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Name

Vachellia campechiana f. houghii

Synonymy and types

Vachellia campeciana (Miller) Seigler & Ebinger f. houghii (Britton & Rose) Seigler & Ebinger. Phytologia 87:148. 2005. - Poponax houghii Britton & Rose, N. Amer. Fl. 23:90. 1928. - Acacia cochliacantha Humbl. & Bonpl. ex Willd. f. houghii (Britton & Rose) Seigler & Ebinger, Syst. Bot. 13:14. 1988. - TYPE: MEXICO. OAXACA: Tomellin Canon, 23 Jun. 1899, J.N.Rose & W.Hough 4669 (holotype: NY; isotype: US).

Formal description

Twigs, petioles, rachises and peduncles white lanata with erect to curved hairs. Leaflet margins ciliate. Calyx lobes, corolla lobes, floral bracts and the inflorescence receptacle pubescent.

Distribution

Relatively moist, disturbed sites from Sinaloa to Chiapas with occasional inland collections from Michoacán, Oaxaca and Veracruz.

Additional info

A common species of western and southern Mexico, Vachellia campechiana can be consistently separated from related species by the presence of flattened, spoon-shaped thorns that commonly exceed 30 mm in length and may be nearly as wide. On young twigs these thorns are not always developed, accounting for some misidentifications.  Even on young twigs, however, the stipular thorns, though small, are usually flattened.  In the field identification is much easier, as on older branches, and commonly on the main stems, enlarged spoon-shaped stipular thorns are common, though not always present on the young twigs.  Even without the enlarged thorns, however, other characteristics may be used for consistent separation from V. pennatula and V. macracantha, its two closest relatives.  The sessile petiolar glands, dense yellowish-green pubescences, and large number of leaflets per pinna in V. pennatula separate this taxon from V. campechiana.  The mostly smaller leaves, leaflets, shorter pinnae length and fewer leaflets per pinna can be used to consistently separate V. campechiana from V. macracantha.

It is very likely that Vachellia campechiana hybridizes with V. macracantha.  Rudd (1966) suggested that some specimens were difficult to place and considered it a strong possibility that hybridization was responsible.  More recently Brimer et al. (1987) found that in areas of sympatry a few individuals were encountered that could not be conveniently assigned to either taxon.  In a study of two populations, where both parents were common, individuals were encountered that fell outside the morphological range of these two taxa using Stepwise Discriminate Analysis (SDA). Most of the probable hybrid individuals clustered between the parental types on the SDA chart.  In these individuals the leaflet size, and the distance between leaflets was typical of V. macracantha, while the shorter petioles and the flattened stipular thorns were typical of V. campechiana (Brimer et al. 1987).

Two forms of Vachellia campechiana have been recognoized, f. campechiana and f. houghii. These forms are sympatric throughout most of their ranges, though they may be ecologically or phenologically distinct. The only distinction between the two forms is the presence of a dense pubescence on the young twigs, petioles, rachises, and on the calyx and corolla lobes of f. houghii. Most accessions of Vachellia campechiana f. campechiana are not cyanogenic (Brimer 1984), however, Seigler and Ebinger (1988) found that 20% of 240 specimens examined tested positive for cyanogenic compounds.  Of the 43 specimens of f. houghii tested for the presence of cyanide production, only five gave a moderate to strong positive test. The glycoside present is proacacipetalin, the same as that found in V. macracantha and a number of other acacias of this section (Seigler et al. 1978, Seigler and Conn 1982).

Key to the forms of Vachellia campechiana

a. Young twigs and petioles lightly pubescent to glabrous   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .Vachellia campechiana f. campechiana

a. Young twigs and petioles densely white lanate   .  .  .  .Vachellia campechiana f. houghii

Flowering time

April - July.

Representative specimens

MEXICO:

Chiapas:

Chihuahua:

Colima:

Guerrero:

Jalisco:

México:

Michoacán:

Oaxaca:

Puebla:

Sinaloa:

Tamaulipas:

Veracruz:

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