Divergence and introgression in small apes, the genus Hylobates, revealed by reduced representation sequencing

Gibbons in the genus Hylobates, which live in Southeast Asia, show great diversity, comprising seven to nine species. Natural hybridisation has been observed in the species contact zones, although the roles played by hybridisation and introgression in the evolution of these species remain unclear. To uncover the divergence history and the contributions of hybridisation and introgression to the evolution of Hylobates, random amplicon sequencing-direct (GRAS-Di) analysis was employed to genotype 47 gibbons, representing eight species from three genera. After quality filtering, over 300,000 autosomal single-nucleotide variant (SNV) sites were identified. The SNV-based autosomal phylogeny, together with the mitochondrial phylogeny, supported a divergence pattern beginning approximately 4.3 million years ago. First, the mainland species, H. pileatus and H. lar, consecutively diverged from the Sundaic island species. Second, H. moloch, in Java (and likely H. klossii, in the Mentawai Islands) diverged from the other species. Third, H. muelleri, in Borneo, and H. agilis/H. albibarbis, in Sumatra and southwestern Borneo, diverged. Lastly, H. agilis and H. albibarbis diverged from each other. The Patterson’s D-statistics indicated significant introgression between H. lar and H. pileatus, between H. lar and H. agilis, and between H. albibarbis and H. muelleri, and weak introgression was identified between H. moloch and H. albibarbis, and between H. moloch and H. muelleri abbotti, suggesting incomplete reproductive barriers among Hylobates species and that hybridisation and introgression occur whenever the distribution ranges contact. Some candidates for introgressed genomic regions were detected, and the functions of these would be revealed by further genome-wide studies.

Emergence of multiple variants of SARS-CoV-2 with signature structural changes

This study explores the divergence pattern of SARS-CoV-2 using whole genome sequences of the isolates from various COVID-19 affected countries. The phylogenomic analysis indicates the presence of at least four distinct groups of the SARS-CoV-2 genomes. The emergent groups have been found to be associated with signature structural changes in specific proteins. Also, this study reveals the differential levels of divergence patterns for the protein coding regions. Moreover, we have predicted the impact of structural changes on a couple of important viral proteins via structural modelling techniques. This study further advocates for more viral genetic studies with associated clinical outcomes and hosts’ response for better understanding of SARS-CoV-2 pathogenesis enabling better mitigation of this pandemic situation.

Rates of ecomorphological trait evolution in passerine bird clades are independent of age

Although the links between species richness and diversification rates with clade age have been studied extensively, few studies have investigated the relationship between the rates of trait evolution and clade age. The rate of morphological trait evolution has repeatedly been shown to vary through time, as expected, for example, for adaptive radiations, but the strength and sources of this variation are not well understood. We compare the relationship between the rates of trait evolution and clade age across eight monophyletic clades of passerine birds by investigating ecomorphological traits, i.e. morphological traits that influence the ecology of the species directly. We study the ecomorphological divergence pattern using analyses of the disparity through time and determine the best-fitting model of evolution for each trait in each clade. We find no support for a consistent dependence of evolutionary rates on clade age across wing, tail, tarsus and beak shape in our eight clades and also show that early burst models of trait evolution are rarely the best-fitting models within these clades. These results suggest that key innovations or adaptive radiations might be less common evolutionary patterns and processes than generally thought or might depend on the taxonomic level investigated.

Phylogeny, transposable element and sex chromosome evolution of the basal lineage of birds

Sex chromosomes of mammals and most birds are heteromorphic, while those of many paleognaths (ratites and tinamous) are inexplicably homomorphic. To dissect the mechanisms underlying the different tempo of sex chromosome evolution, we produced high-quality genomes of 12 paleognathous species, and reconstructed their phylogeny based on alignments of the non-coding sequences extending to nearly 40% of the genome. Our phylogenomic tree grouped the South American rheas and tinamous together, and supported the independent evolution of gigantism and loss of flight among ratites. The small-bodied tinamous have much higher rates of genome-wide substitutions and transposon turnovers. Yet majorities of both have retained exceptionally long recombining regions occupying over half of the entire sex chromosome, with the rest sex-linked regions diverging from each other at a much lower rate relative to neognathous birds. Each species exhibits a punctuated sequence divergence pattern between sex chromosomes termed ‘evolutionary strata’, because of stepwise suppression of recombination. We concluded that all paleognaths share one evolutionary stratum with all other birds, and convergently formed between one to three strata after their rapid speciation. Contrary to the classic notion, we provided clear evidence that the youngest stratum of some tinamous formed without chromosomal inversion. Intriguingly, some of the encompassing W-linked genes have upregulated their expression levels in ovary, probably due to the female-specific selection. We proposed here that the unique male-only parental care system of paleognaths has reduced the intensity of sexual selection, and contributed to these species’ low rates of sex chromosome evolution. We also provided novel insights into the evolution of W-linked genes at their early stages.

Industrial Productivity Divergence and Input-Output Network Structures: Evidence from Japan 1973–2012

Since the early 1990s, there have been larger and increasing labor productivity differences across industries in Japan. More specifically, a clear pattern of sigma and beta divergence across industries is observed. To shed light on these stylized facts, we first evaluate the input–output structure of Japan through the lens of a community-detection algorithm from network theory. Results from this analysis suggest the existence of two input–output network structures: a densely-connected group of industries (a stationary community), whose members remain in it throughout the period; and a group of industries (a transitional community) whose members do not belong to this first group. Next, we re-evaluate the industrial divergence pattern of Japan in the context of each network structure. Results suggest that divergence is mostly driven by the transitional community. Interestingly, since 2007, a pattern of sigma convergence started to re-appear only in the stationary community. We conclude suggesting that industrial divergence and instability in community membership are not necessarily indicative of low productivity performance.