Demographic history and conservation genomics of caribou (Rangifer tarandus) in Québec

The loss of genetic diversity is a challenge many species are facing, and genomics is a potential tool that can inform and prioritize decision making. Caribou populations have experienced significant recent declines throughout Québec, Canada, and some are considered threatened or endangered. We calculated the ancestral and contemporary patterns of genomic diversity of five caribou populations and applied a comparative framework to assess the interplay between demography and genomic diversity. We calculated a caribou specific mutation rate, μ, by extracting orthologous genes from related ungulates. Whole genome re-sequencing was completed on 67 caribou and genotype likelihoods were estimated. We calculated nucleotide diversity, θπ and estimated the coalescent or ancestral Ne, which ranged from 12,030 to 15,513. When compared to the census size, NC, the endangered Gaspésie Mountain caribou population had the highest Ne:NC ratio which is consistent with recent work suggesting high ancestral Ne:NC is of conservation concern. These ratios were highly correlated with genomic signatures (i.e. Tajima’s D) and explicit demographic model parameters. Values of contemporary Ne, estimated from linkage-disequilibrium, ranged from 11 to 162, with Gaspésie having among the highest contemporary Ne:NC ratio. Importantly, conservation genetics theory would predict this population to be of less concern based on this ratio. Of note, F varied only slightly between populations, and runs of homozygosity were not abundant in the genome. Our study highlights how genomic patterns are nuanced and misleading if viewed only through a contemporary lens; a holistic view should integrate ancestral Ne and Tajima’s D into conservation decisions.

Conservation Genomics Reveals Low Connectivity Among Populations of Threatened Roseate Terns in the Atlantic Basin

While the effects of barriers to dispersal such as population declines, habitat fragmentation, and geographic distance have been well-documented in terrestrial wildlife, factors impeding the dispersal of highly vagile taxa such as seabirds are less well understood. The roseate tern (Sterna dougallii) is a globally distributed seabird species, but populations tend to be both fragmented and small, and the species is declining across most of its range. Within the Atlantic Basin, past work has shown differentiation among roseate terns breeding on different continents, but these results were generated with a limited number of microsatellite markers. Relationships between breeding populations in the Northwestern Atlantic and the Caribbean have never been analyzed. We evaluated population structuring of roseate tern populations in North America and the Azores using both microsatellite markers and single-nucleotide polymorphisms generated through targeted sequencing of Ultra-conserved Elements. For both marker types, we found significant genetic differentiation among all 3 populations and evidence for moderate contemporary unidirectional gene flow from the Caribbean to the Azores, but not among other populations. Within the Caribbean metapopulation, we found high rates of unidirectional migration from the Virgin Islands to Florida, potentially indicative of movement from source population to sink or an artifact of dispersal among other unsampled populations in the Caribbean region. These observations have significance for species persistence in the Atlantic, as our results suggest that loss of genetic diversity within populations is unlikely to be buffered by inflow of new alleles from other breeding populations.

The genome of the Balearic shearwater (Puffinus mauretanicus), a Critically Endangered seabird: a valuable resource for evolutionary and conservation genomics

The Balearic shearwater (Puffinus mauretanicus) is the most threatened seabird in Europe. The fossil record suggests that human colonisation of the Balearic Islands resulted in a sharp decrease of the population size. Currently, populations continue to be decimated mainly due to predation by introduced mammals and bycatch in longline fisheries, and some studies predict their extinction by 2070. We present the first high-quality reference genome for the species which was obtained by a combination of short and long-read sequencing. Our hybrid assembly includes 4,169 scaffolds, with a scaffold N50 of 2.1 Mbp, a genome length of 1.2 Gbp, and BUSCO completeness of 96%, which is amongst the highest across sequenced avian species. This reference genome allowed us to study critical aspects relevant to the conservation status of the species, such as an evaluation of overall heterozygosity levels and the reconstruction of its historical demography. Our phylogenetic analysis using whole-genome information resolves current uncertainties in the order Procellariiformes systematics. Comparative genomics analyses uncover a set of candidate genes that may have played an important role into the adaptation to a pelagic lifestyle of Procellariiformes, including those for the enhancement of fishing capabilities, night vision and the development of natriuresis. This reference genome will be the keystone for future developments of genetic tools in conservation efforts for this Critically Endangered species.

The Use of Genomic Information for the Conservation of Animal Genetic Diversity

The conservation of genetic diversity, both among and within breeds, is a costly process. Therefore, choices between breeds and animals within breeds are unavoidable, either for conservation in vitro (gene banks) or in vivo (maintaining small populations alive). Nowadays, genomic information on breeds and individual animals is the standard for the choices to be made in conservation. Genomics may accurately measure the genetic distances among breeds and the relationships among animals within breeds. Homozygosity at loci and at parts of chromosomes is used to measure inbreeding. In addition, genomics can be used to detect potentially valuable rare alleles and haplotypes, their carriers in these breeds and can facilitate in vivo or in vitro conservations of these genomic regions.

State of Shark and Ray Genomics in an Era of Extinction

Chondrichthyan species (sharks, rays, skates, and chimeras) are a class of high ecological, economic, and cultural significance, and yet they are the most threatened taxa in the marine environment. The creation of reference chromosome-length genome assemblies allows for conservation genomics methods, such as population and ecological genomics, to be utilized. Despite being greatly threatened and of great importance in maintaining ecosystem function, chondrichthyan species have been repeatedly absent from conservation-based genome sequencing projects. Less than 1% of these species have a genome sequence, despite their almost 50% either threatened or Data Deficient conservation status. Most notably, there are seven orders within this class without any genome representation. In this review, we identify gaps in chondrichthyan genomic resources and demonstrate how the lack of genomic resources for this major taxonomic class is limiting the conservation of these already difficult to conserve species. We highlight other applications for chondrichthyans genomics, such as evolutionary and developmental biology. Likely, the mismatching sampling protocols and limited computational skills and communication between fields have been preventing the integration of marine and molecular sciences. Here, we propose that this field is in dire need to move forward quickly to increase protection for marine species and ecosystems through improved collaboration between marine, molecular, and computer sciences.

Whole genome approach in conservation biology and its perspectives

Conservation biology aims to maintain biological diversity and to defend species from extinction. The number of endangered species is constantly increasing from year to year, reflecting both a deteriorating situation and an increasing number of studied species. In order to obtain a reliable assessment of the status and conservation planning of threatened species, not only an estimate of current total abundance, but also data on population structure, demographic history, and genetic diversity are needed. The development of new approaches and lower costs of sequencing have made it possible to solve these problems at a level previously inaccessible and have led to the formation of conservation genomics. This review discusses the opportunities and prospects offered by the use of whole genome sequencing in conservation biology, features of sample gathering for sequencing, as well as some features of planning whole genome studies. In addition, emphasis is placed on the importance of the formation of open biobanks of samples and cell cultures at the national level.