Overview
The acuña cactus (Echinomastus erectocentrus var. acunensis) was listed as Endangered on October 1, 2013 under the Endangered Species Act of 1973, as amended. On August 18, 2016, 7,501 hectares of critical habitat was designated for the acuña cactus. The taxon is known from Maricopa, Pima and Pinal counties in southern Arizona and from northern Sonora, Mexico. We are aware of seven extant and one extirpated population in the United States, and one population from Sonora, Mexico. Collectively, these eight extant populations contain approximately 3,893 living plants. Population trends are considered declining, as monitoring within long-term plots at Organ Pipe Cactus National Monument, as well as repeat measures taken on Bureau of Land Management and U.S. Air Force lands, report mortality rates that are higher than recruitment rates. Threats from urbanization, non-native plant invasion and alteration of fire regimes, as well as drought and climate change climate change
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Scientific Name
Identification Numbers
Characteristics
Habitat
The acuña cactus occurs in the Palo-Verde-Saguaro Association of the Arizona upland subdivision of the Sonoran Desert Scrub at 365 to 1,150 meters in elevation. The taxon is generally found on soil that overly various bedrock types in valleys, as well as on small knolls and gravel ridges of up to 30% slope. The acuña cactus is often noted growing under the protective canopy of associated native plant species, which may act as nurse plants, thereby sheltering seedlings from extreme temperatures and providing some protection from mechanical disturbance.
Area of land that receives no more than 25 centimeters (10 inches) of precipitation a year.
Physical Characteristics
The acuña cactus is a small, perennial plant in the cactus family (Cactaceae). The species is a succulent with typically singular stems that reach up to 40 centimeters in height and 9 centimeters in diameter. The acuña cactus has 11 to 15 radial spines up to 2.5 centimeters long and three to four mauve-colored, up-turned central spines that are up to 3.5 centimeters long. The pink to lavender colored flowers open in March and April, with green fruits containing nearly black seeds developing thereafter.
Life Cycle
Winter precipitation is needed for acuña cactus flowering and seed set, while summer precipitation is needed for germination, seedling survival and growth. Although acuña cactus adult and immature plant numbers fluctuate annually, pending drought and other threats, seedling numbers can fluctuate even further due to the vulnerability of this life stage to desiccation.
Although we do not know the life span of acuña cacti, there are individual plants that have been tracked at Organ Pipe Cactus National Monument which range in age from 38 to 42 years old.
Acuña cactus flowering occurs in March and April, with fruit production thereafter. Transporting of acuña cactus seeds by ants has been documented in August and September. Acuña cactus fruit and seed are likely dispersed through gravity, ants, small mammals and birds. Adequate winter precipitation is required for seed germination, seedling growth, flowering and fruiting. Seedling cacti, in general, have very small roots, and therefore, a limited ability to access deeper water sources. The seedling stage of small cacti is the most vulnerable life stage due to the likelihood of desiccation. Cacti, in general, are very slow growing.
Similar Species
Echinomastus erectocentrus var. acunensis, E. e. var. erectocentrus and E. e. var. johnsonii are closely related and morphologically resemble one another. Morphological analyses, as well as genetic testing, have differentiated these varieties from one another. They are also separated geographically.
Geography
Acuña cactus populations are known from Maricopa, Pima and Pinal counties in southern Arizona and from northern Sonora, Mexico.
Timeline
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