Mimosa L., Sp. Pl. 1: 516. 1753.

Bruneau, Anne, de Queiroz, Luciano Paganucci, Ringelberg, Jens J., Borges, Leonardo M., Bortoluzzi, Roseli Lopes da Costa, Brown, Gillian K., Cardoso, Domingos B. O. S., Clark, Ruth P., Conceicao, Adilva de Souza, Cota, Matheus Martins Teixeira, Demeulenaere, Else, de Stefano, Rodrigo Duno, Ebinger, John E., Ferm, Julia, Fonseca-Cortes, Andres, Gagnon, Edeline, Grether, Rosaura, Guerra, Ethiene, Haston, Elspeth, Herendeen, Patrick S., Hernandez, Hector M., Hopkins, Helen C. F., Huamantupa-Chuquimaco, Isau, Hughes, Colin E., Ickert-Bond, Stefanie M., Iganci, Joao, Koenen, Erik J. M., Lewis, Gwilym P., de Lima, Haroldo Cavalcante, de Lima, Alexandre Gibau, Luckow, Melissa, Marazzi, Brigitte, Maslin, Bruce R., Morales, Matias, Morim, Marli Pires, Murphy, Daniel J., O'Donnell, Shawn A., Oliveira, Filipe Gomes, Oliveira, Ana Carla da Silva, Rando, Juliana Gastaldello, Ribeiro, Petala Gomes, Ribeiro, Carolina Lima, Santos, Felipe da Silva, Seigler, David S., da Silva, Guilherme Sousa, Simon, Marcelo F., Soares, Marcos Vinicius Batista & Terra, Vanessa, 2024, Advances in Legume Systematics 14. Classification of Caesalpinioideae. Part 2: Higher-level classification, PhytoKeys 240, pp. 1-552 : 1

publication ID	https://dx.doi.org/10.3897/phytokeys.240.101716
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scientific name	Mimosa L., Sp. Pl. 1: 516. 1753.
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Treatment

Mimosa L., Sp. Pl. 1: 516. 1753. View in CoL

Figs 185 View Figure 185 , 186 View Figure 186 , 187 View Figure 187

Schrankia Willd., Sp. Pl., ed. 4(2): 888, 1041. 1806, nom. cons. Lectotype: Schrankia aculeata Willd. [= Mimosa quadrivalvis L.]

Eburnax Raf., New Fl. [Rafinesque] 1: 42. 1836. Type: Eburnax pudica (L.) Raf. [≡ Mimosa pudica L.]

Sensitiva Raf., Sylva Tellur.: 119. 1838. Type: Sensitiva pudica Raf. [≡ Mimosa pudica L.?]

Lomoplis Raf., Sylva Tellur.: 118. 1838. Lectotype (designated by Britton and Rose 1928): Lomoplis ceratonia (L.) Raf. [≡ Mimosa ceratonia L.]

Leptoglottis DC. ex Torr. & A. Gray, Fl. N. Amer. (Torr. & A. Gray) 1: 695. 1840. Type: Leptoglottis nuttallii DC. ex Torr. & A. Gray [≡ Mimosa quadrivalvis var. nuttallii (DC. ex Torr. & A. Gray) Beard ex Barneby]

Morongia Britton, Mem. Torrey Bot. Club 5: 191. 1894. Lectotype (designated here): Morongia angustata (Torr. & A. Gray) Britton [≡ Mimosa quadrivalvis var. angustata (Torr. & A. Gray) Barneby]

Schranckiastrum Hassl., Repert. Spec. Nov. Regni Veg. 16: 151. 1919. Type: Schranckiastrum insigne Hassl. [≡ Mimosa insignis (Hassl.) Barneby]

Acanthopteron Britton, N. Amer. Fl. 23: 179. 1928. Type: Acanthopteron laceratum (Rose) Britton [≡ Mimosa lacerata Rose]

Haitimimosa Britton, N. Amer. Fl. 23: 179. 1928. Type: Haitimimosa extranea (Benth.) Britton [≡ Mimosa extranea Benth.]

Mimosopsis Britton & Rose, N. Amer. Fl. 23: 174. 1928. Type: Mimosopsis prolifica (S. Watson) Britton & Rose [≡ Mimosa prolifica S. Watson]

Neomimosa Britton & Rose, N. Amer. Fl. 23: 172. 1928. Type: Neomimosa eurycarpa (B.L. Rob.) Britton & Rose [≡ Mimosa eurycarpa B.L. Rob.]

Pteromimosa Britton, N. Amer. Fl. 23: 171. 1928. Type: Pteromimosa bahamensis (Benth.) Britton [≡ Mimosa bahamensis Benth.]

Lectotype.

Mimosa sensitiva L.

Description.

Perennial shrubs, herbs, geoxyle subshrubs, lianas, treelets and trees, occasionally monocarpic; indumentum composed of numerous different combinations of simple, glandular, and complex multicellular trichomes and sharp-pointed setae; brachyblasts sometimes present; branches armed or not with scattered, serial, or nodal prickles. Stipules present, caducous or persistent. Leaves bipinnate, rarely once-pinnate ( M. unipinnata B.D. Parfitt & Pinkava), sometimes reduced to phyllodes bearing ephemeral pinnae ( M. ephedroides (Gillies ex Hook. & Arn.) Benth., M. extranea Benth., M. phyllodinea Benth.), rachis armed or not, sometimes with a spicular projection between pinnae pairs; extrafloral nectaries absent in the vast majority of species, if present, on the petiole and sometimes also on the rachis and pinnae; pinnae 1-many pairs, opposite, armed or not; leaflets 1-many pairs per pinna, sessile, mostly opposite, variable in size and shape; paraphyllidia mostly present. Inflorescences globose or ellipsoid capitula, cylindrical spikes or racemes, white, pink, yellow or red, solitary or fasciculate in the axils of coevally developing leaves, or organised in complex efoliate synflorescences, sometimes developing from short shoots on efoliate branches. Flowers 3-5 (6)-merous, haplo- or diplostemonous; bisexual or staminate, the latter located at the lower parts of the inflorescence, rarely all flowers bisexual; calyx gamosepalous; corolla gamopetalous; anther glands absent; pollen in tetrads or polyads with 8, 12, or rarely 16 grains; ovary glabrous to lanose. Fruit a typical craspedium or an unjointed craspedium, rarely lomentiform or follicular, variable in size, shape, indumentum, armature and seed number. Seeds lenticular, ellipsoid to spheroidal or rhombic.

Chromosome number.

The basic chromosome number in Mimosa is reported to be x = 13 ( Isely 1971; Goldblatt 1981b), with varying sporophytic chromosome counts recorded as 2 n = 26, 2 n = 39, 2 n = 52, 2 n = 104 ( Seijo 1993, 1999, 2000; Seijo and Fernández 2001; Morales et al. 2010, 2011, 2014a, 2014b, 2015, 2018; Dahmer et al. 2011), and approximately 20% of species potentially polyploid ( Dahmer et al. 2011).

Included species and geographic distribution.

615 species. Most are local endemics distributed right across the Americas from the USA to Argentina, with ca. 40 occurring in Africa, Madagascar (32 endemics) and Asia (Fig. 187 View Figure 187 ). A few species of American origin (e.g., Mimosa pigra L.) are introduced pantropically and highly invasive around the globe.

Ecology.

Mimosa is one of the most ecologically adaptable, widespread and ubiquitous genera of Mimoseae , occurring across the full tropical rainfall gradient and in almost all tropical and subtropical vegetation types in the Americas, including seasonally dry tropical and subtropical forests and semi-arid thorn scrub, desert, tropical and subtropical savannas and grasslands, lowland tropical rainforest, mid-elevation moist subtropical forest, wetlands, temperate forests, rarely on sand dunes, and often in disturbed open habitats. Some species become weedy outside their native range. This ecological adaptability is closely correlated with the diversity of growth forms - lianas in wet forests, stiffly-branched xerophytic shrubs in arid and semi-arid ecologies, and geoxyles in savannas ( Barneby 1991). Mimosa is especially abundant, diverse and ecologically important in the Cerrado (with 170 endemics), this facilitated by multiple independent evolutionary adaptations to fire, including numerous functionally herbaceous geoxyles with underground lignotubers, and pachycaul rosette trees with naked trunks ( Simon et al. 2009; Simon and Pennington 2012), and rapid recent species diversification within some of these fire-adapted clades ( Koenen et al. 2013).

Etymology.

Either from Spanish, mimoso (= sensitive; Barneby 1991), or from Greek, mimos (= actor, mimicking; Grether 2023), in reference to the responsiveness of the leaflets and pinnae to touch (seismonasty) in some species.

Human uses.

Mimosa species are used as living fences (e.g., M. caesalpiniifolia Benth. in Brazil), timber (e.g., M. scabrella Benth. in southern Brazil and Argentina), fodder (e.g., M. strigillosa Torr. & A. Gray, in Argentina and the USA; Fernández et al. 1988; Alison et al. 2022), ornamentals, medicinal ( Burkart 1948), firewood, and for soil enrichment and ecological restoration. Many species are a source of nectar for honey production, while some species with sensitive leaves are sold as “pet” plants (e.g., M. pudica ).

Notes.

Mimosa is classified into a complex infrageneric and infraspecific hierarchy (five sections, 41 series, 39 subseries, 18 subspecies and 268 varieties; Barneby 1991). However, almost all of Barneby’s traditional sections and series are not monophyletic ( Bessega et al. 2008; Simon et al. 2011) and a new phylogenetically-based classification is needed. Furthermore, the often complex patterns of morphological variation associated with some clades and widespread species alliances, likely further complicated by extensive polyploidy, which prompted Barneby’s extensive reliance on infraspecific taxa, are the focus of detailed studies of particular species complexes (e.g., Grether 2000; Morales and Fortunato 2010; Morales et al. 2010, 2018; Léon de la Luz et al. 2015; Borges et al. 2017, 2023; Jordão et al. 2018). The re-assessment of taxon delimitations within species complexes in this group has often resulted in the recognition at the specific rank of taxa that were treated by Barneby as subspecies and varieties.

Most species nodulate, particularly with beta-rhizobia (Reis Junior et al. 2010; Bontemps et al. 2016; Platero et al. 2016). Pollinators are unknown for the majority of species but include bees, bats, butterflies, dipterans, hemipterans and wasps ( Vogel et al. 2005). Although most species do not show specialised dispersal mechanisms, species such as M. pigra , a globally widespread and wetland weed, have floating one-seeded articles highly adapted to water dispersal. The presence of setae and prickles on articles of M. diplotricha C. Wright, M. sensitiva , M. skinnerii Benth., M. velloziana Mart. and M. ursina Mart. indicates adaptation for animal dispersal (epizoochory).

Rapid movement of leaves and leaf parts in response to touch is a trademark of Mimosa . Although leaf movement evolved in many lineages within the genus, it is restricted to less than 5% of the species ( Simon et al. 2011). The mechanism of leaf movement in the sensitive plant ( M. pudica ) has been studied in detail and seems to be associated with protection from insect attacks ( Hagihara et al. 2022).

The highly disjunct amphi-Atlantic distribution of Mimosa (Fig. 187 View Figure 187 ), and extremely uneven distribution of species diversity across this range are striking. This diversity anomaly with high species richness in the Neotropics and Madagascar, where the genus has diversified extensively, and Africa / Asia with just a handful of species, is as yet largely unexplained. However, it is clear that the Old World species form a relatively young clade (late Miocene) that is deeply nested within New World Mimosa ( Simon et al. 2011), and that the Madagascan species also form a clade within the Old World clade ( Simon et al. 2011) that shows a signature of a rapid evolutionary radiation ( Ringelberg et al. 2023).

We could not confirm the type species of Sensitiva , one of the many generic synonyms of Mimosa . Although Sensitiva was validly published and circumscribed to include species close to M. pudica and M. sensitiva , Rafinesque (1838) did not make any new combinations under it.

Taxonomic references.

Barneby (1991); Bessega and Fortunato (2011); Bessega et al. (2008); Borges et al. (2023); Burkart (1948); Dutra et al. (2020); Grether (1987; 2000; 2023); Grether et al. (1996); Jordão et al. (2020); Medina-Acosta et al. (2019); Morales and Fortunato (2010); Morales et al. (2010, 2018); Santos-Silva et al. (2015); Simon et al. (2011); Villiers (2002).