The Pima pineapple cactus (Coryphantha scheeri var.robustispina) is a small hemispheric cactus native to Sonoran desert-scrub and semi-desert grassland communities of southern Arizona and far northern Sonora, Mexico. In the U.S., it is found in only Pima and Santa Cruz Counties, between approximately 2,400 to 4,500 feet in elevation. Individuals commonly occur in very low densities, however several areas of higher densities have been identified. Individuals are low growing (< 12 inches), can have one to many stems, and produce brilliant yellow flowers in summer (left photo below). Individual flowers only bloom for a single day and are primarily pollinated by a native, solitary, ground-nesting bee, Diadasia rinconis (right photo below).
Pima pineapple cactus in Sonoran desert scrub habitat (Brian Powell photo)
Flowering Pima pineapple cactus with native pollinator Diadasia rinconis (Iris Rodden photos)
The PPC was listed as endangered under the Endangered Species Act in 1993 by the U.S. Fish and Wildlife Service due to its limited known range and the potential for it to be impactedfrom increasing development and urbanization. The main strategy of the 2018 Recovery Plan is the preservation and restoration of cactus habitat, thereby protecting individuals and their seedbanks in their native habitat. Loss of suitable habitat due to factors such as land conversion, loss of topsoil due to heavy disturbance, and increasing presence of non-native plant species can all lead to plant mortality. Additionally, changing climate patterns may have significant effects on PPC survival or recruitment. Pima County manages much of the known PPC habitat, either through direct ownership or by managing livestock grazing leases from the U.S. Bureau of Land Management and Arizona State Land Department thereby making the County a key player in the conservation of PPC.
Monitoring PPC populations on Pima County managed land is a key element of the County’s Multi-species Conservation Plan. The conventional monitoring method is a full census of any area, by walking back and forth every 5-10 feet apart. Individuals are very broadly distributed so tracking changes in populations across the landscape would require substantial time and resources. To that end, the County partnered with University of Arizona researchers to examine whether distance sampling, a technique commonly used to monitor low-density, cryptic bird species, could be applied to monitoring PPC populations (final report linked below). In short, distance sampling works very well to estimate PPC population sizes, while allowing surveyors to cover 8-10 times the area as the conventional census method. By repeating this monitoring every three years, we can track changes in population sizes and examine trends over time. The first round of PPC monitoring is scheduled to begin in 2021.