Fabales Bromhead

Fabales Bromhead

1. Supertaxonomy Overview

The Fabales are a major order of Rosid flowering plants containing the legumes, milkworts, soapbarks, and Surianaceae. Familiar members include peas, beans, lentils, soybeans, peanuts, chickpeas, clovers, lupines, locusts, redbuds, acacias, mimosas, wisterias, and milkworts, together with the South American soapbark trees and the much less familiar members of Surianaceae. Within the Tree TSAR framework, Fabales belong to the Rosids and, more specifically, to the four-order Fabid or nitrogen-fixing lineage recognized under APG V. The order contains four living families: Fabaceae, Polygalaceae, Quillajaceae, and Surianaceae. Together they comprise well over 20,000 living species and roughly 800 or more genera, but that total is extraordinarily uneven: Fabaceae accounts for the overwhelming majority of species and generic diversity, Polygalaceae contributes a substantial second radiation, and Quillajaceae and Surianaceae survive as very small lineages.

That imbalance is one of the defining evolutionary features of the order. Fabaceae became one of the largest flowering-plant families on Earth and diversified into tropical canopy trees, savanna shrubs, temperate herbs, vines, aquatics, alpine plants, crops, and numerous other ecological forms. Polygalaceae also underwent a substantial radiation, whereas Quillajaceae contains only Quillaja and Surianaceae only a handful of species in five genera. Those differences should not be interpreted as differences in evolutionary age. The four families represent ancient branches whose descendants experienced very different histories of diversification and extinction. Fabales therefore provide a particularly clear example of why modern species richness is a poor proxy for the age or phylogenetic significance of a lineage.

The order is also central to the evolutionary history of root-nodule symbiosis. Fabales are one of the four Fabid orders that collectively contain the great angiosperm nitrogen-fixing radiation, yet actual nodulation is highly uneven. Within Fabales it is overwhelmingly concentrated in Fabaceae, and even there many lineages are non-nodulating. Current phylogenomic research has moved away from treating nodulation as a simple once-evolved, continuously inherited feature. Instead, the evidence points toward a complicated history in which evolutionary predisposition, repeated gains and losses, and reassembly of symbiotic pathways all played roles (Kates et al. 2024; Doyle et al. 2025). Fabales therefore combine a stable ordinal identity with biological traits whose deeper origins remain active research problems.

A second recurring theme is floral convergence. The elaborate keel flowers of most papilionoid legumes have close functional analogues in large portions of Polygalaceae, but the two architectures are assembled from different floral organs and developmental programs. Recent broad analyses indicate repeated gains and losses of keel-flower organization within the order rather than a single, unchanged Fabalean floral type (Aygören Uluer 2025; Cai et al. 2025). This combination of strong molecular unity, extraordinary morphological diversity, and repeated functional convergence makes Fabales an especially useful Tree TSAR supertaxonomy page.

2. Placement in Tree TSAR

Within Tree TSAR, Fabales occupy the pathway Seed Plants → Angiosperms → Core Eudicots → Superrosids → Rosids → Fabales. Phylogenetically, the order belongs to the Fabids, which APG V now restricts to Fabales, Rosales, Fagales, and Cucurbitales. Tree TSAR nevertheless does not require Fabids as an additional fixed ribbon level between Rosids and the individual orders. The Fabid concept remains important in the narrative because it explains the concentration of root-nodule symbiosis across these four orders, but the more durable navigational scaffold passes directly from Rosids to Fabales.

Accordingly, Fabaceae follow the pathway Fabaceae → Fabales → Rosids → Superrosids → Core Eudicots → Angiosperms → Seed Plants, and the same route applies to Polygalaceae, Quillajaceae, and Surianaceae. This direct pathway is especially useful because the internal structure of the Fabids has been reinterpreted substantially between APG IV and APG V, whereas Fabales themselves have remained a stable, well-supported order. The page therefore provides a secure bridge between the Rosid supertaxonomy narrative and the family-level treatments below it.

The hierarchy also prevents the immense size of Fabaceae from obscuring the rest of the order. Fabales and Fabaceae are not interchangeable: legumes constitute the dominant radiation within the order, but Polygalaceae, Quillajaceae, and Surianaceae are independent surviving branches of the same deeper lineage. Tree TSAR should make that relationship explicit rather than allowing a familiar family name to substitute for the order itself.

3. Evolutionary History and Fossil Context

Fabales originated during the Cretaceous diversification of the Rosids. Molecular-clock estimates differ according to taxon sampling, genomic compartment, fossil calibrations, and assumptions about the deepest family relationships, but recent broadly sampled analyses place the crown of the living order in the Late Cretaceous, approximately 75–80 million years ago. Aygören Uluer (2025) and Cai et al. (2025), using large modern datasets, both recover a relatively ancient crown followed by rapid separation of the principal family lineages. The short early internodes inferred among those families are consistent with the continuing difficulty of resolving exactly how Fabaceae, Polygalaceae, Quillajaceae, and Surianaceae are related to one another.

The fossil record is best developed in Fabaceae. Secure Paleocene material demonstrates that recognizable legume diversification was well underway shortly after the Cretaceous–Paleogene boundary, and fossils by approximately 58–56 million years ago already document important branches of the family. An older and potentially transformative record comes from Leguminocarpum olmensis, a pod-like fruit from the Upper Campanian Olmos Formation of northern Mexico, approximately 73.5 million years old. Its two-valved dehiscence, stipe, stylar base, and venation were interpreted as evidence for Fabaceae, which would place the family firmly in the Late Cretaceous if the assignment is correct (Centeno-González et al. 2021). Because isolated fossil fruits can be difficult to place with complete confidence, Tree TSAR should acknowledge the importance of this record without treating it as equivalent to a fossil securely nested within one of the six living legume subfamilies.

The early history of Fabaceae itself was unusually dynamic. Phylogenomic work indicates a complex combination of ancient genome duplication, lineage divergence, and reticulate history near the origin of the family, followed by a rapid radiation of its major subfamilies around the Cretaceous–Paleogene transition (Koenen et al. 2021). This timing has led to the hypothesis that ecological disruption and opportunity following the end-Cretaceous mass extinction helped shape the explosive early diversification of legumes. The family’s later history involved additional radiations in tropical forests, seasonally dry environments, grasslands, and temperate ecosystems, eventually producing one of the most species-rich and ecologically varied clades of flowering plants.

The other families have much poorer fossil records but should not be interpreted as younger. Polygalaceae are an ancient independent Fabalean radiation whose modern diversity is substantial even though their fossil history is less complete. Quillajaceae and Surianaceae preserve still smaller portions of the same early radiation. Their low modern species numbers may reflect low diversification rates, elevated extinction, or both. Fabales therefore illustrate a recurring Tree TSAR principle: tiny living families can represent branches nearly as old as enormous ones, and fossils are most useful when they illuminate that deeper history without being forced prematurely into modern family-level classifications.

4. Classification and Circumscription

Fabales Bromhead was published in 1838, but the modern circumscription of the order is a product of molecular systematics rather than a continuation of every historical use of the name. In many older classifications Fabales functioned essentially as the legume order, centered on Fabaceae or Leguminosae. Polygalaceae were frequently placed in a separate Polygalales because their specialized flowers appeared too distinctive to unite naturally with legumes. Quillaja was often associated with Rosaceae or Rosales, while Surianaceae were compared with Simaroubaceae and other woody groups. Those arrangements were understandable from morphology alone because the four families do not present an obvious common body plan.

DNA sequence analyses during the molecular era repeatedly demonstrated that these four lineages form a single clade. By the early 2000s, the modern concept of Fabales - Fabaceae, Polygalaceae, Quillajaceae, and Surianaceae - had become firmly established, and successive APG classifications retained that circumscription. APG V likewise leaves the order intact. The major recent change occurs one level higher, where Fabids are now restricted to the four nitrogen-fixing orders rather than the broader APG IV assemblage. Fabales themselves therefore represent a case of remarkable ordinal stability within a region of the Rosid tree that has otherwise undergone substantial reinterpretation.

What remains less settled is the branching order among the four families. Different nuclear and plastid analyses have recovered several alternatives, especially for the placements of Quillajaceae and Surianaceae. One increasingly recovered hypothesis places Fabaceae with Polygalaceae and Quillajaceae with Surianaceae, but support for the deepest split has generally been weaker than support for the order or for the families individually (Bello et al. 2009; Aygören Uluer et al. 2020; Aygören Uluer 2025). The short ancient branches inferred at the base of Fabales make incomplete lineage sorting and sensitivity to outgroup choice plausible contributors to this instability.

Tree TSAR should therefore distinguish three levels of confidence. Fabales are strongly monophyletic; the four living families are securely recognized; and the exact sequence of their earliest divergences remains somewhat less certain. That distinction is scientifically more useful than forcing one fully bifurcating family ladder into the page simply because a diagram appears cleaner when every branch is resolved.

5. Morphology, Biology, and Identification

Fabales cannot be identified by a single universal feature, but several broad themes recur. Flowers generally arise from the pentamerous rosid ground plan, with extensive modification of symmetry, organ number, and fusion. Fabaceae typically possess a gynoecium derived from a single carpel, and the classic legume or pod is fundamentally a one-carpelled fruit that usually opens along two sutures. That fruit type remains one of the family’s clearest morphological signatures even though mature legumes have diversified into indehiscent pods, loments, samaroid forms, fleshy fruits, bur-like structures, and many other derivatives. Polygalaceae generally possess a compound gynoecium and different fruit architecture, while Quillajaceae and Surianaceae retain more radially symmetrical flowers that provide useful comparisons with the highly specialized floral systems of the two larger families.

The most famous example of convergence within the order involves the keel flower. In Papilionoideae, a large standard or banner petal, two wing petals, and two keel petals create the familiar pea-flower mechanism around the reproductive organs. Many Polygalaceae produce a strikingly similar functional arrangement, especially within Polygaleae, but the structures performing those roles are not homologous in a simple one-to-one sense. Sepals and petals contribute differently, and floral development follows a distinct pathway. Comparative developmental and phylogenetic studies therefore show that the resemblance arose through repeated evolutionary convergence rather than inheritance of an unchanged keel flower from the common ancestor of Fabales (Bello et al. 2007; Cai et al. 2025).

Vegetative diversity is equally broad. Fabales range from annual herbs to giant tropical trees, from thorny dryland shrubs to vines, aquatics, geophytes, and cushion plants. Leaves may be simple or compound, and Fabaceae alone include pinnate, bipinnate, palmate, trifoliolate, unifoliolate, and highly modified arrangements. Stipules are frequent in legumes but can be minute, deciduous, transformed into spines, or absent. Chemical defenses include alkaloids, tannins, non-protein amino acids, cyanogenic compounds, resins, and saponins; the saponin-rich bark of Quillaja is one of the order’s most conspicuous examples of economically important secondary chemistry.

Practical identification therefore proceeds most effectively at family level. A true legume fruit strongly suggests Fabaceae; the distinctive floral construction of milkworts points toward Polygalaceae; Quillaja combines woody South American habit with characteristic flowers and saponin-rich tissues; and Surianaceae comprise a small set of woody plants with distinctive gynoecial and fruit features. Fabales themselves are best understood primarily as an evolutionary lineage rather than as a field-identification category.

6. Distribution and Ecology

Fabales are nearly cosmopolitan because Fabaceae and Polygalaceae occur across most of the vegetated world. Fabaceae reach from tropical rainforests and seasonally dry forests to savannas, deserts, Mediterranean shrublands, grasslands, alpine habitats, wetlands, and boreal margins. Legumes are particularly influential in tropical and subtropical ecosystems, where they may form major components of forest canopies, dry forests, and savannas, but temperate herbs such as clovers, vetches, lupines, and peas are equally characteristic of open northern habitats. Polygalaceae are likewise widespread and include herbs, shrubs, climbers, and tropical trees, although their woody tropical diversity is often overlooked when the family is imagined primarily through temperate milkworts.

Quillajaceae and Surianaceae occupy much narrower ecological and geographic ranges. Quillaja is native to western and southern South America, with Q. saponaria especially characteristic of central Chilean Mediterranean-climate woodland and scrub. Surianaceae have an unusually fragmented distribution: several genera are Australian, Recchia occurs in Mexico, and Suriana maritima has a pantropical coastal range. The latter grows on dunes, coral islands, strand vegetation, and other exposed shorelines, tolerating salt spray, drought, unstable sand, and nutrient-poor substrates. The ecology of these small families reinforces the point that Fabales cannot be reduced to the familiar ecological profile of legumes.

The ecological influence of the order is nevertheless dominated by Fabaceae and their symbioses. Many legumes form root nodules with rhizobial bacteria and thereby gain access to atmospheric nitrogen, allowing them to influence succession, soil development, restoration, and agricultural nutrient cycles. The deeper evolutionary origin of this capacity remains unsettled, and nodulation should not be generalized to all Fabales or even all Fabaceae. Current evidence instead suggests that the broader Fabid lineage acquired a predisposition that was repeatedly expressed, modified, or lost in descendant branches (Kates et al. 2024; Doyle et al. 2025).

Fabales also support extensive interactions with animals. Bee pollination is especially conspicuous in keel-flowered legumes and Polygalaceae, but bird, bat, moth, beetle, wind, and mixed pollination systems also occur. Fruits and seeds may explode, float, attach to animals, pass through digestive tracts, or be carried and cached by vertebrates. Tropical legume trees provide canopy structure, food, and habitat, while herbaceous legumes and milkworts can dominate or characterize grasslands, savannas, and disturbed communities. The order’s ecological importance therefore extends far beyond nitrogen fixation alone.

7. Human Uses and Cultural Importance

Fabales rank among the most consequential flowering-plant orders for human food and agriculture. Fabaceae provide soybean, common bean, pea, lentil, chickpea, peanut, cowpea, pigeon pea, fava bean, mung bean, lupin, and numerous regional pulses, making the family one of humanity’s principal sources of plant protein. Soybean and peanut are also major oil crops. Forage legumes such as alfalfa, clovers, vetches, and Lotus support livestock systems around the world, while nitrogen-fixing cover crops and rotations can improve soil fertility and reduce dependence on external nitrogen inputs. These same biological properties make many legumes valuable in agroforestry, erosion control, mine-land rehabilitation, and ecological restoration.

Woody legumes are equally important. Rosewoods, Pterocarpus, Afzelia, Intsia, acacias, and numerous other tropical trees provide timber, fuelwood, gums, tannins, dyes, resins, medicines, and specialty materials. Ornamental horticulture draws heavily on wisterias, redbuds, lupines, baptisias, laburnums, locusts, Erythrina, Delonix, mimosoid trees, and many other genera. Legumes have also shaped agricultural history through domestication on several continents and through their capacity to enrich soils in traditional cropping systems.

The smaller families contribute distinctive uses of their own. Polygalaceae include ornamental and medicinal plants, among them Polygala senega, historically important in North American herbal medicine. Quillajaceae have acquired extraordinary modern significance through Quillaja saponaria. Its bark contains abundant triterpenoid saponins that were historically used as natural soaps and emulsifiers; purified fractions, especially QS-21, now serve as potent vaccine adjuvants in modern immunology. Surianaceae have much less global economic importance, but Suriana maritima has local medicinal and environmental uses and contributes to stabilization of tropical coastal vegetation.

Fabales therefore connect systematic botany with food security, livestock production, forestry, horticulture, biotechnology, restoration ecology, medicine, and the history of agriculture. The order’s human importance is concentrated overwhelmingly in Fabaceae, but the smaller families demonstrate that economic significance and evolutionary diversity do not always scale with species richness.

8. Conservation Significance

The global abundance of cultivated legumes can obscure the conservation vulnerability of Fabales as a whole. Fabaceae contain thousands of narrow endemics, tropical forest trees, desert specialists, montane plants, and species restricted to unusual soils. Habitat conversion, logging, fire-regime change, overgrazing, mining, invasive species, and climate change threaten different portions of this diversity. High-value tropical timber legumes are particularly vulnerable to selective exploitation because economically desirable adults may be removed long before forest cover disappears. Rosewoods and related trees illustrate how international demand can deplete slow-growing populations even within landscapes that still appear forested.

Crop-wild-relative conservation is another major priority. Wild relatives of soybean, beans, peas, peanuts, lentils, chickpeas, cowpeas, lupins, and other crops preserve genetic variation for drought tolerance, disease resistance, heat tolerance, salinity response, nutrient efficiency, and other traits important to future breeding. Traditional landraces and locally adapted cultivated populations are similarly vulnerable to genetic erosion as agriculture becomes more uniform. Their conservation requires both wild habitat protection and well-curated germplasm repositories.

The smaller families deserve disproportionate attention because each species represents a large fraction of surviving phylogenetic history. Quillajaceae contain only two living species, and commercial demand for Quillaja bark and saponins makes sustainable management important where harvesting intersects with natural populations. Surianaceae likewise comprise very few species, several with restricted Australian or Mexican distributions. Coastal Suriana maritima is widespread, but other family members depend on much smaller areas. Polygalaceae include numerous habitat specialists and narrow endemics that receive far less public attention than threatened legumes.

Many Fabales can be conserved through conventional seed banking, but long-lived woody species, unusual seed-storage behaviors, and provenance-sensitive populations often require living collections, tissue culture, cryopreservation, or coordinated wild conservation. Botanical gardens, arboreta, seed banks, agricultural repositories, and protected habitats therefore play complementary roles. Accurate taxonomy is especially important in a group containing enormous species complexes, recent generic rearrangements, and commercially traded plants whose conservation status may depend on precise identification.

9. Major Included Groups

Fabaceae

Fabaceae, also known by the conserved alternative name Leguminosae, overwhelmingly dominate Fabales. The family contains roughly 20,000 or more species and hundreds of genera distributed nearly worldwide. Tree TSAR recognizes the modern six-subfamily framework of Cercidoideae, Detarioideae, Duparquetioideae, Dialioideae, Caesalpinioideae, and Papilionoideae, replacing the traditional three-subfamily arrangement in which Caesalpinioideae was paraphyletic (Legume Phylogeny Working Group 2017). Papilionoideae contain the familiar pea- and bean-flowered legumes, but the family also includes massive tropical forest trees, mimosoid radiations, thorny dryland shrubs, aquatics, lianas, and many lineages whose flowers do not resemble a pea. Nearly all known rhizobial nodulation within Fabales occurs in Fabaceae. Its extraordinary size and taxonomic complexity justify a dedicated Tree TSAR family treatment in which generic limits, subfamily placement, hybrids, and other lower-level questions can be handled without allowing the legume radiation to overwhelm the ordinal narrative.

Polygalaceae

Polygalaceae, the milkwort family, form the second major radiation of Fabales, with roughly 30 genera and well over a thousand species. They range from annual and perennial herbs to shrubs, lianas, and tropical trees and are nearly cosmopolitan, although especially diverse in tropical and subtropical regions. The family is evolutionarily important because of its repeated development of strongly bilateral, keel-like flowers that function much like papilionoid legume flowers but are constructed differently. Modern classifications have also reshaped the historically broad genus Polygala, recognizing segregates such as Senega and other lineages where phylogenetic evidence warrants them. Polygalaceae therefore combine significant taxonomic diversity with one of the clearest examples of floral convergence in flowering plants.

Quillajaceae

Quillajaceae contain a single genus, Quillaja, and two accepted living species native to western and southern South America. Quillaja saponaria, the Chilean soapbark tree, is the best-known member and an important component of central Chilean Mediterranean vegetation. Historically, Quillaja was often associated with Rosaceae because its woody habit and flowers suggested affinities there, but molecular evidence established it as one of the four ancient branches of Fabales. Its relatively unspecialized, radially symmetrical flowers provide an important comparison with the highly modified keel flowers of Fabaceae and Polygalaceae, while its saponin-rich bark has made the family disproportionately important in modern biotechnology and vaccine science.

Surianaceae

Surianaceae contain approximately eight living species in five genera: Cadellia, Guilfoylia, Recchia, Stylobasium, and Suriana. Their distribution is strikingly disjunct, with three genera in Australia, Recchia in Mexico, and Suriana maritima distributed across tropical coasts and islands worldwide. The family consists principally of shrubs and trees with flowers that differ markedly from the specialized keel systems of the two larger Fabales families. Surianaceae were historically compared with Simaroubaceae and other woody groups before molecular data revealed their true placement. The contrast between the pantropical coastal ecology of Suriana and the narrow continental distributions of the remaining genera makes the family especially interesting for studies of dispersal, biogeography, and the persistence of species-poor ancient lineages.

10. Similar, Overlapping, or Historically Confused Groups

Fabales and Fabaceae are not synonymous. Fabaceae are by far the largest family in the order, but modern Fabales also contain Polygalaceae, Quillajaceae, and Surianaceae. The common phrase “legume order” is useful shorthand only if it does not erase those three independent lineages. By contrast, Fabaceae and Leguminosae are alternative names for the same family rather than different groups.

Fabids and Fabales are likewise not synonymous. Under APG V, Fabids consist of Fabales, Rosales, Fagales, and Cucurbitales. The informal expression nitrogen-fixing clade refers to that same four-order radiation at broad scale, but neither phrase means that every included plant fixes nitrogen. Most Fabales do not, and even within Fabaceae nodulation is absent from many lineages.

Historical Polygalales correspond to the former treatment of Polygalaceae as an independent order. Molecular evidence places the family firmly inside Fabales. Older Caesalpiniales, Mimosales, and related names reflect systems that elevated major legume groups to ordinal rank; modern classification instead retains those lineages within a monophyletic Fabaceae. Finally, the superficial similarity between papilionoid legume flowers and milkwort keel flowers should not be used to collapse Polygalaceae into Fabaceae. Their comparable pollination mechanisms are a classic case of convergence rather than evidence that the two families are morphologically interchangeable.

11. Additional Information

Angiosperm Phylogeny Group V provides the current higher-level framework used by Tree TSAR. It retains the four-family circumscription of Fabales while redefining Fabids as the four nitrogen-fixing orders Fabales, Rosales, Fagales, and Cucurbitales. The Angiosperm Phylogeny Website is particularly valuable for Fabales because it synthesizes competing family-level phylogenies, morphology, chemistry, fossil evidence, and the history of classification. Plants of the World Online and World Flora Online are useful for accepted family, genus, and species names, while specialist legume resources become essential once the reader moves into the enormous Fabaceae radiation.

Tree TSAR should continue to separate ordinal stability from uncertainty in early family relationships. Fabales are strongly supported and their four living families are secure even though the exact sequence of family divergences has changed among analyses. The same principle applies below family rank. Generic circumscriptions and subfamily hypotheses in Fabaceae or Polygalaceae can be evaluated independently without destabilizing the Fabales pathway itself.

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.

Aygören Uluer D (2025) Possible multiple origins of some important characteristics of the keel (papilionate) flowers within Fabales. Botanical Journal of the Linnean Society 209(1): 100-116. https://doi.org/10.1093/botlinnean/boae093 (opens in a new tab)

Aygören Uluer D, Hawkins JA, Forest F (2020) Supermatrix analyses and molecular clock rooting of Fabales: Exploring the effects of outgroup choice and long branch attraction on topology. Botany 98(4): 231-247. https://doi.org/10.1139/cjb-2019-0109 (opens in a new tab)

Bello MA, Hawkins JA, Rudall PJ (2007) Floral morphology and development in Quillajaceae and Surianaceae (Fabales), the species-poor relatives of Leguminosae and Polygalaceae. Annals of Botany 100(7): 1491-1505. https://doi.org/10.1093/aob/mcm228 (opens in a new tab)

Bello MA, Bruneau A, Forest F, Hawkins JA (2009) Elusive relationships within order Fabales: Phylogenetic analyses using matK and rbcL sequence data. Systematic Botany 34(1): 102-114. https://doi.org/10.1600/036364409787602348 (opens in a new tab)

Cai L, Cardoso D, Tressel LG, Lee C, Shrestha B, Choi I-S, de Lima HC, de Queiroz LP, Ruhlman TA, Jansen RK, Wojciechowski MF (2025) Well-resolved phylogeny supports repeated evolution of keel flowers as a synergistic contributor to papilionoid legume diversification. New Phytologist 247(1): 369-387. https://doi.org/10.1111/nph.70080 (opens in a new tab)

Centeno-González NK, Martínez-Cabrera HI, Porras-Múzquiz H, Estrada-Ruiz E (2021) Late Campanian fossil of a legume fruit supports Mexico as a center of Fabaceae radiation. Communications Biology 4: 41. https://doi.org/10.1038/s42003-020-01533-9 (opens in a new tab)

Doyle JJ, Ren J, Pawlowski K, James EK, et al. (2025) One versus many independent assemblies of symbiotic nitrogen fixation in flowering plants. Nature Communications 16: 5345. https://doi.org/10.1038/s41467-025-60433-w (opens in a new tab)

Kates HR, O’Meara BC, LaFrance R, Stull GW, James EK, Liu S-Y, Tian Q, Yi T-S, et al. (2024) Shifts in evolutionary lability underlie independent gains and losses of root-nodule symbiosis in a single clade of plants. Nature Communications 15. https://doi.org/10.1038/s41467-024-48036-3 (opens in a new tab)

Koenen EJM, Ojeda DI, Bakker FT, Wieringa JJ, Kidner C, Hardy OJ, Pennington RT, Herendeen PS, Bruneau A, Hughes CE (2021) The origin of the legumes is a complex paleopolyploid phylogenomic tangle closely associated with the Cretaceous-Paleogene (K-Pg) mass extinction event. Systematic Biology 70(3): 508-526. https://doi.org/10.1093/sysbio/syaa041 (opens in a new tab)

Legume Phylogeny Working Group (LPWG) (2017) A new subfamily classification of the Leguminosae based on a taxonomically comprehensive phylogeny. Taxon 66(1): 44-77. https://doi.org/10.12705/661.3 (opens in a new tab)

Soltis DE, Soltis PS, Endress PK, Chase MW, Manchester SR, Judd WS, Majure LC, Mavrodiev EV (2018) Phylogeny and Evolution of the Angiosperms: Revised and Updated Edition. University of Chicago Press, Chicago. https://doi.org/10.7208/chicago/9780226441757.001.0001 (opens in a new tab)

Stevens PF (2001 onwards) Angiosperm Phylogeny Website. Missouri Botanical Garden, St. Louis.

Werner GDA, Cornwell WK, Sprent JI, Kattge J, Kiers ET (2014) A single evolutionary innovation drives the deep evolution of symbiotic N2-fixation in angiosperms. Nature Communications 5: 4087. https://doi.org/10.1038/ncomms5087 (opens in a new tab)