The nominate subspecies of the Turk’s Head Cactus Echinocactus horizonthalonius is widespread in limestone areas in the Chihuahuan Desert from southern New Mexico and western Texas south on the Mexican Plateau to San Luis Potosí. In his 1969 book The Cacti of Arizona, Lyman Benson described the western populations as Echinocactus horizonthalonius var. nicholii. In 1976, the variety was listed as an Endangered Species (USDI, Fish and Wildlife Service. 1976). Populations are known in Arizona from the limestone Koht Kohl Hills and Waterman and Vekol Mountains in the Arizona Upland subdivision of the Sonoran Desert. Another population is in Sonora in the Sierra del Viejo about 45 km SSE of Caborca, and 150 km S of the Arizona border in the Lower Colorado River Valley subdivision (Yatskievych and Fischer 1983, Paredes-A et al. 2000). It is not protected in Mexico primarily because the NOM-059-SEMARNAT-2010 legislation does not consider varieties or subspecies. The Mazatán area is distant from the known populations of Echinocactus horizonthalonius var. nicholii. The program will focus on the journey to investigate, follow information, and try to find the species in a new location.

Thomas R. Van Devender Is the Manager of the Madrean Archipelago Biodiversity Assessment program at Sky Island Allianace. He was the Senior Research Scientist at the Arizona-Sonora Desert Museum from 1983 to 2009 where he conducted research on a broad range of natural history activities. He has published well over a hundred research publications including journal articles, book chapters, and books on the cacti of Sonora, desert grassland, packrat middens and the paleoecology of the southwestern deserts, and the Sonoran desert tortoise. He is coeditor with Francisco Molina on a book entitled Diversidad Biológica del Estado de Sonora published by the Universidad Nacional Autónoma de México in Hermosillo, Sonora in 2010. He has a long-term interest in the flora of the Sonoran Desert Region, and has collected over 25,000 herbarium specimens, which are deposited into the herbaria at the University of Arizona (Tucson), Universidad de Sonora (Hermosillo), and many others. In recent years, he has provided photovouchers of cacti to ten herbaria in the United States, Mexico, and Europe. He has surveyed plants in many vegetation types in Sonora. He and his wife Ana Lilia Reina-Guererro have a special interest in the plants of La Frontera, the 100 kilometer zone in northern Sonora just south of the Arizona border, and in the Yécora area in the Sierra Madre Occidental in eastern Sonora. They have studied the ecology of the Chihuahuan Desert night-blooming cereus Peniocereus greggii var. greggii, the Cochise foxtail cactus Coryphantha robbinsorum, the false rainbow cactus Echinocereus pseudopectinatus, the El Trigo hedgehog Echinocereus lauii, and the choyita Mammillaria saboae var. haudeana.

Please make sure you have marked your calendar for this special program. Also, bring a friend or relative who would like to learn more about cacti.