Science of Saving Species

Sean Hoban, Emma Spence, and Patrick Thompson, The Morton Arboretum

The Morton Arboretum seeks to improve the conservation value and genetic representation in ex situ collections by developing guidance for sampling seed. One example regards IUCN Critically Endangered Quercus boyntonii (Boynton sand post oak), which is endemic to Alabama and only occurs on exposed sandstone outcrops.In situ threats include overcrowding by invasive species, off trail disturbance by humans, and the threat of wildfires. To help safeguard this species in case wild populations are lost, we compared genetic diversity of wild Quercus boyntonii populations to ex situ collections. We collected 246 individuals from 11 locations in the wild and 77 samples from 14 botanic gardens across the United States. We used microsatellite DNA markers to quantify genetic variation existing in the wild samples and calculate the proportion of genetic variation that exists in ex situ collections. This is a direct measure of the success of the collective efforts to build conservation collections. We found that current ex situ collections capture approximately 78% of overallgenetic diversity, and 100% of common alleles. We also used a resampling technique to determine how efficient this collection is, and we showed that a smallerex situcollection may be sufficient if it is carefully planned. The overall message is that ex situ collections of a taxon spread across a number of institutions can safeguard a species’ genetic diversity. This work is part of a large, multi-institution project in which genetic variation in ex situ collections of 10 species will be quantified. Our end goal is to provide advice to the garden community about how to establish and maintain ex situ tree collections, which includes initiatives to distribute germplasm collaboratively.

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

Kim McCue, Shannon Felberg and Steve Blackwell
Desert Botanic Garden

Date Recorded: 
Friday, May 4, 2018

Lauren Eserman, Atlanta Botanical Garden

Conradina glabra, or Apalachicola rosemary, is a federally listed endangered species that exists only on a small area of sandhill in Liberty County, Florida. Forestry practices in the last 100 years have resulted in declining populations of C. glabra. In the wild, plants produce very few seeds, but small plants that resemble seedlings are commonly found. Through a grant from the US Fish and Wildlife Service, we are using molecular genetic techniques to understand whether C. glabra is reproducing clonally or via sexual reproduction as well as what factors encourage seed germination. To address this question, we sampled plants from forty locations across Torreya State Park in a spatially explicit experimental design. A plant in the center of a large cluster of individuals was marked and samples were taken from plants in all four cardinal directions from the central plant at designated distances. From these samples, we generated RADseq data resulting in >10,000 SNPs from 564 individual plants. Analyses are still ongoing, but early results point to spatially structured genetic variation. Individuals share highly similar genotypes at distances < 1 meter; however, are genetically distinct at distances greater than 1 meter. These results suggest that Conradina glabra is perhaps clonal at very small geographic scales but is generally reproducing sexually across its range. Furthermore, we identify areas with unique genetic variation that is important for conservation. The results of this study are being communicated to land managers who are tasked with preserving this species on the ground.

Date Recorded: 
Friday, October 9, 2020

Dr. Valerie Pence, Cincinnati Zoo & Botanical Garden

Although there are published protocols for initiating shoot cultures for over 20 oak species, the cryopreservation of oak shoot tips has not been reported. We have applied the droplet vitrification protocol to four species of oaks, including the endangered Q. hinckleyi, in order to evaluate the feasibility of using shoot tip cryopreservation for oak ex situ conservation. Good survival through liquid nitrogen exposure was achieved for Q. virginiana, low survival for Q. hinckley and Q. suber, and no survival for Q. gambelii. Survival of Q. virginiana shoot tips was enhanced further by preculturing and recovering using an alternating temperature culture regime (25oC, 16 hr light/15oC, 8 hr dark). These results suggest that one procedure will not be ideal for all oak species, but that changes to the growth conditions can positively influence survival. Future studies will apply changes that were successful with Q. virginiana to oak species with lower levels of survival and other modifications will be made to work to improve survival for the other three species tested here, as well as for additional species in the CREW collection.

Contributing Author(s): 
Date Recorded: 
Friday, October 9, 2020

Zoe Diaz-Martin, Chicago Botanic Garden

As global biodiversity continues to decline, how can we ensure the long-term conservation of exceptional plant species? Our collaborative project is addressing this question by developing tools and resources that will position botanic gardens as key players in global plant conservation. In adopting the successful framework used in the zoological community, we will provide the digital infrastructure needed to cooperatively manage and breed exceptional plant species across botanic garden collections with the goal of maximizing the genetic diversity of these populations and enhancing their capacity for reintroduction efforts. More specifically, we are working with BGCI to update PlantSearch to host accession data and with Zoological experts to modify the software used to manage captive animal populations. This presentation will review the approach and tools we are developing and provide results from a pilot species, Brighamia insiginis, a Hawaiian endemic.

Date Recorded: 
Friday, October 9, 2020

Alex Seglias, Denver Botanic Gardens

Plant biodiversity is being lost at an accelerated rate. To conserve native plants, many institutions are turning towards ex situ conservation methods, such as storage in seed banks. However, not all seeds are able to survive in seed bank conditions or they may be short-lived. Alpine species in Italy and Australia have been shown to lose viability at a quicker rate in seed banks compared to low-elevation species. To understand if alpine species from the Rocky Mountains of Colorado exhibit this same pattern, I used accelerated ageing experiments to simulate storage in a seed bank and expedite loss of viability. Ten samples of 50 seeds for four species (Castilleja puberula, Heterotheca pumila, Physaria alpina, and Saussurea weberi) were rehydrated in a dark incubator at 20°C and 47% humidity for two weeks. Following rehydration, the seeds were placed in a drying oven at 45°C and 60% humidity to age the seeds at various intervals of time. Following the ageing process, the seeds were placed into previously determined germination conditions (stratification followed by incubation at 20/10°C for one month). All species had P50 (time to 50% germination) values of <13.7 days, which is the threshold to consider a species short-lived in seed banks. These results suggest that we can’t haphazardly store seeds and assume that all species will survive for decades in seed banks. Rather, we need to assess what environmental and evolutionary conditions might preclude a species from being long-lived in storage and determine measures to mitigate loss of viability over time.

Contributing Author(s): 
Date Recorded: 
Friday, October 9, 2020

Michelle DePrenger-Levin, Denver Botanic Gardens; Michael Kunz, North Carolina Botanical Garden; Emily Coffey, Atlanta Botanic Garden; Tom Kaye, Institute for Applied Ecology; Anna Lampei Bucharová, Institute of Landscape Ecology (ILÖK), University of Münster

Seed collection is a vital conservation method used to ensure global food security by maintaining a source of genetic diversity in food crops and prevent the loss of biodiversity from natural or anthropogenic events that cause the extirpation of small populations. The Global Strategy for Plant Conservation facilitates global and national level plant conservation strategies including a target of collecting at least 75% of the threatened plant species in ex-situ collections with at least 20% being available for recovery and restoration. Local participation to reach this goal is facilitated by the Center for Plant Conservation (CPC). However, removing seed from small populations can increase extinction risk for species of conservation concern. Current restrictions on seed harvest meant to limit risk to rare species is based on stochastic simulations of a few perennial species with limited demographic data. Our work examines the universality of this threshold across lifespans (annuals to long-lived perennials). We account for variation in vital rate responses by using many transition matrices and adding predictions of worsening conditions due to climate change and human impacts by simulating different harvesting practices in years with high vs. low seed production.

Date Recorded: 
Thursday, October 8, 2020

Wesley Knapp, North Carolina Natural Heritage Program

Extinction rates are expected to increase during the Anthropocene. Current extinction rates of plants and many animals remain unknown. This study represents the first effort to quantify extinctions among the vascular flora of North America north of Mexico since European settlement. We compiled data on apparently extinct species by querying plant conservation databases, searching literature, and vetting the resulting list with botanical experts. Because taxonomic opinion varies widely, we developed an Index of Taxonomic Uncertainty (ITU). The ITU ranges from A to F, with A indicating unanimous taxonomic recognition and F indicating taxonomic recognition by only a single author. The ITU allowed us to rigorously evaluate extinction rates. Our data suggest 65 taxa (51 species and 14 infraspecific taxa) representing 33 families and 49 genera of vascular plants have become extinct in our study area since European settlement. Seven of these taxa exist in cultivation but are extinct in the wild. We found most extinctions in western North America, but that disparity may reflect the timing of botanical exploration relative to settlement. Sixty-four percent of extinct plants were single-site endemics, and many occurred outside recognized biodiversity hotspots. Given the paucity of plant surveys in many areas of North America, particularly prior to European settlement, the actual extinction rate of vascular plants is undoubtedly much higher than indicated here.

Date Recorded: 
Thursday, October 8, 2020

Authors: Stacy Anderson, Tobin Weatherson, Joe Davitt - San Diego Zoo Native Plant Seed Bank

We are all taught in school that water expands when frozen. That's why ice floats, sealed bottles explode in the freezer, and frost kills living tissues. All living cells are comprised largely of water and can rupture and die when the water they contain expands under freezing conditions. The cells of seeds are no different.  Research has shown there is a "goldilocks zone" of relative humidity that our seeds must reach before freezing. This perfect range of relative humidy is greater than 25% and less than 35%. The final and most crucial step before freezing our seeds, is testing their relative humidy to ensure it lies within this range. At SDZGs native plant seed bank we use small air tight desiccation chambers and color changing silica gel to obtain the relative humidity needed in our seed accessions. It's also common to use salt solutions to desiccate. We have found that a very quick and convenient way to read the relative humidy is to place a BlueMaestro Tempo Disc inside our sealed chambers. Given amble time to stabalize, we can infer the seeds reach an equalibrium with their ambient environment. These discs can quickly tell us the relative humidy inside the desiccation chambers without opening them and exposing the contents to humid air. There is a simple app on our phones that gives us temperature and relative humidity levels, and makes it easy to track these data over time. It's important to note that the size of the desiccation chamber, the amount of silica or salt solution, the number of seeds, and the type of seeds can all affect the time it takes to reach equilibrium (within a sealed chamber). For a more precise relative humidity measurement, or if we are unsure about the equilibrium within a chamber, we use The Rotronic HygroPalm. This hygrometer is also useful for obtaining a baseline RH reading from fresh seeds. The HygroPalm uses a small cup to measure the relative humidity of a sample.We attach the probe to the connection port, and turn it on by pressing the red button. We fill this small cup to the line with seeds and the probe tightly covers the sample. It then slowly draws in air and in about 5 minutes gives a very accurate reading. Note some of the drawbacks of using this hygrometer. Sometimes we have very small amounts of seeds in many maternal lines that we can not combine. We don't always have a large enough sample for this cup. We also have to open our chambers and disrupt equilibrium to test. For this reason, we use both the ibuttons and the hygrometer. We have designated desiccation chambers that are very stable and hold small accessions that stabilize quickly, and others for large bulked accessions. We always open and close these chambers as quickly as possible.  When we know that it is safe to freeze the seed, we place the accession into foil lined bags and heat seal them. The bags are now ready to freeze for long term storage, where they can survive for hundreds or even thousands of years, be preserved for generations to come and act as a safe guard against extinction.

Date Recorded: 
Wednesday, October 14, 2020

Joyce Maschinski, Center for Plant Conservation

Joyce Maschinski interviews world famous plant cryo-biologists to learn about how cryopreservation is imperative for the future of food. Many food crops can't be preserved using traditional seed preservation methods. For some of these species cryopreservation is the only long term option. Plant researchers from across the globe are working to develop and perfect these cryo-technologies in order to conserve these exceptional species for future generations.

Contributing Author(s): 
Date Recorded: 
Wednesday, October 7, 2020