High Nucleotide Diversity Research Articles

Mitochondrial DNA marker (D-loop) reveals high genetic diversity but low population structure in the pale bent-wing bat (Miniopterus pallidus) in Iran

This study investigates the population genetic structure of Miniopterus pallidus using the D-loop region of mitochondrial DNA (331 bp) from 13 localities in Iran. We found a high number of haplotypes (N = 43) and high nucleotide diversity (π = 0.02). The average K2P genetic distance was high within (2.59%) and between (2.54%) the Iranian populations of M. pallidus and analysis of molecular variance revealed that most genetic variability was related to differences within populations. The positive and significant association between pairwise genetic and environmental distances (r = 0.443, p = .01) after accounting for the effect of geographical distances suggests that substantial influence of the climatic factors among different sites have shaped the genetic variation in this species. Neutrality tests showed historical demographic events when applying Fu’s Fs, but Tajima’s statistic was nonsignificant, indicating a deviation from the theoretical model of expansion. The hypothesis of sudden-expansion was not rejected by analyses of mismatch distribution as the Raggedness and SSD were insignificant (p(r)= .39 and p(SSD) = .38). Similarly, BSP results approximately revealed a major historical expansion around 81,000 years ago and a recent population decline around 13,000 years ago. Phylogenetic trees illustrated that all Iranian M. pallidus populations, as well as those from eastern Turkey and Azerbaijan, form a monophyletic clade, whereas the samples from western Turkey, Georgia and Greece belong to M. schreibersii clade. The haplotype network was consistent with these findings for M. pallidus populations in Iran and showed a high level of reticulation.

Population Connectivity and Traces of Mitochondrial Introgression in New Zealand Black-Billed Gulls (Larus bulleri).

Black-billed gulls (Larus bulleri) are endemic to New Zealand and are suspected to be undergoing substantial population declines. They primarily breed on open gravel beds in braided rivers of the South Island—a habitat that is diminishing and becoming increasingly modified. Although management of this species is increasing, little has been published on their movements and demographics. In this study, both mitochondrial DNA (mtDNA) control region domain I and nuclear single nucleotide polymorphisms (SNPs) were examined to help understand the connectivity and population structure of black-billed gulls across the country and to help inform management decisions. Mitochondrial DNA showed no population structure, with high haplotype and low nucleotide diversity, and analyses highlighted mitochondrial introgression with the closely related red-billed gulls (Larus novaehollandiae scopulinus). Nuclear DNA analyses, however, identified two groups, with Rotorua birds in the North Island being distinct from the rest of New Zealand, and isolation-by-distance evident across the South Island populations. Gene flow primarily occurs between nearby colonies with a stepwise movement across the landscape. The importance from a genetic perspective of the more isolated North Island birds (1.6% of total population) needs to be further evaluated. From our results, we infer that the South Island black-billed gull management should focus on maintaining several populations within each region rather than focusing on single specific colonies or river catchments. Future study is needed to investigate the genetic structure of populations at the northern limit of the species’ range, and identify the mechanisms behind, and extent of, the hybridisation between red-billed and black-billed gulls.

Genetic Structure of the Hyrcanian Wood Frog, Rana pseudodalmatina (Amphibia: Ranidae) Using mtDNA Gene Sequences

Population structuring of a species provide basic information for biological conservation. We investigated the genetic structure of seven populations of Rana pseudodalmatina, an endemic species of the Ranidae inhabiting the Hyrcanian forests in northern Iran, based on the genetic variation of two partial mitochondrial DNA sequences (16S rRNA and cytochrome b genes). Molecular genetic analyses revealed remarkable variation among populations of R. pseudodalmatina. The phylogenetic trees clearly indicated two distinct haplogroups, which largely corresponded to their geographic locations. A strong population structure was found (ΦCT = 0.559, P = 0.027) with high haplotype diversity (Hd = 0.88) and low nucleotide diversity (π = 0.0041). Analysis of molecular variance (AMOVA) indicated that most of the observed genetic variation (55.92%) occurred between the two haplogroups. Also, Mantel tests revealed a significant correlation between geographic and genetic distances (R2 = 0.33, P = 0.005). Finally, the star-like topology of haplotype network and also neutrality tests provide strong evidence for population expansion in two haplogroups. All the findings of the present study, suggest a strong evidence for past expansion of isolated populations of R. pseudodalmatina, which their isolation could be largely attributed to rising level of the Caspian Sea during last glacial periods in the Pleistocene.

Population genetic structure of banana corm weevil Cosmopolites sordidus (Germar) in India

Abstract The population genetic structure of Cosmopolites sordidus (Germar), an economically important pest of bananas, was studied using the sequence data of the internal transcribed rDNA (ITS1+ITS2) and the mitochondrial ‘COI-tRNALeu-COII’ region from seventy nine individuals collected from six sampling locations in India. The ITS data revealed 70% within population variation and non-significant genetic differentiation estimates suggesting lack of phylogeographic sub-structuring. 49% within population variation and highly significant genetic differentiation values were obtained with the mitochondrial data. The Mantel test revealed lack of correlation between genetic and geographic distance with both the markers. Demographic expansion of the populations was confirmed by the star shaped haplotype networks, demographic tests and mismatch distribution curves using both the markers. Molecular diversity indices show a high haplotype diversity (Hd) but low nucleotide diversity (π) suggesting that the populations are closely related. Considering the low self-dispersal ability of the weevils, these results suggest that the range expansion of this banana pest in India has taken place mainly through transport of infested corms and plant material resulting in the weevils forming localised populations which are not genetically distinct from each other. The high gene diversity (Hd) has enabled the weevils to adapt to varying environmental conditions which could explain the range expansion of this pest in India. The observed discrepancy in the genetic differentiation estimates using these two markers can be attributed to the evolutionary dynamics of the nuclear and mitochondrial genomes.

Genetic Characterization ofParacentrotus lividus(Lamarck, 1816) Populations from Nw Spain and the Canary Islands

The sea urchin Paracentrotus lividus is the most commercially important sea urchin species harvested in the NE Atlantic and Mediterranean coasts. To improve the management of P. lividus natural stock and its commercial exploitation, the population genetic structure of P. lividus in the Northeast Atlantic coast has been characterized. Populations from three regions of Spain: Asturias, Galicia, and the Canary Islands were sampled, and a 700-bp fragment of the mitochondrial gene cytochrome c oxidase subunit I (COI) was sequenced. The obtained sequences were combined with previously available haplotypes coming from 127 sea urchins from the Canary Islands and the Mediterranean and Atlantic coasts of Spain—they collapsed in 54 haplotypes with 43 polymorphic sites—and 13 of these haplotypes were provided for the obtained sequences. The haplotype network shows high haplotype diversity and low nucleotide diversity values in all the studied populations. The distribution of analyzed haplotypes shows a high genetic homogeneity among populations. With the obtained data, no significant genetic differentiation could be found among populations analyzed in Galicia, Asturias, and the Canary Islands, and the existence of a population structure in this geographical area could not be determined. Based on this study, there would be no loss of genetic variability if the shores of the Canary Islands were repopulated with urchins from the Iberian Peninsula, although it is recommended to repopulate overexploited areas with urchins from the same zone until the study is extended with other molecular markers.

Diversity and natural selection on the thrombospondin-related adhesive protein (TRAP) gene of Plasmodium knowlesi in Malaysia

BackgroundPlasmodium knowlesi a parasite of the macaques is currently the most common cause of human malaria in Malaysia. The thrombospondin-related adhesive protein (TRAP) gene is pre-erythrocytic stage antigen. It is a well-characterized vaccine candidate in Plasmodium vivax and Plasmodium falciparum, however, no study has been done in the orthologous gene of P. knowlesi. This study investigates nucleotide diversity, haplotypes, natural selection and population differentiation of full-length pktrap genes in clinical samples from Malaysia.MethodsForty full-length pktrap sequences from clinical isolates of Malaysia along with the reference H-strain were downloaded from published databases. Genetic diversity, polymorphism, haplotype and natural selection were determined using DnaSP 5.10 software. McDonald–Kreitman test was conducted using P. vivax and Plasmodium coatneyi as ortholog sequence in DnaSP 5.10 software. Population genetic differentiation index (FST) of parasite populations was determined using Arlequin v3.5. Phylogenetic relationships between trap ortholog genes were determined using MEGA 5.0 software.ResultsComparison of 40 full-length pktrap sequences along with the H-strain identified 74 SNPs (53 non-synonymous and 21 synonymous substitutions) resulting in 29 haplotypes. Analysis of the full-length gene showed that the nucleotide diversity was lower compared to its nearest ortholog pvtrap. Domain-wise analysis indicated that the proline/asparagine rich region had higher nucleotide diversity compared to the von Willebrand factor domain and the thrombospondin-type-1 domain. McDonald–Kreitman test identified that the ratio of the number of nonsynonymous to synonymous polymorphic sites within P. knowlesi was significantly higher than that of the number of nonsynonymous to synonymous fixed sites between P. knowlesi and P. vivax. The von Willebrand factor domain also indicated balancing selection using MK test, however, it did not give significant results when tested with P. coatneyi as an outgroup. Phylogenetic analysis of full-length genes identified three distinct sub-clusters of P. knowlesi, one originating from Peninsular Malaysia and two originating from Malaysian Borneo. High population differentiation values was observed within samples from Peninsular Malaysia and Malaysian Borneo.ConclusionsThis study is the first to report on the genetic diversity and natural selection of full-length pktrap. Low level of genetic diversity was found across the full-length gene of pktrap. Balancing selection of the von Willebrand factor domain indicated that TRAP could be a target in inducing immune response against P. knowlesi infections. However, higher number of samples would be necessary to further confirm the findings.

Genetic structure of Octopus minor around Chinese waters as indicated by nuclear DNA variations (Mollusca, Cephalopoda).

Octopus minor is an economically important resource commonly found in Chinese coastal waters. The nuclear gene (RD and ODH) approach of investigation has not reported in this species. Rhodopsin (RD) and octopine dehydrogenase (ODH) genes were used to elaborate the genetic structure collected from eight localities ranging from the northern to the southern coast of China. In total, 118 individuals for the RD gene and 108 for the ODH were sequenced. Overall (RD and ODH) genes resulted in high (0.741±0.032; 0.805±0.038) haplotype and low nucleotide (0.01261±0.00165; 0.00747±0.00086) diversity. Molecular variance displayed higher values among the populations and lower values within the population where the fixation index FST denoted 0.880 and 0.584 in RD and ODH genes respectively. The Dongshan population clustered separately in a phylogenetic tree as in the haplotype networking assessment. The current data suggests that the Dongshan population needs separate management.

Comparative evolutionary and phylogenomic analysis of Avian avulaviruses 1–20

Avian avulaviruses (avulaviruses or AAvVs) infect a wide range of avian species worldwide with variable clinical outcomes and economic impacts. Owing to broad host spectrum, several novel avulaviruses are being reported from both wild and domesticated birds that highlight the potential of the virus to evolve, adapt and emerge in susceptible population. Pathobiological and phylogenetic characterizations of individual avulaviruses are often demonstrated, however, a cumulative and comparative assessment of avulaviruses remains elusive. To assess evolutionary dynamics and potential emergence of novel avulaviruses, we enriched existing databases of all known avulaviruses (specie-type 1–20), and determined their genomics features based on both complete genomes and individual complete genes. While a high nucleotide divergence (up to 65.4%) was observed among avulaviruses, phylogenomic analysis revealed clustering of all avulaviruses into three distinct clades. The major clade (Clade-I) included both oldest and newest avulaviruses (2, 5, 6, 7, 8, 10, 11, 14, 15 and 20) and the second clade (Clade-II) consisted of avulaviruses 1, 9, 12, 13, 16, 17, 18 and 19, whereas the third clade (Clade-III) carried only avulaviruses 3 and 4. Intriguingly, clustering pattern was descriptive for individual gene-based analysis, however, the hemagglutinin-neuraminidase (HN) and polymerase (L) genes showed clear and discrete branching patterns similar to complete genome-based clustering. Therefore, we propose the use of HN, or L genes or complete genome to study epidemiological aspects of the avulaviruses. Genomic and residue characteristics of all genes indicated a continuous evolution of the virus, and substitutions in biologically important motifs warrant future investigations to assess their roles in the pathobiology of the virus. Taken together, this comprehensive analysis of all known avulaviruses ascertains continuous monitoring and surveillance of wild/water-fowls and commercial poultry. These findings further our understanding on the evolutionary dynamics and potential emergence of novel avulaviruses and will establish bases to identify potential of wild-bird origin apathogenic viruses to cause infections in commercial poultry.

Comparative mitogenomics supports synonymy of the genera Ligula and Digramma (Cestoda: Diphyllobothriidae)

BackgroundAfter observing differences in the number of reproductive complexes per proglottid within the genus Ligula, the genus Digramma was erected. However, the validity of Digramma has been previously questioned due to a low variability in the cox1, nad1 and ITS rDNA sequences between the two genera. We undertook a study to greatly increase the amount of sequence data available for resolution of this question by sequencing and characterizing the complete mitogenomes of Digramma interrupta and Ligula intestinalis.ResultsThe circular mtDNA molecules of Digramma interrupta and Ligula intestinalis are 13,685 bp and 13,621 bp in size, respectively, both comprising 12 PCGs, 22 tRNA genes, two rRNA genes, and two mNCRs. Both mitogenomes exhibit the same gene order and share 92.7% nucleotide identity, compared with 85.8–86.5% to the most closely related genus Dibothriocephalus. Each gene from D. interrupta and L. intestinalis is almost of the same size, and the sequence identity ranges from 87.5% (trnD) to 100% (trnH, trnQ and trnV). NCR2 sequences of D. interrupta and L. intestinalis are 249 bp and 183 bp in length, respectively, which contributes to the main difference in length between their complete mitogenomes. A sliding window analysis of the 12 PCGs and two rRNAs indicated nucleotide diversity to be higher in nad5, nad6, nad2, nad4 and cox3, whereas the most conserved genes were rrnL and rrnS. Lower sequence identity was also found in nad2, nad4, nad5, nad6 and cox3 genes between the two diphyllobothriids. Within the Diphyllobothriidae, phylogenetic analysis indicated Ligula and Digramma to be most closely related to one another, forming a sister group with Dibothriocephalus.ConclusionsOwing to higher nucleotide diversity, the genes nad2, nad4, nad5, nad6 and cox3 should be considered optimal candidates to use as molecular markers for population genetics and species identification between the two closely related species. The phylogenetic results in combination with the comparative analysis of the two mitogenomes, consistently support the congeneric status of L. intestinalis and D. interrupta.

Genetic structure analysis of mantis shrimp Oratosquilla oratoria based on mitochondrial DNA control region sequence.

The genetic relationships of mantis shrimp Oratosquilla oratoria between the coastal waters of China and Japan were not well studied. To reveal the genetic differentiation and genetic structure among populations, we collected populations of mantis shrimp O. oratoria from the coastal waters of China and Japan to analyze the mtDNA control region variation. A total of 309 individuals of O. oratoria were collected from 13 localities (11 from China and 2 from Japan) and a segment of mitochondrial DNA control region was sequenced. Three hundred nine haplotypes were defined, yielding a very high haplotype diversity and nucleotide diversity. Two lineages of O. oratoria were revealed and displayed strong differences in the geographical distribution. In the coastal waters of China, the geographic distribution of the two lineages was completely separated by the Yangtze River estuary; however, the lineages showed geographic sympatry in two populations from Japan. Based on the lineage distribution, three groups were defined. There was no significant genetic differentiation among the populations within the three groups, indicating high gene flow within each group. Significant and negative values for Tajima D and Fu's Fs tests, and mismatch distributions for two lineages indicated population expansion. The present result confirmed that the freshwater outflow from the Yangtze River formed a physical barrier and affected gene exchange. The different distribution patterns of the two lineages in coastal waters of China and Japan indicated that the larvae of O. oratoria were transferred from China to the coastal waters of Japan with a one-way gene flow.

Genetic diversity and origin of Namchi cattle breed inferred by matrilineage analyses

In animal genetic studies, mitochondrial DNA (mtDNA) analysis offers a way to detect changes in populations over time along with their maternal origin and migration routes. To determine these patterns in Namchi cattle breeds of Cameroon, analyses of 17 sequences of a 336 base pair fragment of the mtDNA D-loop region from two populations (Namchi Poli and Namchi Ngaoundere) were conducted in conjunction with previously published sequences from African, European, Japanese and Chinese subjects. As expected for an African taurine breed, all individuals in the study were found to be members of haplogroup T1. Due to the size of fragment analyzed, only one sub-haplogroup (T1c)could be detected, at a rate of 5.88%.This suggested that The Namchi cattle breed originated most probably from south west Asia and migrated to Cameroon through the Ismuth of Suez to Egypt and through Arabia to Somalia and Ethiopia. A relatively high nucleotide diversity (π) was found in Namchi Poli population (0.03421±0.00582) while in Namchi Ngaoundere a value of 0.00980±0.00185 was obtained, for a total nucleotide diversity of 0.01387±0.00234. The high genetic diversity observed in Namchi cattle breed reflects not only the presence of sub-haplogroups T1 but also an introgression from hybridization. This study provides new information regarding the sub haplogroups of the Namchi cattle, their origin and migration routes and their genetic diversity which seems to have been affected by gene flow with zebus like White Fulani or Red Fulani. To facilitate the preservation and the conservation of the Namchi cattle breed in Cameroon, it is therefore important to adopt effective breeding management practices.

The host-specific whale louse (Cyamus boopis) as a potential tool for interpreting humpback whale (Megaptera novaeangliae) migratory routes

The whale louse Cyamus boopis is a host-specific amphipod that parasitizes humpback whales (Megaptera novaeangliae) across the world. Humpback whales from the Southern Hemisphere are currently separated into seven breeding stocks, each with its own migration route to/from Antarctic waters. The aim of this study was to determine the population structure of C. boopis from the Southern Hemisphere using cytochrome oxydase I sequences, and compare it to that of its host species found in previous studies. High haplotype and nucleotide diversities in C. boopis were observed, and the populations from western south Atlantic (WSA: Brazil + Argentina − Breeding stock A) and western south Pacific (WSP: Australia - Breeding stock E) did not show any significant difference but were differentiated from populations of eastern south Atlantic (ESA: Namibia - Breeding stock B) and the north Pacific. The genetic homogeneity between WSA and WSP populations, might reveal a higher genetic transfer within the Southern Hemisphere, since the feeding grounds of whales which are distributed throughout the circumpolar Southern Ocean could allow inter-mixing of individuals from different breeding populations during the feeding season. The present data reinforces that population dynamics of humpback whales seem more complex than stable migration routes, which could have implications for both management of the species and cultural transmissions of behaviours.

Structural patterns of selection and diversity for Plasmodium vivax antigens DBP and AMA1

BackgroundPlasmodium vivax is a significant contributor to the global malaria burden, and a vaccine targeting vivax malaria is urgently needed. An understanding of the targets of functional immune responses during the course of natural infection will aid in the development of a vaccine. Antibodies play a key role in this process, with responses against particular epitopes leading to immune selection pressure on these epitopes. A number of techniques exist to estimate levels of immune selection pressure on particular epitopes, with a sliding window analysis often used to determine particular regions likely to be under immune pressure. However, such analysis neglects protein three-dimensional structural information. With this in mind, a newly developed tool, BioStructMap, was applied to two key antigens from Plasmodium vivax: PvAMA1 and PvDBP Region II. This tool incorporates structural information into tests of selection pressure.ResultsSequences from a number of populations were analysed, examining spatially-derived nucleotide diversity and Tajima’s D over protein structures for PvAMA1 and PvDBP. Structural patterns of nucleotide diversity were similar across all populations examined, with Domain I of PvAMA1 having the highest nucleotide diversity and displaying significant signatures of immune selection pressure (Tajima’s D > 0). Nucleotide diversity for PvDBP was highest bordering the dimerization and DARC-binding interface, although there was less evidence of immune selection pressure on PvDBP compared with PvAMA1. This study supports previous work that has identified Domain I as the main target of immune-mediated selection pressure for PvAMA1, and also supports studies that have identified functional epitopes within PvDBP Region II.ConclusionsThe BioStructMap tool was applied to leading vaccine candidates from P. vivax, to examine structural patterns of selection and diversity across a number of geographic populations. There were striking similarities in structural patterns of diversity across multiple populations. Furthermore, whilst regions of high diversity tended to surround conserved binding interfaces, a number of protein regions with very low diversity were also identified, and these may be useful targets for further vaccine development, given previous evidence of functional antibody responses against these regions.

Intraspecific mitochondrial genome comparison identified CYTB as a high-resolution population marker in a new pest Athetis lepigone

A new outbreak pest, Athetis lepigone (Möschler) (Lepidoptera: Noctuidae), has caused severe economic loss in maize crops in China. In order to conduct population genetics study with a more polymorphic and scientific mitochondrial marker, we sequenced the complete mitochondrial genomes of 13 different A. lepigone individuals. Intraspecific comparison of all PCGs showed that the NADH dehydrogenase and cytochrome b genes had the highest nucleotide diversity. We also found evidence of episodic positive selection on two amino acids, which are encoded by NADH dehydrogenase genes (ND3 and ND4L), against a background of widespread neutral selection of all other mitochondrial PCGs. The genetic divergence observed in this study indicated that the cytochrome b gene (CYTB) is better than COI at recovering population structure. The preliminary population genetic analysis illustrated strong gene flow among A. lepigone populations in China. Our study provides basic information for further research on population genetics of A. lepigone.

Spatio-temporal genetic structure of Anopheles gambiae in the Northwestern Lake Victoria Basin, Uganda: implications for genetic control trials in malaria endemic regions

BackgroundUnderstanding population genetic structure in the malaria vector Anopheles gambiae (s.s.) is crucial to inform genetic control and manage insecticide resistance. Unfortunately, species characteristics such as high nucleotide diversity, large effective population size, recent range expansion, and high dispersal ability complicate the inference of genetic structure across its range in sub-Saharan Africa. The ocean, along with the Great Rift Valley, is one of the few recognized barriers to gene flow in this species, but the effect of inland lakes, which could be useful sites for initial testing of genetic control strategies, is relatively understudied. Here we examine Lake Victoria as a barrier between the Ugandan mainland and the Ssese Islands, which lie up to 60 km offshore. We use mitochondrial DNA (mtDNA) from populations sampled in 2002, 2012 and 2015, and perform Bayesian cluster analysis on mtDNA combined with microsatellite data previously generated from the same 2002 mosquito DNA samples.ResultsHierarchical analysis of molecular variance and Bayesian clustering support significant differentiation between the mainland and lacustrine islands. In an mtDNA haplotype network constructed from this and previous data, haplotypes are shared even between localities separated by the Rift Valley, a result that more likely reflects retention of shared ancestral polymorphism than contemporary gene flow.ConclusionsThe relative genetic isolation of An. gambiae on the Ssese Islands, their small size, level terrain and ease of access from the mainland, the relative simplicity of the vectorial system, and the prevalence of malaria, are all attributes that recommend these islands as possible sites for the testing of genetic control strategies.

A Genomic Reference Panel for Drosophila serrata.

Here we describe a collection of re-sequenced inbred lines of Drosophila serrata, sampled from a natural population situated deep within the species endemic distribution in Brisbane, Australia. D. serrata is a member of the speciose montium group whose members inhabit much of south east Asia and has been well studied for aspects of climatic adaptation, sexual selection, sexual dimorphism, and mate recognition. We sequenced 110 lines that were inbred via 17-20 generations of full-sib mating at an average coverage of 23.5x with paired-end Illumina reads. 15,228,692 biallelic SNPs passed quality control after being called using the Joint Genotyper for Inbred Lines (JGIL). Inbreeding was highly effective and the average levels of residual heterozygosity (0.86%) were well below theoretical expectations. As expected, linkage disequilibrium decayed rapidly, with r2 dropping below 0.1 within 100 base pairs. With the exception of four closely related pairs of lines which may have been due to technical errors, there was no statistical support for population substructure. Consistent with other endemic populations of other Drosophila species, preliminary population genetic analyses revealed high nucleotide diversity and, on average, negative Tajima’s D values. A preliminary GWAS was performed on a cuticular hydrocarbon trait, 2-Me-C28 revealing 4 SNPs passing Bonferroni significance residing in or near genes. One gene Cht9 may be involved in the transport of CHCs from the site of production (oenocytes) to the cuticle. Our panel will facilitate broader population genomic and quantitative genetic studies of this species and serve as an important complement to existing D. melanogaster panels that can be used to test for the conservation of genetic architectures across the Drosophila genus.

Genetic variation and diversity in 199 Melilotus accessions based on a combination of 5 DNA sequences.

Melilotus is an important genus of legume plants and an herbage with excellent nitrogen fixation; it can tolerate extreme environmental conditions and possesses important medicinal value. However, there is limited genetic information about the genus; thus, we analysed four chloroplast loci (rbcL, matK, psbA-trnH and trnL-F) and one nuclear region (ITS) to determine the genetic diversity of 199 accessions from 18 Melilotus species. The rbcL and matK sequences were highly conserved, whereas the trnL-F and ITS sequences contained variable and parsimony-informative sites. In our analyses of the single and combined regions, we calculated the pairwise distance, haplotype and nucleotide diversity and gaps and then constructed phylogenetic trees to assess the genetic diversity, and our results revealed significant variations among the different accessions. The genetic distance values were between zero and nine, and based on the combined regions, the highest frequency value was approximately four. Melilotus showed high haplotype and nucleotide diversity, particularly in the ITS sequences, with values of 0.86 and 0.0087, respectively. The single ITS sequence, psbA-trnH, and the combined matK+rbcL+trnL-F (MRT) and matK+rbcL+psbA-trnH+trnL-F+ITS (MRPTI) regions showed interspecific variation in the gap analysis. Phylogenetic trees calculated using ITS, psbA-trnH and MRPTI sequences indicated distinct genetic relationship in 18 species, and these species could be divided into two groups. By determining the genetic diversity of plants, we can evaluate the genetic relationships among species and accessions, providing a basis for preserving and utilizing the genetic resources of Melilotus.

MtDNA genetic diversity and structure of Eurasian Collared Dove (Streptopelia decaocto).

The Eurasian Collared Dove (Streptopelia decaocto) is one of the most successful biological invaders among terrestrial vertebrates. However, little information is available on the genetic diversity of the species. A total of 134 Eurasian Collared Doves from Europe, Asia and the Caribbean (n = 20) were studied by sequencing a 658-bp length of mitochondrial DNA (mtDNA) cytochrome oxidase I (COI). Fifty-two different haplotypes and relatively high haplotype and nucleotide diversities (Hd±SD = 0.843±0.037 and π±SD = 0.026±0.013) were detected. Haplotype Ht1 was particularly dominant: it included 44.03% of the studied individuals, and contained sequences from 75% of the studied countries. Various analyses (FST, AMOVA, STRUCTURE) distinguished 2 groups on the genetic level, designated ‘A’ and ‘B’. Two groups were also separated in the median-joining network and the maximum likelihood tree. The results of the neutrality tests were negative (Fu FS = -25.914; Tajima D = -2.606) and significantly different from zero (P≤0.001) for group A, whereas both values for group B were positive (Fu FS = 1.811; Tajima D = 0.674) and not significant (P>0.05). Statistically significant positive autocorrelation was revealed among individuals located up to 2000 km apart (r = 0.124; P = 0.001). The present results provide the first information on the genetic diversity and structure of the Eurasian Collared Dove, and can thereby serve as a factual and comparative basis for similar studies in the future.

Fine-Scale Recombination Maps of Fungal Plant Pathogens Reveal Dynamic Recombination Landscapes and Intragenic Hotspots.

Meiotic recombination is an important driver of evolution. Variability in the intensity of recombination across chromosomes can affect sequence composition, nucleotide variation, and rates of adaptation. In many organisms, recombination events are concentrated within short segments termed recombination hotspots. The variation in recombination rate and positions of recombination hotspot can be studied using population genomics data and statistical methods. In this study, we conducted population genomics analyses to address the evolution of recombination in two closely related fungal plant pathogens: the prominent wheat pathogen Zymoseptoria tritici and a sister species infecting wild grasses Z. ardabiliae. We specifically addressed whether recombination landscapes, including hotspot positions, are conserved in the two recently diverged species and if recombination contributes to rapid evolution of pathogenicity traits. We conducted a detailed simulation analysis to assess the performance of methods of recombination rate estimation based on patterns of linkage disequilibrium, in particular in the context of high nucleotide diversity. Our analyses reveal overall high recombination rates, a lack of suppressed recombination in centromeres, and significantly lower recombination rates on chromosomes that are known to be accessory. The comparison of the recombination landscapes of the two species reveals a strong correlation of recombination rate at the megabase scale, but little correlation at smaller scales. The recombination landscapes in both pathogen species are dominated by frequent recombination hotspots across the genome including coding regions, suggesting a strong impact of recombination on gene evolution. A significant but small fraction of these hotspots colocalize between the two species, suggesting that hotspot dynamics contribute to the overall pattern of fast evolving recombination in these species.

Mitochondrial signatures revealed panmixia in Lutjanus argentimaculatus (Forsskål 1775)

Mangrove red snapper, Lutjanus argentimaculatus is a commercially important fish. The genetic stock structure of L. argentimaculatus from Indian waters was identified using mitochondrial ATPase 6 and ATPase 8, and cytochrome b (Cytb) genes. A 842 bp region of ATPase 6/8 genes and 1105 bp region of Cytb gene were amplified in 120 samples from six different locations along the Indian coast and obtained 58 and 66 haplotypes, respectively. The high haplotype and low nucleotide diversity values along with mismatch distribution, Tajima's D and Fu's Fs analysis suggested a genetic bottleneck events or founder effect, with subsequent population expansion in L. argentimaculatus. Coefficient of genetic differentiation (FST) values was low and nonsignificant for both ATPase 6/8 gene and Cytb genes indicating low genetic differentiation in L. argentimaculatus which can be managed as a unit stock in Indian waters.