).

The best Early Cretaceous fossil evidence comes from Alismatales, especially Araceae. Mayoa portugallica, known from distinctive inaperturate striate pollen from the Barremian-Aptian of Portugal, was assigned to Araceae and provides a conservative minimum for the existence of a relatively derived alismatid lineage early in the Cretaceous. Spixiarum kipea from the Crato Formation of Brazil, approximately 115-112 million years old, preserves a more complete aroid plant and has been interpreted as closely allied to Orontioideae. These fossils imply that major internal monocot divergences had already occurred well before the middle of the Cretaceous (Friis et al. 2004; Coiffard et al. 2013).

Aquatic adaptation became one of the defining evolutionary experiments of Alismatales. The order contains emergent marsh plants, rooted floating-leaved species, free-floating plants, completely submerged freshwater species, and seagrasses that live and reproduce in marine environments. Phylogenomics indicates that submerged and marine life involved extensive changes to genes associated with stomata, light response, ethylene signaling, ion uptake, and other physiological systems. Whole-genome duplication also occurred repeatedly, including events associated with the core alismatid and seagrass lineages (Chen et al. 2022).

Whether the ancestral Monocot itself was aquatic or wetland-adapted remains unresolved. Givnish et al. (2018) argued that the concentration of aquatic or wetland habits in Acorales and Alismatales supports an aquatic model for the origin of the monocot syndrome. Broader macroevolutionary reconstruction by Meseguer et al. (2022), however, inferred a terrestrial monocot ancestor and interpreted aquatic life as an early transition rather than the ancestral state. Extinction, incomplete sampling of ancient lineages, and the difficulty of reconstructing habitat over deep time leave room for continued debate.

The marine radiation is younger than the origin of Alismatales itself and occurred more than once. Modern seagrasses belong to several families, including Hydrocharitaceae, Cymodoceaceae, Posidoniaceae, and Zosteraceae, and phylogenomic analyses support independent transitions from freshwater ancestors into marine conditions. Their fossil record becomes increasingly informative through the Cenozoic, but the early history of fully marine flowering plants remains less securely documented than the Early Cretaceous history of aroids.

Tree TSAR treats fossils as evolutionary context rather than forcing them into the active extant family hierarchy. Their value is to show that the apparent ecological novelty of modern aquatic Monocots rests on lineages with deep Cretaceous roots.

4. Classification and Circumscription

Alismatid nomenclature is unusually easy to misunderstand because three different ideas have often been expressed with nearly the same word. Historical classifications recognized rank-based groups such as Alismatidae, Helobiae, and Alismatanae for predominantly aquatic Monocots. Modern APG classifications instead recognize Acorales separately and place a broad Alismatales immediately after it in the monocot sequence. Informal authors have then used ‘alismatids’ either for the Acorales + Alismatales early-diverging grade or for the aquatic core nested within Alismatales. Tree TSAR therefore defines its usage explicitly rather than assuming that every occurrence of the name has the same circumscription.

The formal subclass name Alismatidae is most often associated with Takhtajan’s rank-based systems, although suprageneric nomenclature around the name has a longer and more complicated history. Takhtajan’s Alismatidae grouped a series of aquatic monocot orders that later phylogenetic systems reorganized substantially. Araceae and Acorus were often handled outside that subclass, which means historical Alismatidae is not equivalent to the broad Tree TSAR Alismatid grade (Takhtajan 1967; Reveal 2012).

A second usage is ‘core alismatids.’ In the broad APG circumscription of Alismatales, twelve mostly aquatic families form a major radiation apart from Araceae and Tofieldiaceae: Alismataceae, Aponogetonaceae, Butomaceae, Cymodoceaceae, Hydrocharitaceae, Juncaginaceae, Maundiaceae, Posidoniaceae, Potamogetonaceae, Ruppiaceae, Scheuchzeriaceae, and Zosteraceae. These are the lineages most consistently meant by core Alismatids, Helobiae, or Alismatiflorae in modern comparative literature (Luo et al. 2016; Chen et al. 2022).

The deepest relationships within Alismatales illustrate why APG V favors a conservative family-and-order framework. Plastid analyses have variously placed Araceae or Tofieldiaceae near the base of the order. Large nuclear analyses are themselves not completely uniform. Chen et al. (2022) recovered Tofieldiaceae + Araceae as sister to the core alismatids and found that incomplete lineage sorting and introgression best explained substantial gene-tree conflict. Timilsena et al. (2022), using hundreds of nuclear genes, instead strongly recovered Tofieldiaceae as sister to the remainder of Alismatales. These disagreements concern relationships among well-supported families, not the legitimacy of the families themselves or the broader identity of Alismatales.

A recent alternative deserves special attention. Les and Tippery (2026) use Alismatidae for the aquatic core and recognize Alismatales and Potamogetonales as subordinate orders within it. That system is useful for detailed discussion of aquatic monocot evolution and reproductive biology, but it is not the APG V ordinal treatment. Tree TSAR follows APG V for its principal order-level scaffold while acknowledging the alternative so readers encountering recent alismatid literature understand why familiar families may appear under different order names.

Tree TSAR’s Alismatids page therefore has a deliberately broader and more operational purpose. It unites Acorales and Alismatales for navigation because they are successive early branches with shared relevance to early monocot evolution, not because Tree TSAR is asserting that they form a clade or reviving a historical subclass unchanged.

5. Morphology, Biology, and Identification

There is no single morphological synapomorphy for Tree TSAR’s Alismatid grade because the grade is not a clade. Instead, its members share the general monocot developmental architecture while displaying an especially informative concentration of wetland and aquatic traits. Adventitious roots, rhizomatous growth, extensive air spaces, flexible leaves, reduced mechanical tissues, and altered stomatal development recur frequently among aquatic members, but terrestrial and climbing aroids depart strongly from this ecological pattern.

Acorus consists of aromatic rhizomatous wetland herbs with two-ranked, sword-like leaves and dense cylindrical inflorescences. The spike of small flowers can superficially resemble an aroid spadix, which explains why Acorus was historically placed near or within Araceae. Detailed morphology and molecular evidence instead show that the resemblance does not justify placing Acorus inside the aroid family; its isolated phylogenetic position is much deeper.

Araceae are often recognized by the spadix, a fleshy axis bearing numerous small flowers, usually associated with a specialized bract called the spathe. The family includes terrestrial herbs, climbers, epiphytes, hemiepiphytes, aquatics, and the highly reduced duckweeds. Familiar leaf blades may be entire, lobed, fenestrated, sagittate, or compound-like, demonstrating that the usual image of a monocot as a narrow parallel-veined herb is far too restrictive.

The core aquatic lineages display some of the most striking reductions and transformations in angiosperm morphology. Submerged leaves may become ribbon-like or finely dissected; emergent and submerged leaves can differ dramatically on the same plant; vascular and supporting tissues may be reduced; and large intercellular air spaces facilitate internal gas movement. In completely submerged plants, stomata may be absent or developmentally suppressed because ordinary gas exchange with the atmosphere no longer occurs (Chen et al. 2022).

Reproductive biology is equally diverse. Many water-plantains and their relatives retain conspicuous, insect-pollinated flowers held above water, whereas other lineages evolved pollination at the water surface or entirely underwater. Les and Tippery (2026) reconstructed underwater pollination as having arisen independently at least three times among the aquatic alismatid lineages. Surface pollination, floating male flowers, elongated female flower stalks, filamentous pollen, and other specialized mechanisms solve the basic problem of moving pollen in an environment for which ordinary airborne pollination is poorly suited.

Identification must therefore occur at order and family scale rather than by searching for a single ‘alismatid character.’ An aromatic wetland Acorus, a climbing Monstera, a floating duckweed, a Sagittaria with arrow-shaped leaves, a submerged Potamogeton, and a marine Zostera look radically different. Their relationship is an evolutionary conclusion supported by comparative morphology and genomics, not an obvious visual resemblance.

6. Distribution and Ecology

Alismatids occur worldwide, from boreal and temperate wetlands to tropical forests, rivers, lakes, marshes, estuaries, and shallow coastal seas. Their geographic breadth reflects two very different centers of ecological diversity: species-rich terrestrial and epiphytic Araceae are concentrated especially in humid tropical regions, whereas aquatic Alismatales occupy inland and coastal waters across nearly every climatic zone.

Freshwater members span nearly the full range of aquatic vascular-plant life forms. Emergent plants such as Alisma and Sagittaria root in saturated substrates while extending leaves and flowers into the air. Floating-leaved and free-floating forms exploit the water surface. Submerged genera such as Potamogeton, Vallisneria, Elodea, and Hydrilla conduct most vegetative growth below the surface. Duckweeds float unattached and reproduce rapidly through vegetative budding, producing some of the smallest flowering plants on Earth.

Seagrasses represent the most complete return of flowering plants to the sea. They root in marine sediments, tolerate salt, remain submerged, and complete their reproductive cycles in coastal waters. Seagrass meadows stabilize sediments, dampen wave energy, store carbon, cycle nutrients, and provide nursery and feeding habitat for fishes, invertebrates, sea turtles, waterfowl, and marine mammals. Their grass-like appearance is convergent: seagrasses belong to Alismatales, not Poaceae.

The Alismatid grade also illustrates repeated ecological reversals and radiations. Most aroids are not aquatic, despite their position in an order famous for aquatic plants. Some lineages returned to terrestrial forest floors or climbed into forest canopies; others independently became floating or submerged. This mosaic makes Alismatids especially valuable for studying how habitat shifts influence plant morphology, genome evolution, physiology, and diversification.

Aquatic habitats impose strong selective pressures. Light quality changes rapidly with depth, diffusion of gases is much slower in water than in air, water movement places different mechanical demands on leaves and stems, and marine environments add salinity and tidal disturbance. Alismatales repeatedly evolved solutions to these problems rather than relying on a single inherited aquatic syndrome (Chen et al. 2022; Meseguer et al. 2022).

7. Human Uses and Cultural Importance

Alismatids include important food plants, ornamentals, aquarium plants, wetland species, and ecosystem-forming marine plants. Their direct economic importance is smaller than that of grasses or palms, but several members are deeply embedded in regional food systems and global horticulture.

Taro, Colocasia esculenta, is the most important food crop in the group. Its starch-rich corms and leaves are traditional foods across tropical and subtropical regions, especially in the Pacific, Asia, Africa, and the Caribbean, although appropriate preparation is essential because raw tissues contain irritating calcium oxalate crystals. Other edible Alismatids include cultivated or traditionally harvested Sagittaria tubers and Aponogeton distachyos, the South African waterblommetjie used as a vegetable.

Araceae are major horticultural plants. Anthurium, Philodendron, Monstera, Spathiphyllum, Alocasia, Colocasia, Aglaonema, Dieffenbachia, Zamioculcas, and many other genera are foundational to tropical ornamental and houseplant horticulture. Their extraordinary leaf shapes, climbing habits, inflorescences, and shade tolerance have made aroids one of the most visible plant families in contemporary indoor gardening.

Aquatic horticulture and aquaria depend heavily upon Alismatales. Echinodorus, Vallisneria, Cryptocoryne, Anubias, Aponogeton, Sagittaria, and related genera are widely cultivated in ponds and aquaria. The same biological traits that make some species useful ornamentals can make others serious invasive plants when introduced outside their native ranges; Hydrilla verticillata, several Egeria and Elodea, flowering rush, and water lettuce illustrate the management problems created by highly effective aquatic growth and vegetative spread.

Acorus has a long history as an aromatic and culturally important wetland plant in Eurasia and North America, although chemical variation among populations and regulatory concerns mean traditional medicinal claims should not be treated as evidence of modern therapeutic safety or efficacy.

Seagrasses have comparatively limited direct horticultural use but immense indirect human value. Healthy seagrass meadows support fisheries, protect shorelines, store carbon, and maintain coastal biodiversity. Their economic importance therefore comes primarily from ecosystem services rather than cultivation.

8. Conservation Significance

Alismatids combine globally abundant weeds and houseplants with highly vulnerable wetland, freshwater, island, and marine specialists. Conservation risk cannot be generalized across the entire grade, but habitat dependence makes many lineages sensitive to changes in water quality, hydrology, coastlines, and climate.

Freshwater Alismatales are threatened by wetland drainage, channelization, dams, groundwater alteration, eutrophication, sedimentation, herbicide exposure, invasive species, and physical disturbance. Species adapted to clear oligotrophic water or narrow hydrological regimes may decline rapidly when nutrient levels or flow patterns change. Conversely, a subset of aquatic species becomes invasive in disturbed waters, creating the paradox that some of the most conspicuous Alismatids are management targets while close relatives are conservation priorities.

Seagrasses face coastal development, dredging, sedimentation, nutrient enrichment, destructive anchoring and boating, disease, marine heatwaves, and sea-level-related habitat change. Because light availability is essential to submerged photosynthesis, even disturbances that do not directly remove plants can eliminate meadows by increasing turbidity or stimulating algal growth. Global seagrass decline has therefore become a major coastal-conservation concern (Waycott et al. 2009).

Terrestrial and epiphytic aroids face a different suite of pressures. Tropical deforestation, forest fragmentation, limestone quarrying, narrow island distributions, and collection for specialty horticulture can threaten localized species even while common ornamental genera are propagated on an industrial scale. Accurate provenance and legal, nursery-propagated material are particularly important for rare taxa sought by collectors.

Ex situ conservation strategies must match the biology of each lineage. Conventional seed banking is effective for some species, while aquatic plants may require living collections, carefully managed seed storage, cryopreservation, or tissue culture. Botanical gardens and aquaria can maintain documented living material, but preserving functioning wetlands, rivers, estuaries, and seagrass meadows remains indispensable because many ecological interactions and population processes cannot be recreated in cultivation.

9. Major Included Groups

Acorales

Acorales contains Acoraceae and Acorus and represents the earliest-diverging living monocot branch in the prevailing APG V framework. Sweet flags are rhizomatous wetland herbs of the Northern Hemisphere and parts of Asia, recognizable by aromatic tissues, sword-like leaves, and a dense flower-bearing spike. Their small species diversity makes Acorales easy to overlook, but its phylogenetic position gives the order exceptional importance for reconstructing early monocot evolution (Givnish et al. 2018; Timilsena et al. 2022).

Alismatales

Alismatales is the second major living monocot branch and contains nearly all of the diversity represented on the Alismatids page. APG recognizes fourteen families, ranging from the overwhelmingly tropical and often terrestrial Araceae to tiny Tofieldiaceae and the twelve-family core alismatid radiation. Together they encompass approximately 4,500 species and most of the world’s evolutionary diversity of aquatic flowering plants (Luo et al. 2016; Chen et al. 2022).

Araceae

Araceae dominate Alismatid species richness. Aroids include terrestrial herbs, climbers, epiphytes, hemiepiphytes, aquatics, giant herbs, and duckweeds. Their spadix-and-spathe inflorescence architecture is one of the most recognizable floral systems among Monocots. The family’s inclusion within Alismatales was a major departure from older systems that treated Arales separately.

Tofieldiaceae

Tofieldiaceae are a small mostly Northern Hemisphere family of herbaceous plants that occupy a critical position near the root of Alismatales. Their exact relationship to Araceae and the core alismatids has differed among plastid and nuclear analyses, making them disproportionately important for understanding the early radiation of the order (Chen et al. 2022; Timilsena et al. 2022).

Core Alismatids

The core alismatids comprise twelve families: Alismataceae, Aponogetonaceae, Butomaceae, Cymodoceaceae, Hydrocharitaceae, Juncaginaceae, Maundiaceae, Posidoniaceae, Potamogetonaceae, Ruppiaceae, Scheuchzeriaceae, and Zosteraceae. This clade contains most of the highly specialized freshwater and marine forms traditionally associated with Alismatidae or Helobiae. It includes water-plantains and arrowheads, flowering rush, waterweeds and tape-grasses, pondweeds, arrow-grasses, and the principal seagrass lineages. Tree TSAR leaves detailed family relationships to the Alismatales and family pages rather than duplicating them here.

10. Similar, Overlapping, or Historically Confused Groups

Alismatids is not synonymous with Alismatales in Tree TSAR. Alismatales is a monophyletic APG order. Tree TSAR Alismatids is a broader explanatory grade containing both Acorales and Alismatales because they are the first two successive branches of the living monocot tree.

Alismatidae is a historical rank-based name, most commonly encountered as a monocot subclass. Its circumscription varies substantially among authors and generally does not equal the Tree TSAR grade. Recent aquatic-botany literature may use Alismatidae for the core aquatic radiation within Alismatales, again with a different boundary from Tree TSAR’s usage (Reveal 2012; Les & Tippery 2026).

Core alismatids refers specifically to the twelve-family aquatic-rich clade within Alismatales, excluding Araceae and Tofieldiaceae. It is therefore nested several levels below the Tree TSAR Alismatids grade and should never be used interchangeably with it.

Helobiae and Alismatiflorae are historical or morphological names applied to much of the core aquatic radiation. They remain useful search terms in older anatomical and developmental literature but are not principal Tree TSAR navigation units.

Basal monocots is an older informal expression sometimes applied to Acorales and Alismatales. Tree TSAR prefers early-diverging Monocots or Alismatids because ‘basal’ is easily misread as meaning primitive, unchanged, or inferior. Acorus and modern aquatic Alismatales are living endpoints of long independent evolutionary histories, not ancestral forms preserved intact.

Arales is another important historical name. Older classifications commonly separated aroids into Arales, and some recent authors continue to favor a separate Arales for Araceae. APG V instead retains Araceae within Alismatales, which is the framework followed by Tree TSAR.

Aquatic monocots is an ecological description rather than a clade. Numerous aquatic Monocots also occur outside the Alismatid grade, including lineages in Commelinales and Poales. Conversely, many Araceae are terrestrial. Likewise, water lilies are aquatic angiosperms but belong to Nymphaeales, far outside Monocots.

11. Additional Information

The APG V classification is the principal contemporary framework for the order-level arrangement used here. Its Monocot backbone retains Acorales and Alismatales as the first two successive branches and does not replace the broad APG Alismatales with the more finely divided order systems sometimes used by specialists (Angiosperm Phylogeny Group 2026).

The Angiosperm Phylogeny Website is especially useful for comparing morphology, family relationships, fossil evidence, and competing topologies within Acorales and Alismatales. It also documents the historical names Helobiae and core alismatids and is valuable when older literature uses circumscriptions that differ from APG.

Plants of the World Online and World Flora Online are useful for accepted family, genus, and species names, distributions, and synonymy. GBIF and iNaturalist can provide occurrence context, although aquatic-plant records require careful interpretation because floating fragments, cultivated aquarium plants, and invasive populations can complicate distributions.

For the specialized aquatic radiation, Les and Tippery (2026) provide a current synthesis of alismatid phylogeny and pollination evolution, while Chen et al. (2022) provides a genomic perspective on freshwater and marine adaptation. These sources use narrower applications of ‘alismatid’ than Tree TSAR’s page title, so readers should compare circumscriptions before transferring names directly between classification systems.

Tree TSAR’s purpose is not to impose an additional formal rank on the early monocot tree. The Alismatids page instead creates a stable explanatory bridge between Monocots and the two earliest-diverging orders, while the Acorales and Alismatales pages carry the detailed taxonomic treatment.

12. References and Further Reading

Angiosperm Phylogeny Group (2016) An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG IV. Botanical Journal of the Linnean Society 181(1): 1–20. https://doi.org/10.1111/boj.12385 (opens in a new tab)

Angiosperm Phylogeny Group, Byng JW, Chase MW, Christenhusz MJM, Fay MF, Li D-Z, Ma H, Mabberley DJ, Soltis DE, Soltis PS, et al. (2026) Large-scale nuclear and plastid phylogenomic analyses inform an updated Angiosperm Phylogeny Group classification: APG V. Journal of Systematics and Evolution. Published online 18 June 2026.

Chase MW, Reveal JL (2009) A phylogenetic classification of the land plants to accompany APG III. Botanical Journal of the Linnean Society 161(2): 122–127. https://doi.org/10.1111/j.1095-8339.2009.01002.x (opens in a new tab)

Chen L-Y, Lu B, Morales-Briones DF, Moody ML, Liu F, Hu G-W, Huang C-H, Chen J-M, Wang Q-F (2022) Phylogenomic analyses of Alismatales shed light into adaptations to aquatic environments. Molecular Biology and Evolution 39(5): msac079. https://doi.org/10.1093/molbev/msac079 (opens in a new tab)

Coiffard C, Mohr BAR, Bernardes-de-Oliveira MEC (2013) The Early Cretaceous aroid Spixiarum kipea gen. et sp. nov., and implications on early dispersal and ecology of basal monocots. Taxon 62(5): 997–1008. https://doi.org/10.12705/625.21 (opens in a new tab)

Friis EM, Pedersen KR, Crane PR (2004) Araceae from the Early Cretaceous of Portugal: Evidence on the emergence of monocotyledons. Proceedings of the National Academy of Sciences of the United States of America 101(47): 16565–16570. https://doi.org/10.1073/pnas.0407174101 (opens in a new tab)

Givnish TJ, Zuluaga A, Spalink D, Soto Gomez M, Lam VKY, Saarela JM, Sass C, Iles WJD, de Sousa DJL, Leebens-Mack J, et al. (2018) Monocot plastid phylogenomics, timeline, net rates of species diversification, the power of multi-gene analyses, and a functional model for the origin of monocots. American Journal of Botany 105(11): 1888–1910. https://doi.org/10.1002/ajb2.1178 (opens in a new tab)

Les DH, Tippery NP (2026) Alismatid phylogeny and evolution. Aquatic Botany 206: 104024. https://doi.org/10.1016/j.aquabot.2026.104024 (opens in a new tab)

Li Z-Z, Lehtonen S, Chen J-M (2023) The dynamic history of plastome structure across aquatic subclass Alismatidae. BMC Plant Biology 23: 125. https://doi.org/10.1186/s12870-023-04125-x (opens in a new tab)

Luo Y, Ma P-F, Li H-T, Yang J-B, Wang H, Li D-Z (2016) Plastid phylogenomic analyses resolve Tofieldiaceae as the root of the early diverging monocot order Alismatales. Genome Biology and Evolution 8(3): 932–945. https://doi.org/10.1093/gbe/evv260 (opens in a new tab)

Meseguer AS, Carrillo R, Graham SW, Sanmartín I (2022) Macroevolutionary dynamics in the transition of angiosperms to aquatic environments. New Phytologist 235(1): 344–355. https://doi.org/10.1111/nph.18100 (opens in a new tab)

Reveal JL (2012) An outline of a classification scheme for extant flowering plants. Phytoneuron 2012-37: 1–221.

Stevens PF (2001 onwards) Angiosperm Phylogeny Website. Missouri Botanical Garden, St. Louis. http://www.mobot.org/MOBOT/Research/APweb/ (opens in a new tab)

Takhtajan A (1967) Sistema i Filogeniia Tsvetkovykh Rastenii [Systema et Phylogenia Magnoliophytorum]. Nauka, Moscow. [Dated 1966; published 1967.]

Timilsena PR, Wafula EK, Barrett CF, Ayyampalayam S, McNeal JR, Rentsch JD, McKain MR, Heyduk K, Harkess A, Villegente M, et al. (2022) Phylogenomic resolution of order- and family-level monocot relationships using 602 single-copy nuclear genes and 1375 BUSCO genes. Frontiers in Plant Science 13: 876779. https://doi.org/10.3389/fpls.2022.876779 (opens in a new tab)

Waycott M, Duarte CM, Carruthers TJB, Orth RJ, Dennison WC, Olyarnik S, Calladine A, Fourqurean JW, Heck KL Jr, Hughes AR, et al. (2009) Accelerating loss of seagrasses across the globe threatens coastal ecosystems. Proceedings of the National Academy of Sciences of the United States of America 106(30): 12377–12381. https://doi.org/10.1073/pnas.0905620106 (opens in a new tab)