Research Article |
Corresponding author: Dmitry A. German ( oreoloma@rambler.ru ) Corresponding author: Ihsan A. Al-Shehbaz ( ihsan.al-shehbaz@mobot.org ) Academic editor: Karol Marhold
© 2023 Dmitry A. German, Kasper P. Hendriks, Marcus A. Koch, Frederic Lens, Martin A. Lysak, C. Donovan Bailey, Klaus Mummenhoff, Ihsan A. Al-Shehbaz.
This is an open access article distributed under the terms of the CC0 Public Domain Dedication.
Citation:
German DA, Hendriks KP, Koch MA, Lens F, Lysak MA, Bailey CD, Mummenhoff K, Al-Shehbaz IA (2023) An updated classification of the Brassicaceae (Cruciferae). PhytoKeys 220: 127-144. https://doi.org/10.3897/phytokeys.220.97724
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Based on recent achievements in phylogenetic studies of the Brassicaceae, a novel infrafamilial classification is proposed that includes major improvements at the subfamilial and supertribal levels. Herein, the family is subdivided into two subfamilies, Aethionemoideae (subfam. nov.) and Brassicoideae. The Brassicoideae, with 57 of the 58 tribes of Brassicaceae, are further partitioned into five supertribes, including the previously recognized Brassicodae and the newly established Arabodae, Camelinodae, Heliophilodae, and Hesperodae. Additional tribus-level contributions include descriptions of the newly recognized Arabidopsideae, Asperuginoideae, Hemilophieae, Schrenkielleae, and resurrection of the Chamireae and Subularieae. Further detailed comments on 17 tribes in need of clarifications are provided.
classification, subfamily, supertribe, taxonomy, tribe
Rapid advances in our understanding of phylogenetic relationships among taxa are driving the development of modern classification schemes that accurately reflect current knowledge. Brassicaceae (Cruciferae) is a relatively large family, currently comprising ca. 4140 species (original data), for which various classification systems have been proposed, including influential historical classifications contributed by
Brassica L.
Cosmopolitan, centered in temperate regions of the Northern Hemisphere.
All phylogenetic studies over the past two and a half decades identify Aethionema W.T. Aiton as sister to all other Brassicaceae, which supports the recognition of two highly unequal subfamilies, the new unigeneric Aethionemoideae with 58 species and the much bigger Brassicoideae, comprising the other 98.6% of species and the rest of the generic and tribal diversity of the family.
Aethionema W.T. Aiton
Trichomes and multicellular glands absent. Leaves entire, articulate at base. Fruits silicles, angustiseptate, bilocular, few-seeded, dehiscent, or unilocular, one-seeded, indehiscent; sometimes both types present. Most common x = 11, 12.
Primarily SW Asia, especially Turkey, Iran & Transcaucasia.
Aethionemeae Al-Shehbaz, Beilstein & E.A. Kellogg.
For many species of Aethionema a 3-nerved petal claw has been described (e.g.,
Brassica L.
Trichomes (simple and/or variously branched) and multicellular glands absent or present. Leaves entire to variously dissected, simple or compound, not articulate at base. Fruits various in compression, dehiscence, length to width ratio, number of seeds (one to > 100), etc. Base chromosome numbers various; the lowest x = 4.
Same as the whole family.
Brassicoideae is subdivided into the following five supertribes corresponding to the main evolutionary lineages discussed in detail by
Arabis L.
Trichomes present, mainly branched (exclusively or in combination with simple); multicellular glands absent. Leaves predominantly undivided or slightly divided, auriculate at base or not. Most common x = 8.
Mainly Northern Hemisphere (predominantly Holarctis of Eurasia, also of N America and Africa), S America (Andes).
Arabideae DC., Alysseae DC., Asperuginoideae trib. nov., Stevenieae Al-Shehbaz, D.A.German & M.Koch.
Corresponds to evolutionary lineage IV of
Brassica L.
Sisymbriodae V.E. Avet., Thelypodiodae V.E. Avet.
Trichomes absent or simple, rarely branched; multicellular glands absent. Leaves predominantly undivided or slightly divided, rarely much divided, often auriculate at base. Most common x = 7.
Mainly Northern Hemisphere (Holarctis of Eurasia, N America and Africa), to a lesser degree C and S America.
Aphragmeae D.A.German & Al-Shehbaz, Brassiceae DC. [incl. Bivonaeeae M.A. Koch & Warwick], Calepineae Horan., Coluteocarpeae V.I. Dorof., Conringieae D.A. German & Al-Shehbaz, Eutremeae Al-Shehbaz, Beilstein & E.A. Kellogg, Fourraeeae Al-Shehbaz, M.A. Koch, R. Karl & D.A.German, Isatideae DC., Kernereae Al-Shehbaz, Warwick, Mumm. & M.A. Koch, Plagiolobeae Khosravi & Eslami-Farouji, Schrenkielleae trib. nov., Sisymbrieae DC., Thelypodieae Prantl, Thlaspideae DC.
Corresponds to evolutionary lineage II introduced by
Camelina Crantz
Trichomes usually present, simple and/or branched; multicellular glands absent. Leaves not or variously divided to compound, auriculate at base or not. Base numbers various, most common x = 6, 7, 8.
Represented by native taxa at all continents except Antarctica; most diverse in Holarctis of Eurasia and N America.
Alyssopsideae Al-Shehbaz, Warwick, Mumm. & M.A. Koch, Arabidopsideae trib. nov., Boechereae Al-Shehbaz, Beilstein & E.A. Kellogg, Camelineae DC., Cardamineae Dumort., Crucihimalayeae D.A.German & Al-Shehbaz, Descurainieae Al-Shehbaz, Beilstein & E.A. Kellogg, Erysimeae Dumort., Halimolobeae Al-Shehbaz, Beilstein & E.A. Kellogg, Hemilophieae trib. nov., Lepidieae DC., Malcolmieae Al-Shehbaz & Warwick, Microlepidieae Al-Shehbaz, Warwick, Mumm. & M.A. Koch, Oreophytoneae Al-Shehbaz, Warwick, Mumm. & M.A. Koch, Physarieae B.L. Rob., Smelowskieae Al-Shehbaz, Beilstein & E.A. Kellogg, Turritideae Buchenau, Yinshanieae Al-Shehbaz, Warwick, Mumm. & M.A. Koch.
Corresponds to evolutionary lineage I of
Heliophila L.
Trichomes absent or simple, rarely branched; multicellular glands absent. Leaves mainly not or slightly divided, rarely much divided to compound, usually not auriculate at base. Base numbers are various due to post-polyploid diploidization – 12 tribes have originated through whole-genome duplications (data lacking for Hillielleae).
Well-represented in both Hemispheres; Eurasia (mainly SW Asia & S Europe), N, Tropical & S Africa, C & S America, New Zealand.
Anastaticeae DC., Asteae Al-Shehbaz, Warwick, Mumm. & M.A. Koch [incl. Scoliaxoneae Al-Shehbaz & Warwick], Biscutelleae Dumort., Chamireae Sond., Cremolobeae R. Br., Eudemeae Al-Shehbaz, Warwick, Mumm. & M.A. Koch, Heliophileae DC., Hillielleae H.L. Chen, T. Deng, J.P. Yue, Al-Shehbaz & H. Sun, Iberideae Webb & Berthel., Megacarpaeeae Kamelin ex D.A.German, Notothlaspideae Al-Shehbaz, Warwick, Mumm. & M.A. Koch, Schizopetaleae R. Br. ex Barnéoud, Subularieae DC.
This group corresponds to evolutionary lineage V of
Hesperis L.
Trichomes usually present, simple and/or branched; multicellular glands often present. Leaves normally little divided, nearly never auriculate at base. Most common x = 7.
Native to Eurasia (predominantly temperate and dry subtropical Asia).
Anchonieae DC., Buniadeae DC., Chorisporeae C.A. Mey., Dontostemoneae Al-Shehbaz & Warwick, Euclidieae DC., Hesperideae Prantl, Shehbazieae D.A.German.
Corresponds to evolutionary lineage III of
Updates at the tribal level include recognition of additional six tribes, of which four are newly described and another two are resurrected. Tribal names are followed in parenthesis by numbers of genera and species.
Arabidopsis (DC.) Heynh.
Herbs, annual or perennial. Trichomes simple, mixed with stalked 1–3(or 4)-forked. Multicellular glands absent. Cauline leaves petiolate to subsessile and cuneate to attenuate at base, not auriculate. Racemes ebracteate, often elongated in fruit. Flowers actinomorphic; sepals ascending to spreading, base of lateral pair slightly saccate or not; petals white, pink, or purple; claw obscurely differentiated from blade or distinct; filaments unappendaged, wingless; pollen 3-colpate; ovules 15–80 per ovary. Fruits siliques, linear, terete or latiseptate, unsegmented; styles obsolete or to 1 mm long; stigma entire. Seeds uniseriate; cotyledons accumbent or rarely incumbent. x = 5 and 8.
Eurasia, Africa, North America.
Arabidopsideae is distinguished from the Camelineae by the lack of stellate and dendritic trichomes, though both also have simple and stalked forked trichomes, by having petiolate or subsessile cauline leaves not auriculate at base, by the lack of yellow flowers, 15–80 ovules per ovary, silique fruits, and accumbent or rarely incumbent cotyledons. By contrast, the Camelineae usually have some stellate or dendritic trichomes, always sessile and auriculate to sagittate cauline leaves, usually yellow flowers, though white to pink flowers occur just as in the Arabidopsideae, 2–40 ovules per ovary, silicle or rarely silique fruits, and incumbent or rarely accumbent cotyledons.
There has been no agreement among various authors about the tribal assignment of monospecific Asperuginoides Rauschert. For example,
Asperuginoides Rauschert
Herbs annual. Trichomes stalked, stellate or substellate, 4–6-rayed, these mixed with glochidate ones on fruit. Multicellular glands absent. Cauline leaves petiolate, not auriculate. Racemes bracteate throughout, usually elongated in fruit, with strongly recurved fruiting pedicels. Flowers actinomorphic; sepals ascending, base of lateral pair not saccate; petals white, claw undifferentiated from blade; filaments slender at base, unappendaged; pollen 3-colpate; ovules 2 per ovary, apical. Fruits dehiscent silicles, suborbicular, latiseptate, unsegmented, wingless, with long-stalked, setose, stiff trichomes glochidiate at apex; septum complete or absent; style distinct; stigma entire. Seeds aseriate, broadly winged; cotyledons accumbent. x = 16.
Afghanistan, Armenia, Iran, Kazakhstan, Kyrgyzstan, Pakistan, Tajikistan, Turkey, Turkmenistan, Uzbekistan.
Although the tribe Chamireae was first recognized by
Chamira Thunb.
Herbs, annual. Trichomes absent. Leaves sessile or short petiolate, not auriculate at base, lowest pair opposite, representing persistent cotyledons and main photosynthetic part of plant, to 25 cm wide, cauline leaves alternate, much smaller, sometimes fail to develop. Racemes ebracteate, elongated in fruit. Sepals connivent, dimorphic, median (outer) pair not saccate at base, lateral pair with a distinct spur 1–2.5 mm long; petals white, with well-differentiated claw; filaments unappendaged; pollen 3-colpate; ovules 2–8 per ovary. Fruits siliques, dehiscent, terete to sublatiseptate, unsegmented; styles distinct; stigma entire. Seeds uniseriate; cotyledons longitudinally folded and margins deeply folded within. x = 19.
Chamira circaeoides (L. f.) Zahlbr. is endemic to the Western Cape of South Africa.
Dipoma Franch. was first studied by
Hemilophia Franch.
Herbs rhizomatous perennials. Trichomes simple, malpighiaceous, sometime short-stalked forked. Multicellular glands absent. Cauline leaves petiolate to subsessile and cuneate to attenuate at base, not auriculate. Racemes bracteate throughout, elongated or not in fruit. Flowers actinomorphic; sepals ascending to spreading, base of lateral pair not saccate; petals white, pink, or purple; claw obscurely differentiated from blade or distinct; filaments slender or dilated at base and sometimes strongly appendaged; pollen 3-colpate; ovules 2 or 4 per ovary, apical. Fruits dehiscent silicles, oblong to ovoid, terete or slightly angustiseptate, unsegmented, wingless or with narrow wings or crests; septum complete or absent; styles distinct, cylindrical or conical; stigma entire. Seeds aseriate; cotyledons accumbent. Base numbers various.
Endemic to China (Sichuan and Yunnan).
The tribe includes narrowly distributed monospecific Dipoma and Hemilophia (6 spp.).
The first clear relationship of Idahoa and Subularia to other tribes was given in
Subularia L.
Herbs scapose annuals. Trichomes absent. Multicellular glands absent. All leaves in a basal rosette, sessile or petiolate, cauline leaves absent. Racemes ebracteate throughout and elongated or not in fruit, or flowers solitary on long pedicels originating from center of rosette. Flowers actinomorphic; sepals spreading or ascending, base of lateral pair not saccate; petals white, claw obscure or undifferentiated from blade; filaments slender at base; pollen 3-colpate; ovules 4–18. Fruits dehiscent, unsegmented silicles, orbicular and strongly latiseptate or obovoid to ellipsoid and slightly angustiseptate; septum complete; styles minute or absent; stigma entire. Seeds biseriate, broadly winged and accumbent, or wingless and incumbent. x = 14 and 15.
The tribe includes monospecific Idahoa (NW USA and Canadian British Columbia) and two aquatic or littoral species of Subularia, of which S. monticola A. Braun ex Schweinf. is restricted to tropical East Africa, and S. aquatica L. is distributed in northern North America (subsp. americana G.A. Mulligan & Calder) and temperate Eurasia (subsp. aquatica).
This monospecific genus was based on Diplotaxis parvula Schrenk, a species that fluctuated between unrelated genera solely on morphological grounds. It was first shown by
Schrenkiella D.A.German & Al-Shehbaz
Herbs annual, glaucous. Trichomes absent. Multicellular glands absent. Cauline leaves petiolate to subsessile, fleshy, cuneate at base, not auriculate. Racemes ebracteate, elongated in fruit, rachis strongly flexuous. Flowers actinomorphic; sepals suberect, base of lateral pair not saccate; petals absent, rarely present, white, subequaling sepals; claw obsolete; filaments slender, unappendaged; pollen 3-colpate; ovules 24–50 per ovary. Fruits dehiscent siliques, linear, latiseptate, unsegmented; septum complete; styles distinct; stigma entire. Seeds biseriate; cotyledons incumbent. x = 7.
Schrenkiella parvula (Schrenk) D.A.German & Al-Shehbaz is sporadically distributed in Armenia, Azerbaijan, Iran, Kazakhstan, Russia, Turkey, Turkmenistan, and Uzbekistan.
The following alphabetical tribal discussions are based on the phylogenies of
Aethionemeae (1: 58). The tribe is distributed primarily in SW Asia and the Mediterranean region, with the center of greatest diversity located in Turkey, in which 23 of the 40 species are endemic. All previous molecular studies have supported the tribal position as a sister clade to the rest of the Brassicaceae recognized above at subfamilial level.
Alysseae (24: 282). The tribe is almost exclusively distributed in Eurasia, with several native species in North Africa and one in North America. The largest and most complex genera are Alyssum L. and Odontarrhena C.A. Mey. ex Ledeb. with about 114 and 91 species, respectively. The tribe has recently been revised by
Alyssopsideae (4: 9). A small Asian tribe distributed predominantly in Afghanistan, Azerbaijan, Iran, Tajikistan, and Turkmenistan. It is monophyletic in
Anchonieae (9: 75). Except for several species of Matthiola W.T. Aiton in Europe, the tribe is distributed primarily in SW and C Asia, and Africa. Only monospecific Eremoblastus Botsch. is not covered in
Arabideae (18: 559). The tribe is the largest and most complex in the family. It includes ten monospecific genera, and Draba L. (ca. 410 spp.), Arabis L. (ca. 100 spp.), and Aubrieta Adans. (23 spp.) are the most species rich ones. The tribe has been the focal topic for the Koch lab (Heidelberg University) for about three decades and despite carving nearly a dozen segregates into several tribes, Arabis still needs further focus and taxonomic adjustments are under consideration (see
Asteae (2: 2). The findings of
Brassiceae (53: 243). The tribe has been recognized by all authors since it was established by
Monophyly of Brassica is established based on most recent molecular phylogenies (e.g.,
Camelineae (4: 16). As shown by
Herbs, annual or perennial. Trichomes stalked or sessile, stellate, dendritic, or forked, sometimes mixed with simple ones. Multicellular glands absent. Cauline leaves sessile, mostly entire, auriculate or sagittate at base. Racemes ebracteate, often elongated in fruit. Flowers actinomorphic; sepals erect to spreading, lateral pair often not saccate at base; petals white, yellow, orange, pink, or purple, often with a distinct claw; filaments unappendaged, wingless; pollen 3-colpate; ovules 2–40 per ovary. Fruits silicles or siliques, dehiscent or indehiscent, latiseptate, terete, or angustiseptate, unsegmented; styles often distinct; stigma entire or rarely 2-lobed. Seeds biseriate, uniseriate, or aseriate; cotyledons incumbent or rarely accumbent.
Conringieae (1: 3) vs. Plagiolobeae (1: 5). The Conringieae sensu
Cremolobeae (4: 32). As currently recognized (
Descurainieae (6: 48). Except for the monospecific Patagonian Trichotolinum O.E. Schulz, which has not yet been included in any phylogenetic studies, the position of other five genera in
Dontostemoneae (2: 14). Position of Dontostemoneae, Chorisporeae, and their intertribal hybrid Shehbazieae are in full agreement with the initial findings by
Eudemeae (9: 40). Hendriks et al’s. (2022) sampling of five species of five genera supports the monophyly of this tribe. Together with the other exclusively South American tribes, Cremolobeae (see above) and Schizopetaleae of the CES clade sensu
Fourraeeae (2: 3) This tribe has recently been established by
Hillielleae (1: 11). The recently established Hillielleae was previously part of the Yinshanieae, but
Iberideae (2: 30). The tribe includes the primarily European Iberis L. (27 spp.) and Teesdalia (3 spp.). Only
The taxonomic framework presented here reflects a growing body of phylogenetic knowledge derived from continual advances in the sampling of species, broader representation of major groups, and the extensive sampling of genomic regions needed to help robustly resolve relationships across scales (
The work by K.M., F.L, and K.P.H. was supported by the German Research Foundation (DFG; grant number MU1137/17-1 to K.M.). M.A.L. was supported by a research grant from the Czech Science Foundation (no. 21-03909S). This work was also supported by the German Research Foundation (DFG; grant numbers KO2302/23-2 to M.A.K.).