Detecting Genetic Ancestry and Adaptation in the Taiwanese Han People.

The Taiwanese people are composed of diverse indigenous populations and the Taiwanese Han. About 95% of the Taiwanese identify themselves as Taiwanese Han, but this may not be a homogeneous population because they migrated to the island from various regions of continental East Asia over a period of 400 years. Little is known about the underlying patterns of genetic ancestry, population admixture, and evolutionary adaptation in the Taiwanese Han people. Here, we analyzed the whole-genome single-nucleotide polymorphism genotyping data from 14,401 individuals of Taiwanese Han collected by the Taiwan Biobank and the whole-genome sequencing data for a subset of 772 people. We detected four major genetic ancestries with distinct geographic distributions (i.e., Northern, Southeastern, Japonic, and Island Southeast Asian ancestries) and signatures of population mixture contributing to the genomes of Taiwanese Han. We further scanned for signatures of positive natural selection that caused unusually long-range haplotypes and elevations of hitchhiked variants. As a result, we identified 16 candidate loci in which selection signals can be unambiguously localized at five single genes: CTNNA2, LRP1B, CSNK1G3, ASTN2, and NEO1. Statistical associations were examined in 16 metabolic-related traits to further elucidate the functional effects of each candidate gene. All five genes appear to have pleiotropic connections to various types of disease susceptibility and significant associations with at least one metabolic-related trait. Together, our results provide critical insights for understanding the evolutionary history and adaption of the Taiwanese Han population.

Genetic Differentiation and Demographic Trajectory of the Insular Formosan and Orii's Flying Foxes.

Insular flying foxes are keystone species in island ecosystems due to their critical roles in plant pollination and seed dispersal. These species are vulnerable to population decline because of their small populations and low reproductive rates. The Formosan flying fox (Pteropus dasymallus formosus) is one of the 5 subspecies of the Ryukyu flying fox. Pteropus dasymallus formosus has suffered from a severe decline and is currently recognized as a critically endangered population in Taiwan. On the contrary, the Orii's flying fox (Pteropus dasymallus inopinatus) is a relatively stable population inhabiting Okinawa Island. Here, we applied a genomic approach called double digest restriction-site associated DNA sequencing to study these 2 subspecies for a total of 7 individuals. We detected significant genetic structure between the 2 populations. Despite their contrasting contemporary population sizes, both populations harbor very low degrees of genetic diversity. We further inferred their demographic history based on the joint folded site frequency spectrum and revealed that both P. d. formosus and P. d. inopinatus had maintained small population sizes for a long period of time after their divergence. Recently, these populations experienced distinct trajectories of demographic changes. While P. d. formosus suffered from a drastic ~10-fold population decline not long ago, P. d. inopinatus underwent a ~4.5-fold population expansion. Our results suggest separate conservation management for the 2 populations-population recovery is urgently needed for P. d. formosus while long-term monitoring for adverse genetic effects should be considered for P. d. inopinatus.