Crotalaria avonensis

Stephanie Koontz, Archibold Biological Station, Cheryl L. Peterson, Bok Tower Gardens, Valerie C. Pence, Cincinnati Zoo and Botanical Garden, Eric S. Menges, Archbold Biological Station

Translocations are an increasingly utilized tool for rare plant conservation. Urbanization along the Lake Wales Ridge, in southcentral Florida, has led to 85% loss of native Florida scrub and sandhill. The few remaining intact patches hold a plethora of endemics. Our program has translocated several species from unprotected to protected parcels. All translocations are monitored post-outplanting and demographic data used to evaluate success. Here we present case studies for three federally listed species and discuss the challenges in restoring rare plants. Ziziphus celata has few remnant, mostly unprotected populations. Further contributing to its rarity is slow growth and limited sexual reproduction. We implemented 10 translocations between 1998 and 2012. Analyses of vital rates through 2016 determined annual survival of both wild and translocated plants is high (>90%), but growth of transplants is 1/10th the rate of wild plants. Many wild plants flower annually, yet <3% of transplants have reached reproductive maturity. Setting benchmarks for translocation success is challenging when dealing with a slow-growing, reproductively challenged species. Crotalaria avonensis has two protected and one unprotected site. Fruit set is low, requires insect pollination, and seedlings are rare. In 2012, we introduced genetic material from the unprotected site to a protected parcel. Transplants have thrived and expanded through clonal and seedling recruitment, from 84 original transplants to 208 plants in 2019. Germination of sown seeds was also a success (47%) with many surviving, flowering and fruiting. The first decade of this translocation may qualify as a success, but the ultimate test comes in long-term population responses to land management activities and climate change. Dicerandra christmanii has <10 sites, only one is protected. It relies on periodic fire to maintain open sandy gaps within the scrub matrix and persists from post-fire seedling recruitment. We have augmentated (2010) and introduction (2012) populations. Both translocations grew exponentially, but the question remained, were populations demographically viable. Using long-term demographic data from wild plants and integral projection models, we determined vital rates and predicted population trajectories were similar between wild and translocated populations. Wild populations provide a priori knowledge of a species’ basic biology and ecological requirements to inform more successful translocations.

Contributing Author(s): 
Date Recorded: 
Wednesday, March 4, 2020

Valerie Pence and Megan Philpott, Cincinnati Zoo & Botanical Garden

Crotalaria avonensis is a Florida endemic found in three populations and characterized by low seed production. In the late 1990s, CREW developed protocols for tissue culture propagation from field collected shoot cuttings as well as cryopreservation methods. In order to develop a genetically representative collection for conservation, in vitro lines were established from shoots collected at all three populations from 2008-2012. Plants were produced and sent to Bok Tower Garden for further growth and for use in an outplanting by Archbold Biological Station. The resulting collection of genotypes in culture at CREW provides an example of the challenges of a genetically diverse collection of an exceptional species. C. avonensis cultures require maintenance subculturing every 2-3 months. Only a low number of replicates could be maintained for each genotype, resulting in some loss of genotypes over time. Cryopreservation offered a solution to this challenge and over the course of 16 years, a number of lines were cryopreserved. In a study of lines stored for 5.5 Ð 16 years in liquid nitrogen, there was no change in average viability of the collection in storage, although specific survival differed by genotype. A cost estimation indicated that cryopreservation could decrease the cost of maintaining the collection over 20 years by at least 1/3. Genetic analysis of the collection and the wild populations is also underway in order to determine the genetic representation of the collection.

Contributing Author(s): 
Date Recorded: 
Friday, May 3, 2019

Joyce Maschinski, Center for Plant Conservation and Valerie Pence, Cincinnati Zoo & Botanical Garden

Crotalaria avonensis is an endangered legume endemic to Florida that produces few seeds. In vitro shoot cultures of multiple genotypes have been grown at CREW to provide genetic diversity for restoration and for tissue cryopreservation. These cultures harbor a bacterium, identified as Paenibacillus sp., which may be a natural endophyte in the species. The bacterium grows slowly and does not appear to inhibit the in vitro propagation of the species, but its effect on the recovery of shoot tips after the stress of cryopreservation was investigated. Samples banked using encapsulation vitrification and representing 63 genotypes were evaluated after 4 - 15 years in liquid nitrogen. The rate of recovery growth of samples with visible bacteria was significantly less than samples without bacteria. Similarly, when newly banked shoot tips of 15 genotypes were cryopreserved using an improved technique, droplet vitrification, and were recovered, the presence of antibiotic in the medium significantly increased the percent of shoot tips showing recovery growth. Whereas C. avonensis shoots can be propagated, rooted, and acclimatized in the presence of this bacterium, recovery after the stress of cryopreservation is reduced when the bacteria are present. An increasing number of plant species are being shown to have endophytes in the wild and removing such endophytes may not be possible or desirable in culture. These results with C. avonensis demonstrate the potential for controlling the negative effects of such microorganisms in vitro. This is one example of the particular challenges that may be presented in working with wild species and conserving endangered exceptional plants. Supported in part by grants from the Institute of Museum and Library Services.

Contributing Author(s): 
Date Recorded: 
Friday, May 4, 2018