Mimosa L.

Legumes of the World. Edited by G. Lewis, B. Schrire, B. MacKinder & M. Lock. Royal Botanic Gardens, Kew. (2005)

Habit

Trees, shrubs or herbs

Ecology

Seasonally dry tropical and subtropical forest, woodland, wooded grassland, thorn forest, tropical montane woodland, temperate grassland and desert

Distribution

most in the Neotropics: centred in Mexico (62 endemic spp., 15 spp. extending to USA and 7 spp. to C America [3 and 2 spp. endemic to each region respectively]); Caribbean (8 endemic spp.); 7 spp. disjunct between Mexico-C America-Caribbean and S America; 20 spp. widespread in New World, 3 of which are pantropical weeds; c. 350 spp. endemic in S America in a) Brazil (S of Amazonia) and adjacent Paraguay, Argentina and Uruguay; b) Ecuador, Peru and Bolivia; c) Orinoco basin. 35 spp. endemic in the Palaeotropics (30 spp. in Madagascar; 2 spp. in SE tropical Africa and 3 spp. endemic to the Indian subcontinent)

Note

Placed in the Piptadenia group, allied to Parapiptadenia, Piptadenia, Stryphnodendron, Microlobius and Anadenanthera (Luckow et al., 2003)

The tribe Mimoseae (sensu Bentham, 1875) is retained here simply as a matter of convenience. All recent phylogenetic analyses indicate that Ingeae and Acacieae are derived from within Mimoseae (Chappill & Maslin, 1995; Käss & Wink, 1996; Luckow et al., 2000; Bruneau et al., 2001; Luckow et al., 2003; Herendeen et al., 2003a), making it a paraphyletic group at best. The most recent studies indicate that it may not even be monophyletic with respect to the Caesalpinioideae (Luckow et al., 2000; Bruneau et al., 2001; Luckow et al., 2003).

Although the outline of a new tribal classification of the mimosoids is emerging, we await better-supported phylogenies (based on more extensive data) before formalising new stable and useful groups. Some parts of the classification proposed here are better supported than others. Notably, the basal branches in Fig. 24 are poorly supported in most analyses and the relationships among the groups are likely to change as we acquire more data. As presently indicated (Luckow et al., 2003), the type genus Mimosa falls within the derived Piptadenia group which is in turn sister, and basally branching, to elements of Acacia and Ingeae (Fig. 24). A more narrowly circumscribed Mimoseae sens. strict. will thus leave the bulk of Mimoseae sens. lat. (i.e., as treated here) in need of new tribal allocation. The most conspicuous difference between the classification presented here and that of Lewis & Elias (1981) is the inclusion of tribe Parkieae within Mimoseae. The former was circumscribed based on imbricate aestivation of the calyx, and was considered the basal tribe within the Mimosoideae (Elias, 1981a). Recent phylogenetic analyses (Chappill & Maslin, 1995; Luckow et al., 2000; Bruneau et al., 2001; Luckow et al., 2003; Herendeen et al., 2003a), indicate that the two genera in the Parkieae, Parkia and Pentaclethra, are not sister taxa (Fig. 24). Pentaclethra is nested within Mimoseae in Luckow et al. (2000), but is either sister to caesalpinioid taxa in Bruneau et al. (2001) and Herendeen et al. (2003a), or part of a basal polytomy with Mimoseae and caesalpinioid taxa (Luckow et al., 2003). Both Parkia and Pentaclethra are included in the tribe Mimoseae pending additional data and tribal recircumscription.

Recent work (Luckow et al., submitted a) also indicates that the monospecific tribe Mimozygantheae should be subsumed in the Mimoseae near Piptadeniopsis and Prosopidastrum, currently in the Prosopis group. Otherwise, the informal groups within the Mimoseae recognised by Lewis & Elias (1981) are relatively well-supported by current phylogenies and only a few departures have been made from their system. Where relationships are either poorly supported or unresolved, the classification of Lewis & Elias (1981) is retained. The Xylia group is dismantled and the Adenanthera group recircumscribed to include Calpocalyx and Xylia . Desmanthus has been removed from the Dichrostachys group, as has Neptunia, in agreement with recent molecular and morphological phylogenetic studies (Harris et al., 1994; Hughes, 1998; Luckow, 1995, 1997). A new group is erected to accommodate Piptadeniastrum which is well separated from Newtonia in the most recent phylogeny (Luckow et al., 2000; 2003), and another to accommodate Cylicodiscus, which is more closely related to the clade containing the Prosopis, Leucaena, Dichrostachys, and Piptadenia groups than it is to the Newtonia group. Neptunia is well supported as sister to Prosopidastrum in recent analyses (Luckow et al., 2003) and is included in the Prosopis group here. Relationships of genera in the Prosopis group are not resolved, but the group is retained here as there is no evidence that it is not monophyletic. Genera newly described since 1981 include Alantsilodendron, Calliandropsis, Kanaloa, and Lemurodendron. Alantsilodendron and Calliandropsis are placed in the Dichrostachys group, and Kanaloa in the Leucaena group based on phylogenetic analyses (Hughes, 1998; Luckow, 1997; Luckow et al., 2000). Lemurodendron is tentatively included in the Newtonia group as suggested by Villiers & Guinet (1989). As treated here the Mimoseae comprises 40 genera and from (859)– 869–(879) species.

Leguminosae, J.P.M. Brenan. Flora Zambesiaca 3:1. 1970

Morphology General Habit

Mostly herbs or shrubs, rarely trees, sometimes scrambling or climbing, prickles usually present.

Morphology Leaves

Leaves 2-pinnate, or the pinnae seeming almost digitate on account of the very short rhachis, rarely (not in our species) absent or modified to phyllodes; pinnae each with few to many pairs of leaflets.

Morphology Reproductive morphology Inflorescences

Inflorescences of ovoid or sub-globose heads or (not in our species) spikes, which are axillary, solitary or more usually clustered and often ± aggregated.

Morphology Reproductive morphology Flowers

Flowers hermaphrodite or male, small, sessile.

Morphology Reproductive morphology Flowers Calyx

Calyx very small, irregularly laciniate or denticulate in our species.

Morphology Reproductive morphology Flowers Corolla

Corolla gamopetalous, 4- or sometimes 3-, 5- or 6-lobed.

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens as many as or twice as many as the corolla-lobes, fertile.

Morphology Reproductive morphology Flowers Androecium Stamens Anthers

Anthers without any apical gland.

Morphology Reproductive morphology Fruits

Pods straight to circinate, flat, in our species ± bristly or prickly; at maturity the valves between the margins splitting ± transversely into 1-seeded segments or rarely (not in our species) remaining entire; exocarp (at least in our species) not separating from the endocarp; margins persistent.

Leguminosae, J. B. Gillett, R. M. Polhill & B. Verdcourt. Flora of Tropical East Africa. 1971

Morphology General Habit

Mostly herbs or shrubs, rarely trees, sometimes scrambling or climbing; prickles usually present

Morphology Leaves

Leaves bipinnate, or the pinnae seeming almost digitate on account of the very short rhachis, rarely (not in our species) absent or modified to phyllodes; pinnae each with few to many pairs of leaflets

Morphology Reproductive morphology Inflorescences

Inflorescences of ovoid or subglobose heads or (not in our species) spikes, which are axillary, solitary or more usually clustered and often ± aggregated

Morphology Reproductive morphology Flowers

Flowers hermaphrodite or ♂, small, sessile

Morphology Reproductive morphology Flowers Calyx

Calyx very small, irregularly laciniate or denticulate in our species

Morphology Reproductive morphology Flowers Corolla

Corolla gamopetalous, 4- or sometimes 3-, 5- or 6-lobed

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens as many as or twice as many as the corolla-lobes, fertile

Morphology Reproductive morphology Flowers Androecium Stamens Anthers

Anthers without any apical gland

Morphology Reproductive morphology Fruits

Pods straight to circinate, flat, in our species ± bristly or prickly; at maturity the valves between the sutures splitting ± transversely into 1-seeded segments or rarely (not in our species) remaining entire; exocarp (at least in our species) not separating from the endocarp; sutures persistent.

Timothy M. A. Utteridge and Laura V. S. Jennings (2022). Trees of New Guinea. Kew Publishing. Royal Botanic Gardens, Kew

Distribution

A genus of about 490–510 species, most species Neotropical, with 35 Palaeotropical species (30 in Madagascar). There are four species in New Guinea which usually form dense shrubby thickets, although Mimosa scabrella Benth. from Brazil (but collected from Goroka, Papua New Guinea, ?naturalised), can be a small tree.

Morphology General Habit

Herbs, scramblers, shrubs and trees to 10 m tall, prickles present on internodes or absent

Morphology Leaves Stipules

Stipules caducous

Morphology Leaves

Leaves bipinnate, in many species sensitive to touch, glands absent (in New Guinea), leaflets opposite

Morphology Reproductive morphology Inflorescences

Inflorescences axillary, pedunculate glomerules or spikes. Flowers bisexual, uniform, 4-merous (in New Guinea); calyx tubular, irregularly lobed or minutely toothed; corolla tubular, lobed at apex; stamens 4 or 8 (in New Guinea), free, anther glands absent; ovary sessile

Morphology Reproductive morphology Fruits

Fruit membranous to coriaceous, straight (in New Guinea), a craspedium, breaking into 1-seeded segments, the fruit sutures persisting after dehiscence (as a replum), often bristly or prickly

Morphology Reproductive morphology Seeds

Seeds elliptic, testa hard, pleurogram present.

Ecology

In New Guinea, Mimosa species are naturalised and have become weeds of roadsides, plantations, gardens, swamps, sandy riverbeds and disturbed secondary vegetation, below 1000 m.

Recognition

The genus (in New Guinea) can be recognised by the minute 4-merous flowers in globose heads, fruits breaking into 1-seeded segments, leaving the sutures as a frame-like structure (the replum). Many members of the genus are often called ‘sensitive plants’ as their leaves are sensitive to touch, quickly folding inward and drooping down when touched or shaken. In New Guinea, the species of Mimosa have 4 or 8 stamens, and across the genus, stamen number is an important character: the flowers are either haplostemonous (stamens = petals in number) or diplostemonous (stamens 2× petals); i.e. the flowers can be 3 petals/3 stamens, 3 petals /6 stamens, 4 petals /4 stamens, 4 petals/8 stamens, 5 petals/5 stamens or 5 petals/10 stamens.

M. Thulin et al. Flora of Somalia, Vol. 1-4 [updated 2008] https://plants.jstor.org/collection/FLOS

Morphology General Habit

Herbs or shrubs, rarely trees; prickles usually present

Morphology Leaves

Leaves bipinnate, rarely (not in Somalia) absent or modified to phyllodes

Morphology Reproductive morphology Inflorescences

Flowers bisexual or polygamous, sessile, in heads or (not in Somalia) spikes

Morphology Reproductive morphology Flowers Calyx

Calyx very small

Morphology Reproductive morphology Flowers Corolla

Corolla (3–)4(–6)-lobed

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens as many as or twice as many as the corolla-lobes; anthers eglandular at apex

Morphology Reproductive morphology Fruits

Pod straight or curved, flat, at maturity usually splitting ± transversely between persistent sutures into 1-seeded segments.

Distribution

Some 600 species throughout the tropics, the vast majority in Central and South America.