A mitogenome of the Chevrier's field mouse (Apodemus chevrieri) and genetic variations inferred from the cytochrome b gene

Spatio-temporal genetic structure of the striped field mouse (Apodemus agrarius) populations inhabiting national parks in South Korea: Implications for conservation and management of protected areas

Population or habitat connectivity is a key component in maintaining species and community-level regional biodiversity as well as intraspecific genetic diversity. Ongoing human activities cause habitat destruction and fragmentation, which exacerbate the connectivity due to restricted animal movements across local habitats, eventually resulting in the loss of biodiversity. The Baekdudaegan Mountain Range (BMR) on the Korean Peninsula represents “biodiversity hotspots” and eight of the 22 Korean national parks are located within the BMR. Given the striped field mouse (Apodemus agrarius) is the most common and ecologically important small mammals in these protected areas, the population genetic assessment of this species will allow for identifying “genetic diversity hotspots” and also “genetic barriers” that may hinder gene flow, and will therefore inform on effective conservation and management efforts for the national park habitats. We collected samples from hair, tail, or buccal swabs for 252 A. agrarius individuals in 2015 and 2019. By using mitochondrial DNA cytochrome b (cyt b) sequences and nine microsatellite loci, we determined levels of genetic diversity, genetic differentiation, and gene flow among eight national park populations of A. agrarius along the BMR. We found high levels of genetic diversity but the occurrences of inbreeding for all the nine samples analyzed. Our results also indicated that there was detectable temporal genetic variation between the 2015 and 2019 populations in the Jirisan National Park, which is probably due to a short-term decline in genetic diversity caused by reduced population sizes. We also found a well-admixed shared gene pool among the national park populations. However, a significant positive correlation between geographic and genetic distances was detected only in mtDNA but not microsatellites, which might be attributed to different dispersal patterns between sexes. There was a genetic barrier to animal movements around the Woraksan National Park areas. The poor habitat connectivity surrounding these areas can be improved by establishing an ecological corridor. Our findings of the presence of genetic barriers in some protected areas provide insights into the conservation and management efforts to improve the population or habitat connectivity among the national parks.

Characterization of Two New Apodemus Mitogenomes (Rodentia: Muridae) and Mitochondrial Phylogeny of Muridae

Apodemus is the most common small rodent species in the Palearctic realm and an ideal species for biogeographical research and understanding environmental changes. Elucidating phylogenetic relationships will help us better understand species adaptation and genetic evolution. Due to its stable structure, maternal inheritance, and rapid evolution, the mitogenome has become a hot spot for taxonomic and evolutionary studies. In this research, we determined the mitochondrial genome of Apodemus agrarius ningpoensis and Apodemus draco draco and studied the phylogeny of Muridae using ML and BI trees based on all known complete mitogenomes. The mitochondrial genome of Apodemus agrarius ningpoensis was 16,262 bp, whereas that of Apodemus draco draco was 16,222 bp, and both encoded 13 protein-coding genes, 2 ribosomal RNA genes, and 22 transfer RNA genes. Analysis of base composition showed a clear A-T preference. All tRNAs except tRNASer and tRNALys formed a typical trilobal structure. All protein-coding genes contained T- and TAA as stop codons. Phylogeny analysis revealed two main branches in the Muridae family. Apodemus agrarius ningpoensis formed sister species with Apodemus chevrieri, whereas Apodemus draco draco with Apodemus latronum. Our findings provide theoretical basis for future studies focusing on the mitogenome evolution of Apodemus.

Complete mitogenomes of Turkish tree squirrels, Sciurus anomalus and S. vulgaris, (Sciuridae: Rodentia: Mammalia) and their phylogenetic status within the tribe Sciurini

The genus Sciurus, a member of the family Sciuridae, is widely distributed in the Holarctic region. To better understand mitogenomic characteristics and to reveal internal phylogenetic relationships of the genus, 20 complete mitogenomes of Turkish tree squirrels were successfully sequenced for the first time, including 19 for S. anomalus (from 16,505 bp to 16,510 bp) and one for S. vulgaris (16,511 bp). The mitogenomes of two species were AT-biased. All tRNAs for two species displayed a typical clover-leaf structure, except for tRNA^Ser(AGY). The tRNA Serine1 (S1)-GCT structure lacked the dihydrouridine (DHU) loop and stem. Based on mitogenomic dataset for phylogeny of Sciurinae, phylogenetic analyses (Bayesian Inference and Maximum Likelihood) did not support monophyly of Sciurus and proposed that S. anomalus, the most basal taxa in the Sciurini tribe, had at least five mitogenome lineages, which were also supported by network analysis. The dissimilarities among the five linegaes of S. anomalus ranged from 0.0042 (0.42%) to 0.0062 (0.62%) using K2P sequence pairwise distances. In addition to this mitogenomic analysis result, phylogenetic analyses using the CYTB + D-loop dataset proposed the existence of at least nine lineages for S. anomalus, which was different than those of the previous studies. The current study proposed that the use of mitogenomic data for reconstructing the phylogeny of Turkey' Sciurus holds an important value for revealing evolutionary relationships.

Late Pleistocene Expansion of Small Murid Rodents across the Palearctic in Relation to the Past Environmental Changes

We investigated the evolutionary history of the striped field mouse to identify factors that initiated its past demographic changes and to shed light on the causes of its current genetic structure and trans-Eurasian distribution. We sequenced mitochondrial cyt b from 184 individuals, obtained from 35 sites in central Europe and eastern Mongolia. We compared genetic analyses with previously published historical distribution models and data on environmental and climatic changes. The past demographic changes displayed similar population trends in the case of recently expanded clades C1 and C3, with the glacial (MIS 3–4) expansion and postglacial bottleneck preceding the recent expansion initiated in the late Holocene and were related to environmental changes during the upper Pleistocene and Holocene. The past demographic trends of the eastern Asian clade C3 were correlated with changes in sea level and the formation of new land bridges formed by the exposed sea shelf during the glaciations. These data were supported by reconstructed historical distribution models. The results of our genetic analyses, supported by the reconstruction of the historical spatial distributions of the distinct clades, confirm that over time the local populations mixed as a consequence of environmental and climatic changes resulting from cyclical glaciation and the interglacial period during the Pleistocene.

Ring distribution patterns-diversification or speciation? Comparative phylogeography of two small mammals in the mountains surrounding the Sichuan Basin

Studying the genetic differentiation in a unique geographical area contributes to understanding the process of speciation. Here, we explore the spatial genetic structure and underlying formation mechanism of two congeneric small mammal species (Apodemus draco and A. chevrieri), which are mainly distributed in the mountains surrounding the lowland Sichuan Basin, southwest China. We applied a set of comparative phylogeographical analyses to determine their genetic diversification patterns, combining mitochondrial (Cytb and COI) and nuclear (microsatellite loci) markers, with dense sampling throughout the range (411 A. draco from 21 sites and 191 A. chevrieri from 22 sites). Moreover, we performed three complementary statistical methods to investigate the correlation between genotype and geographical and environmental components, and predicted the potential suitable distributional range under the present and historical climate conditions. Our results suggest that both species have experienced allopatric differentiation and admixture in historical periods, resulting in a ring-shape diversification, under the barrier effect of the Sichuan Basin. We infer that the tectonic events of the Qinghai-Tibetan Plateau and climatic oscillations during the Quaternary played an important role on the genetic divergence of the two species by providing environmental heterogeneity and geographical variation. Our study reveals a case of two sympatric small mammals following a ring-shaped diversification pattern and provides insight into the process of differentiation.

Karyotypes of field mice of the genus Apodemus (Mammalia: Rodentia) from China

Karyotypes of four Chinese species of field mice of the genus Apodemus were examined, including Apodemus chevrieri (diploid chromosome number, 2n=48, fundamental number of autosomal arms, FNa=56), A. draco (2n=48, FNa=48), A. ilex (2n=48, FNa=48), and A. latronum (2n=48, FNa=48). Karyotypes of A. chevrieri, A. draco, and A. ilex are reported here for the first time, providing useful information for their species taxonomy. Determining the karyotypes of all species of Apodemus in Asia, both in this and previous studies, provides a solid overview of the chromosome evolution and species differentiation of the genus in East Asia. In addition to allopatric speciation, chromosome rearrangements likely played an important role in the formation of the four Apodemus species groups as well as speciation within each group in East Asia. For example, increased centromeric heterochromatin in A. latronum may have contributed to the post-mating reproductive isolation from the A. draco-A. ilex-A. semotus clade.

Comparative phylogeography clarifies the complexity and problems of continental distribution that drove A. R. Wallace to favor islands

Deciphering the geographic context of diversification and distributional dynamics in continental biotas has long been an interest of biogeographers, ecologists, and evolutionary biologists. Thirty years ago, the approach now known as comparative phylogeography was introduced in a landmark study of a continental biota. Here, I use a set of 455 studies to explore the current scope of continental comparative phylogeography, including geographic, conceptual, temporal, ecological, and genomic attributes. Geographically, studies are more frequent in the northern hemisphere, but the south is catching up. Most studies focus on a Quaternary timeframe, but the Neogene is well represented. As such, explanations for geographic structure and history include geological and climatic events in Earth history, and responses include vicariance, dispersal, and range contraction-expansion into and out of refugia. Focal taxa are biased toward terrestrial or semiterrestrial vertebrates, although plants and invertebrates are well represented in some regions. The use of various kinds of nuclear DNA markers is increasing, as are multiple locus studies, but use of organelle DNA is not decreasing. Species distribution models are not yet widely incorporated into studies. In the future, continental comparative phylogeographers will continue to contribute to erosion of the simple vicariance vs. dispersal paradigm, including exposure of the widespread nature of temporal pseudocongruence and its implications for models of diversification; provide new templates for addressing a variety of ecological and evolutionary traits; and develop closer working relationships with earth scientists and biologists in a variety of disciplines.

Detection of alpha- and betacoronaviruses in rodents from Yunnan, China

Background

Rodents represent the most diverse mammals on the planet and are important reservoirs of human pathogens. Coronaviruses infect various animals, but to date, relatively few coronaviruses have been identified in rodents worldwide. The evolution and ecology of coronaviruses in rodent have not been fully investigated.

Results

In this study, we collected 177 intestinal samples from thress species of rodents in Jianchuan County, Yunnan Province, China. Alphacoronavirus and betacoronavirus were detected in 23 rodent samples from three species, namely Apodemus chevrieri (21/98), Eothenomys fidelis (1/62), and Apodemus ilex (1/17). We further characterized the full-length genome of an alphacoronavirus from the A. chevrieri rat and named it as AcCoV-JC34. The AcCoV-JC34 genome was 27,649 nucleotides long and showed a structure similar to the HKU2 bat coronavirus. Comparing the normal transcription regulatory sequence (TRS), 3 variant TRS sequences upstream the spike (S), ORF3, and ORF8 genes were found in the genome of AcCoV-JC34. In the conserved replicase domains, AcCoV-JC34 was most closely related to Rattus norvegicus coronavirus LNRV but diverged from other alphacoronaviruses, indicating that AcCoV-JC34 and LNRV may represent a novel alphacoronavirus species. However, the S and nucleocapsid proteins showed low similarity to those of LRNV, with 66.5 and 77.4% identities, respectively. Phylogenetic analysis revealed that the S genes of AcCoV-JC34, LRNV, and HKU2 formed a distinct lineage with all known coronaviruses.

Conclusions

Both alphacoronaviruses and betacoronaviruses were detected in Apodemus chevrieri in the Yunnan Province of China, indicating that Apodemus chevrieri is an important host for coronavirus. Several new features were identified in the genome of an Apodemus chevrieri coronavirus. The phylogenetic distance to other coronaviruses suggests a variable origin and evolutionary route of the S genes of AcCoV-JC34, LRNV, and HKU2. These results indicate that the diversity of rodent coronaviruses is much higher than previously expected. Further surveillance and functional studies of these coronaviruses will help to better understand the importance of rodent as host for coronaviruses.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-017-0766-9) contains supplementary material, which is available to authorized users.

An endemic rat species complex is evidence of moderate environmental changes in the terrestrial biodiversity centre of China through the late Quaternary

The underlying mechanisms that allow the Hengduan Mountains (HDM), the terrestrial biodiversity centre of China, to harbour high levels of species diversity remain poorly understood. Here, we sought to explore the biogeographic history of the endemic rat, Niviventer andersoni species complex (NASC), and to understand the long-term persistence of high species diversity in this region. In contrast to previous studies that have proposed regional refuges in eastern or southern of the HDM and emphasized the influence of climatic oscillations on local vertebrates, we found that HDM as a whole acted as refuge for the NASC and that the historical range shifts of NASC mainly occurred in the marginal regions. Demographic analyses revealed slight recent population decline in Yunnan and south-eastern Tibet, whereas of the populations in Sichuan and of the entire NASC were stable. This pattern differs greatly from classic paradigms of temperate or alpine and holarctic species. Interestingly, the mean elevation, area and climate of potential habitats of clade a (N. excelsior), an alpine inhabitant, showed larger variations than did those of clade b (N. andersoni), a middle-high altitude inhabitant. These species represent the evolutionary history of montane small mammals in regions that were less affected by the Quaternary climatic changes.

The complete mitochondrial genome of lesser long-tailed Hamster Cricetulus longicaudatus (Milne-Edwards, 1867) and phylogenetic implications

The complete mitochondrial genome sequence of Cricetulus longicaudatus (Rodentia Cricetidae: Cricetinae) was determined and was deposited in GenBank (GenBank accession no. KM067270). The mitochondrial genome of C. longicaudatus was 16,302 bp in length and contained 13 protein-coding genes, 2 ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes and one control region, with an identical order to that of other rodents' mitochondrial genomes. The phylogenetic analysis was performed with Bayesian inference based on the concatenated nucleotide sequence of 12 protein-coding genes on the heavy strand. The result showed that these species from Cricetidae and its two subfamilies (Cricetinae and Arvicolines) formed solid monophyletic group, respectively. The Cricetulus had close phylogenetic relationship with Tscherskia among three genera (Cricetulus, Cricetulus and Mesocricetus). Neodon irene and Myodes regulus were embedded in Microtus and Eothenomys, respectively. The unusual phylogenetic positions of Neodon irene and Myodes regulus remain further study in the future.

The complete mitochondrial genome of the large white-bellied rat, Niviventer excelsior (Rodentia: Muridae)

The first complete mitochondrial genome of the large white-bellied rat (Niviventer excelsior) was sequenced and annotated in order to provide a source of phylogenetic characters including an assessment of gene order arrangement. The mitochondrial genome sequence (16,298 bp) of N. excelsior contains 13 protein-coding, 2 rRNA and 22 tRNA genes as well as 1 typical control region (D-Loop), which are shared by other mammalian mitochondrial genomes. The codon usage also followed the typical vertebrate pattern except for an unusual CCA stop codon, which was termination codon of Cyt b. The 16 nucleotide insertion was detected in the central conserved domain of d-Loop. The 12 heavy-strand encoded protein-coding genes were used to reconstruct the phylogenetic relationships by the Bayesian inference and maximum likelihood methods. Topologies revealed that N. excelsior clustered together with the species in genus Rattus, indicating their closer phylogenetic relationship.