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Mariosousa acatlensis - habit

Mariosousa acatlensis - habitat

Mariosousa acatlensis - habitat

Mariosousa acatlensis - flowers

Mariosousa acatlensis - flowers

Mariosousa acatlensis - flowers

Mariosousa acatlensis - habit

Mariosousa acatlensis - flowers

Mariosousa acatlensis

Mariosousa acatlensis - flowers

Mariosousa acatlensis - habit

Mariosousa acatlensis

Name

Mariosousa acatlensis (Bentham) Seigler & Ebinger

Synonymy and types

Acacia acatlensis Bentham, London J. Bot. 1:513. 1842. - Senegalia acatlensis  (Bentham) Britton & Rose, N. Amer. Fl. 23:112. 1928. - TYPE: Mexico,  Puebla, Acatlan, May 1830, G.Andrieux 396 (holotype: K!, F photo!, MICH  photo!, NY photo!, TEX photo!, isotypes: G!, US!).

 Senegalia submontana Britton & Rose, N. Amer. Fl. 23:113. 1928. - TYPE:  Mexico, Oaxaca, cerro San Antonio, alt. 1800 m, 12 Oct. 1907, C.Conzatti  2046 (holotype: US!, isotypes: F!, MEXU!, NY!). Britton and Rose (1928)  listed the  type as Conzatti 25,346. On the NY isotype, Britton wrote "the  number of this specimen was erroneously printed 25,346".

Formal description

Shrub or small tree to 15 m tall. Bark dark gray, shallowly furrowed.  Twigs light brown to greenish brown, not flexuous, glabrous to lightly puberulent.  Short shoots absent.  Leaves alternate, 50-150 mm long. Stipules herbaceous, light brown, narrowly linear, to 3 x 0.5 mm near the base, usually glabrous, persistent.  Petiole adaxially shallowly grooved, 15-40 mm long, glabrous or nearly so, but commonly with minute purple glands; petiole gland solitary, located between the lower pinna pairs or along the upper half of the petiole, sessile, nearly circular to slightly elongated, 0.7-2.3 mm long, saucer-shaped to cup-shaped, glabrous, rarely absent.  Rachis adaxially grooved, 20-110 mm long, glabrous to lightly puberulent and usually with minute purple glands, a sessile, cup-shaped gland, 0.4-0.9 mm across, between the upper pinna pair.  Pinnae 7 to 30 pairs per leaf, 25-60 mm long, 3-7 mm between pinna pairs.  Petiolules 1.0-2.4 mm long.  Leaflets 36 to 60 pairs per pinna, opposite, 0.5-1.2 mm between leaflets, linear, 2.5-4.8 x 0.7-1.1 mm, glabrous and commonly light greenish-purple above, lateral veins obvious, a midvein and 1 to 2 smaller veins from the base, base oblique, margins ciliate, apex narrowly acute to acuminate.  Inflorescence a loosely flowered cylindrical spike 40-100 mm long, 1 to 4 from the leaf axil. Peduncle 5-10 x 0.5-1.0 mm, glabrous to lightly puberulent and commonly with scattered minute purple glands.  Involucre absent.  Floral bracts linear, to 1 mm long, early deciduous.  Flowers sessile, creamy-white; calyx 5-lobed, 1.0-1.6 mm long, lightly appressed pubescent; corolla 5-lobed, 2.1-2.8 mm long, lightly appressed pubescent; stamen filaments 4.5-6.5 mm long, distinct; ovary glabrous, on a stipe to 0.4 mm long.  Legumes light to dark brown, straight, flattened, not constricted between the seeds, oblong, 80-170 x 13-25 mm, cartilaginous, transversely striate, glabrous, eglandular, dehiscent along both sutures; stipe to 20 mm long; apex broadly acute.  Seeds uniseriate, no pulp, dark reddish-brown, oval, strongly flattened, 7-10 x 4.5-7.2 mm, smooth; pleurogram U-shaped, 1.2-2.3 mm across.   Flowers: March-June.  Chromosome number: Not determined. 

Distribution

Dry, deciduous, tropical forests and thorn -scrub forests between 500 and 2100 m elevation in the states of Chiapas, Guerrero, Jalisco, México, Michoacan, Oaxaca and Puebla, Mexico.

Additional info

Mariosousa acatlensis is very similar morphologically to M. centralis.  Both are widely distributed in southern Mexico, although M. centralis has been collected more frequently in the very south of Mexico and, unlike M. acatlensis, it occurs across the border in Guatemala and countries to the south.  These two taxa are difficult to separate, and it is possible that they should be considered as subspecies of a single species.  The two can be separated based on the presence or absence of minute purple glands that are common at the base of the leaflets, in the grooves of the rachis and petiole, and not uncommonly along the axis of the inflorescence in M. acatlensis.  On young leaves these glands are extremely common, becoming less abundant on mature leaves, some becoming deciduous as the leaves mature. Rarely these glands are clear, lacking the purple color, but are easily observed under magnification.  None of these glands were found on specimens of M. centralis examined.  No other characteristic could be found that consistently separate these two species, though most specimens of M. centralis have leaflets with long hairs at the base on the ventral surface.  These hairs are particularly evident on young leaflets, sometimes falling-off as the leaflets mature.

Mariosousa acatlensis is also similar to M. usumacintensis, differing by having narrower leaflets (less than 1.1 mm across) and lacking the large flattened petiolar gland of that taxon. Mariosousa acatlensis is sympatric with M. sericea and M. mammifera in Oaxaca; these two taxa also have minute purple glands on the leaves.  Mariosousa acatlensis is easily separated from M. mammifera, which has fewer than 33 pairs of leaflets per pinna, leaflets that are commonly more than 1.5 mm wide, and a stalked petiolar gland.  The dense, erect pubescence of M. sericea petioles and fruits usually separates this species from M. acatlensis.  These species may occasionally hybridize where they are sympatric.  In the northern parts of its range in Guerrero, Jalisco and Michoacan, M. acatlensis is sympatric with, and possibly hybridizes with, M. salazari.  The minute glands, the large number of leaflets per pinna pair (more than 36), and the short petiolules (less than 2.5 mm long) separate it from that taxon.

Flowering time

March-June.

Representative specimens

MEXICO:

Chiapas:

Guerrero:

Jalisco:

México:

Michoacán:

Oaxaca:

Puebla:

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