Genetic variation and population structure of the Japanese sika deer (Cervus nippon) in the Tohoku District based on mitochondrial D-loop sequences

A historic religious sanctuary may have preserved ancestral genetics of Japanese sika deer (Cervus nippon)

Deer have been a major resource for human populations for thousands of years. Anthropogenic activities, such as hunting, have influenced the genetic structure and distribution of deer populations. In Japan, wild Japanese sika deer (Cervus nippon) have been hunted since ancient times but have also been historically protected as sacred animals in several sanctuaries. Sika deer have been protected for over a thousand years in the religious sanctuary around the Kasuga Taisha Shrine on the Kii Peninsula, located in the center of Japan. Here, we used short sequence repeats (SSR) and mitochondrial DNA (mtDNA) to investigate the genetic diversity, population structure, and demography of Japanese sika deer inhabiting the Kii Peninsula, Japan, and discuss possible anthropogenic influences. Using SSR, three distinct genetic groups were distinguished on the Kii Peninsula: an Eastern genetic group, a Western genetic group, and an isolated genetic group with individuals in the religious sanctuary of Kasuga Taisha Shrine in Nara city. The isolated genetic sanctuary group had only the mtDNA haplotype S4. The SSR genotype data suggested a newer divergence time of the genetic groups of the religious sanctuary than would have occurred as a result of Late Quaternary climate change. This time scale coincided with the establishment of the sanctuary with Kasuga Taisha Shrine. Thus, the religious protection conserved genetic variation over a thousand years.

Genetic Variation in Y-Chromosome Genes of Sika Deer (Cervus nippon) in Japan

Sika deer (Cervus nippon) in Japan are classified into southern and northern groups. However, previous studies primarily relied on maternally inherited mitochondrial DNA (mtDNA). The paternally inherited Y-chromosome is useful for analyzing the contribution of males to the population genetic history of sika deer. In total, approximately 16 kb of partial sequences of four Y-chromosomal genes, Y-linked, sex-determining region Y, DEAD-box helicase 3 Y-linked, and Zinc finger protein Y-linked, were sequenced to investigate intraspecific variation. As a result, we identified nine intronic single nucleotide polymorphisms (SNPs) in 478 sika deer samples collected over the entire Japanese archipelago from Hokkaido to Kyushu. SNP genotyping revealed 10 distinct haplotypes (SYH1-SYH10). The most common haplotype (SYH1) was present in all populations and was the most abundant haplotype, identified in 80.3% of the sampled individuals. The remaining haplotypes were unique to a single locality. SYH1 was also central to all other haplotypes that diverged by a SNP, resulting in this haplotype being the core of a star-like cluster topography. We found that contrary to mtDNA patterns, there was no clear differentiation of Y-chromosome markers between the southern and the northern populations. Due to the female philopatry of sika deer, mtDNA may provide a highly structured differentiation of populations. On the other hand, the male-biased gene flow may provide a reduced differentiation of populations. Our findings revealed that the genetic structure of the Japanese sika deer is more complex than previously thought based on mtDNA-based phylogeographic studies.

Genome-Wide SNP Discovery and Analysis of Genetic Diversity in Farmed Sika Deer (Cervus nippon) in Northeast China Using Double-Digest Restriction Site-Associated DNA Sequencing

Sika deer are an economically valuable species owing to their use in traditional Chinese medicine, particularly their velvet antlers. Sika deer in northeast China are mostly farmed in enclosure. Therefore, genetic management of farmed sika deer would benefit from detailed knowledge of their genetic diversity. In this study, we generated over 1.45 billion high-quality paired-end reads (288 Gbp) across 42 unrelated individuals using double-digest restriction site-associated DNA sequencing (ddRAD-seq). A total of 96,188 (29.63%) putative biallelic SNP loci were identified with an average sequencing depth of 23×. Based on the analysis, we found that the majority of the loci had a deficit of heterozygotes (F_IS >0) and low values of H_obs, which could be due to inbreeding and Wahlund effects. We also developed a collection of high-quality SNP probes that will likely be useful in a variety of applications in genotyping for cervid species in the future.