CPC Plant Profile: Thornber's Fishhook Cactus
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Plant Profile

Thornber's Fishhook Cactus (Mammillaria thornberi)

M. thornberi is found underneath the overhanging side branches of Ambrosia dumosa, making this small clumping cactus very difficult to find. Photo Credit: Lynda Pritchett-Kozak
Description
  • Global Rank: G4 - Apparently Secure
  • Legal Status: N/A
  • Family: Cactaceae
  • State: AZ, MX, SI
  • Nature Serve ID: 128379
  • Date Inducted in National Collection: 03/14/1986

Mamillaria thornberi is a small, clumping columnar cactus with a soft body and numerous tubercules without dorsal grooves (as in Coryphantha). The stems are approximately 15 cm high, and ca 2 cm in diameter. Each tubercule has 10-20 straw-colored radial spines, and a single darker large hooked central spine-hence the name 'fishook cactus' (Benson 1982). Pinkish-white flowers bloom sporadically, usually following heavy rains. Flowers form in a ring around the upper portion of the stem, but not at the apex. The edible fruits are bright red, fleshy, ca. 2 cm long, and shaped like little chili-peppers. Species in the genus Mammillaria often go through "boom and bust" population cycles. This species is a good example of that, as it occurred in the millions in the Avra Valley west of Tucson in the 1930's, but most of the population disappeared in a catastrophic freeze in 1937. The population never recovered, and the species was considered for federal threatened status in the mid-1980's.

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Updates
  • 10/10/2020
  • Propagation Research

Initial tests on seed that had been processed and frozen yielded percentages of approximately 30%, but tests conducted on desiccated seed stored at room temperature for 2 years resulted in 75% germination. Germination tests are in progress on seeds stored using a variety of storage methods.

  • 10/10/2020
  • Orthodox Seed Banking

Additionally the Garden has at least 250,000 seeds produced in cultivation.

  • 10/10/2020
  • Living Collection

Desert Botanical Garden has 110 accessioned plants which were salvaged from an area slated as right-of-way for the Central Arizona Project Canal, and 42 clones of the accessioned plants.

Nature Serve Biotics
  • 05/02/2017

Small population size, about 600 plants in 2 population areas. Limited distribution increases the species vulner- ability to natural and man-made stresses.

Kathleen C. Rice
  • 01/01/2010

Threats to M. thornberi include urban development and maintenance of the Central Arizona Project Canal (Nabhan et al. 1986).

Kathleen C. Rice
  • 01/01/2010

There are eight major populations, with only 2 sites on protected lands. The majority of other populations are found on the Tohono O'odham, and the San Xavier reservations, and on private land (Rutman 1995).

Kathleen C. Rice
  • 01/01/2010

Desert Botanical Garden has 110 accessioned plants which were salvaged from an area slated as right-of-way for the Central Arizona Project Canal, and 42 clones of the accessioned plants. Additionally the Garden has at least 250,000 seeds produced in cultivation. Plants are prolific seed producers, fruiting as frequently as they flower. Initial tests on seed that had been processed and frozen yielded percentages of approximately 30%, but tests conducted on desiccated seed stored at room temperature for 2 years resulted in 75% germination. Germination tests are in progress on seeds stored using a variety of storage methods.

Kathleen C. Rice
  • 01/01/2010

Habitat protection would aid in conserving this species. Understanding the impact of Ambrosia dumosa on the population dynamics of Mammillaria thornberi would be useful as would knowing this species general reproductive biology and ecology.

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Photos
Nomenclature
Taxon Mammillaria thornberi
Authority Orcutt
Family Cactaceae
CPC Number 2795
ITIS 19789
USDA MATH
Common Names Thornber's fishhook cactus | Thornber's pincushion cactus | Biznaga de Thornber | Thornber's nipple cactus
Associated Scientific Names Mammillaria thornberi | Mammillaria thornberi subsp. thornberi
Distribution South-central Arizona
State Rank
State State Rank
Arizona S4
Mexico *FR83
Sonora S3
Habitat

The microhabitat preferred by M. thornberi is the area beneath the overhanging side branches of Ambrosia dumosa (Rutman 1995). In order to find plants, one must lift these branches up to inspect the area beneath each Ambrosia plant, an onerous task as Ambrosia dumosa is highly abundant in southern Arizona.

Ecological Relationships

Relationships between root systems of M. thornberi and the mycorrhizal community has been investigated. A relationship indeed exists, but it's exact nature requires further study.

Pollinators
Common Name Name in Text Association Type Source InteractionID
Reintroduction
Lead Institution State Reintroduction Type Year of First Outplanting

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