Bayesian Analysis Of Population Structure Research Articles

Population Genetic Structure of the Threatened Amazon River Turtle,Podocnemis sextuberculata(Testudines, Podocnemididae)

Abstract Podocnemis sextuberculata (Pleurodira: Podocnemididae) is widely distributed throughout the Amazon drainage basin in Brazil, Colombia, and Peru. Telemetry and previous molecular data suggest that P. sextuberculata lacks population structure in the central Amazon basin of Brazil. Generalization of these results, however, requires much-broader sampling across a range of habitats of this broadly distributed species. For this reason, we tested the hypothesis of panmixia in P. sextuberculata, analyzing a total of 319 specimens sequenced for the mitochondrial control region. Our sampling included localities from 16 areas in the Amazon basin from rivers characteristic of the Amazon basin (whitewater), clearwater rivers of the Guiana shield (Branco, Trombetas, and Nhamunda rivers), and the Brazilian shield (Xingu River). The hypothesis of panmixia was rejected because the results of analysis of molecular variance, pairwise ФST, and Bayesian analysis of population structure indicated population structure ...

AFLP diversity and spatial structure of Calycophyllum candidissimum (Rubiaceae), a dominant tree species of Nicaragua's critically endangered seasonally dry forest.

The Central American seasonally dry tropical (SDT) forest biome is one of the worlds' most endangered ecosystems, yet little is known about the genetic consequences of its recent fragmentation. A prominent constituent of this biome is Calycophyllum candidissimum, an insect-pollinated and wind-dispersed canopy tree of high socio-economic importance, particularly in Nicaragua. Here, we surveyed amplified fragment length polymorphisms across 13 populations of this species in Nicaragua to elucidate the relative roles of contemporary vs historical factors in shaping its genetic variation. Genetic diversity was low in all investigated populations (mean HE=0.125), and negatively correlated with latitude. Overall population differentiation was moderate (ΦST=0.109, P<0.001), and Bayesian analysis of population structure revealed two major latitudinal clusters (I: 'Pacific North'+'Central Highland'; II: 'Pacific South'), along with a genetic cline between I and II. Population-based cluster analyses indicated a strong pattern of 'isolation by distance' as confirmed by Mantel's test. Our results suggest that (1) the low genetic diversity of these populations reflects biogeographic/population history (colonisation from South America, Pleistocene range contractions) rather than recent human impact; whereas (2) the underlying process of their isolation by distance pattern, which is best explained by 'isolation by dispersal limitation', implies contemporary gene flow between neighbouring populations as likely facilitated by the species' efficient seed dispersal capacity. Overall, these results underscore that even tree species from highly decimated forest regions may be genetically resilient to habitat fragmentation due to species-typical dispersal characteristics, the necessity of broad-scale measures for their conservation notwithstanding.

New Mycobacterium tuberculosis Beijing clonal complexes in China revealed by phylogenetic and Bayesian population structure analyses of 24-loci MIRU-VNTRs

Beijing lineage of Mycobacterium tuberculosis constitutes the most predominant lineage in East Asia. Beijing epidemiology, evolutionary history, genetics are studied in details for years revealing probable origin from China followed by worldwide expansion, partially linked to higher mutation rate, hypervirulence, drug-resistance, and association with cases of mixed infections. Considering huge amount of data available for 24-loci Mycobacterial Interspersed Repetitive Units-Variable Number of Tandem Repeats, we performed detailed phylogenetic and Bayesian population structure analyses of Beijing lineage strains in mainland China and Taiwan using available 24-loci MIRU-VNTR data extracted from publications or the SITVIT2 database (n = 1490). Results on genetic structuration were compared to previously published data. A total of three new Beijing clonal complexes tentatively named BSP1, BPS2 and BSP3 were revealed with surprising phylogeographical specificities to previously unstudied regions in Sichuan, Chongqing and Taiwan, proving the need for continued investigations with extended datasets. Such geographical restriction could correspond to local adaptation of these “ecological specialist” Beijing isolates to local human host populations in contrast with “generalist pathogens” able to adapt to several human populations and to spread worldwide.

Pre-vaccine serotype composition within a lineage signposts its serotype replacement - a carriage study over 7 years following pneumococcal conjugate vaccine use in the UK.

Serotype replacement has been reported in carriage and disease after pneumococcal conjugate vaccine (PCV) introductions in the UK and globally. We previously described concurrent expansion and decline of sequence types associated with serotype replacement over 5 years following PCV introductions in the UK. Here we use whole-genome sequencing to fully characterise the population structure of pneumococcal isolates collected over seven winters encompassing PCV7 and PCV13 introductions in the UK, investigating the importance of lineages in serotype replacement. We analysed 672 pneumococcal genomes from colonised children of 4 years old or less. The temporal prevalence of 20 lineages, defined by hierarchical Bayesian analysis of population structure (BAPS), was assessed in the context of serotype replacement. Multiple serotypes were detected in the primary winter of sampling within three vaccine-type (VT) lineages BAPS4, BAPS10 and BAPS11, in which serotype replacement were observed. In contrast, serotype replacement was not seen in the remaining three VT lineages (BAPS1, BAPS13 and BAPS14), that expressed a single serotype (6B, 6A and 3, respectively) in the primary winter. One lineage, BAPS1 serotype 6B was undetectable in the population towards the end of the study period. The dynamics of serotype replacement, in this UK population, was preceded by the presence or absence of multiple serotypes within VT lineages, in the pre-PCV population. This observation could help predict which non-vaccine types (NVTs) may be involved in replacement in future PCV introductions here and elsewhere. It could further indicate whether any antibiotic resistance associated with the lineages is likely to be affected by replacement.

Population genetics of wild and managed pollinators: implications for crop pollination and the genetic integrity of wild bees

Loss of habitat and chemical use associated with agriculture can cause population declines of wild pollinators. Less is known about the evolutionary consequences of interactions between species used in commercial agriculture and wild pollinators. Given population declines of many wild bee species, it is crucial to understand if commercial queens become established in natural areas, if wild bees visit agricultural fields and have the potential to interact with commercial bees, and if gene flow occurs between commercial and wild bees. We drew on a long-term data set that documents commercial bumble bee (Bombus impatiens) use in New England, and we conducted genetic analyses of foraging B. impatiens from areas with varying intensities of commercial bee use. In agricultural areas with a history of commercial bee use we also sampled bees directly from commercial hives. We found significant genetic differences among foraging B. impatiens and B. impatiens sampled directly from hives (average pairwise F′ST = 0.14), but not among samples of foraging bees from natural areas (average F′ST among foraging bees = 0.002). Furthermore, Bayesian analysis of population structure revealed that foraging bees caught in areas with a history of commercial bee use grouped with samples from natural areas. These results document an agricultural setting where there was no widespread introgression of alleles from commercial bumble bees to wild bumble bees, commercial bumble bees did not become established in natural areas, and wild bees were providing pollination services to crops.

Distribution of antimicrobial resistance determinants, virulence-associated factors and clustered regularly interspaced palindromic repeats loci in isolates of Enterococcus faecalis from various settings and genetic lineages.

Enterococcus faecalis represents an important factor of hospital-associated infections (HAIs). The knowledge on its evolution from a commensal to an opportunistic pathogen is still limited; thus, we performed a study to characterise distribution of factors that may contribute to this adaptation. Using a collection obtained from various settings (hospitalised patients, community carriers, animals, fresh food, sewage, water), we investigated differences in antimicrobial susceptibility, distribution of antimicrobial resistance genes, virulence-associated determinants and phenotypes, and CRISPR loci in the context of the clonal relatedness of isolates. Bayesian Analysis of Population Structure revealed the presence of three major groups; two subgroups comprised almost exclusively HAI isolates, belonging to previously proposed enterococcal high-risk clonal complexes (HiRECCs) 6 and 28. Isolates of these two subgroups were significantly enriched in antimicrobial resistance genes, presumably produced a polysaccharide capsule and often carried the aggregation substance asa1; distribution of other virulence-associated genes, such as esp and cyl, formation of a biofilm and gelatinase production were more variable. Moreover, both subgroups showed a low prevalence of CRISPR-Cas 1 and 3 and presence of small CRISPR2 variants. Our study confirms the importance of HiRECCs in the population of E. faecalis and their confinement to the hospital settings.

Bayesian population structure analysis reveals presence of phylogeographically specific sublineages within previously ill-defined T group of Mycobacterium tuberculosis.

Mycobacterium tuberculosis genetic structure, and evolutionary history have been studied for years by several genotyping approaches, but delineation of a few sublineages remains controversial and needs better characterization. This is particularly the case of T group within lineage 4 (L4) which was first described using spoligotyping to pool together a number of strains with ill-defined signatures. Although T strains were not traditionally considered as a real phylogenetic group, they did contain a few phylogenetically meaningful sublineages as shown using SNPs. We therefore decided to investigate if this observation could be corroborated using other robust genetic markers. We consequently made a first assessment of genetic structure using 24-loci MIRU-VNTRs data extracted from the SITVIT2 database (n = 607 clinical isolates collected in Russia, Albania, Turkey, Iraq, Brazil and China). Combining Minimum Spanning Trees and Bayesian population structure analyses (using STRUCTURE and TESS softwares), we distinctly identified eight tentative phylogenetic groups (T1-T8) with a remarkable correlation with geographical origin. We further compared the present structure observed with other L4 sublineages (n = 416 clinical isolates belonging to LAM, Haarlem, X, S sublineages), and showed that 5 out of 8 T groups seemed phylogeographically well-defined as opposed to the remaining 3 groups that partially mixed with other L4 isolates. These results provide with novel evidence about phylogeographically specificity of a proportion of ill-defined T group of M. tuberculosis. The genetic structure observed will now be further validated on an enlarged worldwide dataset using Whole Genome Sequencing (WGS).

Phylogeography of the reef‐building polychaetes of the genus Phragmatopoma in the western Atlantic Region

AbstractAimTo verify the synonymy of the reef‐building polychaete Phragmatopoma caudata (described for the Caribbean) and Phragmatopoma lapidosa (described for Brazil) using molecular data. To evaluate the patterns of genetic diversity and connectivity among populations from Florida to South Brazil.LocationIntertidal zone in the western Atlantic biogeographical Region: Brazil, eastern Caribbean and Florida (USA).MethodsDNA sequence data from one mitochondrial (cox‐1) and one nuclear ribosomal (ITS‐1) loci were obtained from 11 populations of P. caudata spanning the coasts of Brazil, eastern Caribbean and Florida. Phylogenetic relationships among populations of P. caudata and other members of the genus were inferred by Bayesian methods. Population differentiation was evaluated by Bayesian analysis of population structure (baps), AMOVA and pairwise φst. Demographic history was inferred by Bayesian skyline plots.ResultsPhylogenetic inference supported the interpretation of a single species of Phragmatopoma spanning the Brazilian and Caribbean Provinces of the western Atlantic Region. Little population structure was observed across the species distribution, with the exception of the Florida population. The baps analysis supported a 2‐population model, with population differentiation being strong and significant between Florida and all other Atlantic populations for cox‐1, and significant between Florida and most populations for ITS‐1. Differences in genetic diversity were not significant between Caribbean and Brazilian populations, although several populations in Brazil had low values for diversity indices. Bayesian skyline plots indicate population expansion starting at c. 200 ka.Main conclusionsPhragmatopoma caudata is able to maintain genetic connectivity across most of its geographical range, with population differentiation being observed only between Florida and all other localities, possibly due to ecological speciation in the transition zone between tropical and subtropical environments. Long‐distance connectivity across much of the species range is likely the result of long‐lived larvae that are tolerant to a wide range of environmental conditions.

Rapid detection of high-risk Enterococcus faecium clones by matrix-assisted laser desorption ionization time-of-flight mass spectrometry

We aimed to explore the potential of matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) for early identification of dominant Enterococcus faecium (Efm) clones involved in human infections. Well-characterized Efm isolates (n=77), analyzed by pulsed-field gel electrophoresis and multilocus sequence typing(eBURST and BAPS [Bayesian analysis of population structure] algorithms), and belonging to different hospital (n=53) and community (n=24) phylogenomic groups, were tested. Mass spectra (Bruker) were analyzed by visual inspection and different chemometric tools. Discrimination between groups comprising isolates commonly found in hospitals (BAPS 2.1a, 3.3a1, 3.3a2) and community (BAPS 2.1b and 3.2) was achieved with >99% accuracy, while identification of sequence types belonging to different BAPS subgroups was associated with >95% correct predictions. Our work is a proof of concept with regard to the suitability of MALDI-TOF MS in the identification of high-risk Efm clones. Further studies including strains from a wider variety of clones and sources will strengthen the potential of the workflow here described.

Utilization of Molecular, Phenotypic, and Geographical Diversity to Develop Compact Composite Core Collection in the Oilseed Crop, Safflower (Carthamus tinctorius L.) through Maximization Strategy.

Safflower (Carthamus tinctorius L.) is a dryland oilseed crop yielding high quality edible oil. Previous studies have described significant phenotypic variability in the crop and used geographical distribution and phenotypic trait values to develop core collections. However, the molecular diversity component was lacking in the earlier collections thereby limiting their utility in breeding programs. The present study evaluated the phenotypic variability for 12 agronomically important traits during two growing seasons (2011–12 and 2012–13) in a global reference collection of 531 safflower accessions, assessed earlier by our group for genetic diversity and population structure using AFLP markers. Significant phenotypic variation was observed for all the agronomic traits in the representative collection. Cluster analysis of phenotypic data grouped the accessions into five major clusters. Accessions from the Indian Subcontinent and America harbored maximal phenotypic variability with unique characters for a few traits. MANOVA analysis indicated significant interaction between genotypes and environment for both the seasons. Initially, six independent core collections (CC1–CC6) were developed using molecular marker and phenotypic data for two seasons through POWERCORE and MSTRAT. These collections captured the entire range of trait variability but failed to include complete genetic diversity represented in 19 clusters reported earlier through Bayesian analysis of population structure (BAPS). Therefore, we merged the three POWERCORE core collections (CC1–CC3) to generate a composite core collection, CartC1 and three MSTRAT core collections (CC4–CC6) to generate another composite core collection, CartC2. The mean difference percentage, variance difference percentage, variable rate of coefficient of variance percentage, coincidence rate of range percentage, Shannon's diversity index, and Nei's gene diversity for CartC1 were 11.2, 43.7, 132.4, 93.4, 0.47, and 0.306, respectively while the corresponding values for CartC2 were 9.3, 58.8, 124.6, 95.8, 0.46, and 0.301. Each composite core collection represented the complete range of phenotypic and genetic variability of the crop including 19 BAPS clusters. This is the first report describing development of core collections in safflower using molecular marker data with phenotypic values and geographical distribution. These core collections will facilitate identification of genetic determinants of trait variability and effective utilization of the prevalent diversity in crop improvement programs.

Analysis of mitochondrial genetic diversity of Ustilago maydis in Mexico

The current understanding of the genetic diversity of the phytopathogenic fungus Ustilago maydis is limited. To determine the genetic diversity and structure of U. maydis, 48 fungal isolates were analyzed using mitochondrial simple sequence repeats (SSRs). Tumours (corn smut or ‘huitlacoche’) were collected from different Mexican states with diverse environmental conditions. Using bioinformatic tools, five microsatellites were identified within intergenic regions of the U. maydis mitochondrial genome. SSRMUM4 was the most polymorphic marker. The most common repeats were hexanucleotides. A total of 12 allelic variants were identified, with a mean of 2.4 alleles per locus. An estimate of the genetic diversity using analysis of molecular variance (AMOVA) revealed that the highest variance component is within states (84%), with moderate genetic differentiation between states (16%) (FST = 0.158). A dendrogram generated using the unweighted paired-grouping method with arithmetic averages (UPGMA) and the Bayesian analysis of population structure grouped the U. maydis isolates into two subgroups (K = 2) based on their shared SSRs.

Cryptic diversity and multiple origins of the widespread mayfly species group Baetis rhodani (Ephemeroptera: Baetidae) on northwestern Mediterranean islands.

How the often highly endemic biodiversity of islands originated has been debated for decades, and it remains a fervid research ground. Here, using mitochondrial and nuclear gene sequence analyses, we investigate the diversity, phylogenetic relationships, and evolutionary history of the mayfly Baetis gr. rhodani on the three largest northwestern Mediterranean islands (Sardinia, Corsica, Elba). We identify three distinct, largely co‐distributed, and deeply differentiated lineages, with divergences tentatively dated back to the Eocene–Oligocene transition. Bayesian population structure analyses reveal a lack of gene exchange between them, even at sites where they are syntopic, indicating that these lineages belong to three putative species. Their phylogenetic relationships with continental relatives, together with the dating estimates, support a role for three processes contributing to this diversity: (1) vicariance, primed by microplate disjunction and oceanic transgression; (2) dispersal from the continent; and (3) speciation within the island group. Thus, our results do not point toward a prevailing role for any of the previously invoked processes. Rather, they suggest that a variety of processes equally contributed to shape the diverse and endemic biota of this group of islands.

Using genetic monitoring to inform best practice in a captive breeding programme: inbreeding and potential genetic rescue in the freshwater pearl mussel Margaritifera margaritifera

Freshwater pearl mussel (Margaritifera margaritifera) populations are declining in Northern Ireland to the extent that a captive breeding programme was established on the Upper Ballinderry river in 1998. Previous genetic analysis of the hatchery broodstock and their first cohort of offspring showed significant levels of inbreeding (F IS = 0.166). The broodstock, which currently numbers ca. 90 individuals, was supplemented with new individual mussels, whilst in 2013, a previously unknown population was discovered on the Lower Ballinderry river. The aim of the present study was to determine whether the rotation of the broodstock has led to a decrease in the levels of inbreeding in the second cohort of juveniles, and to determine whether the new population found in the Lower Ballinderry was genetically distinct from the captive bred population and populations from the Upper Ballinderry, which represent the source of the hatchery broodstock. Genotyping using eight microsatellite markers indicated that levels of inbreeding in the second cohort of captive-bred mussels were high, (F IS = 0.629), and were comparable to those sampled from the original cohort and the hatchery broodstock (F IS = 0.527 and 0.636 respectively). Bayesian analysis of population structure indicated that the newly discovered Lower Ballinderry population was genetically distinct from the broodstock and its source populations on the Upper Ballinderry. The observed differentiation was primarily due to differences in allele frequencies, and was most likely a result of genetic drift. The occurrence of ten alleles, albeit at low frequency, in the Lower Ballinderry population, including four private alleles, suggests that this new population could be incorporated into the broodstock with the aim of decreasing levels of inbreeding in the future.

The genetic diversity of triticale genotypes involved in Polish breeding programs.

Genetic diversity analysis of triticale populations is useful for breeding programs, as it helps to select appropriate genetic material for classifying the parental lines, heterotic groups and predicting hybrid performance. In our study 232 breeding forms were analyzed using diversity arrays technology markers. Principal coordinate analysis followed by model-based Bayesian analysis of population structure revealed the presence of weak data structuring with three groups of data. In the first group, 17 spring and 17 winter forms were clustered. The second and the third groups were represented by 101 and 26 winter forms, respectively. Polymorphic information content values, as well as Shannon’s Information Index, were higher for the first (0.319) and second (0.309) than for third (0.234) group. AMOVA analysis demonstrated a higher level of within variation (86 %) than among populations (14 %). This study provides the basic information on the presence of structure within a genetic pool of triticale breeding forms.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-016-1997-8) contains supplementary material, which is available to authorized users.

Genetic diversity and hybridization in the two species Inga ingoides and Inga edulis: potential applications for agroforestry in the Peruvian Amazon

Slash and burn practices affect tropical forests. Our results showed strong introgression between Inga ingoides and Inga edulis in the species contact area. Interspecific hybridization could be sought to improve yield and tolerance to flooding and further increase the economic potential of the poorly drained Amazonian soils and minimize deforestation. Inga species are important components of tropical American forests, as well as a local food source. Little is known about the genetic structure of these species; in particular the amount of introgression among species remains unknown. We assessed the degree of genetic divergence and introgression among populations of I. ingoides (Rich.) Willd. and I. edulis Mart. (Fabaceae) from three Peruvian Amazon tributary rivers. Using microsatellite markers we determined the genetic structure of populations using an analysis of molecular variance and a Bayesian analysis of population structure in areas affected by seasonal river fluctuations and in ‘terra firme’ forests. Overall genetic differentiation was weak. The degree of genetic variation was similar in the two species. A putatively strong introgression was detected between the two species and an intense gene flow was identified among populations. This indicates that an intense gene flow had happened in the past, leading also to a small differentiation among populations within species. Selection of natural hybrids or artificial hybridization between I. edulis and I. ingoides could be applied to improve legume size and yield in the later species, while maintaining tolerance to flooding. Improved I. ingoides could be used in multipurpose agroforestry on open areas along the rivers, instead of using the usual slash and burn practice to create inland open areas.

The conservation status of the Galápagos marine iguanas, Amblyrhynchus cristatus: a molecular perspective

Traditionally, conservation management focuses efforts on taxonomic units. However, when the taxa used do not reflect biologically meaningful units, such methods should be reconsidered to avoid the loss of irreplaceable biodiversity. The Galápagos marine iguana (Amblyrhynchus cristatus) is listed as Vulnerable on the IUCN Red List of Threatened Species and is facing growing anthropogenic threats. Currently, management is based on a taxonomy which is questionable in the light of recent molecular data. As such, there is a danger that evolutionarily significant populations may be left vulnerable to extirpation. Herein, we apply molecular data to elucidate the population structure of this species across the Galápagos archipelago, and thus advise conservation management in the absence of a revised taxonomy. Applying a wealth of molecular data including 12 microsatellite loci and 1181 bp of the mitochondrial control region in over 1200 individuals, we delineate distinct populations and prioritize their management. Bayesian population structure analysis revealed 10 distinct population clusters, which we propose as management units (MUs). All MUs are significantly differentiated, with one unit on San Cristóbal Island being particularly distinct in terms of both microsatellite loci and mitochondrial data. Based on estimates of the genetic effective population size (Ne), we find the MUs comprised of populations occurring on Floreana, Española, Marchena, and San Cristóbal to be alarmingly small. In consideration of both Neand anthropogenic threats, we recommend that conservation practitioners focus efforts on Floreana and San Cristóbal islands, and argue that better census size estimates of populations are urgently needed.

Ecological and historical determinants of population genetic structure and diversity in the Mediterranean shrubRosmarinus officinalis(Lamiaceae)

Population genetic studies of widespread Mediterranean shrubs are scarce compared with those of trees and narrow endemics or studies from phylogeographical perspectives, despite the key role these species may play in Mediterranean ecosystems. Knowledge on the effect of ecological factors in shaping their genetic patterns is also limited. In this study we investigate genetic diversity and population structure across 18 populations of Rosmarinus officinalis, a Mediterranean shrubland plant. Populations were sampled along two elevational gradients, one each on calcareous and siliceous soils in a mountain system in the eastern Iberian Peninsula, to decipher the effect of ecological factors on the genetic diversity and structure based on 11 microsatellite loci. We found overall high levels of genetic diversity and weak population structure. Genetic diversity increased with elevation, whereas population differentiation was stronger among populations growing on siliceous soils. The nested analysis of elevational gradients within soil types revealed that these general patterns were mostly driven by siliceous populations, whereas calcareous populations were more homogeneous along elevational belts. Bayesian analysis of population structure revealed genetic membership of lowland and high-elevation populations to different genetic clusters and a higher admixture of intermediate-elevation populations to both clusters. High-elevation populations were less differentiated from a hypothetical ancestral cluster, suggesting the persistence of their gene pool during the Pleistocene glaciations. In contrast, lowland populations resulted from more recent divergence. We propose that life-history and reproductive traits mostly contribute to explain the high levels of genetic diversity and weak population structure, whereas ecological and historical factors mostly contribute to the stronger differentiation of siliceous populations and a rapid expansion of R. officinalis on calcareous soils possibly mediated by human landscape transformations.

Phylogeographic data revealed shallow genetic structure in the kelp Saccharina japonica (Laminariales, Phaeophyta).

BackgroundPopulation structure and genetic diversity of marine organisms in the Northwestern Pacific Ocean exhibited complex patterns. Saccharina japonica is a commercially and ecologically important kelp species widely distributed along the coast of Japan Sea. However, it is still poorly known about population genetics and phylogeographic patterns of wild S. japonica populations on a large geographic scale, which is an important contribution to breeding and conservation of this marine crop.ResultsWe collected 612 mitochondrial COI and trnW-trnL sequences. Diversity indices suggested that S. japonica populations along the coast of Hokkaido exhibited the highest genetic diversity. Bayesian Analysis of Population Structure (BAPS) revealed four clusters in the kelp species (cluster 1: Hokkaido and South Korea; cluster 2: northwestern Hokkaido; cluster 3: Far Eastern Russia; cluster 4: China). The network inferred from concatenated data exhibited two shallow genealogies corresponding to two BAPS groups (cluster 2 and cluster 3). We did not detect gene flow between the two shallow genealogies, but populations within genealogy have asymmetric gene exchange. Bayesian skyline plots and neutrality tests suggested that S. japonica experienced postglacial expansion around 10.45 ka.ConclusionsThe coast of Hokkaido might be the origin and diversification center of S. japonica. Gene exchange among S. japonica populations could be caused by anthropogenic interference and oceanographic regimes. Postglacial expansions and gene exchange apparently led to more shared haplotypes and less differentiation that in turn led to the present shallow phylogeographical patterns in S. japonica.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0517-8) contains supplementary material, which is available to authorized users.

Genetic diversity and distribution patterns of Ecuadorian capuli (Prunus serotina)

Prunus serotina subsp. capuli (Cav.) is an arboreal species with promising economic prospects in the timber, health-food and neutraceutical markets. Despite its cultural and commercial significance, limited information exists with regards to the degree of genetic variation and ecological history of P. serotina in Ecuador. The main objective of this study was to evaluate the degree of genetic diversity and population structure of Ecuadorian P. serotina, as a preliminary step towards understanding the distribution history of this species in Ecuador and establishing germplasm conservation programs. P. serotina samples (217, representing 8 provinces from the Ecuadorian highlands) were characterized using 8 heterologous SSR markers derived from related Prunus species. Expected heterozygosity across samples (He = 0.71) reveals a moderate level of genetic diversity for Ecuadorian P. serotina. Nevertheless, simple allele-count analysis indicates that Ecuadorian capuli has a narrower degree of allelic richness relative to collections from the species’ center of origin in North America. Furthermore, pairwise F statistics (0.0069 ≤ Fst ≤ 0.0319) and Nei genetic distance estimates (0.02 ≤ Ds ≤ 0.09) indicate minimal population differentiation within Ecuadorian capuli. However, Bayesian population structure analysis suggests a subtle genetic contrast between germplasm from the Northern and Southern highlands. Certainly, it is of interest to analyze whether this underlying genetic differentiation between the Northern- and Southern-Highland groups is also manifested in morphological, agronomic or other phenotypic characters that could indicate adaptive differences to divergent agro-ecosystems.

Genetic relatedness and risk factor analysis of ampicillin-resistant and high-level gentamicin-resistant enterococci causing bloodstream infections in Tanzanian children.

BackgroundWhile enterococci resistant to multiple antimicrobials are spreading in hospitals worldwide, causing urinary tract, wound and bloodstream infections, there is little published data on these infections from Africa.MethodsWe assessed the prevalence, susceptibility patterns, clinical outcome and genetic relatedness of enterococcal isolates causing bloodstream infections in children in a tertiary hospital in Tanzania, as part of a prospective cohort study of bloodstream infections among 1828 febrile children admitted consecutively from August 2001 to August 2002.ResultsEnterococcal bacteraemia was identified in 2.1% (39/1828) of admissions, and in 15.3% (39/255) of cases of culture-confirmed bloodstream infections. The case-fatality rate in children with Enterococcus faecalis septicaemia (28.6%, 4/14) was not significantly different from those with Enterococcus faecium septicaemia (6.7%, 1/15, p = 0.12). E. faecium isolates commonly had combined ampicillin-resistance and high-level gentamicin resistance (HLGR), (9/17), while E. faecalis frequently displayed HLGR (6/15), but were ampicillin susceptible. None of the tested enterococcal isolates displayed vancomycin resistance by Etest or PCR for vanA and vanB genes. Multi-locus sequence-typing (MLST) showed that the majority of E. faecium (7/12) belonged to the hospital associated Bayesian Analysis of Population Structure (BAPS) group 3–3. Pulsed-field gel electrophoresis (PFGE) indicated close genetic relationship particularly among E. faecium isolates, but also among E. faecalis isolates. There was also correlation between BAPS group and PFGE results. Risk factors for enterococcal bloodstream infection in univariate analysis were hospital-acquired infection and clinical diagnosis of sepsis with unknown focus. In multivariate analysis, neonates in general were relatively protected from enterococcal infection, while both prematurity and clinical sepsis were risk factors. Malnutrition was a risk factor for enterococcal bloodstream infection among HIV negative children.ConclusionThis is the first study to describe bloodstream infections caused by ampicillin-resistant HLGR E. faecium and HLGR E. faecalis in Tanzania. The isolates of E. faecium and E. faecalis, respectively, showed high degrees of relatedness by genotyping using PFGE. The commonly used treatment regimens at the hospital are insufficient for infections caused by these microbes. The study results call for increased access to microbiological diagnostics to guide rational antibiotic use in Tanzania.