Astrophytum

Astrophytum asterias or star cactus

South Texas

Introducing Astrophytum asterias

Astrophytum asterias botanical illustration

Astrophytum asterias is a species of cactus in the genus Astrophytum, and is native to very small parts of Texas in the United States and Mexico. Common names include sand dollar cactus, sea urchin cactus, star cactus and star peyote.

Previously more abundant, this species is today restricted to a a very small area in South Texas, where there are around 2,000 individuals, and a few small sites in Tamaulipas.

As with certain other slowly maturing cacti, A. asterias is listed as endangered by the United States Fish and Wildlife Service, vulnerable on the International Union for Conservation of Nature’s Red List, and critically imperilled by The Nature Conservancy, listed on Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), meaning that international trade in wild-collected specimens is prohibited. 

Read more about star cactus in Texas:

A curious resemblance in the form of a fossilized sand dollar; also from Texas (Freer).

Star cactus in South Texas

Star cactus in habitat in South Texas

Green succulent leaved plants, visible on some of the pictures above, are Varilla texana. This is a common nurse plant for star cactus.

According to Janssen et al. 2010 V. texana was observed to be a nurse plant for around a quarter of the A. asterias specimens examined within fifteen vegetation transects on nine properties.

Other commonly associated plants that are visible in some of the images above include Hamatocactus setispinus & Opuntia leptocaulis.

 

Star cactus in Mexico

Star cactus in habitat in Tamaulipas, Mexico.

Known challenges

Despite existing protection, illegal collection continues to threaten the future of this species and its decline in the wild has been largely attributed to over-collection and poaching. It is sometimes accidentally harvested due to its similarity to the somewhat similar looking and coexisting peyote (Lophophora williamsii). Other contributing factors are thought to be urban development and herbicides.

We have documented additional challenges:

  • Digging by feral pigs
  • Drought-induced predation by rodents

Digging by feral pigs has made the future of this individual uncertain.

Drought-induced predation by rodents has almost certainly resulted in the death of these individuals (if not already accomplished).

CCI Astrophytum asterias research

Below you can find our articles and book chapters, arranged here in reverse chronological order.

Peer-reviewed articles

Terry et al. (2012). Genetic Structure of a Population of the Endangered Star Cactus (Astrophytum asterias) in Southern Texas.
JOURNAL ARTICLE

Genetic Structure of a Population of the Endangered Star Cactus (Astrophytum asterias) in Southern Texas

Martin K Terry, Alan E Pepper, Anna W Strong, Daniel M Tarin, Dana M Price, and James R Manhart 

The Southwestern Naturalist, 57(2), 182-188, (1 June 2012).

PDF DOI

Abstract

We used data on alleles of seven polymorphic microsatellite loci in 142 individuals of the star cactus Astrophytum asterias from five subpopulations to estimate genetic parameters. Four of the subpopulations had high levels of heterozygosity and allelic diversity compatible with efficient outcrossing, and low FST-values that suggested high rates of gametic gene flow effected by winged-insect pollinators. The fifth subpopulation that was small and occupied the smallest area had low levels of heterozygosity and allelic diversity, which can be caused by small populations, inbreeding, geographic isolation, and founder effect. Our research indicated that all subpopulations, except one, were genetically suitable sources of propagules for reintroduction or for augmentation of other populations.

Terry, Price and Poole (2007). A tale of two cacti-the complex relationship between peyote (Lophophora williamsii) and endangered star cactus (Astrophytum asterias).
JOURNAL ARTICLE

A tale of two cacti-the complex relationship between peyote (Lophophora williamsii) and endangered star cactus (Astrophytum asterias)

Terry M, Price D, Poole J.

In: Barlow-Irick, P.; Anderson, J.; McDonald, C., tech eds. Southwestern rare and endangered plants: Proceedings of the Fourth Conference; March 22-26, 2004; Las Cruces, New Mexico. Proceedings. RMRS-P-48CD. Fort Collins, CO: US Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 115-121 2007 (Vol. 48).

PDF DOI

Abstract

Astrophytum asterias, commonly called star cactus, is a federally listed endangered cactus endemic to the Tamaulipan thornscrub ecoregion of extreme southern Texas, USA, and Tamaulipas and Nuevo Leon, Mexico. Only three metapopulations totaling less than 4000 plants are presently known in Texas. Star cactus, known locally as “star peyote”, is highly sought by collectors. This small, dome-shaped, spineless, eightribbed cactus is sometimes mistaken for peyote (Lophophora williamsii), which grows in the same or adjacent habitats. Peyote is harvested from native thornscrub habitats in Texas by local Hispanic people and sold to peyoteros, licensed distributors who sell the peyote to Native American Church members. Annual peyote harvests in Texas approach 2,000,000 “buttons” (crowns). Although the peyoteros do not buy star cactus from harvesters, they cultivate star cactus in peyote gardens at their places of business and give star cacti to their customers as lagniappe. If even 0.1% of harvested “peyote” is actually star cactus, the annual take of this endangered cactus approaches the total number of wild specimens known in the U.S. This real but unquantifiable take, together with information from interviews with local residents, suggests the existence of many more star cactus populations than have been documented.

Terry et al. (2006) Development and characterisation of microsatellite loci in endangered Astrophytum asterias (Cactaceae).
JOURNAL ARTICLE

Development and characterization of microsatellite loci in endangered Astrophytum asterias (Cactaceae)

Martin K Terry, Alan E Pepper and James R Manhart 

Molecular ecology notes, (2006), 6(3), 865-866.

PDF DOI

Abstract

We report the development of polymorphic microsatellite markers for the endangered North American cactus Astrophytum asterias (Cactaceae). Six loci, averaging 8.5 alleles per locus, were found to amplify genomic DNA consistently in 94 individuals from four geographically defined demes in South Texas. These markers will permit the generation of appropriate data for estimating population genetic parameters, population structure and the degree of inbreeding in the small, fragmented populations of A. asterias that currently exist. These are the first microsatellites reported for the genus Astrophytum and for the tribe Cacteae.

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