Genetic Diversity Assessment in Plants from Reduced Representation Sequencing Data.

Genetic diversity refers to the variety of genetic traits within a population or a species. It is an essential aspect of both plant ecology and plant breeding because it contributes to the adaptability, survival, and resilience of populations in changing environments. This chapter outlines a pipeline for estimating genetic diversity statistics from reduced representation or whole genome sequencing data. The pipeline involves obtaining DNA sequence reads, mapping the corresponding reads to a reference genome, calling variants from the alignments, and generating an unbiased estimation of nucleotide diversity and divergence between populations. The pipeline is suitable for single-end Illumina reads and can be adjusted for paired-end reads. The resulting pipeline provides a comprehensive approach for aligning and analyzing sequencing data to estimate genetic diversity.

Building a Teleost Fish Traceability Program Based on Genetic Data from Pacific Panama Fish Markets.

Fish tissue samples from 203 adult individuals were collected in the main ports and markets of the Pacific coast of Panama. Molecular identification based on a cytochrome oxidase I gene segment of all species was verified by GENBANK reference sequences. A total of 34 species from 14 families (Ariidae, Caranjidae, Centropomidae, Gerreidae, Haemulidae, Lobotidae, Lutjanidae, Malacanthidae, Mugilidae, Scianidae, Scombridae, Serranidae, Sphyraenidae, Stromateidae) were identified at the species level from 164 sequences. Additionally, three Caribbean species were molecularly identified among the analyzed samples (Mycteroperca xenarcha, Paralonchurus brasilensis and Lobotes surinamensis). Species diversity was slightly higher in the Gulf of Panama than in the Gulf of Chiriquí. For species with five or more individual sequences, genetic diversity and genetic connectivity parameters such as total number of haplotypes (H), haplotype diversity (Hd), and nucleotide diversity (π) were calculated. Overall, pelagic-migratory species showed higher values of genetic diversity than coastal and estuarine species with some exceptions. Connectivity between Gulf areas was compared using values of genetic distances and genetic differentiation (Fst). The high level of connectivity observed between the Gulf of Chiriqui and the Gulf of Montijo indicates the existence of a single stock in that area for the following species: Scomberomorus sierra, Caranx caninus and Lutjanus guttatus. The demographic history of the most common species was examined using Tajima's D values, suggesting population expansion for two snapper species, L. peru and L. argentiventris, having significant and higher values. Another important contribution from this research was the production of primers and dual-labeled probes for environmental DNA detection using qPCR for the five most abundant species (spotted rose snapper, yellow snapper, green jack, Pacific crevalle jack and the Pacific sierra fish). These markers represent a new set of tools for environmental DNA (eDNA) detection and molecular traceability of three commercially important fish species along the supply chain including landing sites and markets of the main fishery areas.

Population genetics and molecular identification of Crocodylus acutus and C. moreletii (Crocodilia: Crocodylidae) in captive and wildlife populations / Genética de poblaciones e identificación molecular de Crocodylus acutus y C. moreletii (Crocodilia: Crocodylidae) en poblaciones de cautiverio y de vida libre

Abstract Introduction: There is low evidence of genetic diversity and hybridization processes within Crocodylus acutus and C. moreletii populations. Objetive: To evaluate genetic diversity and some phylogenetic relationships in wild and captive populations of C. acutus and C. moreletii using the Barcode of Life Data System (COX1, cytochrome C oxidase subunit 1 gene). Methods: 28 individuals phenotypically like C. acutus located in the state of Guerrero, Oaxaca and Quintana Roo were sampled, as well as animals belonging to C. moreletii located in the states of Tabasco, Campeche, and Quintana Roo. 641 base pairs of nucleotide sequence from COX1 were used to obtain the haplotype and nucleotide diversity per population, and a phylogenetic and network analysis was performed. Results: Evidence of hybridization was found by observing C. moreletti haplotypes in animals phenotypically determined as C. acutus, as well as C. acutus haplotypes in animals classified as C. moreletti. Low haplotypic diversity was observed for C. acutus (0.455 ± 0.123) and for C. moreletii (0.505 ± 0.158). A phylogenetic tree was obtained in which the sequences of C. acutus and C. moreletii were grouped into two well-defined clades. Organisms identified phenotypically as C. acutus but with C. moreletii genes were separated into a different clade within the clade of C. moreletii. Conclusions: There are reproductive individuals with haplotypes different from those of the species. This study provides a small but significant advance in the genetic knowledge of both crocodile species and the use of mitochondrial markers, which in this case, the COX1 gene allowed the detection of hybrid organisms in wild and captive populations. Conservation efforts for both species of crocodiles should prevent the crossing of both threatened species and should require the genetic identification of pure populations, to design effective conservation strategies considering the possibility of natural hybridization in areas of sympatry.

Resumen Introducción: Existe poca evidencia de la diversidad genética y los procesos de hibridación dentro de las poblaciones de Crocodylus acutus y C. moreletii. Objetivo: Evaluar la diversidad genética y algunas relaciones filogenéticas en poblaciones silvestres y cautivas de C. acutus y C. moreletii utilizando el Sistema de Código de Barras de la vida (COX1, subunidad I del gen del citocromo C oxidasa). Métodos: Se muestrearon 28 individuos fenotípicamente similares a C. acutus ubicados en los estados de Guerrero, Oaxaca y Quintana Roo, así como animales pertenecientes a C. moreletii ubicados en los estados de Tabasco, Campeche y Quintana Roo. Se utilizaron 641 pares de bases de la secuencia de nucleótidos de la subunidad I del gen del citocromo C oxidasa para obtener el haplotipo y la diversidad de nucleótidos por población, y se realizó un análisis filogenético y de redes. Resultados: Se encontró evidencia de hibridación al observar haplotipos de C. moreletti en animales determinados fenotípicamente como C. acutus, así como haplotipos de C. acutus en animales clasificados como C. moreletti. Se observó una baja diversidad haplotípica para C. acutus (0.455 ± 0.123) y para C. moreletii (0.505 ± 0.158). Se obtuvo un árbol filogenético en el que las secuencias propias de C. acutus y C. moreletii se agruparon en dos grandes y bien definidos clados. Los organismos identificados fenotípicamente como C. acutus pero con genes de C. moreletii se separaron en un clado diferente dentro del clado de C. moreletii. Conclusiones: Existen individuos reproductores con haplotipos diferentes a los de la especie. Este estudio aporta un pequeño pero significativo avance en el conocimiento genético tanto de las especies de cocodrilos como del uso de marcadores mitocondriales, que, en este caso, el gen COX1 permitió la detección de organismos híbridos en poblaciones silvestres y cautivas. Los esfuerzos de conservación para ambas especies de cocodrilos deben evitar el cruce de ambas especies amenazadas y deben requerir la identificación genética de poblaciones puras, para diseñar estrategias de conservación efectivas considerando la posibilidad de hibridación natural en áreas de simpatría.

Genomic Diversity of SARS-CoV-2 Omicron Variant in South American Countries.

Genomic surveillance of SARS-CoV-2 is one of the tools that provide genomic information on circulating variants. Given the recent emergence of the Omicron (B.1.1.529) variant, this tool has provided data about this lineage's genomic and epidemiological characteristics. However, in South America, this variant's arrival and genomic diversity are scarcely known. Therefore, this study determined the genomic diversity and phylogenetic relationships of 21,615 Omicron genomes available in public databases. We found that in South America, BA.1 (n = 15,449, 71%) and BA.1.1 (n = 6257, 29%) are the dominant sublineages, with several mutations that favor transmission and antibody evasion. In addition, these lineages showed cryptic transmission arriving on the continent in late September 2021. This event may have contributed to the dispersal of Omicron sublineages and the acquisition of new mutations. Considering the genomic and epidemiological characteristics of these lineages, especially those with a high number of mutations in their genome, it is important to conduct studies and surveillance on the dynamics of these lineages to identify the mechanisms of mutation acquisition and their impact on public health.

Detection of Persistent Viruses by High-Throughput Sequencing in Tomato and Pepper from Panama: Phylogenetic and Evolutionary Studies.

High-throughput sequencing from symptomatic tomato and pepper plants collected in Panama rendered the complete genome of the southern tomato virus (isolate STV_Panama) and bell pepper endornavirus (isolate BPEV_Panama), and almost-complete genomes of three other BPEV isolates. Tomato chlorosis virus, tomato mosaic virus, and impatiens necrotic spot virus were also detected. Analysis of the complete genome of STV and BPEV worldwide isolates revealed nucleotide diversities of 0.004246 and 0.070523, respectively. Bayesian phylogenetic analysis showed two main groups for each virus (I and II), and several subgroups for BPEV (IA, IB, IC, IIA and IIB). Isolate STV_Panama clustered with NC_12-03-08 from USA and Tom3-T from France (99.97% nucleotide identity) in Group I and BPEV_Panama was close to the Canadian isolate BPEV_Ontario (99.66% nucleotide identity) in Subgroup IB. No correlation was observed between geographic and genetic distances for both viruses. Panamanian BPEV isolates were divergent, belonging to Groups I and II (nucleotide identities > 87.33%). Evolutionary analysis showed purifying selection in all encoding regions of both viruses, being stronger in the overlapping region of both STV genes. Finally, recombination was detected in BPEV but not in STV. This is the first report of STV and BPEV in Panama.

CO1-Based DNA barcoding for assessing diversity of Pteropus giganteus from the state of Azad Jammu Kashmir, Pakistan / Código de barras de DNA à base de CO1 para avaliar a diversidade de Pteropus giganteus do estado de Azad Jammu e Caxemira, Paquistão

Abstract The flying fox (Pteropus giganteus) also familiar with the name of the greater Indian fruit Bat belongs to the order Chiroptera and family Pteropodidae. Current research emphasis on the DNA barcoding of P. giganteus in Azad Jammu Kashmir. Bat sequences were amplified and PCR products were sequenced and examined by bioinformatics software. Congeneric and conspecific, nucleotide composition and K2P nucleotide deviation, haplotype diversity and the number of haplotypes were estimated. The analysis showed that all of the five studied samples of P. giganteus had low G contents (G 19.8%) than C (27.8%), A (25.1%) and T (27.3%) contents. The calculated haplotype diversity was 0.60% and the mean intraspecific K2P distance was 0.001% having a high number of transitional substitutions. The study suggested that P. giganteus (R=0.00) do not deviate from the neutral evolution. It was determined from the conclusion that this mtDNA gene is a better marker for identification of Bat species than nuclear genes due to its distinctive characteristics and may serve as a landmark for the identification of interconnected species at the molecular level and in the determination of population genetics.

Resumo A raposa-voadora (Pteropus giganteus), também conhecida como morcego indiano, pertence à ordem dos Chiroptera e à família Pteropodidae. A presente pesquisa dá ênfase ao código de barras de DNA de P. giganteus em Azad Jammu e Caxemira. Sequências genéticas dos morcegos foram amplificadas, e os produtos de PCR foram sequenciados e examinados por software de bioinformática. De espécies congenérica e coespecífica, foram estimados composição nucleotídica e desvio de nucleotídeos K2P, diversidade de haplótipos e número de haplótipos. A análise mostrou que todas as cinco amostras estudadas de P. giganteus apresentaram baixos teores de G (19,8%) em comparação com C (27,8%), A (25,1%) e T (27,3%). A diversidade de haplótipos calculada foi de 0,60%, e a distância média intraespecífica de K2P foi de 0,001%, com um elevado número de substituições transicionais. O estudo sugeriu que P. giganteus (R = 0,00) não se desviou da evolução neutra. É possível concluir que o gene mtDNA é um marcador favorável para identificação de espécies de morcegos do que genes nucleares por causa de suas características distintivas e pode servir como um marco para a identificação de espécies interconectadas em nível molecular e para a determinação genética de populações.

CO1-based DNA barcoding for assessing diversity of Pteropus giganteus from the state of Azad Jammu Kashmir, Pakistan / Código de barras de DNA à base de CO1 para avaliar a diversidade de Pteropus giganteus do estado de Azad Jammu e Caxemira, Paquistão

The flying fox (Pteropus giganteus) also familiar with the name of the greater Indian fruit Bat belongs to the order Chiroptera and family Pteropodidae. Current research emphasis on the DNA barcoding of P. giganteus in Azad Jammu Kashmir. Bat sequences were amplified and PCR products were sequenced and examined by bioinformatics software. Congeneric and conspecific, nucleotide composition and K2P nucleotide deviation, haplotype diversity and the number of haplotypes were estimated. The analysis showed that all of the five studied samples of P. giganteus had low G contents (G 19.8%) than C (27.8%), A (25.1%) and T (27.3%) contents. The calculated haplotype diversity was 0.60% and the mean intraspecific K2P distance was 0.001% having a high number of transitional substitutions. The study suggested that P. giganteus (R=0.00) do not deviate from the neutral evolution. It was determined from the conclusion that this mtDNA gene is a better marker for identification of Bat species than nuclear genes due to its distinctive characteristics and may serve as a landmark for the identification of interconnected species at the molecular level and in the determination of population genetics.(AU)

A raposa-voadora (Pteropus giganteus), também conhecida como morcego indiano, pertence à ordem dos Chiroptera e à família Pteropodidae. A presente pesquisa dá ênfase ao código de barras de DNA de P. giganteus em Azad Jammu e Caxemira. Sequências genéticas dos morcegos foram amplificadas, e os produtos de PCR foram sequenciados e examinados por software de bioinformática. De espécies congenérica e coespecífica, foram estimados composição nucleotídica e desvio de nucleotídeos K2P, diversidade de haplótipos e número de haplótipos. A análise mostrou que todas as cinco amostras estudadas de P. giganteus apresentaram baixos teores de G (19,8%) em comparação com C (27,8%), A (25,1%) e T (27,3%). A diversidade de haplótipos calculada foi de 0,60%, e a distância média intraespecífica de K2P foi de 0,001%, com um elevado número de substituições transicionais. O estudo sugeriu que P. giganteus (R = 0,00) não se desviou da evolução neutra. É possível concluir que o gene mtDNA é um marcador favorável para identificação de espécies de morcegos do que genes nucleares por causa de suas características distintivas e pode servir como um marco para a identificação de espécies interconectadas em nível molecular e para a determinação genética de populações.(AU)

High genetic diversity detected in the mitochondrial Control Region of the Serra Spanish Mackerel, Scomberomorus brasiliensis (Collette, Russo & Zavala, 1978) along the Brazilian coast.

The Serra Spanish mackerel, Scomberomorus brasiliensis, is one of the most important fishery resources in the western tropical Atlantic, including northern and eastern Brazil. Despite its economic importance, few genetic markers have been sequenced in this species, and little is known of its population genetics. The present study evaluated the genetic variability of 110 individuals, representing three distinct Brazilian populations (Macapá, Fortaleza and Paranaguá), based on a segment of the mitochondrial Control Region. The sequences revealed high levels of genetic diversity, and suggested marked connectivity among the studied populations. A variable repeat was also found in the 3' portion of the studied Control Region fragment, which may prove useful as a marker in future genetic population studies of S. brasiliensis.

Evolutionary rate and genetic load in an emblematic Mediterranean tree following an ancient and prolonged population collapse.

Severe bottlenecks significantly diminish the amount of genetic diversity and the speed at which it accumulates (i.e., evolutionary rate). They further compromise the efficiency of natural selection to eliminate deleterious variants, which may reach fixation in the surviving populations. Consequently, expanding and adapting to new environments may pose a significant challenge when strong bottlenecks result in genetic pauperization. Herein, we surveyed the patterns of nucleotide diversity, molecular adaptation and genetic load across 177 gene-loci in a circum-Mediterranean conifer (Pinus pinea L.) that represents one of the most extreme cases of genetic pauperization in widespread outbreeding taxa. We found very little genetic variation in both hypervariable nuclear microsatellites (SSRs) and gene-loci, which translated into genetic diversity estimates one order of magnitude lower than those previously reported for pines. Such values were consistent with a strong population decline that began some ~1 Ma. Comparisons with the related and parapatric maritime pine (Pinus pinaster Ait.) revealed reduced rates of adaptive evolution (α and ωa ) and a significant accumulation of genetic load. It is unlikely that these are the result from differences in mutation rate or linkage disequilibrium between the two species; instead they are the presumable outcome of contrasting demographic histories affecting both the speed at which these taxa accumulate genetic diversity, and the global efficacy of selection. Future studies, and programs for conservation and management, should thus start testing for the effects of genetic load on fitness, and integrating such effects into predictive models.

CO1-Based DNA barcoding for assessing diversity of Pteropus giganteus from the state of Azad Jammu Kashmir, Pakistan

Abstract The flying fox (Pteropus giganteus) also familiar with the name of the greater Indian fruit Bat belongs to the order Chiroptera and family Pteropodidae. Current research emphasis on the DNA barcoding of P. giganteus in Azad Jammu Kashmir. Bat sequences were amplified and PCR products were sequenced and examined by bioinformatics software. Congeneric and conspecific, nucleotide composition and K2P nucleotide deviation, haplotype diversity and the number of haplotypes were estimated. The analysis showed that all of the five studied samples of P. giganteus had low G contents (G 19.8%) than C (27.8%), A (25.1%) and T (27.3%) contents. The calculated haplotype diversity was 0.60% and the mean intraspecific K2P distance was 0.001% having a high number of transitional substitutions. The study suggested that P. giganteus (R=0.00) do not deviate from the neutral evolution. It was determined from the conclusion that this mtDNA gene is a better marker for identification of Bat species than nuclear genes due to its distinctive characteristics and may serve as a landmark for the identification of interconnected species at the molecular level and in the determination of population genetics.

Resumo A raposa-voadora (Pteropus giganteus), também conhecida como morcego indiano, pertence à ordem dos Chiroptera e à família Pteropodidae. A presente pesquisa dá ênfase ao código de barras de DNA de P. giganteus em Azad Jammu e Caxemira. Sequências genéticas dos morcegos foram amplificadas, e os produtos de PCR foram sequenciados e examinados por software de bioinformática. De espécies congenérica e coespecífica, foram estimados composição nucleotídica e desvio de nucleotídeos K2P, diversidade de haplótipos e número de haplótipos. A análise mostrou que todas as cinco amostras estudadas de P. giganteus apresentaram baixos teores de G (19,8%) em comparação com C (27,8%), A (25,1%) e T (27,3%). A diversidade de haplótipos calculada foi de 0,60%, e a distância média intraespecífica de K2P foi de 0,001%, com um elevado número de substituições transicionais. O estudo sugeriu que P. giganteus (R = 0,00) não se desviou da evolução neutra. É possível concluir que o gene mtDNA é um marcador favorável para identificação de espécies de morcegos do que genes nucleares por causa de suas características distintivas e pode servir como um marco para a identificação de espécies interconectadas em nível molecular e para a determinação genética de populações.

CO1-Based DNA barcoding for assessing diversity of Pteropus giganteus from the state of Azad Jammu Kashmir, Pakistan

Abstract The flying fox (Pteropus giganteus) also familiar with the name of the greater Indian fruit Bat belongs to the order Chiroptera and family Pteropodidae. Current research emphasis on the DNA barcoding of P. giganteus in Azad Jammu Kashmir. Bat sequences were amplified and PCR products were sequenced and examined by bioinformatics software. Congeneric and conspecific, nucleotide composition and K2P nucleotide deviation, haplotype diversity and the number of haplotypes were estimated. The analysis showed that all of the five studied samples of P. giganteus had low G contents (G 19.8%) than C (27.8%), A (25.1%) and T (27.3%) contents. The calculated haplotype diversity was 0.60% and the mean intraspecific K2P distance was 0.001% having a high number of transitional substitutions. The study suggested that P. giganteus (R=0.00) do not deviate from the neutral evolution. It was determined from the conclusion that this mtDNA gene is a better marker for identification of Bat species than nuclear genes due to its distinctive characteristics and may serve as a landmark for the identification of interconnected species at the molecular level and in the determination of population genetics.

Resumo A raposa-voadora (Pteropus giganteus), também conhecida como morcego indiano, pertence à ordem dos Chiroptera e à família Pteropodidae. A presente pesquisa dá ênfase ao código de barras de DNA de P. giganteus em Azad Jammu e Caxemira. Sequências genéticas dos morcegos foram amplificadas, e os produtos de PCR foram sequenciados e examinados por software de bioinformática. De espécies congenérica e coespecífica, foram estimados composição nucleotídica e desvio de nucleotídeos K2P, diversidade de haplótipos e número de haplótipos. A análise mostrou que todas as cinco amostras estudadas de P. giganteus apresentaram baixos teores de G (19,8%) em comparação com C (27,8%), A (25,1%) e T (27,3%). A diversidade de haplótipos calculada foi de 0,60%, e a distância média intraespecífica de K2P foi de 0,001%, com um elevado número de substituições transicionais. O estudo sugeriu que P. giganteus (R = 0,00) não se desviou da evolução neutra. É possível concluir que o gene mtDNA é um marcador favorável para identificação de espécies de morcegos do que genes nucleares por causa de suas características distintivas e pode servir como um marco para a identificação de espécies interconectadas em nível molecular e para a determinação genética de populações.

Comparison of the genetic variability of Blastocystis subtypes between human carriers from two contrasting climatic regions of México.

Blastocystis sp. is an anaerobic intestinal microorganism commonly identified in the feces of several animals, including humans. Blastocystis exhibits high genetic polymorphism and at least 17 subtypes (ST) have been identified; ST1-ST3 are frequently found in the Americas. Furthermore, in vitro assays have shown that temperature and humidity can affect the viability of Blastocystis cysts. In this study, we describe the genetic variability and genetic differentiation among and within Blastocystis STs in adults and children from the cities of Hermosillo and Morelia cities, which represent arid and humid subtropical climatic regions of México, respectively. Phylogenetic and genetic diversity was assessed by analyzing a region of the small subunit ribosomal DNA (SSU rDNA) gene as a marker. Blastocystis ST3 and ST1 were associated with children from Hermosillo and Morelia, respectively. An analysis of the nucleotide diversity (π) and haplotype polymorphism (θ) indexes showed that they were similar within each ST, but different between ST1 and ST3. Interestingly, the group of symptomatic carriers from Hermosillo showed scarce mean nucleotide diversity compared to the asymptomatic carriers (0.0039±0.0030 and 0.0329±0.0286, respectively). Furthermore, the gene flow and genetic differentiation indexes between the children and adults suggested that the Blastocystis haplotypes in the adult carriers were "highly mobile" among humans, while the haplotypes found in the children were more isolated and genetically differentiated between them.

Unique haplotypes of cacao trees as revealed by trnH-psbA chloroplast DNA.

Cacao trees have been cultivated in Mesoamerica for at least 4,000 years. In this study, we analyzed sequence variation in the chloroplast DNA trnH-psbA intergenic spacer from 28 cacao trees from different farms in the Soconusco region in southern Mexico. Genetic relationships were established by two analysis approaches based on geographic origin (five populations) and genetic origin (based on a previous study). We identified six polymorphic sites, including five insertion/deletion (indels) types and one transversion. The overall nucleotide diversity was low for both approaches (geographic = 0.0032 and genetic = 0.0038). Conversely, we obtained moderate to high haplotype diversity (0.66 and 0.80) with 10 and 12 haplotypes, respectively. The common haplotype (H1) for both networks included cacao trees from all geographic locations (geographic approach) and four genetic groups (genetic approach). This common haplotype (ancient) derived a set of intermediate haplotypes and singletons interconnected by one or two mutational steps, which suggested directional selection and event purification from the expansion of narrow populations. Cacao trees from Soconusco region were grouped into one cluster without any evidence of subclustering based on AMOVA (F ST = 0) and SAMOVA (F ST = 0.04393) results. One population (Mazatán) showed a high haplotype frequency; thus, this population could be considered an important reservoir of genetic material. The indels located in the trnH-psbA intergenic spacer of cacao trees could be useful as markers for the development of DNA barcoding.

Genome-wide patterns of recombination, linkage disequilibrium and nucleotide diversity from pooled resequencing and single nucleotide polymorphism genotyping unlock the evolutionary history of Eucalyptus grandis.

We used high-density single nucleotide polymorphism (SNP) data and whole-genome pooled resequencing to examine the landscape of population recombination (ρ) and nucleotide diversity (Ï´w ), assess the extent of linkage disequilibrium (r(2) ) and build the highest density linkage maps for Eucalyptus. At the genome-wide level, linkage disequilibrium (LD) decayed within c. 4-6 kb, slower than previously reported from candidate gene studies, but showing considerable variation from absence to complete LD up to 50 kb. A sharp decrease in the estimate of ρ was seen when going from short to genome-wide inter-SNP distances, highlighting the dependence of this parameter on the scale of observation adopted. Recombination was correlated with nucleotide diversity, gene density and distance from the centromere, with hotspots of recombination enriched for genes involved in chemical reactions and pathways of the normal metabolic processes. The high nucleotide diversity (Ï´w = 0.022) of E. grandis revealed that mutation is more important than recombination in shaping its genomic diversity (ρ/Ï´w = 0.645). Chromosome-wide ancestral recombination graphs allowed us to date the split of E. grandis (1.7-4.8 million yr ago) and identify a scenario for the recent demographic history of the species. Our results have considerable practical importance to Genome Wide Association Studies (GWAS), while indicating bright prospects for genomic prediction of complex phenotypes in eucalypt breeding.

Tracing the geographic origins of weedy Ipomoea purpurea in the southeastern United States.

Ipomoea purpurea (common morning glory) is an annual vine native to Mexico that is well known for its large, showy flowers. Humans have spread morning glories worldwide, owing to the horticultural appeal of morning glory flowers. Ipomoea purpurea is an opportunistic colonizer of disturbed habitats including roadside and agricultural settings, and it is now regarded as a noxious weed in the Southeastern US. Naturalized populations in the Southeastern United States are highly polymorphic for a number of flower color morphs, unlike native Mexican populations that are typically monomorphic for the purple color morph. Although I. purpurea was introduced into the United States from Mexico, little is known about the specific geographic origins of US populations relative to the Mexican source. We use resequencing data from 11 loci and 30 I. purpurea accessions collected from the native range of the species in Central and Southern Mexico and 8 accessions from the Southeastern United States to infer likely geographic origins in Mexico. Based on genetic assignment analysis, haplotype composition, and the degree of shared polymorphism, I. purpurea samples from the Southeastern United States are genetically most similar to samples from the Valley of Mexico and Veracruz State. This supports earlier speculation that I. purpurea in the Southeastern United States was likely to have been introduced by European colonists from sources in Central Mexico.

Nucleotide diversity patterns of local adaptation at drought-related candidate genes in wild tomatoes.

We surveyed nucleotide diversity at two candidate genes LeNCED1 and pLC30-15, involved in an ABA (abscisic acid) signalling pathway, in two closely related tomato species Solanum peruvianum and Solanum chilense. Our six population samples (three for each species) cover a range of mesic to very dry habitats. The ABA pathway plays an important role in the plants' response to drought stress. LeNCED1 is an upstream gene involved in ABA biosynthesis, and pLC30-15 is a dehydrin gene positioned downstream in the pathway. The two genes show very different patterns of nucleotide variation. LeNCED1 exhibits very low nucleotide diversity relative to the eight neutral reference loci that were previously surveyed in these populations. This suggests that strong purifying selection has been acting on this gene. In contrast, pLC30-15 exhibits higher levels of nucleotide diversity and, in particular in S. chilense, higher genetic differentiation between populations than the reference loci, which is indicative of local adaptation. In the more drought-tolerant species S. chilense, one population (from Quicacha) shows a significant haplotype structure, which appears to be the result of positive (diversifying) selection.