Introduction

Although initially recognised at the tribal level, subfamily Cercidoideae has always been considered monophyletic and only the generic divisions have changed over the past decades. In the current taxonomy, the subfamily includes 14 genera, several of which are newly recognised or reinstated from Bauhinia sl. The vast majority of species in the subfamily (c. 400 spp) are Bauhinia segregates. Recent phylogenetic analyses have led to the re-circumscription of the paraphyletic Bauhinia sl into several smaller monophyletic genera that form two sister clades, a Bauhinia clade with Bauhinia L. (c. 230 spp), Brenieria Humbert (1 sp) and Piliostigma Hochst. (6 spp), and a Phanera clade with Phanera Lour. (74 spp), Schnella Raddi (45 spp), Cheniella R.Clark & Mackinder (10 spp), Lysiphyllum (Benth.) de Wit (8 spp), Tylosema (Schweinf.) Torre & Hillc. (5 spp), Gigasiphon Drake (5 spp), Barklya F.Muell. (1 sp) and Tournaya A.Schmitz (1 sp). Sister to this large clade, are the small genera Griffonia Baill. (5 spp), Adenolobus (Harv. ex Benth. & Hook.f.) Torre & Hillc. (2 spp) and Cercis L. (9-10 spp) that form a grade, with Cercis sister to the entire group. The latter is diploid (2n=14), whereas all other genera are polyploid, suggesting that a whole genome duplication may have occurred in the ancestor of all Cercidoideae except Cercis.

Several phylogenetic analyses have suggested that Cercidoideae is sister to all legumes, but the most recent phylogenomic analyses place Cercidoideae as sister to Detarioideae, the two occurring as sister to the rest of the legumes. Diversification time analyses calibrated with fossils of Bauhinia sl leaf impressions (46 Ma) and of Cercis leaf and fruit impressions (34 Ma) suggest a mid-Eocene crown node age for the subfamily. The most conspicuous distinguishing features of Cercidoideae are the unifoliolate bilobed leaves, zygomorphic, almost papilionate flowers (with the median petal innermost) and apical crescent-shaped hilum of the seeds – not all these characteristics occurring in all Cercidoideae genera.

Key Features

Cercidoideae are trees, shrubs or lianas, many with tendrils, and mostly unarmed but frequently with prickles or infrastipular spines. In Brenierea the branches are modified into cladodes. Leaves of Cercidoideae are unifoliolate and often bilobed, or bifoliolate with opposite leaflets. The flowers are slightly to strongly bilaterally symmetrical, and sometimes papilionate (with the median petal innermost). The sepals are united in a spathaceous or two- to five-lobed calyx or they can be free. Generally five free petals are present, but sometimes two or six are present, and in some species petals are absent. When present the petals are imbricate, with the adaxial petal innermost and frequently differentiated from the other petals.. Usually there are 10 stamens in two whorls of alternate length. The pods are dehiscent, often explosive with twisting valves, or indehiscent and then generally samaroid. Seeds of most Cercidoideae are recognised by their unusual apical crescent-shaped hilum.

Distribution and Ecology

Species of Cercidoideae occur across several biomes on all continents. They are found in the Temperate Biome in Eurasia, China and North America, in the Succulent Biome in southern Africa, and in the Rainforest Biome in South and Central America, Asia and Africa.

Formal Botanical Description

As published in LPWG (2017), Taxon 66: 44-77, doi.org/10.12705/661.3

Subfam. Cercidoideae Legume Phylogeny Working Group, stat. nov. ≡ Cercideae Bronn, Form. Pl. Legumin.: 134, 131. 1822 (“Cerceae”)

Type: Cercis L.

Trees, shrubs or tendriled lianas, mostly unarmed but frequently with prickles or infrastipular spines, branches rarely modified into flattened cladodes (Brenierea Humbert); specialised extrafloral nectaries stipular when present (Bauhinia L.), never on petiole and leaf rachis. Stipules in lateral position, free. Leaves uni- or bifoliolate (bipinnate, pinnate, palmate and trifoliolate leaves totally lacking), pulvinate, leaflet blade (when unifoliolate) entire or bilobed with a small mucro at the apex or between the lobes, exstipellate. Inflorescence racemose or pseudoracemose; bracteoles minute or large. Flowers bisexual, rarely unisexual (plants polygamous or dioecious), slightly to strongly bilaterally symmetrical, sometimes papilionate (Cercis), hypanthium greatly elongated to almost absent; sepals united in a spathaceous or 2–5-lobed calyx or free; petals free, 5, rarely 2, 6 (some Bauhinia) or absent (Brenierea), imbricate, the adaxial petal innermost and frequently differentiated; stamens usually 10 (sometimes fewer) in two whorls of alternate length, the filaments partly connate or free, anthers mostly uniform and dorsifixed, opening by a longitudinal slit or central pore in each theca, reduced stamens or staminodes sometimes present; pollen 3-colporate, 3–6-colpate, 3-porate, 3-pororate, 3–4-colporoidate or inaperturate monads, rarely in tetrads (only in some Bauhinia); gynoecium 1-carpellate, stipe of ovary free or adnate to abaxial wall of the hypanthium, ovary 1–many-ovulate. Fruits dehiscent (often explosively with twisting valves) or indehiscent and then generally samaroid. Seeds with apical crescent-shaped hilum, rarely circular (Cercis), lens inconspicuous, lacking pleurograms, pseudopleurograms, or wing or aril (in Brenierea two funicular aril-like lobes adnate to the testa leaving a short crescent-shaped scar or a long scar running nearly around the seed circumference); embryo straight, very rarely curved (Barklya F.Muell.). Vestured pits lacking in secondary xylem; silica bodies absent; septate fibres and storeyed rays sometimes present. Root nodules absent. 2n = 14, 24, 26, 28 (42, 56). Coumarins and cyanogenic glucosides reported; non-protein amino acids common (5-hydroxy-L-tryptophan only reported in this subfamily, Griffonia Baill., Brenierea).

To learn more

Clark, R.P., Mackinder, B.A. & Banks, H. 2017. Cheniella gen. nov. (Leguminosae: Cercidoideae) from southern China, Indochina and Malesia. Eur. J. Taxon. 360: 1–37. https://doi.org/10.5852/ejt.2017.360

Hao, G., Zhang, D.X., Zhang, M.-Y., Guo, L.-X. & Li, S.-J. 2003. Phylogenetics of Bauhinia subgenus Phanera (Leguminosae: Caesalpinioideae) based on ITS sequences of nuclear ribosomal DNA. Bot. Bull. Acad. Sin. 44(3): 223–228.

Lewis, G.P. & Forest, F. 2005. Cercideae. Pp. 57–67 in: Lewis, G., Schrire, B., Mackinder, B. & Lock, M. (eds.), Legumes of the World. Richmond: Royal Botanic Gardens, Kew.

Mackinder, B. & Clark, R. 2014. A synopsis of the Asian and Australasian genus Phanera Lour. (Cercideae: Caesalpinioideae: Leguminosae) including 19 new combinations. Phytotaxa 66: 49–68. https://doi.org/10.11646/phytotaxa.166.1.3

Meng, H.H., Jacques, F.M., Su, T., Huang, Y.J., Zhang, S.T., Ma, H.J. & Zhou, Z.K. 2014. New biogeographic insight into Bauhinia s.l. (Leguminosae): Integration from fossil records and molecular analyses. B. M. C. Evol. Biol. 14(1): 181. https://doi.org/10.1186/s12862-014-0181-4

Queiroz, L.P. de 2006. New species and new combinations in Phanera Lour. (Caesalpinioideae: Cercideae) from the Caatinga Biome. Neodiversity 1: 6–10. https://doi.org/10.13102/neod.11.2

Sinou, C., Forest, F., Lewis, G.P. & A. Bruneau. 2009. The genus Bauhinia s.l. (Leguminosae): a phylogeny based on the plastid trn L- trn F region. Botany 87: 947 – 960.

Sinou, C., Cardinal-McTeague, W. & Bruneau, A. 2020. Testing generic limits in Cercidoideae (Leguminosae): Insights from plastid and duplicated nuclear gene sequences. TAXON, 69: 67-86. https://doi.org/10.1002/tax.12207

Trethowan, L.A., Clark, R.P. & Mackinder, B.A. 2015. Asynopsis of the neotropical genus Schnella (Cercideae: Caesalpinioideae: Leguminosae) including 12 new combinations. Phytotaxa 204: 237–252. https://doi.org/10.11646/phytotaxa.204.4.1

Wang, Y.-H., Wicke, S., Wang, H., Jin, J.-J., Chen, S.-Y., Zhang, S.-D., Li, D.-Z. & Yi, T.-S. 2018. Plastid genome evolution in the early-diverging Legume subfamily Cercidoideae (Fabaceae). Frontiers Pl. Sci. 9: 138. https://doi.org/10.3389/ fpls.2018.00138.

Wunderlin, R.P. 2010. Reorganization of the Cercideae (Fabaceae: Caesalpinioideae). Phytoneuron 2010-48: 1–5.

Wunderlin, R.P. 2010. New combinations in Schnella (Fabaceae: Caesalpinioideae: Cercideae). Phytoneuron 2010-49: 1–5.

List of genera

Below is an alphabetical list of all genera accepted by the LPWG with links out to the taxonomic pages on our portal, GBIF and World Checklist of Vascular Plants (Kew). Over time this list will be updated to reflect the evolving taxonomy.

Please see the Species List and Synonyms and Legume Taxonomy Working Group pages for more taxonomic information. The current taxonomy is accessible by Browse or Advanced Search.