Acacia greggii

Acacia greggii is a species of Acacia native to the southwestern United States and northern Mexico, from the extreme south of Utah (where, at 37°10' N it is the northernmost naturally-occurring Acacia species anywhere in the world) south through southern Nevada, southeast California, Arizona, New Mexico and western Texas to Baja California, Sinaloa and Nuevo León in Mexico.

Common names include Catclaw Acacia, Gregg's Catclaw, Devil's Claw, Paradise Flower, Wait-a-minute tree, and Wait-a-bit tree; these names mostly come from the fact that the tree has numerous hooked thorns with the shape and size of a cat's claw, that tend to hook onto passers-by; the hooked person must stop ("wait a minute") to remove the thorns carefully to avoid injury or shredded clothing.

The patronym "greggii" refers to Josiah Gregg, author, explorer, and amateur naturalist of the American Southwest and northern Mexico.

Ecology
A. greggii is most common in washes where its roots have access to deep water. Its seeds require physical scarification in order to germinate. This effectively prevents germination unless a flash flood disturbs the area and deposits enough water to increase the likelihood that seedlings will be able to establish deep enough roots to survive the dry season. Catclaw is fully drought deciduous, and will usually lack leaves for most of the year. A. greggii has extrafloral nectaries, a trait shared with other acacias. A tentative connection has been made between these glands and insects that would suggest a mutualistic relationship (as found in other acacias). Ants are known to use the glands as a source of food and water, and may provide some defence for the plant against herbivorous insects. Like other desert wash trees in family Fabaceae, A. greggii is frequently afflicted with desert mistletoe, Phoradendron californicum. Unlike other legumes, A. greggii is not known to form root nodule associations with nitrogen-fixing bacteria.

Devil's claw may be an example of an evolutionary anachronism, in which the range and renewal of the species is limited due to the extinction of the mammallian megafauna responsible for seed dispersal. Within this model, the scarification required to germinate the seeds would have occurred during the chewing and digestion of the fruit by a large mammal, who later passes the seed intact some distance from the original tree.

Morphology
It is a large shrub or small tree growing to 10 m tall with a trunk up to 20-30 cm diameter. The grey-green leaves are deciduous, and bipinnate, divided into 1-3 pairs of pinnae, each pinna 2-3 cm long with 10-18 leaflets 3-6 mm long. Pinnae are most frequently in two pairs, with the proximal pair perpendicular to the petiolule and the distal pair forming a V at the tip. The flowers are produced in dense cylindrical spikes, each flower with five yellow petals 3 mm long and numerous yellow stamens 6 mm long. The fruit is a flat, twisted legume (pod) 6-15 cm long, containing several hard, dark brown seeds. The seed pod is constricted between seeds (a loment, and seed dispersal occurs both through dehiscence and breaks at these constrictions.

Ethnobotany
A. greggii, even though it is used as forage for livestock, contains a potentially poisonous cyanogenic glycoside called prunasin.

A. greggii beans were gathered and eaten by desert tribes of North America, including the Chemehuevi of the Southern Paiute, and stems were used in construction and tool making. Some sources also suggest that the plant was used as a laxative. Chemical compounds called amines are present in the tree.

Some chemical compounds found in Acacia greggii

 * Beta-methyl-phenethylamine
 * Catechin
 * Fisetin
 * Hordenine
 * Phenethylamine
 * Quercetin
 * Tyramine

Botanical varieties
Acacia greggii var. wrightii is found in Texas, USA while Acacia greggii var. greggii is found throughout the Southwestern United States.
 * Acacia greggii var. greggii
 * Acacia greggii var. wrightii

General references

 * Barlow, C. (2000).  The Ghosts of Evolution:  Nonsensical fruit, missing partners and other echological anachronisms.  Basic Books:NY.
 * Jepson Manual Treatment: Acacia greggii
 * U.S. Forest Service FEIS Database: Acacia greggii
 * Lawor, Elizabeth Jane (1995). Archaeological Site-formation Processes Affecting Plant Remains in the Mojave Desert..  University of California, Riverside.
 * Range Shrubs