PS 22-41 - Experimental introduction of Crotalaria avonensis (Fabaceae), a narrow endemic of the Florida scrub

Abstract: Avon Park Harebells (Crotalaria avonensis) is an endangered perennial legume that is narrowly endemic to Florida scrub habitats in only three sites in Highlands and Polk Counties. Translocation of seeds or propagated individuals from unprotected to protected lands is needed to conserve this species, yet several aspects of the plant’s biology and best propagation practices remain undetermined. We conducted an experimental introduction of C. avonensis that investigated aspects of its seed ecology (scarification, seed burial, litter) in two habitats (scrubby flatwoods, rosemary scrub) and propagation methods (stem cuttings, tissue culture). Two introductions of seeds (N = 400 for each) and one introduction of transplants (N = 84) were made to the state-owned Lake Wales Ridge Wildlife and Environmental Area (Silver Lake Tract) in 2012 and 2015. Demographic data including germination, survival, size, reproduction, and recruitment of seeds or clonal offshoots were collected at least 3 times each year. In the first seed introduction (began 2012), 48% of seeds had germinated by 2022, with most seeds germinating within the first three years, and cumulative survival of germinated seeds was 12%. Total germination was significantly higher in scrubby flatwoods than rosemary scrub but not affected by scarification. In the second seed introduction (began 2015), germination was increased by seed burial (37% buried vs. 10% surface-sown) and litter addition (29% with litter vs. 14% with no litter). For the transplant introduction (began 2012), 43 plants survived their first year and 27 plants (32%) survived through 2022. Transplant survival was not affected by propagation type. Clonal (19.5 offshoots/yr) and seedling (3.0/yr) recruitment were observed surrounding transplants while few recruits were observed surrounding the seed introductions, indicating that transplanting individuals is the more effective introduction method. Finally, we evaluated the success of the introduction using a demographic approach, and found that the vital rates of the introduced population were roughly equivalent to those of a nearby, protected wild population. In conclusion, the experimental introduction has resulted in a new, protected population of C. avonensis.