Exceptional Species

Megan Philpott, Valerie PenceL*, Cincinnati Zoo & Botanical Garden, United States *Speaker

Threats to global plant biodiversity compel the need for ex situ collections of species worldwide. However, the subset of species known as exceptional plants are often overlooked. These species produce few or no seeds or produce recalcitrant seeds. The Center for Conservation and Research of Endangered Wildlife (CREW) at the Cincinnati Zoo & Botanical Garden maintains a liquid nitrogen bank of exceptional plant seeds and tissues known as the CryoBioBank®. CREW has partnered with the Lyon Arboretum in Honolulu to develop cryopreservation protocols for 21 endangered exceptional Hawaiian plant species and bank them in the CryoBioBank®. To date, micropropagation protocols to produce target tissues have been tested in 13 species, and cryopreservation protocols have been tested in 7 species. As an example, in Cyrtandra gracilis, micropropagation on medium containing 2mg/L of the auxin indole-3-acetic acid and 0.1mg/L of the cytokinin 6-benzylaminopurine induces shoot organogenesis on excised leaves. These leaves were dissected into leaf bud segments and compared with shoot tips for survival after liquid nitrogen storage. Cryopreservation of shoot tips using droplet vitrification (DV) with PVS2 yielded 0% survival, while leaf bud segments yielded 20% survival. DV using PVS3 increased survival in these leaf buds to 60%. Cryopreservation of leaf bud segments immediately after bud primordia formed yielded 25% survival compared to 50% survival if the buds were left to develop into shoots before cryopreservation. Shoot tips from another species, Melicope mucronulata, have been banked in the CryoBioBank® using the DV method following an experimental survival rate of 57% after 2 days of pre- culture on a 0.3M mannitol medium instead of one day on 0.3M mannitol and one day on 0.5M mannitol medium. This project will result in the long-term protection of many endangered exceptional Hawaiian species that would otherwise be unbankable using conventional methods. (Supported by IMLS grant #MG-30-17-0055-17).

Contributing Author(s): 
Date Recorded: 
Thursday, July 25, 2019

Jeremie Fant, Chicago Botanic Garden

This talk highlights the Chicago Botanic Garden’s work on adapting zoo conservation approaches for exceptional plant species. Challenges in ex situ conservation include genetic issues that arise from limited numbers of individuals and founders, and husbandry and hybridization issues encountered during the growing out of collections. A significant advantage in plant conservation is that seeds can be collected for a vast majority of plants. One example is the CBG's Dixon Tallgrass Prairie Seedbank, which has more than 1,700 species and 10,000 accessions. 

Although banking options are more restricted in animal conservation, other approaches used by the zoo community can be adapted to improve success rates in ex situ plant conservation programs. One such approach is pedigree analysis, which shifts focus from high numbers of individuals to equal numbers of founders. The CBG is testing pedigree analysis on several species, as illustrated by work done with Brighamia insignis. The steps include tracking founders by creating a pedigree of collections, calculating relatedness between all individuals, and making management decisions. This method enables researchers to identify genetically valuable individuals across collections, use life span of a species in collections to determine the sample size needed to maintain a collection, and identify crosses needed to increase diversity and improve collection robustness.

One of the next steps planned by the CBG is to identify collection plants less valuable for maintaining genetic diversity, and use them to test restoration techniques. The ultimate goal is to use ex situ collections for restoration of rare species in the field.

Contributing Author(s): 
Date Recorded: 
Thursday, May 2, 2019

What is the standard for determination of Exceptional Species status?

Is it only species that have seeds that exhibit no viability in both desiccation and cold? Or is it a lower bar of reduced viability in both, and if so, how reduced?

Question Category: 

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

Although many rare plants have seeds that can be stored by conventional methods, not all species have seeds that can live after drying or freezing. Sometimes called "Exceptional plants, " these species have a wide range of variation. Some produce few or no seeds, thus they cannot be seed banked, others have seeds or spores that will die if dried or frozen, while others have seeds that can tolerate drying, but not freezing, and another group have seeds that live less than 10 years at freezing temperatures. Recent studies suggest that there are many rare plant species that need alternative storage for conservation. This video describes a procedure for  testing whether rare plants can be stored in liquid nitrogen successfully.

Date Recorded: 
Friday, March 1, 2019

Jordan Wood, Jeremie Fant, Andrea Kramer and Kay Havens, Chicago Botanic Garden

Genetics becomes important whenever populations become small (<100). This includes loss o fgenetic diversity from drift, increased expression of deleterious genes due to inbreeding, and limiting local adaptation. Since many species of plants are able to be seed banked, it is possible to maintain numbers well above these critical genetic thresholds. However for exceptional species, which can only be maintained as living plants, or for critically endangered species where remaining individuals are already below these numbers, the need to consider the remaining genetic diversity becomes critical. Importantly, the management focus shifts from saving a population to preserving each genetically unique individual. When you have such small numbers, it is critical to know how each individual contributes to the overall genetic diversity remaining. We are working with National Tropical Botanic Gardens (Hawaiʻi) to develop a multi-institution species management and breeding plan for Ālula(Brighamia insignis)that will ultimately support its restoration to the wild. To do this we are working with scientists at the Chicago Zoological Society to modify management software that incorporates genetics and demography information to maintain the long-term health of their captive populations of animals over the long term. Through this case study, we hope to develop collections management practices for plants that preserve important genetic diversity while identifying genetically appropriate individuals to using in crosses and that can ultimately be used to create resilient populations that can be used in reintroductions.

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