Ecology and Conservation of the Federally-Listed Coastal Cactus Harrisia aboriginum in SW Florida

Shawn C. McCourt, Sally M. Chambers, and Bruce K. Holst, Marie Selby Botanical Gardens

The genus Harrisia (Cactaceae) comprises 20 narrowly endemic species of night-blooming cacti with two widely separated geographic ranges, including South America south of Amazonia, as well as the West Indies and southern Florida. Commonly known as aboriginal prickly-apple, H. aboriginum is a sprawling, multi–stemmed, columnar cactus endemic to ancient native American shell mounds, as well as coastal berms, coastal grasslands, and maritime hammocks in four counties along the southwest coast of Florida. This federally-listed species is in steep decline, primarily due to the development of beachfront property, invasive species dominance, and the erosion of coastal barrier islands. Some populations have disappeared entirely. Researchers at MSBG have been conducting an inventory of extant populations, assessing the health of each population, and determining what genetic variation (if any) occurs across the species’ geographic range. When possible, a small portion of seed has been collected for seed banking and to grow plants for the augmentation of shrinking populations and introduction to ecologically suitable sites situated above projected rises in sea level. To date, we have visited nine sites and collected detailed demographic data for 89 plants. Spines were collected from all 89 plants for DNA extraction and the testing and developing of microsatellite loci. Seeds from seven fruits were collected from three sites. Data presented represent the preliminary findings of our work, which has a focus on the importance of maintaining genetic diversity in ex situ collections for the purpose of rare plant conservation.

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