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Mariosousa dolichostachya
Mariosousa dolichostachya - flowers and leaves
Mariosousa dolichostachya
Mariosousa dolichostachya - leaf
Mariosousa dolichostachya
Mariosousa dolichostachya - flowers
Mariosousa dolichostachya

Name

Mariosousa dolichostachya (S. F. Blake) Seigler & Ebinger

Synonymy and types

Acacia dolichostachya S. F. Blake, Proc. Biol. Soc. Washington 34:43. 1921. - Senegalia dolichostachya (S. F. Blake) Britton & Rose, N. Amer. Fl. 23:112. 1928. - TYPE: Mexico, Yucatan, Las Bocas de Silam, May 1916, G.J.Gaumer & Sons 23329 (holotype: F!, isotype: F!, G!, NY photo!).

Formal description

Small tree to 15 m tall. Bark dark brown to dark gray, scaly in rectangular plates.  Twigs light brown to greenish brown, not flexuous, glabrous.  Short shoots absent.  Leaves alternate, 40-120 mm long. Stipules herbaceous, light brown, narrowly triangular, to 1.3 x 0.3 mm near the base, glabrous, persistent.  Petiole adaxially shallowly grooved, 30-80 mm long, glabrous; petiole gland solitary, located on the lower half of the petiole, sessile, circular to more commonly elliptic, 1.0-2.5 mm long, flattened or with slightly raised margins, glabrous.  Rachis adaxially grooved, 20-62 mm long, lightly puberulent, a sessile, saucer-shaped gland, 0.6-1.5 mm across, between the pinnae of the upper 1 to 2 pinna pairs.  Pinnae 2 to 6(8) pairs per leaf, 40-75 (90) mm long, 4-9 mm between pinna pairs.  Petiolules 2.5-4.0 mm long.  Leaflets 36 to 65 pairs per pinna, opposite, 0.7-1.1 mm between leaflets, oblong, 3.5-5.5 (7.5) x 0.8-1.3 mm, glabrous, lateral veins usually not obvious, only one vein from the base, base oblique, margins ciliate, apex acute to obtuse.  Inflorescence a loosely flowered cylindrical spike 20-90 mm long, 1 to 3 from the leaf axil, or rarely in terminal racemose clusters. Peduncle 3-10 x 0.5-0.9 mm, glabrous to lightly puberulent.  Involucre absent.  Floral bracts linear, to 1 mm long, glabrous to lightly pubescent, usually not deciduous.  Flowers sessile, creamy-white; calyx 5-lobed, 0.5-1.0 mm long, lightly appressed pubescent; corolla 5-lobed, 1.2-2.2 mm long, lightly appressed pubescent; stamen filaments 3-5 mm long, distinct; ovary glabrous, on a stipe to 0.3 mm long.  Legumes light yellowish-green to light brown, straight, flattened, not constricted between the seeds, oblong, 80-130 x 13-20 mm, cartilaginous, transversely striate, glabrous, eglandular, dehiscent along both sutures; stipe to 12 mm long, apex acute to acuminate.  Seeds not seen.   Flowers: April-July.   Chromosome number: Not determined.

Distribution

Common in thorn -scrub thickets, and disturbed dry forests in the lowlands of the states of Campeche, Quintana Roo and Yucatán, Mexico.

Additional info

Restricted to the Yucatan Peninsula, Mariosousa dolichostachya appears to be a relatively common component of thorn-scrub thickets and disturbed sites.  It is relatively uniform in most characteristics, some variation occurring in the number of pinna pairs, the shape of the petiolar gland and leaflet size. Generally, the number of pinna pairs on a leaf is six or fewer, but occasional leaves have up to eight pinna pairs.  Much of the variation in petiolar gland shape is probably due to the age of the leaves when dried.  Generally the gland, which usually occurs on the lower half of the petiole, is flat, but on young leaves the margins of the glands become raised when the specimen is dried.  Leaflets are generally 3.0-5.5 mm long; on some material, however, leaflets exceed 7 mm in length.

The fact that most leaves have fewer than seven pinna pairs separates Mariosousa dolichostachya from most other species of this genus.  Other species with six or fewer pinna pairs differ by having pinnae with fewer than 35 pairs of leaflets, along with smaller leaflets (M. compacta), much longer petioles (M. willardiana), or pubescent leaves (M. mammifera and M. sericea).

Considering the restricted distribution of this species, the only other taxon that Mariosousa dolichostachya might be confused with is M. usumacintensis.  Both taxa have more than 35 pairs of leaflets on each pinna, flattened petiolar glands on the lower half of the petiole, and petiolules that are more than 2.5 mm long.  They are easily separated as M. dolichostachya has fewer pinna pairs per leaf (mostly six or fewer), smaller stipules (less than 1.3 mm long), less distance between the leaflets on the pinna rachis (less than 1.2 mm), and smaller sepals (mostly less than 1.0 mm long).

Flowering time

April-July.

Representative specimens

MEXICO:

Campeche:

Chiapas:

Quintana Roo:

Yucatán:

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