Conservation in Progress
The Rare Plant Conservation Program at Bok Tower Gardens is committed to rare plant preservation. Conservation in Progress is a biannual summary posted on the Bok Tower Gardens website as a rare plant informational tool for website visitors.
July – December 2018 Highlights:
Re-establishing rare species in the scrub
Sometimes there is just a small area of land remaining after construction or development projects, but these remnants can be extremely important for species conservation. Bok Tower Gardens works with developers and land owners to help restore remnant patches into habitat that can support a wealth of listed species.
In partnership with corporate representatives, we have been working to help restore a strip of remnant scrub back into a healthy condition that can support the numerous listed plant and animal species that once lived there. Over several years during planning of transfer station construction and railway widening, Bok Tower Gardens rescued hundreds of plants and thousands of seeds of six rare plant species from an impact site. Following completion of the construction project, we have worked to clear overgrowth, remove invasive species and fill dirt, and re-introduce the rescued rare plant material back into their original home. In July, 60 seedlings of three rare species were transplanted back into the site with the help of The Natives, Inc., who then provided water to the plants until they were established. Survival has been very high for these transplants, and we are planning the next phase of this restoration project for 2019.
Learning what remains…
One of the roles of the Rare Plant Conservation Program is to help track rare plant species in the wild. As continued development wipes out populations and remaining habitat is unable to be burned or managed, plant numbers can quickly decline. Factors such as a decrease or change in pollinators, hurricanes, droughts, or predators can also lead to a substantial decline in the number of plants remaining in the wild. On the other hand, events like unexpected wildfires that help improve habitat, or a series of favorable weather years, can have a profound positive impact on plant numbers. Effective conservation strategies are based on regular updates of the status of the remaining populations, allowing us to study how each species responds to various environmental events.
In October, we surveyed several populations of Carter’s Mustard, Warea carteri. One of the populations had not been surveyed in decades, and no one was certain it was still in existance. Happily, over 200 plants were located and mapped. In addition to the number of plants and mapping the ‘footprint’ of the population, information was collected on habitat quality, health of plants and whether pollinators or predators were observed. Although many pollinators were seen, we also documented caterpillars feeding on several developing seed pods (“siliques”), which could lead to a decrease in viable seed production. Dr. Mark Deyrup (ret.) of Archbold Biological Station identified the caterpillars as belonging to the Great Southern White butterly, Ascia montuste.
Gopher tortoises and Florida Ziziphus conservation
In 2018, the Rare Plant Conservation Program (RPCP) required the assistance of Gopher tortoises to aid in their efforts for plant conservation. Yes, you read that correctly! The RPCP is investigating whether seed germination of the extremely rare, state and federally endangered Ziziphus celata (Florida Ziziphus) is affected after seeds are digested by Gopher tortoises. Z. celata is a deciduous thorny shrub endemic to the Lake Wales Ridge in central Florida. Threats of extinction include both ecological and biological factors. Beyond the loss of quality habitat, the species is self-incompatible, and the plants need to interbreed with genetically different individuals. This is of great concern considering nine of the 15 known wild populations consist of a single clone. Flowering in each of the populations is profuse, but successful fertilization is not possible. Little to no fruit is produced in the wild, no seeds contribute to a seedbank, and no new seedlings are added to the population. However, at least one of the populations introduced by Archbold Biological Station consist of individuals with mixed genetics, and have begun to form seeds. This makes our research into the effect of Gopher tortoises on seed germination of Ziziphus timely, as it has long been suspected that tortoises historically fed on Ziziphus fruits, and may have contributed to their dispersal.
This research project was done through a partnership between Bok Tower Gardens, where the ex situ collection of Z. celata is held, and Circle B Bar Reserve, which is home to a captive population of Gopher tortoises. Fresh fruit was harvested in May-June, 2018, and were fed to three resident Gopher tortoises at Circle B Bar Reserve. The incredible volunteers at Circle B then collected the scat daily. Each week an exchange occurred: BTG staff delivered fresh fruit to Circle B, and in-turn collected the week’s scat. Scat was brought back to BTG, and placed in drying cages until four weeks after the last fruit was consumed to help ensure all seeds were recovered. After four weeks, volunteer Bea Armstrong excavated the digested seeds from the scat, and on July 13th, the first-ever germination trial to compare germination rates of digested versus un-digested Z. celata seeds was set up.
A total of 73 seeds were digested and sown in the germination trial, along with 73 un-digested seeds for comparison. To date, 11 of the digested seeds and just two of the undigested seeds have germinated. This is more than a 4x increase in germination of Gopher tortoise-digested seeds over undigested seeds.
Z. celata seeds typically exhibit a very low germination rate, as low as 0.14%. Many species of Ziziphus have woody endocarps that inhibit seed germination, which likely contributed to this low rate. In the wild, Florida Ziziphus seeds may be further threatened. Conditions such as drought or high moisture leading to mold have been known to destroy seed viability. Other factors are likely to reduce the chances for seed germination the longer the seed sits on the ground. This includes predators like insects and small mammals who eat the fruit and damage the seeds, and the pink scavenger moth, whose larvae feeds on the embryo.
Because Gopher tortoises are widespread in environments where the Florida Ziziphus grows, it is very good news that tortoises can actually enhance seed germination.
International Seed Scientists Invade Colorado Town
Bok Tower Gardens’ National Collection of endangered plants includes approximately 2.8 million seeds belonging to over 70 species of endangered plants, many of which are found only in the state of Florida. The goal of the Collection is to use these seeds to prevent the extinction of these species. However, the storage conditions necessary to keep the seeds of most of the seeds in the Collection alive are not well known.
To improve the Rare Plant Conservation Program’s ability to achieve this goal, Rare Plant Curator Phil Gonsiska traveled to the Second International Workshop on Seed Longevity, held in Fort Collins, CO, from July 30 through August 1, 2018. This workshop brought together 110 scientists from 25 different countries for three days of presentations, discussions, and commiseration over the difficulties of seed science. Participants in the meeting fit into one of two broad categories: those who study seeds of crops or model organisms (about which much is known), and those who study seeds of rare or endangered plant species (about which comparatively almost nothing is known). The workshop also included a tour of the National Laboratory for Genetic Resources Preservation, at which BTG stores some of its seeds over liquid nitrogen. As a result of discussions at this meeting, Phil brought back ideas for improving BTG’s seed storage processes and procedures, as well as a sense of community with like minded researchers engaged in similar pursuits.
Behind the Scenes at Bok: Propagation of Endangered Species
One of the goals of BTG’s National Collection of endangered plants is to house, as much as is possible, a representative genetic sampling of endangered plant species as they exist in the wild. Florida’s endangered flora includes species in the genus Dicerandra, which, like many of Florida’s endangered plants, is threatened by development, agriculture, and fire suppression. There are two varieties of Dicerandra immaculata, as well as four other species of Dicerandra maintained in the BTG collection. Because Dicerandra seeds lose their viability within one or two years, we must maintain ex situ germplasm of Dicerandra as whole, actively growing plants. These plants are useful as a source of cuttings, but not as a source of seeds.
These species are geographically and genetically isolated from each other in the wild. However, because in the Collection they grow within pollination distance of each other, and the flowering periods of most of these species overlap, hybridization can easily occur. Hybridization can create new types of plants that are entirely different from those that we aim to preserve, and therefore seeds of the Dicerandra that are produced in the collection cannot be used for conservation purposes. An additional complication in this endeavor is that the plants themselves are fairly short-lived. As a result, plants in the collection must be propagated vegetatively from cuttings every few years in order to maintain plants with the same genetic makeup as those found in the wild. In 2018, cuttings to maintain the living plants in the collection were collected and new plants propagated to replace the aging ones. Currently, there are hundreds of Dicerandra plants in our greenhouse, belonging to four species, waiting to grow large enough to be planted out in the beds.
A Partnership for the conservation of a very rare species
Bok Tower Gardens and Lake Louisa State Park have be working together for a number of years now to restore areas of remnant sandhill habitat within the Park and to establish robust genetically diverse populations of Clasping Warea (Warea amplexifolia). Clasping Warea is a state and federally endangered annual wildflower endemic to the Lake Wales Ridge of central Florida. The species is globally rare, found nowhere else in the world, and is in decline because much of the xeric upland habitat along the Ridge has been decimated by development. What remains has been severely fragmented and often degraded.
Recovery objectives for this species outlined by the U.S. Fish and Wildlife Service include that there be a sufficient number of self-sustaining populations on protected lands. The efforts of this partnership between Bok Tower Gardens and Lake Louisa State Park are helping to meet these objectives. Although Clasping Warea has not been historically documented within its boundaries, the Park lies within its historically known range, and the remnant sandhill areas contain the appropriate soil type. We have been working to introduce Clasping Warea into the Park for several years. The new population introduced in 2018 marked the fifth introduced population at Lake Louisa State Park.
In June 2018, staff and volunteers from the Gardens and the Park transplanted over 1,200 Clasping Warea seedlings within two adjacent locations. The seedlings, derived from a genetically diverse mix of regional seeds in order to create a healthy, self-sustaining population, were carefully propagated in the greenhouse at Bok Tower Gardens. Once in their new home, the plants grew throughout the summer, and then formed cleome-like flowers in the fall, attracting numerous butterfly, bee and other pollinators.
Staff and volunteers will continue revisit these populations each fall to record survival and phenology, and collect seeds from a small subset of plants in order to estimate the number of seeds produced within the population that will begin to establish a seedbank. Thousands of seeds are expected to be produced each year in this new population, which will greatly help conserve this highly endangered species.