Wednesday, August 5, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
Background/Question/Methods Translocation is a necessary component in the recovery strategy for many imperiled species. However, long-term detailed demographic and genetic evaluation of translocation success is rare. Florida ziziphus (Ziziphus celata) is a genetically depauperate shrub known only from cattle pastures and fire-suppressed sandhills in two central Florida counties. Most populations consist of a single genotype and produce no fruits. Restoring viable populations of Florida ziziphus requires introducing genetically diverse and cross-compatible mating types to protected areas. An ex situ population comprising several cross-compatible genotypes provides seeds and seedlings for translocation projects. Since 2002, we have carried out six such projects encompassing 664 transplants and 5,298 seeds. The translocations include three genetic augmentations of previously uniclonal populations and three multi-genotype introductions to new sites with appropriate habitat within the species’ range. To evaluate the success of our translocations, we compared survival and relative growth rates of transplants to plants in wild populations, monitored seed germination and seedling survival and growth, and compared survival and growth among transplants of known maternal genotype. We also monitored resprouting rates of transplants top-killed by one experimental prescribed fire and one accidental fire.
Results/Conclusions We found that transplants outperformed seeds as effective propagules in all translocations. Although seed introduction had the advantages of being more cost effective and less labor intensive than transplants, low rates of germination (<5%) and cumulative seedling survival (<35%) were weaknesses. Annual transplant survival (mean 90.6%) was equal to or greater than annual survival of wild plants (mean 85.6%). Relative growth rates of transplants were negative initially, but eventually became positive and stabilized to rates comparable to plants from wild populations within 2-3 years of transplanting. Cumulative survival rates showed modest variation among transplants differing in maternal genotype, but were generally >60%. There was no loss of genetic diversity among transplants representing the original wild populations. Z. celata is a strong post-fire resprouter. Postburn resprouting by transplants was slightly higher than among wild plants (89.7 vs. 84.1%), despite the small aboveground size of transplants, suggesting they had accumulated significant belowground reserves. Translocations of Z. celata show reasonable initial success (both in demographic and genetic censuses), but their ultimate success depends on fruit production and seedling establishment. Integrated genetic and demographic monitoring, along with comparisons to benchmarks from wild populations, provides depth and context to evaluations of translocation success.
Results/Conclusions We found that transplants outperformed seeds as effective propagules in all translocations. Although seed introduction had the advantages of being more cost effective and less labor intensive than transplants, low rates of germination (<5%) and cumulative seedling survival (<35%) were weaknesses. Annual transplant survival (mean 90.6%) was equal to or greater than annual survival of wild plants (mean 85.6%). Relative growth rates of transplants were negative initially, but eventually became positive and stabilized to rates comparable to plants from wild populations within 2-3 years of transplanting. Cumulative survival rates showed modest variation among transplants differing in maternal genotype, but were generally >60%. There was no loss of genetic diversity among transplants representing the original wild populations. Z. celata is a strong post-fire resprouter. Postburn resprouting by transplants was slightly higher than among wild plants (89.7 vs. 84.1%), despite the small aboveground size of transplants, suggesting they had accumulated significant belowground reserves. Translocations of Z. celata show reasonable initial success (both in demographic and genetic censuses), but their ultimate success depends on fruit production and seedling establishment. Integrated genetic and demographic monitoring, along with comparisons to benchmarks from wild populations, provides depth and context to evaluations of translocation success.
