Genetic diversity of the Japanese Marten (Martes melampus) and its implications for the conservation unit

Biogeography of Korea's top predator, the yellow-throated Marten: evolutionary history and population dynamics

BACKGROUND

Peninsulas often harvest high genetic diversity through repeated southward migrations of species during glacial maxima. Studies addressing within-species evolutionary responses to climate fluctuations in northeast Asia are limited compared to other regions of the world, and more so in the Korean Peninsula. In this study, we conducted the first population-level study of the yellow-throated marten, Martes flavigula, from the Korean Peninsula, Russian, Taiwanese and Chinese localities in a biogeographic framework using mitochondrial (cyt-b, nd2, cr) and nuclear gene sequencing (ghr).

RESULTS

Bayesian analyses revealed a rather young population, with a split from the most recent common ancestor at around 125 kya. Martes flavigula likely colonized the Korean Peninsula from Mainland China through the Yellow Sea twice, ca. 60 kya and 20 kya. Korean martens diversified during the Late Pleistocene with at least two dispersal events out of Korea, towards the southwest to Taiwan (ca. 80 kya) and towards the North into Russia and eastern China; most likely after the Last Glacial Maxima (ca. 20 kya). We argue that the lack of population structure and mixed populations is possibly a consequence of the high dispersal capability of the species. The Bayesian skyline plot revealed a population decline within the last 5000 years, suggesting potential negative biotic and anthropogenic effects in the area. We find that local populations are not genetically differentiated, therefore no perceptible population structure within Korea was found.

CONCLUSIONS

The topography and geography of the Korean Peninsula has played a pivotal role in its colonization. Connections between the Korean Peninsula and the Mainland through sea-level drops of the Yellow Sea at times of glacial maxima and the high dispersal capability of M. flavigula adds to the lack of geographical structure in this species and the paraphyly of Korean lineages.

A mitogenomic phylogeny and genetic history of sable (Martes zibellina)

We assessed phylogeny of sable (Martes zibellina, Linnaeus, 1758) by sequence analysis of nearly complete, new mitochondrial genomes in 36 specimens from different localities in northern Eurasia (Primorye, Khabarovsk and Krasnoyarsk regions, the Kamchatka Peninsula, the Kuril Islands and the Urals). Phylogenetic analysis of mtDNA sequences demonstrates that two clades, A and BC, radiated about 200-300 thousandyears ago (kya) according to results of Bayesian molecular clock and RelTime analyses of different mitogenome alignments (nearly complete mtDNA sequences, protein-coding region, and synonymous sites), while the age estimates of clades A, B and C fall within the Late Pleistocene (~50-140 kya). Bayesian skyline plots (BSPs) of sable population size change based on analysis of nearly complete mtDNAs show an expansion around 40 kya in the warm Karganian time, without a decline of population size around the Last Glacial Maximum (21 kya). The BSPs based on synonymous clock rate indicate that M. zibellina experienced demographic expansions later, approximately 22 kya. The A2a clade that colonized Kamchatka ~23-50 kya (depending on the mutation rate used) survived the last glaciation there as demonstrated by the BSP analysis. In addition, we have found evidence of positive selection acting at ND4 and cytochrome b genes, thereby suggesting adaptive evolution of the A2a clade in Kamchatka.

Genetic distinctness and variation in the Tsushima Islands population of the Japanese marten, Martes melampus (Carnivora: Mustelidae), revealed by microsatellite analysis

A carnivoran mammal endemic to Japan, the Japanese marten (Martes melampus) is native in forested regions on Honshu, Shikoku, Kyushu (main islands of Japan), and the Tsushima Islands. The Tsushima population is classified as a different subspecies (M. m. tsuensis) from populations on the main islands (M. m. melampus). To elucidate the genetic structure of the Tsushima population, we genotyped 101 individuals from the Tsushima Islands and 43 individuals from Honshu and Kyushu using 10 microsatellite loci, and performed population genetic analyses on the genotype data. Genetic diversity was lower in the Tsushima population than in three geographic populations on the main islands: heterozygosity was 0.189-0.364 in the former, compared to 0.457-0.747 in the latter. In addition, high pairwise Fst values (0.485-0.682) and Nei's standard distance (0.550-1.183) between the Tsushima and main-island populations indicated a high degree of genetic differentiation. Finally, a Bayesian clustering analysis showed that the Tsushima population is apparently differentiated from the main-island populations and comprises two genetic clusters. A factorial correspondence analysis corroborated these results. Our results suggest that restricted gene flow or inbreeding may have reduced genetic diversity in the Tsushima population, which has been geographically isolated from the main-island populations since the formation of Tsushima Strait.

Investing in evolutionary history: implementing a phylogenetic approach for mammal conservation

Under the impact of human activity, global extinction rates have risen a thousand times higher than shown in the fossil record. The resources available for conservation are insufficient to prevent the loss of much of the world's threatened biodiversity during this crisis. Conservation planners have been forced to prioritize their protective activities, in the context of great uncertainty. This has become known as 'the agony of choice'. A range of methods have been proposed for prioritizing species for conservation attention; one of the most strongly supported is prioritizing those species that maximize phylogenetic distinctiveness (PD). We evaluate how a composite measure of extinction risk and phylogenetic isolation (EDGE) has been used to prioritize species according to their degree of unique evolutionary history (evolutionary distinctiveness, ED) weighted by conservation urgency (global endangerment, GE). We review PD-based approaches and provide an updated list of EDGE mammals using the 2010 IUCN Red List. We evaluate how robust this method is to changes in phylogenetic uncertainty, knowledge of taxonomy and extinction risk, and examine how mammalian species that rank highly in EDGE score are representative of the collective from which they are drawn.

Microsatellite variability of Sardinian pine martens, Martes martes

The pine marten, Martes martes, is a medium-sized terrestrial carnivore associated with woodland habitats of the western Palearctic region. The present distribution area of the species also includes six islands of the western Mediterranean basin. The origin of these insular populations and their taxonomic status are still debated; their molecular characterization appears relevant for conservation purposes. To describe the genetic variability of the pine martens from Sardinia we characterized 40 insular and 14 Italian individuals at seven nuclear microsatellite loci. The identification of private alleles and the calculated F(ST) value of 0.074 revealed some genetic differentiation between the two populations, which accounts for the high percentages of correct allocation (96.39-98.80%) scored by the genotype assignment test. The presence of two distinct clusters corresponding to Sardinia and mainland Italy was further confirmed by the multivariate Factorial Correspondence Analysis of individual genotypes. Moreover, the genome of the Sardinian individuals bore signs of past demographic fluctuations, i.e. the presence of the monomorphic locus Ma-4, a lower allelic richness and a lower number of private alleles, which may derive from the combination of drift, founder effects, and human overexploitation. Anyway, if such events ever affected the Sardinian population, this is likely to have happened in the past since, according to our microsatellite data, the present-day population does not show evidence of recent bottlenecks or inbreeding, the Wilcoxon sign-rank test and the F(IS) index being not statistically significant (both P > 0.05). Based on this genetic evidence, we advance hypotheses about the distinctiveness of the Sardinian population and its significance for taxonomy and conservation.

Phylogenetic history of mustelid fauna in Taiwan inferred from mitochondrial genetic loci

Phylogenetic relationships among species of the family Mustelidae were examined using the combined nucleotide sequences of the three mitochondrial genetic loci (cytochrome b (MT-CYB; 1140 bp), NADH dehydrogenase subunit 2 (MT-ND2; 1044 bp), and displacement loop (MT-DLOOP; 540 bp)), with special emphasis on the phylogenetic history of four Taiwanese mustelid species: Martes flavigula (Boddaert, 1785), Melogale moschata (Gray, 1831), Mustela nivalis L., 1766, and Mustela sibirica Pallas, 1773. Maximum likelihood phylogenetic analysis of the combined sequences of the mitochondrial genetic loci produced a topology largely congruent with that of previous studies at the species level. Analyses of intraspecific genetic variations revealed two Melogale moschata individuals from Taiwan and Vietnam that showed genetic distances comparable with interspecific variations within the mustelid lineages. Furthermore, Mustela nivalis, recently discovered in Taiwan, was not as genetically differentiated from other continental conspecific individuals as a previous morphological survey suggested. Divergence time estimations for the mustelid lineages of Taiwan and the Eurasian continent by the Bayesian relaxed molecular clock approach suggested multiple colonization of Taiwan by mustelids from the continent during the Pleistocene, creating a hierarchical pattern of endemism based on the differential isolation history of the mustelid species in Taiwan.