Population genomic analysis provides evidence of the past success and future potential of South China tiger captive conservation.

BACKGROUND: Among six extant tiger subspecies, the South China tiger (Panthera tigris amoyensis) once was widely distributed but is now the rarest one and extinct in the wild. All living South China tigers are descendants of only two male and four female wild-caught tigers and they survive solely in zoos after 60 years of effective conservation efforts. Inbreeding depression and hybridization with other tiger subspecies were believed to have occurred within the small, captive South China tiger population. It is therefore urgently needed to examine the genomic landscape of existing genetic variation among the South China tigers. RESULTS: In this study, we assembled a high-quality chromosome-level genome using long-read sequences and re-sequenced 29 high-depth genomes of the South China tigers. By combining and comparing our data with the other 40 genomes of six tiger subspecies, we identified two significantly differentiated genomic lineages among the South China tigers, which harbored some rare genetic variants introgressed from other tiger subspecies and thus maintained a moderate genetic diversity. We noticed that the South China tiger had higher FROH values for longer runs of homozygosity (ROH > 1 Mb), an indication of recent inbreeding/founder events. We also observed that the South China tiger had the least frequent homozygous genotypes of both high- and moderate-impact deleterious mutations, and lower mutation loads than both Amur and Sumatran tigers. Altogether, our analyses indicated an effective genetic purging of deleterious mutations in homozygous states from the South China tiger, following its population contraction with a controlled increase in inbreeding based on its pedigree records. CONCLUSIONS: The identification of two unique founder/genomic lineages coupled with active genetic purging of deleterious mutations in homozygous states and the genomic resources generated in our study pave the way for a genomics-informed conservation, following the real-time monitoring and rational exchange of reproductive South China tigers among zoos.

Chromosome-scale genomes reveal genomic consequences of inbreeding in the South China tiger: A comparative study with the Amur tiger.

The South China tiger (Panthera tigris amoyensis, SCT) is the most critically endangered subspecies of tiger due to functional extinction in the wild. Inbreeding depression is observed among the captive population descended from six wild ancestors, resulting in high juvenile mortality and low reproduction. We assembled and characterized the first SCT genome and an improved Amur tiger (P. t. altaica, AT) genome named AmyTig1.0 and PanTig2.0. The two genomes are the most continuous and comprehensive among any tiger genomes yet reported at the chromosomal level. By using the two genomes and resequencing data of 15 SCT and 13 AT individuals, we investigated the genomic signature of inbreeding depression of the SCT. The results indicated that the effective population size of SCT experienced three phases of decline, ~5.0-1.0 thousand years ago, 100 years ago, and since captive breeding in 1963. We found 43 long runs of homozygosity fragments that were shared by all individuals in the SCT population and covered a total length of 20.63% in the SCT genome. We also detected a large proportion of identical-by-descent segments across the genome in the SCT population, especially on ChrB4. Deleterious nonsynonymous single nucleotide polymorphic sites and loss-of-function mutations were found across genomes with extensive potential influences, despite a proportion of these loads having been purged by inbreeding depression. Our research provides an invaluable resource for the formulation of genetic management policies for the South China tiger such as developing genome-based breeding and genetic rescue strategy.

Food handling shapes the laterality of paw use in the Chinese red panda (Ailurus styani).

Limb preference, associated with behavioural laterality and hemispheric lateralization, has long received high attention from both ethologists and psychologists. Chinese red pandas in Shanghai Zoo perform natural unimanual actions in two different ways during food handling, making it an appropriate subject to investigate the effect of food handling on pawedness. In this study, we estimated the direction and the strength of pawedness in spontaneous feeding behaviours in zoo-housed Chinese red pandas. All the subjects exclusively used the preferred paw when handling fruit pieces throughout the observational period, with three of them preferred the left paw while the other two the right paw. By contrast, both paws were found to be used alternately in consuming bamboo. Our results indicate that different food manipulations have effects on pawedness in the Chinese red panda where more complex handling could probably enhance its pawedness.

The gut microbiota of gibbons across host genus and captive site in China.

Gut microbiota influences nutrient metabolism and immunity of animal hosts. Better understanding of the composition and diversity of gut microbiota contributes to conservation and management of threatened animals both in situ and ex situ. In this study, we applied 16S rRNA gene amplicon sequencing to evaluate the composition and diversity of the fecal bacterial community of four gibbon genera (Family Hylobatidae) at four Chinese zoos. The results showed that the dominant bacterial phyla were Bacteroidetes, Firmicutes, and Proteobacteria and dominant families were Prevotellaceae (Bacteroidetes), Spirochaetaceae (Spirochaetes) and Ruminococcaceae (Firmicutes) in the gut of all gibbons. Both captive site and host genus had significant effects on the relative abundance of dominant bacteria and structure of gut bacterial community. We found that captive site and host genus did not solely impact gut bacterial diversity, but the interaction between them did. This study provides basic knowledge for gut microbiota of all four gibbon genera and contributes to management and conservation of captive gibbons.

Horizontal transmission and recombination of Wolbachia in the butterfly tribe Aeromachini Tutt, 1906 (Lepidoptera: Hesperiidae).

Wolbachia is arguably one of the most ubiquitous heritable symbionts among insects and understanding its transmission dynamics is crucial for understanding why it is so common. While previous research has studied the transmission pathways of Wolbachia in several insect lineages including Lepidoptera, this study takes advantage of data collected from the lepidopteran tribe Aeromachini in an effort to assess patterns of transmission. Twenty-one of the 46 species of Aeromachini species were infected with Wolbachia. Overall, 25% (31/125) of Aeromachini specimens tested were Wolbachia positive. All Wolbachia strains were species-specific except for the wJho strain which appeared to be shared by three host species with a sympatric distribution based on a cophylogenetic comparison between Wolbachia and the Aeromachini species. Two tests of phylogenetic congruence did not find any evidence for cospeciation between Wolbachia strains and their butterfly hosts. The cophylogenetic comparison, divergence time estimation, and Wolbachia recombination analysis revealed that Wolbachia acquisition in Aeromachini appears to have mainly occurred mainly through horizontal transmission rather than codivergence.

Mirror responses in the common hill myna (Gracula religiosa) and the African grey parrot (Psittacus erithacus).

Scientists have spent great efforts exploring self-recognition in non-human animals using the mirror test. In avian species, some of the passerines have passed the test, although the findings are still under debate. The present study aimed at investigating mirror self-recognition ability and making a comparative study of mirror responses in two avian species, the common hill myna from the Passeriformes and the African grey parrot from the Psittaciformes. The subjects underwent four stages of experiment: habituation, baseline, mirror exposure and mark test. Our subjects spent significantly longer time in gazing into the mirror than the plexiglass as control. We also found they significantly increased the durations of grooming behaviour when presented with the mirror. No species difference was detected in the above two behaviours. However, the African grey parrots were more likely to approach the mirror than the common hill mynas, indicating their different ways of mirror exploration. All subjects failed to pass the mark test. In this study, we found no evidence of mirror self-recognition in the common hill myna and the African grey parrot.

The complete mitochondrial genome of De Brazza's monkey (Cercopithecus neglectus).

The complete mitochondrial genome of Cercopithecus neglectus was described. The mitogenome is 16,490 bp in length and consists 13 protein-coding genes (PCGs), 22 transfer-RNA genes, two ribosomal-RNA genes, and one non-coding region. All the 13 PCGs were 11,398 bp in length with most common start codon of ATG and termination codon of TAA. The overall GC content was 42.5%. The result of phylogenetic analysis showed that the relationship of C. neglectus was close to C. mona, C. pogonias, C. wolfi and C. denti.

Accelerated evolution of an Lhx2 enhancer shapes mammalian social hierarchies.

Social hierarchies emerged during evolution, and social rank influences behavior and health of individuals. However, the evolutionary mechanisms of social hierarchy are still unknown in amniotes. Here we developed a new method and performed a genome-wide screening for identifying regions with accelerated evolution in the ancestral lineage of placental mammals, where mammalian social hierarchies might have initially evolved. Then functional analyses were conducted for the most accelerated region designated as placental-accelerated sequence 1 (PAS1, P = 3.15 × 10-18). Multiple pieces of evidence show that PAS1 is an enhancer of the transcription factor gene Lhx2 involved in brain development. PAS1s isolated from various amniotes showed different cis-regulatory activity in vitro, and affected the expression of Lhx2 differently in the nervous system of mouse embryos. PAS1 knock-out mice lack social stratification. PAS1 knock-in mouse models demonstrate that PAS1s determine the social dominance and subordinate of adult mice, and that social ranks could even be turned over by mutated PAS1. All homozygous mutant mice had normal huddled sleeping behavior, motor coordination and strength. Therefore, PAS1-Lhx2 modulates social hierarchies and is essential for establishing social stratification in amniotes, and positive Darwinian selection on PAS1 plays pivotal roles in the occurrence of mammalian social hierarchies.

Molecular Phylogeny and Historical Biogeography of the Butterfly Tribe Aeromachini Tutt (Lepidoptera: Hesperiidae) from China.

: The butterfly tribe Aeromachini Tutt, 1906 is a large group of skippers. In this study, a total of 10 genera and 45 species of putative members of this tribe, which represent most of the generic diversity and nearly all the species diversity of the group in China, were sequenced for two mitochondrial genes and three nuclear genes (2093 bp). The combined dataset was analyzed with maximum likelihood inference using IQtree. We found strong support for monophyly of Aeromachini from China and support for the most recent accepted species in the tribe. Two paraphyletic genera within Aeromachini are presented and discussed. The divergence time estimates with BEAST and ancestral-area reconstructions with RASP provide a detailed description about the historical biogeography of the Aeromachini from China. The tribe very likely originated from the Hengduan Mountains in the late Ecocene and expanded to the Himalaya Mountains and Central China Regions. A dispersal-vicariance analysis suggests that dispersal events have played essential roles in the distribution of extant species, and geological and climatic changes have been important factors driving current distribution patterns.