Superasterids
| Superasterids Temporal range: | |
|---|---|
 | |
| Torenia fournieri, a member of the asterid order Lamiales | |
Scientific classification  | |
| Kingdom: | Plantae |
| Clade: | Embryophytes |
| Clade: | Tracheophytes |
| Clade: | Spermatophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Core eudicots |
| Clade: | Superasterids |
| Clades[1] | |
The superasterids are a major clade of flowering plants within the core eudicots. In the APG IV system of flowering-plant classification, the clade comprises Berberidopsidales, Santalales, Caryophyllales, and the large clade known as the asterids.[1][2][3] The superasterids include more than 90,000 described species; the asterids alone contain more than 80,000 species.[3][4]
APG IV recognizes 20 orders and 146 families within the superasterids. Subsequent plastid and nuclear phylogenomic studies broadly support this circumscription, although the branching order of several early-diverging lineages and the limits of some families remain subjects of research.[1][5][6]
Members of the clade are extraordinarily diverse in form and ecology. They include forest trees, shrubs, vines, annual and perennial herbs, aquatic plants, desert succulents, carnivorous plants, epiphytes, and both partially and completely parasitic plants. Familiar superasterids include asters, daisies, sunflowers, lettuces, carrots, celery, coffee, tea, potatoes, tomatoes, sweet potatoes, olives, mints, heaths, blueberries, cacti, carnations, beets, spinach, quinoa, buckwheat, sandalwoods, mistletoes, and numerous ornamental plants.[3][7]
The name is based on Asteridae, a name historically used for a subclass or other high-ranking group of flowering plants. In APG IV, “superasterids” is an informal, unranked clade name rather than a traditional Linnaean rank.[1][2]
Circumscription and nomenclature
[edit source]The modern concept of the superasterids developed from molecular studies of flowering-plant relationships. Earlier classifications based mainly on morphology generally treated the major constituent groups (particularly the traditional Asteridae, Caryophyllales and Santalales) as separate assemblages whose close relationship was not apparent. Multigene analyses showed that these groups belong to a larger branch of the core-eudicot tree.[2][8]
Soltis and colleagues formally named Superasteridae in 2011, defining it as the most inclusive crown clade containing an asterid exemplar but not a rosid exemplar. Their analysis included Berberidopsidales, Santalales, Caryophyllales, Asteridae, and, under that particular topology the Dilleniaceae; other analyses placed Dilleniaceae elsewhere.[2] APG IV subsequently introduced the lowercase informal names “superasterids” and “superrosids” for the two large clades dominated by asterids and rosids, respectively, and treated Dilleniales separately.[1]
Because the superasterids are unranked, the name does not denote a fixed Linnaean category such as subclass or superorder. The capitalized form Superasteridae belongs to phylogenetic-nomenclature usage, whereas the lowercase “superasterids” follows APG IV's convention for informal clade names.[2][1]
APG IV also recognized several superasterid orders that had not been accepted as separate orders in APG III, including Boraginales, Icacinales, Metteniusales, and Vahliales. Their recognition reflected improved resolution of relationships among the lamiids.[1]
Diversity and characteristics
[edit source]The superasterids are diagnosed primarily by common ancestry rather than by a single readily visible morphological synapomorphy. Their constituent lineages diverged early enough that many structural and chemical characters have been modified, reduced, or independently evolved. Nevertheless, broad evolutionary patterns characterize major parts of the clade.[3]
As members of Pentapetalae, superasterids descend from plants with an ancestrally five-parted, whorled floral organization. Five sepals and five petals remain common, but departures are frequent: flowers may have four parts, numerous parts, fused organs, strongly reduced structures, or no conspicuous petals.[3]
The four principal lineages display markedly different combinations of features:
- Berberidopsidales
- Berberidopsidales is a small lineage containing two families of woody plants, Aextoxicaceae and Berberidopsidaceae. Its living species occur in South America and eastern Australia. The two families were not generally regarded as close relatives before molecular analyses placed them together among the early-diverging superasterids.[2][3]
- Santalales
- Santalales includes sandalwoods, mistletoes, and their relatives. Most species are parasitic, including both photosynthetic hemiparasites and non-photosynthetic holoparasites. They connect to host tissues through specialized organs called haustoria; hemiparasites obtain principally water and mineral nutrients from hosts, whereas holoparasites also depend on hosts for organic carbon. The order includes root and stem parasites ranging from herbs and vines to shrubs and trees.[9][10][3]
- Caryophyllales
- Caryophyllales is morphologically and ecologically diverse. It includes cacti and many other succulents, carnations, beets, spinach, amaranths, quinoa, buckwheats, tamarisks, sundews, Venus flytraps, and tropical pitcher plants. Its members occupy deserts, salt marshes, alpine regions, tropical forests, aquatic habitats, and nutrient-poor wetlands. Carnivory evolved repeatedly within the order, while extreme succulence and drought or salt tolerance characterize other lineages. Many members of the core Caryophyllales produce red or yellow betalain pigments in place of the anthocyanin pigments used by most other flowering plants.[11][12][3]
- Asterids
- The asterids form by far the largest superasterid lineage. Their flowers frequently have petals fused into a tubular or bell-shaped corolla (sympetaly), often with stamens attached to the corolla. Other recurring features include unitegmic or otherwise reduced ovules, tenuinucellate ovules, and iridoid compounds, although none of these characters is universal across the clade.[4][3] The asterids include such large families as Asteraceae, Rubiaceae, Lamiaceae, Apocynaceae, Ericaceae, Gesneriaceae, Solanaceae, and Apiaceae.
Within the asterids, Cornales and Ericales are the earliest-diverging major branches. Most remaining species belong to the euasterids, which are divided into two large clades, the lamiids and the campanulids. Lamiids include the mint, olive, potato, tomato, coffee, gentian, milkweed, borage, and morning-glory families. Campanulids include the holly, daisy, bellflower, carrot, ginseng, honeysuckle, and viburnum families.[1][3]
Ecology
[edit source]Superasterids occur on every continent, including Antarctica. The Antarctic pearlwort, Colobanthus quitensis (Caryophyllaceae), is one of only two vascular plant species native to maritime Antarctica. Elsewhere, superasterids occupy nearly every terrestrial biome in which flowering plants can survive, as well as many freshwater and coastal habitats.[13][3]
The clade contains numerous ecological specializations. Many Caryophyllales are adapted to arid or saline conditions through succulence, reduced leaves, salt-excreting glands, or specialized photosynthetic pathways. Carnivorous Caryophyllales supplement their nutrient supply by trapping small animals in nutrient-poor habitats. Members of Santalales connect to the vascular systems of host plants, while parasitism also evolved independently in asterid groups such as Orobanchaceae.[11][10][3]
Pollination systems are similarly diverse. Flowers may be pollinated by wind, water, insects, birds, or bats. Tubular, bilaterally symmetrical flowers are widespread in the lamiids and are often associated with specialized animal pollinators. In Asteraceae, numerous small flowers are grouped into a flower-like pseudanthium or head that functions as a pollination unit. Other superasterids have tiny, inconspicuous flowers or, in some parasitic species, highly reduced reproductive structures.[3]
Superasterids participate in varied seed-dispersal, herbivory, and symbiotic interactions. Their fruits include berries, capsules, nuts, drupes, schizocarps, and wind-dispersed achenes; seeds and fruits may be dispersed by wind, water, birds, mammals, or ants.[3]
Human uses
[edit source]Many plants central to agriculture and horticulture belong to the superasterids. Food and beverage crops include potato and tomato in Solanaceae, sweet potato in Convolvulaceae, coffee in Rubiaceae, tea in Theaceae, carrot and celery in Apiaceae, lettuce and sunflower in Asteraceae, beet, spinach, and quinoa in Amaranthaceae, buckwheat in Polygonaceae, and blueberries and cranberries in Ericaceae.[7][3]
Culinary herbs and flavouring crops include mint, basil, rosemary, sage, oregano, thyme, and lavender, while olives are cultivated for their fruit and oil. Chicory, endive, artichoke, and numerous edible roots and leafy vegetables also belong to the clade.[7]
Many species are sources of medicines, fragrances, timber, dyes, oils, and other materials. Sandalwood is valued for fragrant wood and oil, while jojoba produces a liquid wax widely used in cosmetics. Members of Apocynaceae, Solanaceae, Plantaginaceae, and other families produce biologically active compounds used in medicine or pharmacological research, although some are also highly toxic.[7][3]
Ornamental superasterids include petunias, snapdragons, gentians, primroses, heaths, azaleas, rhododendrons, hydrangeas, dogwoods, carnations, cacti, sunflowers, chrysanthemums, asters, and numerous cultivated mints and sages.[7][3]
Evolution and fossil record
[edit source]Molecular dating places the origin and early splitting of the principal superasterid lineages in the Cretaceous, most likely during the Early Cretaceous. Estimated ages vary among studies because they depend on fossil calibrations, taxon and gene sampling, molecular-clock models, and assumptions about rate variation. Plastome-scale analyses suggest that several of the earliest superasterid divergences occurred in a relatively short interval.[14][8][3]
Studies focused on the asterids likewise indicate Early Cretaceous origins for the asterids, euasterids, lamiids, and campanulids. Cornales, Ericales, and Aquifoliales may also have Early Cretaceous crown-group origins, while many extant ordinal lineages diversified later in the Cretaceous.[14]
The securely identified fossil record is younger than many molecular estimates. Reliable fossils assigned to asterid lineages extend back to the Turonian stage of the Late Cretaceous, about 89 million years ago. Cretaceous asterid fossils include pollen, flowers, fruits, seeds, leaves, and wood attributed to lineages such as Cornales and Ericales. Exceptionally preserved flowers and fruits show that substantial asterid diversity was present before the end of the Cretaceous.[15]
Fossil identifications at this evolutionary depth require caution. Similar floral or fruit characters may evolve independently, and incomplete specimens may lack the character combinations needed for secure placement within a living family or order. Fossils therefore provide minimum ages for lineages rather than exact dates of origin. Reviews of the asterid record have rejected or questioned several older assignments while recognizing a smaller set of well-supported calibration fossils.[15]
The modern diversity of the superasterids did not arise from a single uniform radiation. Diversification analyses infer multiple, nested rate shifts within lineages including Ericales, Caryophyllales, lamiids, and campanulids, with especially species-rich radiations in groups such as Asteraceae and Campanulaceae. These shifts span the Cretaceous and Paleogene.[16]
Classification
[edit source]APG IV recognizes 20 orders in the superasterids. Their arrangement into major informal groups is summarized below. Common names and examples are illustrative and do not represent every family in each order.[1]
| Major lineage | Orders | Representative members |
|---|---|---|
| Early-diverging, non-asterid superasterids | Berberidopsidales Santalales Caryophyllales |
Berberidopsis, sandalwoods, mistletoes, cacti, carnations, beets, buckwheats, sundews, and pitcher plants |
| Early-diverging asterids | Cornales Ericales |
Dogwoods, hydrangeas, heaths, blueberries, tea, primroses, and persimmons |
| Lamiids | Icacinales Metteniusales Garryales Boraginales Gentianales Vahliales Lamiales Solanales |
Borages, forget-me-nots, gentians, coffee, milkweeds, olives, mints, snapdragons, potatoes, tomatoes, and morning glories |
| Campanulids | Aquifoliales Asterales Escalloniales Bruniales Apiales Dipsacales Paracryphiales |
Hollies, daisies, sunflowers, bellflowers, carrots, celery, ginseng, ivy, honeysuckles, and viburnums |
The two large euasterid branches were called “euasterids I” and “euasterids II” in earlier APG classifications. They are now generally known as lamiids and campanulids, respectively.[1]
Relationships
[edit source]The superasterids form part of Pentapetalae, the large core-eudicot clade with an ancestrally five-parted floral organization. Pentapetalae includes the superasterids, the superrosids, and Dilleniales, although the position of Dilleniales relative to the other two lineages has differed among analyses.[2][3][6]
Molecular data strongly support a broad clade containing the asterids, Caryophyllales, Santalales, and Berberidopsidales. A 17-gene analysis recovered these groups as Superasteridae, but some relationships among the earliest branches were weakly supported.[2]
The branching order among the three non-asterid orders and the asterids remains sensitive to dataset and analytical method. The APG IV consensus tree depicts Berberidopsidales, Santalales, and Caryophyllales as successive branches toward the asterids.[1] A 2021 plastid-phylogenomic study instead recovered Santalales, Berberidopsidales, and Caryophyllales, in that order, as successive sisters to the asterids.[5]
A 2024 nuclear-phylogenomic analysis sampled all recognized angiosperm families and broadly supported the principal APG groupings, but found substantial gene-tree conflict at several deep nodes, including the placement of Caryophyllales. Such conflict can reflect rapid ancient divergence, incomplete lineage sorting, ancient hybridization or introgression, differences between plastid and nuclear inheritance, and limitations of taxon or gene sampling.[6]
Phylogeny
[edit source]The following cladogram deliberately collapses the uncertain relationships among the three non-asterid orders. It shows the well-supported major membership of the superasterids and the principal divisions of the asterids, rather than presenting one contested deep topology as definitive.[1][5][6]
See also
[edit source]References
[edit source]- 1 2 3 4 5 6 7 8 9 10 11 12 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. doi:10.1111/boj.12385.
- 1 2 3 4 5 6 7 8 Soltis, Douglas E.; Smith, Stephen A.; Cellinese, Nico; Wurdack, Kenneth J.; Tank, David C.; Brockington, Samuel F.; Refulio-Rodriguez, Natalia F.; Walker, Jennifer B.; Moore, Michael J.; et al. (2011). "Angiosperm phylogeny: 17 genes, 640 taxa". American Journal of Botany. 98 (4): 704–730. doi:10.3732/ajb.1000404.
- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Soltis, Douglas E.; Soltis, Pamela S.; Endress, Peter K.; Chase, Mark W.; Manchester, Steven R.; Judd, Walter S.; Majure, Lucas C.; Mavrodiev, Evgeny V. (2018). Phylogeny and Evolution of the Angiosperms (Revised and updated ed.). Chicago: University of Chicago Press. doi:10.7208/chicago/9780226441757.001.0001. ISBN 978-0-226-38361-3.
- 1 2 Schönenberger, Jürg; von Balthazar, Maria (2013). "Asterids". Botanical Journal of the Linnean Society. 173 (3): 321–324. doi:10.1111/boj.12120.
- 1 2 3 Li, Hong-Tao; Luo, Yang; Gan, Lu; Ma, Peng-Fei; Gao, Lian-Ming; Yang, Jun-Bo; et al. (2021). "Plastid phylogenomic insights into relationships of all flowering plant families". BMC Biology. 19: 232. doi:10.1186/s12915-021-01166-2.
- 1 2 3 4 Zuntini, Alexandre R.; Carruthers, Tom; Maurin, Olivier; Bailey, Paul C.; Leempoel, Kevin; Brewer, Grace E.; et al. (2024). "Phylogenomics and the rise of the angiosperms". Nature. 629: 843–850. doi:10.1038/s41586-024-07324-0.
- 1 2 3 4 5 Mabberley, David J. (2017). Mabberley's Plant-book: A Portable Dictionary of Plants, their Classification and Uses (4th ed.). Cambridge: Cambridge University Press. doi:10.1017/9781316335581. ISBN 978-1-107-11502-6.
- 1 2 Moore, Michael J.; Soltis, Pamela S.; Bell, Charles D.; Burleigh, J. Gordon; Soltis, Douglas E. (2010). "Phylogenetic analysis of 83 plastid genes further resolves the early diversification of eudicots". Proceedings of the National Academy of Sciences of the United States of America. 107 (10): 4623–4628. doi:10.1073/pnas.0907801107. PMC 2842043.
- ↑ Nickrent, Daniel L.; Malécot, Valéry; Vidal-Russell, Romina; Der, Joshua P. (2010). "A revised classification of Santalales". Taxon. 59 (2): 538–558. doi:10.1002/tax.592019.
- 1 2 Nickrent, Daniel L. (2020). "Parasitic angiosperms: How often and how many?". Taxon. 69 (1): 5–27. doi:10.1002/tax.12195.
- 1 2 Walker, Joseph F.; Yang, Ya; Feng, Tao; Timoneda, Alfonso; Mikenas, Jessica; Hutchison, Vera; et al. (2018). "From cacti to carnivores: Improved phylotranscriptomic sampling and hierarchical homology inference provide further insight into the evolution of Caryophyllales". American Journal of Botany. 105 (3): 446–462. doi:10.1002/ajb2.1069.
- ↑ Timoneda, Alfonso; Feng, Tao; Sheehan, Hester; Walker-Hale, Nathanael; Pucker, Boas; Lopez-Nieves, Samuel; Guo, Rui; Brockington, Samuel (2019). "The evolution of betalain biosynthesis in Caryophyllales". New Phytologist. 224 (1): 71–85. doi:10.1111/nph.15980.
- ↑ Biersma, Elisabeth M.; Torres-Díaz, Cristian; Molina-Montenegro, Marco A.; Newsham, Kevin K.; Vidal, Marcelo A.; et al. (2020). "Multiple late-Pleistocene colonisation events of the Antarctic pearlwort Colobanthus quitensis (Caryophyllaceae) reveal the recent arrival of native Antarctic vascular flora". Journal of Biogeography. 47 (8): 1663–1673. doi:10.1111/jbi.13843.
- 1 2 Bremer, Kåre; Friis, Else Marie; Bremer, Birgitta (2004). "Molecular phylogenetic dating of asterid flowering plants shows Early Cretaceous diversification". Systematic Biology. 53 (3): 496–505. doi:10.1080/10635150490445913.
- 1 2 Manchester, Steven R.; Grímsson, Friðgeir; Zetter, Reinhard (2015). "Assessing the fossil record of asterids in the context of our current phylogenetic framework". Annals of the Missouri Botanical Garden. 100 (4): 329–363. doi:10.3417/2014033.
- ↑ Magallón, Susana; Sánchez-Reyes, Luna L.; Gómez-Acevedo, Sandra L. (2019). "Thirty clues to the exceptional diversification of flowering plants". Annals of Botany. 123 (3): 491–503. doi:10.1093/aob/mcy182.
