Targeted conservation genetics of the endangered chimpanzee

Insights for the Captive Management of South China Tigers Based on a Large-Scale Genetic Survey

There is an urgent need to find a way to improve the genetic diversity of captive South China tiger (SCT, Panthera tigris amoyensis), the most critically endangered taxon of living tigers, facing inbreeding depression. The genomes showed that 13 hybrid SCTs from Meihuashan were divided into two groups; one group included three individuals who had a closer relationship with pureblood SCTs than another group. The three individuals shared more that 40% of their genome with pureblood SCTs and might be potential individuals for genetic rescuing in SCTs. A large-scale genetic survey based on 319 pureblood SCTs showed that the mean microsatellite inbreeding coefficient of pureblood SCTs decreased significantly from 0.1789 to 0.0600 (p = 0.000009) and the ratio of heterozygous loci increased significantly from 38.5% to 43.2% (p = 0.02) after one individual of the Chongqing line joined the Suzhou line and began to breed in the mid-1980s, which is a reason why the current SCTs keep a moderate level of microsatellite heterozygosity and nucleotide diversity. However, it is important to establish a back-up population based on the three individuals through introducing one pureblood SCT into the back-up population every year. The back-up population should be an important reserve in case the pureblood SCTs are in danger in the future.

From genomic threat assessment to conservation action

Genomic approaches have the potential to play a pivotal role in conservation, both to detect threats to species and populations and to restore biodiversity through actions. We here separate these approaches into two subdisciplines, vulnerability and restoration genomics, and discuss current applications, outstanding questions, and future potential.

Estimating admixture pedigrees of recent hybrids without a contiguous reference genome

The genome of recently admixed individuals or hybrids has characteristic genetic patterns that can be used to learn about their recent admixture history. One of these are patterns of interancestry heterozygosity, which can be inferred from SNP data from either called genotypes or genotype likelihoods, without the need for information on genomic location. This makes them applicable to a wide range of data that are often used in evolutionary and conservation genomic studies, such as low-depth sequencing mapped to scaffolds and reduced representation sequencing. Here we implement maximum likelihood estimation of interancestry heterozygosity patterns using two complementary models. We furthermore develop apoh (Admixture Pedigrees of Hybrids), a software that uses estimates of paired ancestry proportions to detect recently admixed individuals or hybrids, and to suggest possible admixture pedigrees. It furthermore calculates several hybrid indices that make it easier to identify and rank possible admixture pedigrees that could give rise to the estimated patterns. We implemented apoh both as a command line tool and as a Graphical User Interface that allows the user to automatically and interactively explore, rank and visualize compatible recent admixture pedigrees, and calculate the different summary indices. We validate the performance of the method using admixed family trios from the 1000 Genomes Project. In addition, we show its applicability on identifying recent hybrids from RAD-seq data of Grant's gazelle (Nanger granti and Nanger petersii) and whole genome low-depth data of waterbuck (Kobus ellipsiprymnus) which shows complex admixture of up to four populations.

Genomics reveals introgression and purging of deleterious mutations in the Arabian leopard (Panthera pardus nimr)

In endangered species, low-genetic variation and inbreeding result from recent population declines. Genetic screenings in endangered populations help to assess their vulnerability to extinction and to create informed management actions toward their conservation efforts. The leopard, Panthera pardus, is a highly generalist predator with currently eight different subspecies. Yet, genomic data are still lacking for the Critically Endangered Arabian leopard (P. p. nimr). Here, we sequenced the whole genome of two Arabian leopards and assembled the most complete genomic dataset for leopards to date. Our phylogenomic analyses show that leopards are divided into two deeply divergent clades: the African and the Asian. Conservation genomic analyses indicate a prolonged population decline, which has led to an increase in inbreeding and runs of homozygosity, with consequent purging of deleterious mutations in both Arabian individuals. Our study represents the first attempt to genetically inform captive breeding programmes for this Critically Endangered subspecies.

Population dynamics and genetic connectivity in recent chimpanzee history

Knowledge on the population history of endangered species is critical for conservation, but whole-genome data on chimpanzees (Pan troglodytes) is geographically sparse. Here, we produced the first non-invasive geolocalized catalog of genomic diversity by capturing chromosome 21 from 828 non-invasive samples collected at 48 sampling sites across Africa. The four recognized subspecies show clear genetic differentiation correlating with known barriers, while previously undescribed genetic exchange suggests that these have been permeable on a local scale. We obtained a detailed reconstruction of population stratification and fine-scale patterns of isolation, migration, and connectivity, including a comprehensive picture of admixture with bonobos (Pan paniscus). Unlike humans, chimpanzees did not experience extended episodes of long-distance migrations, which might have limited cultural transmission. Finally, based on local rare variation, we implement a fine-grained geolocalization approach demonstrating improved precision in determining the origin of confiscated chimpanzees.

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.

The Diversity of Primates: From Biomedicine to Conservation Genomics

Until now, the field of primate genomics has focused on two major themes: understanding human evolution and advancing biomedical research. We propose that it is now time for a third theme to receive attention: conservation genomics. As a result of anthropogenic effects, the majority of primate species have become threatened with extinction. A more robust primate conservation genomics will allow for genetically informed population management. Thanks to a steady decline in the cost of sequencing, it has now become feasible to sequence whole primate genomes at the population level. Furthermore, technological advances in noninvasive genomic methods have made it possible to acquire genome-scale data from noninvasive biomaterials. Here, we review recent advances in the analysis of primate diversity, with a focus on genomic data sets across the radiation.