Pediocactus knowltonii - L. Benson
Knowlton's Cactus
Other English Common Names: Knowlton's Miniature Cactus
Other Common Names: Knowlton's miniature cactus
Taxonomic Status: Accepted
Related ITIS Name(s): Pediocactus knowltonii L. Benson (TSN 19771)
Unique Identifier: ELEMENT_GLOBAL.2.158158
Element Code: PDCAC0E020
Informal Taxonomy: Plants, Vascular - Flowering Plants - Cactus Family
 
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Dicotyledoneae Caryophyllales Cactaceae Pediocactus
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Concept Reference
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Concept Reference: Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Pediocactus knowltonii
Conservation Status
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NatureServe Status

Global Status: G1
Global Status Last Reviewed: 16Sep2013
Global Status Last Changed: 07Feb1984
Ranking Methodology Used: Ranked by calculator
Rounded Global Status: G1 - Critically Imperiled
Reasons: Known from only one viable population in New Mexico's San Juan County. Extensive searches of nearby potential habitat in New Mexico and adjacent Colorado have failed to locate additional natural populations. This species was nearly driven to extinction by cactus collectors within two decades of its discovery; starting from an estimated population size of more than 100,000 plants in 1958, the population was reduced to less than 100 plants by 1978. Although the population was 14,000 in 1994, from 1994 to 2008, a gradual, continuous decline has been documented, likely in response to drought. An increase in rabbit or rodent predation in conjunction with depressed seed production and germination has also been observed. Collection of this species has been greatly reduced but still, some illegal theft is likely occurring.
Nation: United States
National Status: N1

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States New Mexico (S1)

Other Statuses

U.S. Endangered Species Act (USESA): LE: Listed endangered (29Oct1979)
U.S. Fish & Wildlife Service Lead Region: R2 - Southwest

NatureServe Global Conservation Status Factors

Range Extent Comments: Known only from one site in northwestern New Mexico in northern San Juan County. Extensive searches in nearby potential habitat in La Plata County, Colorado have failed to locate additional natural populations (Sivinski 2005). The northern-most plants in the Knowlton's cactus population are at least 30 m (94 ft) south of the New Mexico/Colorado border (Robert Sivinski, unpublished observation, 2007 cited by USFWS 2010).

Area of Occupancy: 1-5 4-km2 grid cells
Area of Occupancy Comments: Covers 12 acres with the highest density on less than 2 1/2 acres.

Number of Occurrences: 1 - 5
Number of Occurrences Comments: One extant occurrence. There have been plants transplanted to three other locations but none are considered viable populations (USFWS 2010).

Population Size Comments: There were 9,000 individuals documented in the wild in 1986. In 1992, there were about 12,000 individuals (Sivinski and McDonald 2007 cited by USFWS 2010). The peak was about 14,000 individuals in 1994. By 2008, the population had declined to about 6,100 (Sivinski 2008 cited by USFWS 2010).

Number of Occurrences with Good Viability/Integrity: Very few (1-3)
Viability/Integrity Comments: One occurrence with excellent viability.

Overall Threat Impact: High
Overall Threat Impact Comments: The single, viable population is vulnerable to extinction from from human activities (including collecting; oil and gas exploration and development; livestock grazing; off-road vehicles; destruction of habitat) and natural causes (including predation by rabbits or rodents, genetic bottlenecks) (Cully 1996; USFWS 2010). Northwestern New Mexico is a major oil and gas production area, with attendant roads, well pads, and pipelines that directly threaten the existence of the cactus and its habitat (Cully 1996). Energy firms hold mineral rights beneath the TNC lands so this potential threat exists (USFWS 2010). Commercial availability and endangered species statues have greatly reduced collection but illegal collecting is still a threat (USFWS 2010). Recent declines appear to be associated with long-term drought; the frequency and duration of droughts is predicted to increase due to climate change (USFWS 2010).

Short-term Trend: Decline of 10-30%
Short-term Trend Comments: The population increased through the late 1980s and early 1990s; since then, the population has been gradually and steadily declining, likely in response to drought (USFWS 2010). There were 9,000 individuals documented in the wild in 1986. In 1992, there were about 12,000 individuals (Sivinski and McDonald 2007 cited by USFWS 2010). The peak was about 14,000 individuals in 1994. In 2008, the population estimate was about 6,100 (Sivinski 2008 cited by USFWS 2010).

Long-term Trend: Decline of >90%
Long-term Trend Comments: This species was nearly driven to extinction by cactus collectors within 2 decades of its discovery: starting from an estimated population size of more than 100,000 plants in 1958, the population was reduced to less than 100 plants by 1978. The population had increased by the late 1980's and early 1990's but began to decrease again and was down to 6,100 in 2008 (USFWS 2010).

Intrinsic Vulnerability Comments: Pediocactus knowltonii is unlike most cacti in that it initiates flower-creation in the early autumn months. In other words, the condition of the flowers the following spring are influenced by the condition of the plant in the previous growing season and winter months. Further, it is known that this species is not a prolific bloomer even when precipitation is good (Sinvinski and McDonal 2004). In some years, most of the seeds are harvested by rodents before they can drop from mature fruits; seeds that escape predation, germinate, and survive the dry early summer months take three to four years to become flowering adults (USFWS 2010).

Other NatureServe Conservation Status Information

Distribution
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Global Range: Known only from one site in northwestern New Mexico in northern San Juan County. Extensive searches in nearby potential habitat in La Plata County, Colorado have failed to locate additional natural populations (Sivinski 2005). The northern-most plants in the Knowlton's cactus population are at least 30 m (94 ft) south of the New Mexico/Colorado border (Robert Sivinski, unpublished observation, 2007 cited by USFWS 2010).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map

U.S. & Canada State/Province Distribution
United States NM

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
NM San Juan (35045)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
14 Upper San Juan (14080101)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: A small succulent with solitary or clustered stems, up to 5.5 cm tall, but usually only barely protruding from the soil. The stem is dotted with small projections, each encircled at the top by a ring of white spines. From mid-April through early May, pink, yellow-centered flowers bloom on top of the stems.
Reproduction Comments: Flowering occurs in early May and fruits ripen in June and July (Sivinski and McDonald 2004).
P. knowltonii has dry fruits and probably is dispersed by wind and water given the scattered high-density colonies, and not often dispersed long distances by animals (Gucker 2007).

Ecology Comments: Favors rocky soils and important tissue is contained underground therefore it is unlikely that moderate increases in fire frequency will have a significant effect on this species (Gucker 2007).
Terrestrial Habitat(s): Forest/Woodland, Woodland - Conifer
Habitat Comments: It occurs on tertiary alluvial deposits that have formed gravelly, dark, sandy loams on slopes or hills. It is found under the shade of trees and shrubs and in open areas in dry pinyon-juniper woodlands at 1800-2000 m elevation.
Economic Attributes Not yet assessed
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Management Summary Not yet assessed
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Population/Occurrence Delineation
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Minimum Criteria for an Occurrence: Only one viable population is known for this species. The EO rank specifications apply to naturally occurring populations. In the future, reintroductions will take place as part of the recovery plan for this species (USFWS 1985). At that time the EO specifications should be reevaluated to include these populations.
Date: 27Sep2000
Author: Spackman, S. and D. Anderson
Population/Occurrence Viability
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Excellent Viability: Size: 1000 or more individuals. Condition: occurrences with an excellent likelihood of long-term viability as evidenced by the presence of multiple age classes and evidence of flowering and fruiting are represented, indicating that the reproductive mechanisms are intact. This occurrence should be in a high-quality site with less than 1% cover exotic plant species and/or no significant anthropogenic disturbances. Landscape Context: the occurrence is surrounded by an area that is unfragmented and includes the ecological processes needed to sustain this species.
Good Viability: Size: 100 to 1000 individuals in a small (less than 1 hectare) area. Condition: the occurrence should have a good likelihood of long-term viability, with evidence of successful seed set and multiple age classes observed. Anthropogenic disturbance within the occurrence is minimal. If exotic species are present, they comprise less than 10% of the total ground cover. Landscape Context: the surrounding landscape should contain the ecological processes needed to sustain the occurrence but may be fragmented and/or affected by human impacts.
Fair Viability: Size: 5 to 100 individuals. Condition: The occurrence may be less productive than the above situations, but is still viable, with multiple age classes and evidence of flowering and fruiting, indicating that the reproductive mechanisms are intact. The occupied habitat is somewhat degraded (exotic plant species make up between 10-50% of the total ground cover and/or there is a moderate level of anthropogenic disturbance). Landscape Context: there may be significant human disturbance, but the ecological processes needed to sustain the species are still intact.
Poor Viability: Size: 5 or fewer individuals. Condition: little or no evidence of successful reproduction is observed (poor seedling recruitment, no flowering or fruiting observed, or poor age class distribution). Exotic plant species make up greater than 50% of the total ground cover, and/or there is a significant level of human disturbance. Landscape context: the surrounding area is fragmented with many ecological processes no longer intact. The occurrence has a low probability of long-term persistence due to inbreeding depression, natural stochastic events, and its intrinsic vulnerability to human impacts.
Justification: A Rank: the type locality is the only known viable population of this species. Large populations in high quality sites are presumed to contain a high degree of genetic variability, have a low susceptibility to the effects of inbreeding depression, and to be relatively resilient. If other natural populations are found, the eospecs should be reassessed.

C Rank: EOs not meeting "C"-rank criteria are likely to have a very high probability of inbreeding depression and extirpation due to natural stochastic processes and/or occur in degraded habitat with low long-term potential for survival.

Key for Ranking Species Element Occurrences Using the Generic Approach (2008).
Date: 27Sep2000
Author: Spackman, S. and D. Anderson
Notes: COHP
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 20Sep2013
NatureServe Conservation Status Factors Author: Roth, E., rev. Maybury/DeBruin (1996), rev. Doyle, G. (2006), rev. A. Tomaino (2013)

Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

References
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  • Butterworth, C., and J.M. Porter. 2013. Pediocactus knowltonii. IUCN Red List of Threatened Species. Version 2013.1. Online. Available: http://www.iucnredlist.org (accessed 11 July 2013).

  • Colorado Native Plant Society. 1989. Rare plants of Colorado. Rocky Mountain Nature Association, Colorado Native Plant Society, Estes Park, Colorado. 73 pp.

  • Colorado Natural Heritage Program. 2004. The First Annual Colorado Rare Plant Symposium: Threatened, Endangered and Candidate Plants of Colorado. Symposium Minutes.

  • Cully, A. 1996. Knowlton's Cactus (Pediocactus knowltonii) Reintroduction. A chapter in Restoring Diversity, strategies for reintroduction of endangered plants. Editors Falk, D.A., C.I. Miller, and M. Olwell. Island Press.

  • Flora of North America Editorial Committee. 2003b. Flora of North America North of Mexico. Vol. 4, Magnoliophyta: Caryophyllidae, part 1. Oxford University Press, New York. 559 pp.

  • Gucker, C. L. 2007. Pediocactus knowltonii. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [2011, March 30].

  • Heil, K., B. Armstrong and D. Schleser. 1981. A review of the genus Pediocactus. Cactus and Succulent Journal 53:17-39.

  • Heil, K.D. 1985. Recovery plan for the Knowlton cactus Pediocactus knowltonii L. Benson. Prepared for the U.S. Fish and Wildlife Service, Region 2. Albuquerque, NM. 59 pp.

  • Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.

  • McDonald, C., and D.J. Ferguson. 2008. New Mexico rare plants: Pediocactus knowltonii (Knowlton cactus). New Mexico Rare Plant Technical Council, Albuquerque, New Mexico. Online. Available: http://nmrareplants.unm.edu (Accessed 2013).

  • New Mexico Native Plant Protection Advisory Committee. 1984. A handbook of rare and endemic plants of New Mexico. Univ. New Mexico Press, Albuquerque. 291 pp.

  • Olwell, P. 1986. Audubon wildlife report. National Audubon Society, New York, NY.

  • Peterson, S.J. 1982. Threatened and endangered plants of Colorado. U.S. Fish and Wildlife Service, Denver, CO. 35 pp.

  • Sivinski, R. C. and C. McDonald. 2004a. Knowlton's cactus (Pediocactus knowltonii): Eighteen years of monitoring and recovery actions. Pages 98-107 in P. Barlow-Irck, J. Anderson, C. McDonald, eds. Southwestern rare and endangered plants: Proceedings of the Fourth Conference; March 22-24, 2004, Las Cruces, NM. Proceedings. RMRS-P-48CD. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. Accessed online on May 11, 2011 at: http://www.treesearch.fs.fed.us/pubs/29594

  • Sivinski, R. C. and C. McDonald. 2004b. Knowlton's cactus (Pediocactus knowltonii): Eighteen years of monitoring and recovery action. Accessed online at http://www.fs.fed.us/rm/pubs/rmrs_p048/rmrs_p048_098_107.pdf [March 30, 2011].

  • Stafford, R. 1989. Botanists find cactus better neighborhood. Plant Conservation 4(1): 3.

  • U.S. Fish and Wildlife Service (USFWS). 2010. Knowlton's Cactus (Pediocactus knowltonii) 5-year review: summary and evaluation. U.S. Fish and Wildlife Service, New Mexico Ecological Field Services Office, Albuquerque, NM.

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