Aaron B.A. Shafer

Comparative Analysis of the Gut Microbial Communities in Forest and Alpine Musk Deer Using High-Throughput Sequencing

The gut ecosystem is characterized by dynamic and reciprocal interactions between the host and bacteria. Although characterizing microbiota for herbivores has become recognized as important tool for gauging species health, no study to date has investigated the bacterial communities and evaluated the age-related bacterial dynamics of musk deer. Moreover, gastrointestinal diseases have been hypothesized to be a limiting factor of population growth in captive musk deer. Here, high-throughput sequencing of the bacterial 16S rRNA gene was used to profile the fecal bacterial communities in juvenile and adult alpine and forest musk deer. The two musk deer species harbored similar bacterial communities at the phylum level, whereas the key genera for the two species were distinct. The bacterial communities were dominated by Firmicutes and Bacteroidetes, with the bacterial diversity being higher in forest musk deer. The Firmicutes to Bacteroidetes ratio also increased from juvenile to adult, while the bacterial diversity, within-group and between-group similarity, all increased with age. This work serves as the first sequence-based analysis of variation in bacterial communities within and between musk deer species, and demonstrates how the gut microbial community dynamics vary among closely related species and shift with age. As gastrointestinal diseases have been observed in captive populations, this study provides valuable data that might benefit captive management and future reintroduction programs.

Recombination and selection in the major histocompatibility complex of the endangered forest musk deer ( Moschus berezovskii )

The forest musk deer (Moschus berezovskii) is a high elevation species distributed across western China and northern Vietnam. Once abundant, habitat loss and poaching has led to a dramatic decrease in population numbers prompting the IUCN to list the species as endangered. Here, we characterized the genetic diversity of a Major Histocompatibility Complex (MHC) locus and teased apart driving factors shaping its variation. Seven DRB exon 2 alleles were identified among a group of randomly sampled forest musk deer from a captive population in the Sichuan province of China. Compared to other endangered or captive ungulates, forest musk deer have relatively low levels of MHC genetic diversity. Non-synonymous substitutions primarily occurred in the putative peptide-binding region (PBR), with analyses suggesting that recombination and selection has shaped the genetic diversity across the locus. Specifically, inter-allelic recombination generated novel allelic combinations, with evidence for both positive selection acting on the PBR and negative selection on the non-PBR. An improved understanding of functional genetic variability of the MHC will facilitate better design and management of captive breeding programs for this endangered species.

Cross-Species Application of SNP Chips is Not Suitable for Identifying Runs of Homozygosity

Cross-species application of single-nucleotide polymorphism (SNP) chips is a valid, relatively cost-effective alternative to the high-throughput sequencing methods generally required to obtain a genome-wide sampling of polymorphisms. Kharzinova et al. (2015) examined the applicability of SNP chips developed in domestic bovids (cattle and sheep) to a semi-wild cervid (reindeer). The ancestors of bovids and cervids diverged between 20 and 30 million years ago (Hassanin and Douzery 2003; Bibi et al. 2013). Empirical work has shown that for a SNP chip developed in a bovid and applied to a cervid species, approximately 50% genotype success with 1% of the loci being polymorphic is expected (Miller et al. 2012). The genotyping of Kharzinova et al. (2015) follows this pattern; however, these data are not appropriate for identifying runs of homozygosity (ROH) and can be problematic for estimating linkage disequilibrium (LD) and we caution readers in this regard.

Blood transcriptomics of captive forest musk deer ( Moschus berezovskii ) and possible associations with the immune response to abscesses

Forest musk deer (Moschus berezovskii; FMD) are both economically valuable and highly endangered. A problem for FMD captive breeding programs has been the susceptibility of FMD to abscesses. To investigate the mechanisms of abscess development in FMD, the blood transcriptomes of three purulent and three healthy individuals were generated. A total of ~39.68 Gb bases were generated using Illumina HiSeq 4000 sequencing technology and 77,752 unigenes were identified after assembling. All the unigenes were annotated, with 63,531 (81.71%) mapping to at least one database. Based on these functional annotations, 45,798 coding sequences (CDS) were detected, along with 12,697 simple sequence repeats (SSRs) and 65,536 single nucleotide polymorphisms (SNPs). A total of 113 unigenes were found to be differentially expressed between healthy and purulent individuals. Functional annotation indicated that most of these differentially expressed genes were involved in the regulation of immune system processes, particularly those associated with parasitic and bacterial infection pathways.

Recent demographic histories and genetic diversity across pinnipeds are shaped by anthropogenic interactions and mediated by ecology and life-history

A central paradigm in conservation biology is that population bottlenecks reduce genetic diversity and negatively impact population viability and adaptive potential. In an era of unprecedented biodiversity loss and climate change, understanding both the determinants and consequences of bottlenecks in wild populations is therefore an increasingly important challenge. However, as most studies have focused on single species, the multitude of potential drivers and the consequences of bottlenecks remain elusive. Here, we used a comparative approach by integrating genetic data from over 11,000 individuals of 30 pinniped species with demographic, ecological and life history data to elucidate the consequences of large-scale commercial exploitation by 18th and 19th century sealers. We show that around one third of these species exhibit strong genetic signatures of recent population declines, with estimated bottleneck effective population sizes reflecting just a few tens of surviving individuals in the most extreme cases. Bottleneck strength was strongly associated with both breeding habitat and mating system variation, and together with global abundance explained a large proportion of the variation in genetic diversity across species. Overall, there was no relationship between bottleneck intensity and IUCN status, although three of the four most heavily bottlenecked species are currently endangered. Our study reveals an unforeseen interplay between anthropogenic exploitation, ecology, life history and demographic declines, sheds new light on the determinants of genetic diversity, and is consistent with the notion that both genetic and demographic factors influence population viability.

Inferring Demographic History Using Genomic Data

Characterizing population histories has been a major focus in evolutionary and conservation biology for decades. Driven by a desire to understand population histories, researchers have been modeling simple demographic scenarios with genetic data since the 1970s. In the last decade, the availability of genomic data and the number of demographic inference methods have dramatically increased and constitute a continuously evolving sub-discipline within population genetics. Genome sequences—both reduced representation and whole-genome sequencing and re-sequencing—contain a trove of information related to population histories and permit reconstructing complex demographic scenarios. In combination with new powerful and flexible analytical methods, population demographic inference from genomic data has revealed surprising, dynamic, and conservation-relevant histories. This chapter discusses recent advancements in demographic inference made possible by genome sequence and new analytical tools. As the theory and models of demographic inference have matured, and data sets have grown, likewise has the recognition of limitations and confounding effects. We caution that the increasing sophistication of methods should not override the critical evaluation of the researcher. Demographic inferences with genomic data offer powerful windows into the past but we encourage users to recognize inherent limitations of model assumptions, use simulations to identify potential biases, and include complementary and supporting analyses.

Methylation patterns reveal cryptic structure and a pathway for adaptation in a panmictic carnivore

ABSTRACT Determining the molecular signatures of adaptive differentiation is a fundamental component of evolutionary biology. A key challenge remains for identifying such signatures in wild organisms, particularly between populations of highly mobile species that undergo substantial gene flow. The Canada lynx (Lynx canadensis) is one species where mainland populations appear largely undifferentiated at traditional genetic markers, despite inhabiting diverse environments and displaying phenotypic variation. Here, we used high-throughput sequencing to investigate both neutral genetic structure and epigenetic differentiation across the distributional range of Canada lynx. Using a customized bioinformatics pipeline we scored both neutral SNPs and methylated nucleotides across the lynx genome. Newfoundland lynx were identified as the most differentiated population at neutral genetic markers, with diffusion approximations of allele frequencies indicating that divergence from the panmictic mainland occurred at the end of the last glaciation, with minimal contemporary admixture. In contrast, epigenetic structure revealed hidden levels of differentiation across the range coincident with environmental determinants including winter conditions, particularly in the peripheral Newfoundland and Alaskan populations. Several biological pathways related to morphology were differentially methylated between populations, with Newfoundland being disproportionately methylated for genes that could explain the observed island dwarfism. Our results indicate that epigenetic modifications, specifically DNA methylation, are powerful markers to investigate population differentiation and functional plasticity in wild and non-model systems. SIGNIFICANCE Populations experiencing high rates of gene flow often appear undifferentiated at neutral genetic markers, despite often extensive environmental and phenotypic variation. We examined genome-wide genetic differentiation and DNA methylation between three interconnected regions and one insular population of Canada lynx (Lynx canadensis) to determine if epigenetic modifications characterized climatic associations and functional molecular plasticity. Demographic approximations indicated divergence of Newfoundland during the last glaciation, while cryptic epigenetic structure identified putatively functional differentiation that might explain island dwarfism. Our study suggests that DNA methylation is a useful marker for differentiating wild populations, particularly when faced with functional plasticity and low genetic differentiation.Determining molecular signatures of population divergence is a fundamental component of evolutionary biology. Identifying divergence is particularly challenging between populations of highly mobile species that undergo substantial gene flow, such as the Canada lynx (Lynx canadensis), where populations are considered panmictic when only neutral genetic markers are considered. Here, we used high-throughput bisulfite sequencing to examine the environmental determinants of methylation structure across the distributional range of Canada lynx. Despite a high degree of genetic similarity among mainland populations, epigenetic structure did not mirror these neutral patterns, instead showing environmental associations and high levels of divergence in the peripheral Newfoundland and Alaskan populations. Interestingly, a disproportionate number of genes related to body-size were hypermethylated on the island of Newfoundland, providing a possible mechanism for adaptive evolution and the observed island effect on organism size. Our results indicate that epigenetic modifications, specifically DNA methylation, are powerful markers to investigate adaptive divergence and rapid evolutionary response.

Population Genomics of Ungulates

Humans have long relied on ungulates for food, clothing, manual labor, and transportation. Ungulates were among the first species to be domesticated and managed in the wild, but more than one-third of species are currently of conservation concern. Starting in the late twentieth century, ungulate research and management began employing genetic tools to assess attributes like the degree of population structure, inbreeding, and variation in functionally important genes. As sequencing technology advanced, research on ungulates shifted to now assay variation across the entire genome. More than 20 ungulates have had their genome assembled with a mean length of 2.6 Gb and N50 of 26 Mb. Genomic studies have provided deeper insights into the evolutionary relationships among giraffes and bovids, while camelids and horses have had their entire species demographic histories reconstructed using novel Markovian coalescent models. Moreover, artificial and natural selection has left clear signatures on ungulate genomes with high-throughput sequencing techniques being used to identify the genetic basis to important phenotypic traits. Novel assembly strategies and genomic assays are regularly being employed on ungulates, and research on this ecological and economically valuable group will help chart the course of the emerging field of wildlife genomics.

Genome Sequence of Peacock Reveals the Peculiar Case of a Glittering Bird

The unique ornamental features and extreme sexual traits of Peacock have always intrigued scientists and naturalists for centuries. However, the genomic basis of these phenotypes are yet unknown. Here, we report the first genome sequence and comparative analysis of peacock with the high quality genomes of chicken, turkey, duck, flycatcher and zebra finch. Genes involved in early developmental pathways including TGF-β, BMP, and Wnt signaling, which have been shown to be involved in feather patterning, bone morphogenesis, and skeletal muscle development, revealed signs of adaptive evolution and provided useful clues on the phenotypes of peacock. Innate and adaptive immune genes involved in complement system and T-cell response also showed signs of adaptive evolution in peacock suggesting their possible role in building a robust immune system which is consistent with the predictions of the Hamilton–Zuk hypothesis. This study provides novel genomic and evolutionary insights into the molecular understanding toward the phenotypic evolution of Indian peacock.

Meta-barcoding insights into the spatial and temporal dietary patterns of the threatened Asian Great Bustard (Otis tarda dybowskii) with potential implications for diverging migratory strategies

Abstract Food resources are often not sufficient to satisfy the nutritional and energetic requirements during winter conditions at high latitudes. Dietary analysis is a prerequisite to fully understanding the feeding ecology of a species and the nature of trophic interactions. Previous dietary studies of Asian Great Bustard (Otis tarda dybowskii) relied on behavioral observations, resulting in categorization of diet limited to broad taxonomic groupings. Here, we applied a high‐throughput sequencing meta‐barcoding approach to quantify the diet of resident and migratory Asian Great Bustard in three wintering sites during early winter and late winter. We detected 57 unique plant taxa in the bustard diet, among which 15 species were confirmed by a local plant database we generated. Both agricultural and natural foods were detected, indicating a relatively broad dietary niche. Spatiotemporal dietary changes were discovered, revealing diet differences among wintering sites and a general shift toward lower plant diversity later in winter. For the nonmigratory population, we detected a significantly more diverse array of plant species in their diet. We hypothesize that dietary variation between resident and migratory populations could be involved in the recent transition to partial migration in this species, although climate change can not be excluded. Collectively, these results support protecting unharvested grain fields and naturally unplowed lands to help conserve and promote population growth of Asian Great Bustard.