Applying the zoo model to conservation of threatened exceptional plant species

Using pedigree tracking of the ex situ metacollection of Amorphophallus titanum (Araceae) to identify challenges to maintaining genetic diversity in the botanical community

BACKGROUND AND AIMS

Rapid global biodiversity loss emphasizes the need to employ strategies that conserve the long-term viability of ex situ plant collections. A pedigree-based management approach is an effective strategy to track genetic diversity of living collections; however, its implementation requires accession-level data for all individuals across all botanic garden collections. Here, we use historic accession records to construct a pedigree and test how effective current protocols have been in managing ex situ diversity.

METHODS

We selected the titan arum, Amorphophallus titanum (Araceae), for this study, as it is exceptional, endangered, and has been globally held in collections for nearly 150 years. A pedigree-based data management approach would benefit the ex situ conservation of many similar species. Using accession data from nearly 1200 individual plants from 111 institutions worldwide, we constructed a pedigree to track the history of this species in collections and evaluate how well genetic diversity has been maintained in the metacollection.

KEY RESULTS

We found that data and records for the ex situ metacollection of Amorphophallus titanum are severely lacking and are not standardized within the botanical community. Using the available data, we found that the metacollection is derived from few founders, material is rarely exchanged between institutions on different continents, and nearly a quarter of known crosses are between related individuals.

CONCLUSIONS

Our work highlights the need for consistent, detailed record-keeping for effective implementation of an informed pedigree-based management approach and long-term maintenance of collections of endangered plant species in botanic gardens.

Review of Mimusops zeyheri Sond. (Milkwood): Distribution, Utilisation, Ecology and Population Genetics

Mimusops zeyheri Sond. (Milkwood) is an indigenous fruit tree species with considerable ecological, cultural, and nutritional significance that remains underexploited. This review synthesizes current knowledge on its distribution, taxonomy, phytochemistry, ethnomedicinal applications, ecological functions, genetic diversity, and biotechnological potential. A systematic literature search, spanning 1949 to April 2024, yielded 87 relevant publications from an initial 155. Mimusops zeyheri plays a crucial role in supporting the cultural traditions and economic activities of Indigenous Southern African Communities. Its distribution encompasses South, East, and Southern Tropical Africa, with substantial populations across South African provinces. Ethnomedicinally, various plant parts treat conditions including wounds, gastrointestinal issues, and diabetes. The leaves (34%) and roots (32%) are used, with infusion (33%) and decoction (31%) as primary preparation methods. Oral administration (70%) is the most common, primarily addressing skin conditions (18%). Despite its nutritional richness, a standardized nutrient profile is lacking. Limited genetic diversity studies underscore the need for further research. This study highlights Mimusops zeyheri's multifaceted importance and research gaps, particularly in other Southern African countries. Future investigations should focus on comprehensive phytochemical analysis, ethnomedicinal validation, ecological conservation, genetic diversity assessment, and biotechnological applications. Multidisciplinary collaborations are recommended to promote sustainable utilization while preserving traditional practices.

Extinct in the wild: The precarious state of Earth's most threatened group of species

Extinct in the Wild (EW) species are placed at the highest risk of extinction under the International Union for Conservation of Nature Red List, but the extent and variation in this risk have never been evaluated. Harnessing global databases of ex situ animal and plant holdings, we report on the perilous state of EW species. Most EW animal species-already compromised by their small number of founders-are maintained at population sizes far below the thresholds necessary to ensure demographic security. Most EW plant species depend on live propagation by a small number of botanic gardens, with a minority secured at seed bank institutions. Both extinctions and recoveries are possible fates for EW species. We urgently call for international effort to enable the latter.

Supporting long-term sustainability of ex situ collections using a pedigree-based population management approach

Premise

Living collections maintained for generations are at risk of diversity loss, inbreeding, and adaptation to cultivation. To address these concerns, the zoo community uses pedigrees to track individuals and implement crosses that maximize founder contributions and minimize inbreeding. Using a pedigree management approach, we demonstrate how conducting strategic crosses can minimize genetic issues that have arisen under current practices.

Methods

We performed crosses between collections and compared progeny fitness, including plant performance and reproductive health. We genotyped the progeny and parental accessions to measure changes in diversity and relatedness within and between accessions.

Results

The mean relatedness values among individuals within each accession suggest they are full siblings, demonstrating that there was high inbreeding and low diversity within accessions, although less so among accessions. Progeny from the wider crosses had increased genetic diversity and were larger and more fertile, while self-pollinated accessions were smaller and less fertile.

Discussion

Institutions that hold exceptional species should consider how diversity is maintained within their collections. Implementing a pedigree-based approach to managing plant reproduction ex situ will slow the inevitable loss of genetic diversity and, in turn, result in healthier collections.

Assessing ex situ genetic and ecogeographic conservation in a threatened but widespread oak after range-wide collecting effort

Although the genetic diversity and structure of in situ populations has been investigated in thousands of studies, the genetic composition of ex situ plant populations has rarely been studied. A better understanding of how much genetic diversity is conserved ex situ, how it is distributed among locations (e.g., botanic gardens), and what minimum sample sizes are needed is necessary to improve conservation outcomes. Here we address these issues in a threatened desert oak species, Quercus havardii Rydb. We assess the genetic, geographic, and ecological representation of 290 plants from eight ex situ locations, relative to 667 wild individuals from 35 in situ locations. We also leverage a recent dataset of >3000 samples from 11 other threatened plants to directly compare the degree of genetic conservation for species that differ in geographic range size. We found that a majority of Q. havardii genetic diversity is conserved; one of its geographic regions is significantly better conserved than the other; genetic diversity conservation of this widespread species is lower than documented for the 11 rarer taxa; genetic diversity within each garden is strongly correlated to the number of plants and number of source populations; and measures of geographic and ecological conservation (i.e., percent area and percent of ecoregions represented) were typically lower than the direct assessment of genetic diversity (i.e., percent alleles). This information will inform future seed sampling expeditions to ensure that the intraspecific diversity of threatened plants can be effectively conserved.

Tropical Important Plant Areas, plant species richness and conservation in the British Virgin Islands

The global loss of biodiversity is a pressing and urgent issue and halting loss is the focus of many international agreements and targets. However, data on species distribution, threats and protection are limited and sometimes lacking in many parts of the world. The British Virgin Islands (BVI), part of the Puerto Rican Bank Floristic Region in the Caribbean Biodiversity Hotspot, is rich in plant diversity and regional endemism. Despite the established network of National Parks in the BVI and decades of botanical data from international collaboration between the Royal Botanic Gardens, Kew and the National Parks Trust of the Virgin Islands, there was a need for consolidated data on species distribution across the archipelago and national lists for threatened and rare plants of conservation concern. The process of identifying the network of 18 Tropical Important Plant Areas (TIPAs) in the BVI, completed in 2018, delivered national lists and accurate data for all 35 Species of Conservation Concern. These data (3688 georeferenced records) are analysed here to reveal species distribution across the archipelago, within the TIPAs network and the National Parks System. The TIPAs network contained all 35 Species of Conservation Concern and 91% of all the records, as expected. Ten out of the 21 National Parks had one or more of the species present. Most species occur across the archipelago, while some are restricted range and/or endemics. These new data will help management of plant conservation efforts and resources in the BVI, contributing to the revision of the Protected Areas System Plan and local environmental policies and have relevance to the wider Caribbean Region.

New developments in the field of genomic technologies and their relevance to conservation management

Recent technological advances in the field of genomics offer conservation managers and practitioners new tools to explore for conservation applications. Many of these tools are well developed and used by other life science fields, while others are still in development. Considering these technological possibilities, choosing the right tool(s) from the toolbox is crucial and can pose a challenging task. With this in mind, we strive to inspire, inform and illuminate managers and practitioners on how conservation efforts can benefit from the current genomic and biotechnological revolution. With inspirational case studies we show how new technologies can help resolve some of the main conservation challenges, while also informing how implementable the different technologies are. We here focus specifically on small population management, highlight the potential for genetic rescue, and discuss the opportunities in the field of gene editing to help with adaptation to changing environments. In addition, we delineate potential applications of gene drives for controlling invasive species. We illuminate that the genomic toolbox offers added benefit to conservation efforts, but also comes with limitations for the use of these novel emerging techniques.

Plant Diversity Conservation Challenges and Prospects-The Perspective of Botanic Gardens and the Millennium Seed Bank

There is a pressing need to conserve plant diversity to prevent extinctions and to enable sustainable use of plant material by current and future generations. Here, we review the contribution that living collections and seed banks based in botanic gardens around the world make to wild plant conservation and to tackling global challenges. We focus in particular on the work of Botanic Gardens Conservation International and the Millennium Seed Bank of the Royal Botanic Gardens, Kew, with its associated global Partnership. The advantages and limitations of conservation of plant diversity as both living material and seed collections are reviewed, and the need for additional research and conservation measures, such as cryopreservation, to enable the long-term conservation of 'exceptional species' is discussed. We highlight the importance of networks and sharing access to data and plant material. The skill sets found within botanic gardens and seed banks complement each other and enable the development of integrated conservation (linking in situ and ex situ efforts). Using a number of case studies we demonstrate how botanic gardens and seed banks support integrated conservation and research for agriculture and food security, restoration and reforestation, as well as supporting local livelihoods.

The relevance of pedigrees in the conservation genomics era

Over the past 50 years conservation genetics has developed a substantive toolbox to inform species management. One of the most long‐standing tools available to manage genetics—the pedigree—has been widely used to characterize diversity and maximize evolutionary potential in threatened populations. Now, with the ability to use high throughput sequencing to estimate relatedness, inbreeding, and genome‐wide functional diversity, some have asked whether it is warranted for conservation biologists to continue collecting and collating pedigrees for species management. In this perspective, we argue that pedigrees remain a relevant tool, and when combined with genomic data, create an invaluable resource for conservation genomic management. Genomic data can address pedigree pitfalls (e.g., founder relatedness, missing data, uncertainty), and in return robust pedigrees allow for more nuanced research design, including well‐informed sampling strategies and quantitative analyses (e.g., heritability, linkage) to better inform genomic inquiry. We further contend that building and maintaining pedigrees provides an opportunity to strengthen trusted relationships among conservation researchers, practitioners, Indigenous Peoples, and Local Communities.

Global Commitments to Conserving and Monitoring Genetic Diversity Are Now Necessary and Feasible

Global conservation policy and action have largely neglected protecting and monitoring genetic diversity—one of the three main pillars of biodiversity. Genetic diversity (diversity within species) underlies species’ adaptation and survival, ecosystem resilience, and societal innovation. The low priority given to genetic diversity has largely been due to knowledge gaps in key areas, including the importance of genetic diversity and the trends in genetic diversity change; the perceived high expense and low availability and the scattered nature of genetic data; and complicated concepts and information that are inaccessible to policymakers. However, numerous recent advances in knowledge, technology, databases, practice, and capacity have now set the stage for better integration of genetic diversity in policy instruments and conservation efforts. We review these developments and explore how they can support improved consideration of genetic diversity in global conservation policy commitments and enable countries to monitor, report on, and take action to maintain or restore genetic diversity.

Comparing Genetic Diversity in Three Threatened Oaks

Genetic diversity is a critical resource for species’ survival during times of environmental change. Conserving and sustainably managing genetic diversity requires understanding the distribution and amount of genetic diversity (in situ and ex situ) across multiple species. This paper focuses on three emblematic and IUCN Red List threatened oaks (Quercus, Fagaceae), a highly speciose tree genus that contains numerous rare species and poses challenges for ex situ conservation. We compare the genetic diversity of three rare oak species—Quercus georgiana, Q. oglethorpensis, and Q. boyntonii—to common oaks; investigate the correlation of range size, population size, and the abiotic environment with genetic diversity within and among populations in situ; and test how well genetic diversity preserved in botanic gardens correlates with geographic range size. Our main findings are: (1) these three rare species generally have lower genetic diversity than more abundant oaks; (2) in some cases, small population size and geographic range correlate with genetic diversity and differentiation; and (3) genetic diversity currently protected in botanic gardens is inadequately predicted by geographic range size and number of samples preserved, suggesting non-random sampling of populations for conservation collections. Our results highlight that most populations of these three rare oaks have managed to avoid severe genetic erosion, but their small size will likely necessitate genetic management going forward.