ABSTRACT
Pangolins are among the most critically endangered animals due to heavy poaching and worldwide trafficking. However, their demographic histories and the genomic consequences of their recent population declines remain unknown. We generated high-quality de novo reference genomes for critically endangered Malayan (Manis javanica, MJ) and Chinese (M. pentadactyla, MP) pangolins and re-sequencing population genomic data from 74 MJs and 23 MPs. We recovered the population identities of illegally traded pangolins and previously unrecognized genetic populations that should be protected as evolutionarily distinct conservation units. Demographic reconstruction suggested environmental changes have resulted in a population size fluctuation of pangolins. Additionally, recent population size declines due to human activities have resulted in an increase in inbreeding and genetic load. Deleterious mutations were enriched in genes related to cancer/diseases and cholesterol homeostasis, which may have increased their susceptibility to diseases and decreased their survival potential to adapt to environmental changes and high-cholesterol diets. This comprehensive study provides not only high-quality pangolin reference genomes, but also valuable information concerning the driving factors of long-term population size fluctuations and the genomic impact of recent population size declines due to human activities, which is essential for pangolin conservation management and global action planning.
ABSTRACT
With rapid advances in next-generation sequencing technologies, the genomes of many organisms have been sequenced and widely applied in different settings. Mitochondrial genome data is equally important and the high-throughput whole-genome data typically contain mitochondrial genome (mitogenome) sequences. How to extract and assemble the mitogenome from massive whole-genome sequencing (WGS) data remain a hot area in molecular biology, genetics and medicine. The cataloging and analysis of accumulating mitogenome data promotes the development of assembly strategies and corresponding software applications related to mitochondrial DNA from the WGS data. Mitogenome assembly strategies can be divided into mitogenome-reference strategy and de novo strategy. Each strategy has different advantages and limitations with respect to the difference of bait mitogenome-linked short reads from the WGS data and corresponding assembly strategy. In this review, we summarize and compare current mitogenome assembly strategies and the software applications available. We also provide suggestions related to use different assembly strategies and software applications, and the expected benefits and limitations of methods references in life science.
Subject(s)
Genome, Mitochondrial , Software , High-Throughput Nucleotide Sequencing , Sequence Analysis, DNA , Whole Genome SequencingABSTRACT
The origin and population history of the endangered golden snub-nosed monkey (Rhinopithecus roxellana) remain largely unavailable and/or controversial. We here integrate analyses of multiple genomic markers, including mitochondrial (mt) genomes, Y-chromosomes, and autosomes of 54 golden monkey individuals from all three geographic populations (SG, QL, and SNJ). Our results reveal contrasting population structures. Mt analyses suggest a division of golden monkeys into five lineages: one in SNJ, two in SG, and two in QL. One of the SG lineages (a mixed SG/QL lineage) is basal to all other lineages. In contrast, autosomal analyses place SNJ as the most basal lineage and identify one QL and three SG lineages. Notably, Y-chromosome analyses bear features similar to mt analyses in placing the SG/QL-mixed lineage as the first diverging lineage and dividing SG into two lineages, while resembling autosomal analyses in identifying one QL lineage. We further find bidirectional gene flow among all three populations at autosomal loci, while asymmetric gene flow is suggested at mt genomes and Y-chromosomes. We propose that different population structures and gene flow scenarios are the result of sex-linked differences in the dispersal pattern of R. roxellana. Moreover, our demographic simulation analyses support an origin hypothesis suggesting that the ancestral R. roxellana population was once widespread and then divided into SNJ and non-SNJ (SG and QL) populations. This differs from previous mt-based "mono-origin (SG is the source population)" and "multiorigin (SG is a fusion of QL and SNJ)" hypotheses. We provide a detailed and refined scenario for the origin and population history of this endangered primate species, which has a broader significance for Chinese biogeography. In addition, this study highlights the importance to investigate multiple genomic markers with different modes of inheritance to trace the complete evolutionary history of a species, especially for those exhibiting differential or mixed patterns of sex dispersal.
