Plant Diversity ›› 2016, Vol. 38 ›› Issue (05): 238-246.DOI: 10.1016/j.pld.2016.09.004

• Articles • Previous Articles    

Adaptive introductions: How multiple experiments and comparisons to wild populations provide insights into requirements for long-term introduction success of an endangered shrub

Eric S. Menges, Stacy A. Smith, Carl W. Weekley   

  1. Archbold Biological Station, 123 Main Drive, Venus, FL 33960, USA
  • Received:2016-05-06 Revised:2016-09-01 Published:2021-11-05
  • Contact: Eric S. Menges
  • Supported by:
    Susan Wallace and Tamera Race did early research and conservation on Florida ziziphus that helped pave the way for our work. Cheryl Peterson and her crew at Bok Tower Gardens raised nearly all the plants for introductions and augmentations and were also very helpful in collecting seeds and outplanting. We also appreciate the efforts of land managers who have cooperated with us at introduction sites, including Steve Morrison (The Nature Conservancy), Dorn Whitmore (US Fish and Wildlife Service), Dave Butcher (Florida Forestry Service) and their agency colleagues. Special thanks to Nancy Bissett for her insights. The project would not have proceeded without continuing funding and support from the Rare Plant Conservation program of the Florida Forestry Service, managed by Dennis Hardin and Mike Jenkins, from the National Science Foundation (DEB98-15370, DEB02-33899, DEB08-12717, DEB-1347843), from the US Fish and Wildlife Service, and from Archbold Biological Station. In particular, we appreciate the strong support of David Bender (US Fish and Wildlife Service). The Florida ziziphus Ad-Hoc Recovery Team has provided important leadership for introductions and other aspects of Florida ziziphus conservation. We also thank the private landowners and their managers for allowing us access to their properties. Finally, numerous volunteers, interns, and others helped with the hard work: caging, irrigating, outplanting and measuring this thorny shrub in conditions that were generally hot and humid.

Abstract: Recovery of an imperiled plant species may require augmentation of existing populations or creation of new ones. Hundreds of such projects have been conducted over the last few decades, but there is a bias in the literature favoring successes over failures. In this paper, we evaluate a series of introductions that experimentally manipulated microhabitat and fire in an adaptive introduction framework. Between 2002 and 2012, we (and our collaborators) carried out ten introductions and augmentations of Florida ziziphus Pseudoziziphus (Condalia, Ziziphus) celata, a clonal shrub limited to very small populations and narrowly endemic to pyrogenic central Florida sandhills. Six of the introductions were designed as experiments to test hypotheses about how demographic performance was affected by microhabitat, fire, and propagule type. Introduced transplants had high survival (<90% annually), inconsistent growth, and little transition to reproduction, while introduced seeds had low germination and survival. Transplants were more efficient than seeds as translocation propagules. Shaded (vs. open) sites supported generally higher transplant and seedling survival and seed germination percentages, but growth responses varied among experiments. Supplemental irrigation increased transplant survival and seed germination, but otherwise seedling and plant survival and growth were not significantly affected. Contrary to expectations based on wild populations, introduced propagules have not been more successful in unshaded sites, suggesting that Florida ziziphus has broader microhabitat preferences than hypothesized. Compared to wild plants, introduced plants had similar survival and responses to fire, slower growth, and more delayed flowering. Introduced plants had no clonal spread. While no introduced population has demonstrated a capacity for long-term viability, one augmented population has flowered and produced viable fruits. Given that Florida ziziphus genets are long-lived, low levels of sexual reproduction may be adequate for the establishment of viable populations. Thus, after many translocations over more than a decade, it is premature to characterize any single translocation as a success or a failure, underscoring the need for a long view of translocation success.

Key words: Florida ziziphus, Translocation, Augmentation, Rare plant, Florida sandhill, Microhabitat