The divergence of two independent lineages of an endemic Chinese gecko, Gekko swinhonis, launched by the Qinling orogenic belt

Contrasting demographic history and mutational load in three threatened whitebark pines (Pinus subsect. Gerardianae): implications for conservation

Demographic history and mutational load are of paramount importance for the adaptation of the endangered species. However, the effects of population evolutionary history and genetic load on the adaptive potential in endangered conifers remain unclear. Here, using population transcriptome sequencing, whole chloroplast genomes and mitochondrial DNA markers, combined with niche analysis, we determined the demographic history and mutational load for three threatened whitebark pines having different endangered statuses, Pinus bungeana, P. gerardiana and P. squamata. Demographic inference indicated that severe bottlenecks occurred in all three pines at different times, coinciding with periods of major climate and geological changes; in contrast, while P. bungeana experienced a recent population expansion, P. gerardiana and P. squamata maintained small population sizes after bottlenecking. Abundant homozygous-derived variants accumulated in the three pines, particularly in P. squamata, while the species with most heterozygous variants was P. gerardiana. Abundant moderately and few highly deleterious variants accumulated in the pine species that have experienced the most severe demographic bottlenecks (P. gerardiana and P. squamata), most likely because of purging effects. Finally, niche modeling showed that the distribution of P. bungeana might experience a significant expansion in the future, and the species' identified genetic clusters are also supported by differences in the ecological niche. The integration of genomic, demographic and niche data has allowed us to prove that the three threatened pines have contrasting patterns of demographic history and mutational load, which may have important implications in their adaptive potential and thus are also key for informing conservation planning.

Across a phylogeographic break in the Qinling Mountains-Huaihe River Line: Quaternary evolutionary history of a medicinal and edible homologous plant (Allium macrostemon) in China

Biogeographic barriers to gene flow are central to studies of plant phylogeography. There are many physical and geographic barriers in China, but few studies have used molecular ecological evidence to investigate the natural geographic isolation barrier of the Qinling Mountains-Huaihe River Line (QHL). Allium macrostemon is a precious Chinese perennial herb belonging to the Amaryllidaceae family. It is used as a food and medicine, with a variety of health and healing properties. Five SSR markers, three chloroplast DNA (cpDNA) markers (psbA-trnH, rps16 and trnL-F), one nuclear ribosomal DNA (nrDNA) marker (ITS), and simplified genome GBS sequencing were used to analyse the genetic diversity and structure of A. macrostemon. Combining SSR, cpDNA, nrDNA ITS data and GBS analysis results, we divided A. macrostemon populations into northern and southern groups, with the southern group further divided into southwestern and central-southeastern groups. Niche simulation results reveal that the distribution area of A. macrostemon will reach its maximum in the future. These data indicate that the regional separation of A. macrostemon has been maintained by the combined influence of a geographical barrier and Quaternary climate, and that the back-and-forth fluctuations of QHL and Quaternary climate have played an important role in this process. QHL acts as a north-south dividing line in phylogeography and population genetic structure, promoting physical geographic isolation. This study provides a theoretical basis for the conservation, development, and utilization of A. macrostemon resources. It further provides a reference for understanding the systematic geographical pattern of the large-scale spatial distribution of plants in China and enriches our understanding of Quaternary plant evolution in areas with complex terrain.

The influence of climate oscillations and geological events on population differentiation of Camponotus japonicus in the Chinese mainland

Camponotus japonicus (Hymenoptera: Formicidae) is an omnivorous social insect which builds sizable colonies in sparse woodlands or cropland and spreads across multiple climatic zones in the Chinese mainland. This study aims to reveal the role of climate changes and geological events in driving the genetic structure of social insect populations by investigating the phylogenetics and historical demography of C. japonicus in the Chinese mainland. Phylogenetic analyses were conducted based on the mitochondria DNA dataset using MrBayes and IQ-TREE. We constructed a haplotype network, calculated analyses of molecular variance, estimated the divergence time, and reconstructed the maximum clade credibility tree. Mismatch distribution and Bayesian skyline plots were used to infer historical population fluctuations. Additionally, ecological niche modeling was employed to predict the potential distribution of the species during the present, mid-holocene, and last glacial maximum periods in the Chinese mainland. The phylogenetic tree and median-joining network analyses support the presence of four distinct lineages in C. japonicus. These lineages exhibit significant genetic differentiation and limited gene flow. The divergence among the four lineages began in the early Pleistocene, approximately 1.41 million years ago (Ma). Subsequently, the central lineage diverged from both the northern and southern lineages around 1.16 Ma, while the northern and southern lineages diverged from each other at approximately 1.07 Ma. Population expansion was observed in the southern, central, and northern lineages prior to the last glacial maximum, while the Yunnan-Sichuan lineage experienced a slight increase in population size in more recent times. The predicted distribution of the species corresponds well with the actual distribution. Furthermore, the current suitable habitat areas in northern Xinjiang, southern Tibet, and the southeast coastal regions have significantly decreased compared to the last glacial maximum and the mid-holocene periods. Our results suggest that climate oscillations and geological events play an important role in driving genetic patterns and differentiation of C. japonicus. Mountain barriers isolate populations from each other, hinder the flow of genes, and effectively prevent the spread of this species. But at the same time, it also formed refugia at low altitudes areas such as Qinling-Bashan Mountains and Yanshan-Taihang Mountains and provide suitable habitats during glaciation. This study provides a good model for understanding how complex climate changes and geological events affect population genetic differentiation of social insects in the Chinese mainland.

Phylogenetic Analysis and Genetic Structure of Schlegel's Japanese Gecko (Gekko japonicus) from China Based on Mitochondrial DNA Sequences

Gekko japonicus, i.e., Schlegel's Japanese Gecko, is an important species which is widely distributed in East Asia. However, the information about population genetics of this species from China remains unclear. To address this issue, we used sequences from a fragment of the mitochondrial protein-coding gene cytochrome c oxidase I to estimate genetic diversity, genetic structure, and historical demography of G. japonicus populations from China. Phylogenetic analysis indicated that G. japonicus had a close relationship with Gekko wenxianensis. A total of 14 haplotypes were obtained, of which haplotype 1 was the most common and widely distributed. The genetic diversity of G. japonicus was comparatively low across different geographic populations. The populations of G. japonicus were divided into four groups which exhibited low levels of genetic differentiation, and expressed an unclear pattern of population structuring. In addition, potential population expansion of G. japonicus has occurred as well. Overall, these results demonstrate that the populations of G. japonicus reveal low genetic diversity in China, which is attributed to the founder and bottleneck events among populations. Our results will provide meaningful information on the population genetics of G. japonicus and will provide some insights into the study of origin of populations.

The mutual history of Schlegel's Japanese gecko (Reptilia: Squamata: Gekkonidae) and humans inscribed in genes and ancient literature

Knowing how the present distribution of organisms was formed is an essential issue in evolutionary ecology. Recently, the distribution of organisms on Earth has been significantly changed by human-mediated dispersal due to globalization. Therefore, significant attention has been paid to such processes. However, although humankind has taken considerable time to achieve modernization, the impact of ancient human activity on ecosystems has not yet been thoroughly studied. We hypothesized that ancient urban development and transitions had a non-negligible effect on species distribution. Inferring the impact of past human activity on ecosystems from ancient literature and verifying that impact by genetic analysis and human history is an effective means of tackling this problem. As geckos, a popular neighbor of human dwellings, are good material for this model, we performed this combination approach using Schlegel's Japanese gecko, Gekko japonicus. We show that G. japonicus migrated from China to the western Japanese archipelago before Christ. The gecko species dispersed itself from western to eastern the archipelago on a time scale of thousands of years. There are many synchronizations between the dispersal history of G. japonicus and the historical development of human society. It is suggested by such synchronizations that humans have influenced the distribution of G. japonicus many times throughout its dispersal history.

Pleistocene climate and geomorphology drive the evolution and phylogeographic pattern of Triplophysa robusta (Kessler, 1876)

Montane systems provide excellent opportunities to study the rapid radiation influenced by geological and climatic processes. We assessed the role of Pleistocene climatic oscillations and mountain building on the evolution history of Triplophysa robusta, a cold-adapted species restricted to high elevations in China. We found seven differentiated sublineages of T. robusta, which were established during the Mid Pleistocene 0.87–0.61 Mya. The species distribution modeling (SDM) showed an expansion of T. robusta during the Last Glacial Maximum (LGM) and a considerable retraction during the Last Interglacial (LIG). The deep divergence between Clade I distributed in Qinling Mountains and Clade II in Northeastern Qinghai-Tibet Plateau (QTP) was mainly the result of a vicariance event caused by the rapid uplifting of Qinling Mountains during the Early Pleistocene. While the middling to high level of historical gene flow among different sublineages could be attributed to the dispersal events connected to the repetition of the glacial period during the Pleistocene. Our findings suggested that frequent range expansions and regressions due to Pleistocene glaciers likely have been crucial for driving the phylogeographic pattern of T. robusta. Finally, we urge a burning question in future conservation projection on the vulnerable cold-adapted species endemic to high elevations, as they would be negatively impacted by the recent rapid climate warming.

Population genomics reveal deep divergence and strong geographical structure in gentians in the Hengduan Mountains

Understanding the evolutionary and ecological processes driving population differentiation and speciation can provide critical insights into the formation of biodiversity. Here, we examine the link between population genetic processes and biogeographic history underlying the generation of diversity in the Hengduan Mountains (HM), a region harboring a rich and dynamic flora. We used restriction site-associated DNA sequencing to generate 1,907 single-nucleotide polymorphisms (SNPs) and four-kb of plastid sequence in species of the Gentiana hexaphylla complex (Gentianaceae). We performed genetic clustering with spatial and non-spatial models, phylogenetic reconstructions, and ancestral range estimation, with the aim of addressing the processes influencing diversification of G. hexaphylla in the HM. We find the G. hexaphylla complex is characterized by geographic genetic structure with clusters corresponding to the South, North and the central HM. Phylogenetic reconstruction and pairwise F _ST analyses showed deep differentiation between Southern and Northern populations in the HM. The population in Mount Taibai exhibited the highest genetic similarity to the North HM. Ancestral range estimation indicated that the G. hexaphylla complex originated in the central HM and then diverged in the Pliocene and the Early Pleistocene, before dispersing widely, resulting in the current distinct lineages. Overall, we found deep genomic differentiation in the G. hexaphylla complex corresponds to geographic barriers to dispersal in the HM and highlights a critical role of the uplift of the Daxue Mountains and subsequent climatic fluctuations underlying diversification. The colonization of G. hexaphylla in the Mount Taibai region suggests directional dispersal between the alpine flora of the Qinling Mountains and the HM.

A Phylogeographical Analysis of the Beetle Pest Species Callosobruchus chinensis (Linnaeus, 1758) in China

Callosobruchus chinensis (Coleoptera Bruchidae), is a pest of different varieties of legumes. In this paper, a phylogeographical analysis of C. chinensis was conducted to provide knowledge for the prevention and control of C. chinensis. A total of 224 concatenated mitochondrial sequences were obtained from 273 individuals. Suitable habitat shifts were predicted by the distribution modelling (SDM). Phylogeny, genetic structure and population demographic history were analyzed using multiple software. Finally, the least-cost path (LCP) method was used to identify possible dispersal corridors and genetic connectivity. The SDM results suggested that the distribution of C. chinensis experienced expansion and contraction with changing climate. Spatial distribution of mtDNA haplotypes showed there was partial continuity among different geographical populations of C. chinensis, except for the Hohhot (Inner Mongolia) population. Bayesian skyline plots showed that the population had a recent expansion during 0.0125 Ma and 0.025 Ma. The expansion and divergent events were traced back to Quaternary glaciations. The LCP method confirmed that there were no clear dispersal routes. Our findings indicated that climatic cycles of the Pleistocene glaciations, unsuitable climate and geographic isolation played important roles in the genetic differentiation of C. chinensis. Human activities weaken the genetic differentiation between populations. With the change in climate, the suitable areas of C. chinensis will disperse greatly in the future.

Spatial Genetic Structure and Demographic History of the Wild Boar in the Qinling Mountains, China

Simple Summary

The wild boar is native to the temperate region of Eurasia, which is now one of the most widely distributed mammals worldwide. The recent expansion in the wild boar population has attracted a lot of attention, which may cause great damage to ecosystems. Elucidating the patterns of the population structure, genetic diversity, population origin, and colonization route of wild boar is very helpful in the conservation and management of wild populations. Phylogeographic analysis has proven to be a powerful tool. Here, 82 samples of wild boars in 16 sampling locations were collected in Qinling Mountains (QM). Genetic analysis was conducted based on the mitochondrial control region and nuclear genes. The level of genetic diversity of wild boars in QM was lower than the total population in East Asia, but higher than European population. No obvious phylogeographic pattern were found. The effective population size was under demographic equilibrium in the past.

Abstract

Species dispersal patterns and population genetic structure can be influenced by geographical features. Qinling Mountains (QM) provide an excellent area for phylogeographic study. The phylogeography of Asian-wide wild boars revealed the colonization route. However, the impact of the QM on genetic diversity, genetic structure and population origin is still poorly understood. In this study, genetic analysis of wild boar in the QM was conducted based on the mitochondrial control region (943 bp) and twelve microsatellite loci of 82 individuals in 16 sampling locations. Overall genetic haplotype diversity was 0.86, and the nucleotide diversity was 0.0079. A total of 17 new haplotypes were detected. The level of genetic diversity of wild boars in QM was lower than in East Asia, but higher than in Europe. Phylogenetic analysis showed the weak genetic divergence in QM. Mismatch analysis, neutrality tests, and Bayesian Skyline Plot (BSP) results revealed that the estimates of effective population size were under demographic equilibrium in the past. Spatial analysis of molecular variance indicated no obvious phylogeographic structure.

Evolutionary history of endangered and relict tree species Dipteronia sinensis in response to geological and climatic events in the Qinling Mountains and adjacent areas

Geological and climatic events are considered to profoundly affect the evolution and lineage divergence of plant species. However, the evolutionary histories of tree species that have responded to past geological and climate oscillations in central China's mountainous areas remain mostly unknown. In this study, we assessed the evolutionary history of the endangered and relict tree species Dipteronia sinensis in the Qinling Mountains (QM) and adjacent areas in East Asia based on variations in the complete chloroplast genomes (cpDNA) and reduced-genomic scale single nucleotide polymorphisms (SNPs). Population structure and phylogenetic analysis based on the cpDNA variations suggested that D. sinensis could be divided into two intraspecific genetic lineages in the eastern and western sides of the QM (EQM and WQM, respectively) in East Asia. Molecular dating suggested that the intraspecific divergence of D. sinensis occurred approximately 39.2 million years ago during the later Paleogene. It was significantly correlated with the orogeny of the QM, where the formation of this significant geographic barrier in the region may have led to the divergence of independent lineages. Bayesian clustering and demographic analysis showed that intraspecific gene flow was restricted between the EQM and WQM lineages. Isolation-with-migration analysis indicated that the two genetic lineages experienced significant demographic expansions after the Pleistocene ice ages. However, the genetic admixture was determined in some populations between the two lineages by the large scale of SNP variations due to DNA incompatibility, the large significant population size, and rapid gene flow of nuclear DNA markers. Our results suggest that two different conservation and management units should be constructed for D. sinensis in the EQM and WQM areas. These findings provide novel insights into the unprecedented effects of tectonic changes and climatic oscillations on lineage divergence and plant population evolution in the QM and adjacent areas in East Asia.

Molecular phylogeny and biogeography of Triplophysa stone loaches in the Central Chinese Mountains

The geological structure and history of mountains often cause highly complex patterns of evolution. The origin and diversity of the genus Triplophysa is considered to be closely associated with the rapid and persistent rise of the Qinghai-Tibet Plateau (QTP). Species of the genus are widely distributed in the QTP and adjacent regions, and are strongly adapted to its extreme environments. However, the Central Chinese Mountains (CCM), which are far apart from the QTP, also have many Triplophysa populations and yet their taxonomy, phylogeny and origin are unknown. We used three mitochondrial genes of 266 individuals from 29 sites in the CCM to shed light on the evolution of these Triplophysa populations. Phylogenetic analyses and species delimitation revealed seven distinct molecular operational taxonomic units (mOTUs) in the CCM, each with low genetic diversity. Molecular clock and biogeographic analyses suggested that vicariance events resulting from the rapid uplifting of the Qinling and Taihang Mountains initialized diversification in the Pliocene. During the early Pleistocene, dispersal events in the central parts of the Yellow River drainage altered genetic diversity and led to the currently observed biogeographic patterns. Our results suggest the presence of at least six species of Triplophysa in the CCM and more are likely to be discovered in the future.

Genetic diversity and inferred dispersal history of the Schlegel's Japanese Gecko (Gekko japonicus) in Northeast Asia based on population genetic analyses and paleo-species distribution modelling

To understand the genetic diversity and dispersal history of Schlegel's Japanese gecko (Gekko japonicus), we performed genetic analyses and paleo-species distributional modelling. For the genetic analysis, we analyzed mitochondrial DNA (mtDNA) (cytochrome b [Cytb] and NADH dehydrogenase 2 [ND2]) and seven microsatellite loci of 353 individuals from 11 populations (2 east coast China, 4 west and central coast Japan and 5 Korea). For the paleo-species distribution modelling, we used 432 occurrence data points (125 China, 291 Japan and 16 Korea) over the Pleistocene and Holocene. China is inferred to be the source population, which had higher genetic diversity (mtDNA) and more private alleles (mtDNA) compared to Japanese and Korean populations. Differences between the three counties were very small in the mtDNA haplotype network despite some genetic structure among the three countries. Microsatellite analysis inferred that genetic exchange has actively occurred among the Chinese, Japanese and Korean populations. Suitable habitats in Japan should have been plentiful by the mid-Holocene, but have only recently become available in Korea. These results suggest that dispersal of G. japonicus occurred after the Holocene warming from the east coast of China to the west and central coasts of Japan and Korea, and gene flow is actively occurring among the three countries.

Phylogeography and demographic history of Gyrodactylus konovalovi (Monogenoidea: Gyrodactylidae), an ectoparasite on the East Asia Amur minnow (Cyprinidae) in Central China

Gyrodactylus konovalovi is an ectoparasite on the Amur minnow (Rhynchocypris lagowskii) that is widely distributed in the cold fresh waters of East Asia. In the present study, the phylogeography and demographic history of G. konovalovi and the distribution of its host in the Qinling Mountains are examined. A total of 79 individual parasites was sequenced for a 528 bp region of the mitochondrial NADH dehydrogenase subunit 5 (ND5) gene, and 25 haplotypes were obtained. The substitution rate (dN/dS) was 0.068 and indicated purifying selection. Haplotype diversity (h) and nucleotide diversity (π) varied widely in the Qinling Mountains. Phylogenetic trees based on Bayesian inference (BI), maximum likelihood (ML), and maximum parsimony (MP) methods and network analysis revealed that all haplotypes were consistently well-supported in three different lineages, indicating a significant geographic distribution pattern. There was a significant positive correlation between genetic differentiation (F st) and geographic distance. The results of mismatch distribution, neutrality test and Bayesian skyline plot analyses showed that whole populations underwent population contraction during the Pleistocene. Based on the molecular clock calibration, the most common ancestor was estimated to have emerged in the middle Pleistocene. Our study suggests for the first time that a clearly phylogeography of G. konovalovi was shaped by geological events and climate fluctuations, such as orogenesis, drainage capture changes, and vicariance, during the Pleistocene in the Qinling Mountains.

Genetic diversity analysis of Peking gecko (Gekko swinhonis) in mid-Eastern China based on mitochondrial COI and Cyt b gene sequences

To understand the genetic diversity of Peking gecko (Gekko swinhonis) populations in its endemic region, 60 individuals were sampled from Lushan, Qi, and Linying counties in Henan Province, China. Through PCR amplification and Sanger sequencing, 120 sequences with lengths of 652 bp (COI) and 739 bp (Cyt b) were obtained, and nine haplotypes were detected for each gene. Overall, results indicated that Peking gecko populations in China have high genetic diversity and significant genetic differentiation. This study provides necessary scientific basis for the protection of Peking gecko germplasm resources.

Late Pleistocene speciation of three closely related tree peonies endemic to the Qinling-Daba Mountains, a major glacial refugium in Central China

Determining the factors promoting speciation is a major task in ecological and evolutionary research and can be aided by phylogeographic analysis. The Qinling-Daba Mountains (QDM) located in central China form an important geographic barrier between southern subtropical and northern temperate regions, and exhibit complex topography, climatic, and ecological diversity. Surprisingly, few phylogeographic analyses and studies of plant speciation in this region have been conducted. To address this issue, we investigated the genetic divergence and evolutionary histories of three closely related tree peony species (Paeonia qiui, P. jishanensis, and P. rockii) endemic to the QDM. Forty populations of the three tree peony species were genotyped using 22 nuclear simple sequence repeat markers (nSSRs) and three chloroplast DNA sequences to assess genetic structure and phylogenetic relationships, supplemented by morphological characterization and ecological niche modeling (ENM). Morphological and molecular genetic analyses showed the three species to be clearly differentiated from each other. In addition, coalescent analyses using DIYABC conducted on nSSR variation indicated that the species diverged from each other in the late Pleistocene, while ecological niche modeling (ENM) suggested they occupied a larger area during the Last Glacial Maximum (LGM) than at present. The combined genetic evidence from nuclear and chloroplast DNA and the results of ENM indicate that each species persisted through the late Pleistocene in multiple refugia in the Qinling, Daba, and Taihang Mountains with divergence favored by restricted gene flow caused by geographic isolation, ecological divergence, and limited pollen and seed dispersal. Our study contributes to a growing understanding of the origin and population structure of tree peonies and provides insights into the high level of plant endemism present in the Qinling-Daba Mountains of Central China.

Phylogeographical structure and demographic expansion in the endemic alpine stream salamander (Hynobiidae: Batrachuperus) of the Qinling Mountains

The Qinling Mountains of China provide an excellent study area for assessing the effect of Pleistocene climatic oscillations and paleogeological events on intraspecific diversification. To assess genetic diversity of an endemic stream salamander, Batrachuperus tibetanus, for its conservation, a phylogeographical survey was performed based on mitochondrial DNA and morphological data. The mitochondrial data revealed three lineages of B. tibetanus in the Qinling Mountains. A lineage present in the northwestern Qinling Mountains groups with the Tibet lineage of B. tibetanus, and the remaining Qinling populations are eastern and western lineages that separated ~3–4 million years ago (Ma). The eastern and western Qinling lineage delineation is supported by three morphological variables (snout length, eye diameter and axilla-groin length). The divergence of the two major lineages was likely caused by orogenesis of the Qinling Mountains during the late Cenozoic, and the two lineages were subsequently affected at different levels by Pleistocene climatic oscillations showing different signals of demographic expansion. A large suitable area of B. tibetanus through the Qinling Mountains since the last glacial maximum (LGM) indicated the adaptation of this species to the climatic changes. However, low genetic diversity within populations indicate the urgency of preserving the vulnerable populations and endemic lineages.

Geologic events coupled with Pleistocene climatic oscillations drove genetic variation of Omei treefrog (Rhacophorus omeimontis) in southern China

BACKGROUND

Pleistocene climatic oscillations and historical geological events may both influence current patterns of genetic variation, and the species in southern China that faced unique climatic and topographical events have complex evolutionary histories. However, the relative contributions of climatic oscillations and geographical events to the genetic variation of these species remain undetermined. To investigate patterns of genetic variation and to test the hypotheses about the factors that shaped the distribution of this genetic variation in species of southern China, mitochondrial genes (cytochrome b and NADH dehydrogenase subunit 2) and nine microsatellite loci of the Omei tree frog (Rhacophorus omeimontis) were amplified in this study.

RESULTS

The genetic diversity in the populations of R. omeimontis was high. The phylogenetic trees reconstructed from the mitochondrial DNA (mtDNA) haplotypes and the Bayesian genetic clustering analysis based on microsatellite data both revealed that all populations were divided into three lineages (SC, HG and YN). The two most recent splitting events among the lineages coincided with recent geological events (including the intense uplift of the Qinghai-Tibet Plateau, QTP and the subsequent movements of the Yun-Gui Plateau, YGP) and the Pleistocene glaciations. Significant expansion signals were not detected in mismatch analyses or neutrality tests. And the effective population size of each lineage was stable during the Pleistocene.

CONCLUSIONS

Based on the results of this study, complex geological events (the recent dramatic uplift of the QTP and the subsequent movements of the YGP) and the Pleistocene glaciations were apparent drivers of the rapid divergence of the R. omeimontis lineages. Each diverged lineages survived in situ with limited gene exchanges, and the stable demographics of lineages indicate that the Pleistocene climatic oscillations were inconsequential for this species. The analysis of genetic variation in populations of R. omeimontis contributes to the understanding of the effects of changes in climate and of geographical events on the dynamic development of contemporary patterns of genetic variation in the species of southern China.

Vicariance and Its Impact on the Molecular Ecology of a Chinese Ranid Frog Species-Complex (Odorrana schmackeri, Ranidae)

Paleogeological events and Pleistocene climatic fluctuations have had profound influences on the genetic patterns and phylogeographic structure of species in southern China. In this study, we investigated the population genetic structure and Phylogeography of the Odorrana schmackeri species complex, mountain stream-dwelling odorous frogs, endemic to southern China. We obtained mitochondrial sequences (1,151bp) of the complete ND2 gene and two flanking tRNAs of 511 individuals from 25 sites for phylogeographic analyses. Phylogenetic reconstruction revealed seven divergent evolutionary lineages, with mean pairwise (K2P) sequence distances from 7.8% to 21.1%, except for a closer ND2 distance (3.4%). The complex geological history of southern China drove matrilineal divergence in the O. schmackeri species complex into highly structured geographical units. The first divergence between lineage A+B and other lineages (C-G) had likely been influenced by the uplift of coastal mountains of Southeast China during the Mio-Pliocene period. The subsequent divergences between the lineages C-G may have followed the formation of the Three Gorges and the intensification of the East Asian summer monsoon during the late Pliocene and early Pleistocene. Demographic analyses indicated that major lineages A and C have been experienced recent population expansion (c. 0.045–0.245 Ma) from multiple refugia prior to the Last Glacial Maximum (LGM). Molecular analysis suggest that these seven lineages may represent seven different species, three described species and four cryptic species and should at least be separated into seven management units corresponding to these seven geographic lineages for conservation.

Geological events and Pliocene climate fluctuations explain the phylogeographical pattern of the cold water fish Rhynchocypris oxycephalus (Cypriniformes: Cyprinidae) in China

Background

Rhynchocypris oxycephalus is a cold water fish with a wide geographic distribution including the relatively warm temperate regions of southern China. It also occurs in second- and third-step geomorphic areas in China. Previous studies have postulated that high-altitude populations of R. oxycephalus in southern China are Quaternary glacial relics. In this study, we used the mitochondrial gene Cytb and the nuclear gene RAG2 to investigate the species phylogeographical patterns and to test two biogeographic hypotheses: (1) that divergence between lineages supports the three-step model and (2) climatic fluctuations during the Quaternary resulted in the present distribution in southern China.

Results

Phylogenetic analysis detected three major matrilines (A, B, and C); with matrilines B and C being further subdivided into two submatrilines. Based on genetic distances and morphological differences, matriline A potentially represents a cryptic subspecies. The geographic division between matrilines B and C coincided with the division of the second and third geomorphic steps in China, suggesting a historical vicariance event. Pliocene climatic fluctuations might have facilitated the southwards dispersal of R. oxycephalus in matriline C, with the subsequent warming resulting in its split into submatrilines C1 and C2, leaving submatriline C2 as a relic in southern China.

Conclusions

Our study demonstrates that geological events (three steps orogenesis) and climate fluctuations during the Pliocene were important factors in shaping phylogeographical patterns in R. oxycephalus. Notably, no genetic diversity was detected in several populations, all of which possessed unique genotypes. This indicates the uniqueness of local populations and calls for a special conservation plan for the whole species at the population level.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-014-0225-9) contains supplementary material, which is available to authorized users.

Population genetic structure of golden pheasant Chrysolophus pictus in the Qinling Mountains, China

The golden pheasant (Chrysolophus pictus) is an endemic pheasant of central China and is protected under national legislation. The Qinling Mountains form a natural barrier between northern and southern China. We investigated the population genetic structure using 1123 nucleotides of mitochondrial DNA (mtDNA) control-region from 55 individuals sampled from five populations of gold pheasant in the Qinling Mountains. We found sixteen haplotypes defined by fourteen polymorphic sites. Phylogenetic analyses showed that the haplotypes sampled from the five putative populations did not cluster into separate geographic branches. There was an insignificant genetic differentiation among the putative populations (except GSTS population), probably due to high levels of gene flow. Results from the mismatch distribution and neutrality test analyses indicated the populations did not experience a range expansion over the course of their histories. They also suggested there was no geographical isolation shaped by the Qingling Mountains for Chrysolophus pictus.