Variation In Natural Populations Research Articles

Mitotic recombination between homologous chromosomes drives genomic diversity in diatoms

Diatoms, an evolutionarily successful group of microalgae, display high levels of intraspecific genetic variability in natural populations. However, the contribution of various mechanisms generating such diversity is unknown. Here we estimated the genetic micro-diversity within a natural diatom population and mapped the genomic changes arising within clonally propagated diatom cell cultures. Through quantification of haplotype diversity by next-generation sequencing and amplicon re-sequencing of selected loci, we documented a rapid accumulation of multiple haplotypes accompanied by the appearance of novel protein variants in cell cultures initiated from a single founder cell. Comparison of the genomic changes between mother and daughter cells revealed copy number variation and copy-neutral loss of heterozygosity leading to the fixation of alleles within individual daughter cells. The loss of heterozygosity can be accomplished by recombination between homologous chromosomes. To test this hypothesis, we established an endogenous readout system and estimated that the frequency of interhomolog mitotic recombination was under standard growth conditions 4.2 events per 100 cell divisions. This frequency is increased under environmental stress conditions, including treatment with hydrogen peroxide and cadmium. These data demonstrate that copy number variation and mitotic recombination between homologous chromosomes underlie clonal variability in diatom populations. We discuss the potential adaptive evolutionary benefits of the plastic response in the interhomolog mitotic recombination rate, and we propose that this may have contributed to the ecological success of diatoms.

Genetic diversity in natural populations of Sorbus pohuashanensis based on EST-SSR markers

Genetic diversity in natural populations of Sorbus pohuashanensis based on EST-SSR markers

Developing a monitoring program of genetic diversity: what do stakeholders say?

Genetic diversity is a fundamental component of biological diversity, and its conservation is considered key to ensure the long-term survival of natural populations and species. National and international legislation increasingly mandates a monitoring of genetic diversity. Examples are the United Nation’s Convention on Biological Diversity (CBD) Aichi target 13 and the current post-2020 negotiations to specify a new target for maintaining genetic diversity. To date, only a few pilot projects have been launched that systematically monitor genetic diversity over time in natural populations of a broad variety of wild species. The Swiss Federal Office for the Environment mandated a feasibility study in 2019 for implementing a national monitoring of genetic diversity in natural populations. To obtain information on whether stakeholders are interested in such a systematic monitoring, what they would expect from such a monitoring and where they see respective caveats, we conducted an online survey, which 138 (42% of those surveyed) Swiss stakeholders answered. We find that Swiss stakeholders are generally aware of the lacking evidence regarding the status of genetic diversity in wild populations and species. Accordingly, most stakeholders are interested in a monitoring of genetic diversity and see opportunities for the application of its results in their work. Nevertheless, stakeholders also expressed concerns regarding financial resources and that the results of a genetic diversity monitoring program would not benefit conservation practice. Our findings highlight the importance of stakeholder engagement and demonstrate the value of a detailed stakeholder analysis prior to developing and implementing a genetic diversity monitoring program. A powerful tool for examining the constellation and interactions of the different stakeholders are social network analyses (SNAs). Finally, it is particularly important to communicate transparently about the possibilities and limitations of a genetic diversity monitoring program as well as to closely involve stakeholders from the beginning to increase the acceptance of genetic diversity monitoring and facilitate its implementation.

Allelic polymorphism at foxo contributes to local adaptation in Drosophila melanogaster.

The insulin/insulin-like growth factor signalling pathway has been hypothesized as a major determinant of life-history profiles that vary adaptively in natural populations. In Drosophila melanogaster, multiple components of this pathway vary predictably with latitude; this includes foxo, a conserved gene that regulates insulin signalling and has pleiotropic effects on a variety of fitness-associated traits. We hypothesized that allelic variation at foxo contributes to genetic variance for size-related traits that vary adaptively with latitude. We first examined patterns of variation among natural populations along a latitudinal transect in the eastern United States and show that thorax length, wing area, wing loading, and starvation tolerance exhibit significant latitudinal clines for both males and females but that development time does not vary predictably with latitude. We then generated recombinant outbred populations and show that naturally occurring allelic variation at foxo, which exhibits stronger clinality than expected, is associated with the same traits that vary with latitude in the natural populations. Our results suggest that allelic variation at foxo contributes to adaptive patterns of life-history variation in natural populations of this genetic model.

Extreme Y chromosome polymorphism corresponds to five male reproductive morphs of a freshwater fish.

Loss of recombination between sex chromosomes often depletes Y chromosomes of functional content and genetic variation, which might limit their potential to generate adaptive diversity. Males of the freshwater fish Poecilia parae occur as one of five discrete morphs, all of which shoal together in natural populations where morph frequency has been stable for over 50 years. Each morph uses a different complex reproductive strategy and morphs differ dramatically in colour, body size and mating behaviour. Morph phenotype is passed perfectly from father to son, indicating there are five Y haplotypes segregating in the species, which encode the complex male morph characteristics. Here, we examine Y diversity in natural populations of P. parae. Using linked-read sequencing on multiple P. parae females and males of all five morphs, we find that the genetic architecture of the male morphs evolved on the Y chromosome after recombination suppression had occurred with the X. Comparing Y chromosomes between each of the morphs, we show that, although the Ys of the three minor morphs that differ in colour are highly similar, there are substantial amounts of unique genetic material and divergence between the Ys of the three major morphs that differ in reproductive strategy, body size and mating behaviour. Altogether, our results suggest that the Y chromosome is able to overcome the constraints of recombination loss to generate extreme diversity, resulting in five discrete Y chromosomes that control complex reproductive strategies.

The serotonin transporter gene and female personality variation in a free-living passerine

Quantifying variation in behaviour-related genes provides insight into the evolutionary potential of repeatable among-individual variation in behaviour (i.e. personality). Yet, individuals typically also plastically adjust their behaviour in response to environmental conditions and/or age, thereby complicating the detection of genotype–phenotype associations. Here, using a population of free-living great tits (Parus major), we assessed the association between single nucleotide polymorphisms (SNPs) in the serotonin transporter gene (SERT) and two repeatable behavioural traits, i.e. female-female aggression and female hissing behaviour. For female-female aggression, a trait showing age-related plasticity, we found no evidence for associations with SERT SNPs, even when assessing potential age-dependent effects of SERT genotype on aggression. We also found no strong support for associations between SERT SNPs and hissing behaviour, yet we identified two synonymous polymorphisms (exon 13 SNP66 and exon 12 SNP144) of particular interest, each explaining about 1.3% of the total variation in hissing behaviour. Overall, our results contribute to the general understanding of the biological underpinning of complex behavioural traits and will facilitate further (meta-analytic) research on behaviour-related genes. Moreover, we emphasize that future molecular genetic studies should consider age-dependent genotype–phenotype associations for behavioural trait (co)variation, as this will vastly improve our understanding of the proximate causes and ultimate consequences of personality variation in natural populations.

Genetic reconstruction of potential invasion pathways of Ligustrum lucidum into Argentina

The study of the genetic characteristics of invasive plant species in native and invaded ranges is an increasingly important attempt for understanding current patterns of invasive plants distribution. While Argentina holds a significant number of invasive woody plant species, scant research has been conducted to determine their invasion pathways. Here we aimed to reconstruct the invasion pathways of Glossy privet (Ligustrum lucidum W.T. Aiton, Oleaceae) from its native range in China to Argentina using nuclear and chloroplastidial molecular markers (ITS1-5.8S-ITS2 and rpl16). Because invasion processes imply an initial founder effect in the new range, we expect to find higher haplotype diversity in native populations. Also, we hypothesize that the invasion route from China to Argentina was through Europe due to the human migratory pathways of the late XIXth century. We sampled 9 locations in the native Chinese range (N = 30), and 15 locations from invaded ranges in Argentina, Mexico and Spain (N = 45). We observed higher haplotype diversity across the three invaded ranges studied here, where we also found two nDNA haplotypes that were not present in the native range examined. The haplotype network revealed that all haplotypes found in Argentina are shared with Spain and Mexico. While the sharing of haplotypes in the three invaded ranges hints towards a single source of introduction, the number of different haplotypes in the invaded ranges in such a short time period suggests multiple introductions. Based on our genetic results and on first records of L. lucidum in Europe (Spain, Italy, UK) and México, we discuss potential invasion routes into Argentina considering historical human commerce and migratory patterns.

Signatures of local adaptation to climate in natural populations of sweet chestnut (Castanea sativa Mill.) from southern Europe

• Key message Understanding the adaptive mechanisms of forest species is vital to ensure their survival in a climate change scenario. This study aimed at uncovering the relationship between genetic variability and environmental variables in natural Castanea sativa populations, unveiling how different climate scenarios drove local adaption processes using a landscape genomics approach. Our findings provide useful data for future management of this species. • Context Temperate forest species, such as chestnut (Castanea sativa Mill.), are currently threatened by increasing temperature together with disruption and reduction of precipitation due to climate change. In this context, understanding the adaptation processes of species will help to manage and ensure the conservation of forests.• Aims We studied the relationship between genetic variability and climate variables in natural populations of C. sativa using a landscape genomics approach aimed to identify local adaption processes.• Methods Using five genomic SSRs and eight functional EST-SSRs markers, 268 individuals belonging to ten different natural European chestnut populations distributed in contrasting climatic sites were genotyped. In addition, associations between allelic variation and climatic variables (environmental association analyses approach) were performed using Samβada and LFMM.• Results Results highlighted a strong inter-relationship between climate variables and evolutionary processes resulting in adaptive variation. STRUCTURE analysis based on functional markers split the populations in three separate gene pools (K = 3), mostly in agreement with the different climatic conditions existing in the studied areas. Divergent spatial patterns of genetic variation between rainy and arid areas were found. We detected a total of 202 associations with climate among 22 different alleles, 9% of which related with the outlier locus FIR059, known to be implicated in regulatory mechanisms during water stress adaptation processes.• Conclusion Landscape genomics analyses revealed a pattern of adaptive variation, where specific climatic variables influenced the frequencies distribution and fixation of several alleles, resulting in local adaptation processes of the populations in the investigated areas. Our findings underline the close inter-relationship existing between climate and genetic variability and indicate how this approach could provide valuable information for the management of forest species in a rapidly changing environment.

Accurate, ultra-low coverage genome reconstruction and association studies in Hybrid Swarm mapping populations.

Genetic association studies seek to uncover the link between genotype and phenotype, and often utilize inbred reference panels as a replicable source of genetic variation. However, inbred reference panels can differ substantially from wild populations in their genotypic distribution, patterns of linkage-disequilibrium, and nucleotide diversity. As a result, associations discovered using inbred reference panels may not reflect the genetic basis of phenotypic variation in natural populations. To address this problem, we evaluated a mapping population design where dozens to hundreds of inbred lines are outbred for few generations, which we call the Hybrid Swarm. The Hybrid Swarm approach has likely remained underutilized relative to pre-sequenced inbred lines due to the costs of genome-wide genotyping. To reduce sequencing costs and make the Hybrid Swarm approach feasible, we developed a computational pipeline that reconstructs accurate whole genomes from ultra-low-coverage (0.05X) sequence data in Hybrid Swarm populations derived from ancestors with phased haplotypes. We evaluate reconstructions using genetic variation from the Drosophila Genetic Reference Panel as well as variation from neutral simulations. We compared the power and precision of Genome-Wide Association Studies using the Hybrid Swarm, inbred lines, recombinant inbred lines (RILs), and highly outbred populations across a range of allele frequencies, effect sizes, and genetic architectures. Our simulations show that these different mapping panels vary in their power and precision, largely depending on the architecture of the trait. The Hybrid Swam and RILs outperform inbred lines for quantitative traits, but not for monogenic ones. Taken together, our results demonstrate the feasibility of the Hybrid Swarm as a cost-effective method of fine-scale genetic mapping.

Development of microsatellite markers for Calyptranthes clusiifolia (Myrtaceae)

The endemic tree species Calyptranthes clusiifolia (Myrtaceae) plays a relevant ecological role in the forest fragments where it has a common occurrence. In this study, we reported the development of microsatellite markers for C. clusiifolia what will allow a better understanding of the relationship between the forest fragmentation process and the genetic structure and diversity of tree populations. Seven microsatellite markers were developed using an enriched genomic library and characterized in 30 individuals (from three populations). These seven loci were polymorphic and resulted in a total of 23 alleles. The expected heterozygosity (HE) varied from 0.14 (Caly 06) to 0.73 (Caly 22). Linkage disequilibrium between the loci (p > 0.0007) pairs was not detected. The parentage exclusion power of the first (Pe-1) and the second (Pe-2) parents were 0.6099 and 0.8548, respectively. The microsatellite markers developed are indicated for future studies of the genetic diversity in natural populations of C. clusiifolia.

Toward genetic modification of plant-parasitic nematodes: delivery of macromolecules to adults and expression of exogenous mRNA in second stage juveniles.

Plant-parasitic nematodes are a continuing threat to food security, causing an estimated 100 billion USD in crop losses each year. The most problematic are the obligate sedentary endoparasites (primarily root knot nematodes and cyst nematodes). Progress in understanding their biology is held back by a lack of tools for functional genetics: forward genetics is largely restricted to studies of natural variation in populations and reverse genetics is entirely reliant on RNA interference. There is an expectation that the development of functional genetic tools would accelerate the progress of research on plant-parasitic nematodes, and hence the development of novel control solutions. Here, we develop some of the foundational biology required to deliver a functional genetic tool kit in plant-parasitic nematodes. We characterize the gonads of male Heterodera schachtii and Meloidogyne hapla in the context of spermatogenesis. We test and optimize various methods for the delivery, expression, and/or detection of exogenous nucleic acids in plant-parasitic nematodes. We demonstrate that delivery of macromolecules to cyst and root knot nematode male germlines is difficult, but possible. Similarly, we demonstrate the delivery of oligonucleotides to root knot nematode gametes. Finally, we develop a transient expression system in plant-parasitic nematodes by demonstrating the delivery and expression of exogenous mRNA encoding various reporter genes throughout the body of H. schachtii juveniles using lipofectamine-based transfection. We anticipate these developments to be independently useful, will expedite the development of genetic modification tools for plant-parasitic nematodes, and ultimately catalyze research on a group of nematodes that threaten global food security.

Striking habitat reduction, decreased genetic diversity, and imperilled conservation of natural populations of Terrapenecoahuila

Abstract Long‐term evolutionary history and demographic processes shape current patterns of genetic variation in natural populations. Genetic diversity is of prime importance for the long‐term survival of species, especially those threatened or endangered, which can be lost in a few generations and can take hundreds to recover. Notably, turtles are among the most endangered vertebrate taxa in the world. The Coahuilan box turtle Terrapene coahuila is the only aquatic species within the genus, microendemic to the desert‐spring ecosystem of the Cuatrociénegas Basin (CCB). The CCB has experienced significant habitat changes during recent decades, fragmenting otherwise interconnected wetlands systems. We aimed to perform a detailed evaluation of the evolutionary and genetic patterns of T. coahuila, both historical and contemporary, linked to the biogeography of the CCB and processes governing the species distribution. We assessed the contributions of historical and contemporary population demographic processes to genetic diversity and structure, by using two mitochondrial DNA genes (cytochrome b and d‐loop), one nuclear gene (GAPD), and 12 nuclear microsatellite loci. We comprehensively analysed these data to address historical patterns of demography, migration, genetic diversity, and times of divergence across the valley for T. coahuila. We also evaluated recent patterns of genetic variation and structure, inbreeding, bottleneck signals, and effective population size. Our results dated the time to the most recent common ancestor for T. coahuila in the CCB at c. 10.1 million years ago, with highest diversification during the Holocene. Structure consistently comprised two genetic clusters, Cuatrociénegas East and Cuatrociénegas West on either side of the main historical barrier, the Sierra San Marcos. Demographic results supported a divergence between western and eastern populations from 47,500 to 110,950 years ago, and colonisation of the southernmost Cuatrociénegas West distribution (Churince) 28,500–66,500 years ago, which experienced a recent bottleneck. All populations showed low values of haplotype and nuclear genetic diversity, migration, effective population size, and relatedness; significant inbreeding and bottleneck signals were also identified within genetic clusters. In accordance with the biogeographic history of the basin, our results show that T. coahuila’s diversification across the Cuatrociénegas valley continued throughout the Pleistocene, peaking during the Holocene, when the valley started to gradually dry. As predicted, T. coahuila exhibited an overall, long‐term, and probably continuing decrement in genetic variation, increased genetic differentiation, and low population sizes, as a consequence of contemporary habitat loss and fragmentation across the CCB. Changes in species demography and population connectivity have the potential to permanently alter the genetic patterns of freshwater species. Hence, given its restricted distribution, high habitat specificity and habitat loss, Terrapene coahuila is at utmost risk of extinction. Captive breeding programmes of the Coahuilan box turtle should consider our results, to prevent further loss of genetic diversity and truly expect reintroduction success. Also, it is crucial to restore connectivity among wetlands, for the conservation of species and the Cuatrociénegas valley altogether.

Morphological and genetic variation in natural populations of Quercus vulcanica and Q. frainetto

Quercus vulcanica, an endemic species with scattered distribution, and Q. frainetto are naturally distributed in Turkey. Although they have been reported as closely related species, Q. vulcanica differs from Q. frainetto in the longer petioles and the leaves evenly distributed along the shoots. Knowledge of the amount and distribution of genetic variation in the species and potential hybridization with related species is crucial for the conservation of the species. Therefore, the aims of the study were to analyze leaf morphological and stomatal variation, and to assess patterns of genetic variation at 3 gSSR and 17 expressed sequence tag (EST)-SSR markers within and between four Q. vulcanica and two Q. frainetto populations sampled from Turkey. Based on canonical discriminant and principal component analyses, petiole length, petiole ratio and number of lobes mainly accounted for the discrimination between Q. vulcanica and Q. frainetto. The means of stomatal densities for Q. vulcanica and Q. frainetto were 810 and 862 stomata per mm2, respectively. The mean genetic differentiation between Q. frainetto and Q. vulcanica at 20 microsatellite loci was very low (FST = 0.047). Two loci, 2P24 (FST = 0.119, P = 0.003) and PIE102 (FST = 0.127, P < 0.000), showed comparatively high interspecific differentiation and were identified as outlier loci. Genetic assignment analyses and discriminant analyses based on phenotypic traits assigned most individuals to the one or the other species. Further studies including more populations and genome-wide markers are necessary to assess the level of adaptive genetic variation and potential introgression between Q. vulcanica and other related species.

Geographical and environmental contributions to genomic divergence in mangrove forests

Abstract Assessing the relative importance of geographical and environmental factors to the spatial distribution of genetic variation can provide information about the processes that maintain genetic variation in natural populations. With a globally wide but very restricted habitat distribution, mangrove trees are a useful model for studies aiming to understand the contributions of these factors. Mangroves occur along the continent–ocean interface of tropical and subtropical latitudes, regions considered inhospitable to many other types of plants. Here, we used landscape genomics approaches to investigate the relative contributions of geographical and environmental variables to the genetic variation of two black mangrove species, Avicennia schaueriana and Avicennia germinans, along the South American coast. Using single nucleotide polymorphisms, our results revealed an important role of ocean currents and geographical distance in the gene flow of A. schaueriana and an isolation-by-environment pattern in the organization of the genetic diversity of A. germinans. Additionally, for A. germinans, we observed significant correlations between genetic variation with evidence of selection and the influence of precipitation regimens, solar radiation and temperature patterns. These discoveries expand our knowledge about the evolution of mangrove trees and provide important information to predict future responses of coastal species to the expected global changes during this century.

Assessing the genetic diversity of Myrsine umbellata (Primulaceae) in Brazilian Atlantic Forest remnants - an important step towards reforestation efforts

Abstract The investigation of genetic diversity in natural populations of species that show potential for use in reforestation programs is a key step in making management decisions. However, reforestation programs with native species in Brazil are still rarely based on a genetic understanding of the seed matrices used for seedling production. This is also the case for Myrsine umbellata, a dioecious shrub within the family Primulaceae that has been used in reforestation programs in Brazil, mainly due to its high production capacity of fruits attractive to the avifauna. The goal of this study was to measure intra- and interpopulational genetic diversity in natural populations of M. umbellata in six forest remnants of the Atlantic Forest using ISSR markers. The results revealed that the intrapopulational genetic diversity was greater than the genetic diversity among the studied populations. For this reason, the cultivation of seedlings from seeds obtained in more than one population seems the most appropriate strategy for reforestation purposes. Even though the most isolated populations are also the ones with highest genetic structure, all populations of M. umbellata included in this study revealed to be an important germplasm bank conserved in situ.

Beyond genetic differences: epigenetic variation in common bottlenose dolphins Tursiops truncatus from contrasting marine ecosystems

Recent genetic and morphological studies have indicated an incipient ecological divergence between 2 ecotypes of common bottlenose dolphinTursiops truncatusin the Southwestern Atlantic. However, genetic variation is not the only molecular mechanism that alters the phenotype of these animals: epigenetics can also influence phenotypic plasticity, as well as the ecological adaptation and divergence of natural populations. Nevertheless, very little is known about the role that epigenetics plays in the population ecology of marine mammals. In this work, we tested whether there are differences in DNA methylation patterns between a coastal and an offshore ecotype of common bottlenose dolphin. Methylation patterns were analyzed using the methylation-sensitive amplified polymorphism technique on biopsy samples collected from animals of both ecotypes. We found consistent differences in DNA methylation patterns between coastal and offshore individuals. We also confirmed the genetic differences described in previous studies, indicating that the divergence between ecotypes has both genetic and epigenetic components. Our data show that it is possible to differentiate animals from the coastal and offshore ecotypes using DNA methylation markers, supporting the hypothesis that contrasting environments—which are decisive for the ecological divergence of these populations—lead to epigenetic modifications in common bottlenose dolphins.

Genetic diversity and structure of Dorstenia elata (Moraceae) in an Atlantic Forest remnant

Abstract Plant species that show gregarious spatial distribution and endemism to the Atlantic Forest, such as Dorstenia elata, are particularly sensitive to the effects of genetic diversity loss. In the present study, we aimed to quantify the genetic diversity in native populations of this species in an Atlantic Forest remnant. The sample included three aggregates of individuals, and molecular characterization was performed with twelve ISSR primers. Intrapopulation analyses were based on the calculation of the Shannon index; total expected heterozygosity and the matrix of distances between pairs of individuals were also calculated. The obtained grouping dendrogram evinced the formation of two groups. Interpopulation investigations were based on the analysis of molecular variance and the estimate of historical gene flow. The results demonstrate that one group comprised the genotypes from two subpopulations, and the other contained exclusively the genotypes of a third subpopulation. The greatest genetic variability was observed within rather than among populations, indicating that the geographical distance and the road that divides the studied populations are not causing loss of genetic diversity.

Host-shift as the cause of emerging infectious diseases: Experimental approaches using Drosophila-virus interactions.

Host shifts, when a cross-species transmission of a pathogen can lead to successful infections, are the main cause of emerging infectious diseases, such as COVID-19. A complex challenge faced by the scientific community is to address the factors that determine whether the cross-species transmissions will result in spillover or sustained onwards infections. Here we review recent literature and present a perspective on current approaches we are using to understand the mechanisms underlying host shifts. We highlight the usefulness of the interactions between Drosophila species and viruses as an ideal study model. Additionally, we discuss how cross-infection experiments — when pathogens from a natural reservoir are intentionally injected in novel host species— can test the effect cross-species transmissions may have on the fitness of virus and host, and how the host phylogeny may influence this response. We also discuss experiments evaluating how cooccurrence with other viruses or the presence of the endosymbiont bacteria Wolbachia may affect the performance of new viruses in a novel host. Finally, we discuss the need of surveys of virus diversity in natural populations using next-generation sequencing technologies. In the long term, these approaches can contribute to a better understanding of the basic biology of host shifts.

Morphological and Genetic Diversities of Habenaria radiata (Orchidaceae) in the Kinki Area, Japan.

Floral organs have evolved from leaves for reproduction, and the morphological analyses help to understand the plant diversity and evolution. Habenaria radiata (syn. Pecteilis radiata) is a terrestrial orchid living in wetlands in Japan, Russia, South Korea, and China. The habitats of this plant in Japan have been reduced because of environmental destruction and overexploitation, and thus it is on the Red List of Japan as a Near Threatened species. One of the three petals of the H. radiata flower is called a lip or labellum, which resembles a flying white bird, egret, or white heron, with its proposed function being to attract pollinators. To understand the diversity of H. radiata plants in different areas, we examined the lip morphology and phylogeny of populations from eight habitats in the Kinki area, Japan. The complex shapes of the lips were quantified and presented as a radar chart, enabling characterization of the morphological difference among populations. Phylogenetic analysis with microsatellite markers that we generated showed the variation of genetic diversity among populations, suggesting the different degrees of inbreeding, outbreeding, and vegetative propagation. Our approach offers a basic method to characterize the morphological and genetic diversity in natural populations.

Testing accession genetic composition of a germ-plasm bank for mangabeira (Hancornia speciosa)

The objective of the current study was to measure the genetic variability of natural populations of Hancornia speciosa using RAPD type molecular markers to assay variation in existing sampled genotypes, using morphological variables, and so assess germplasm bank composition. Morphological and chemical characteristics H. speciosa fruits and seeds were evaluated using descriptive statistics and principal components analysis. Cluster analyzes was conducted using Jaccard's similarity index, via the UPGMA hierarchical agglomerative method. Phenotypic variability was found in the two studied populations. However, variability was higher in the São Judas population, where the variables: pulp yield and soluble solids content were higher than those in the Canaã population. High genetic variability was found in both study populations, and between- and within-population morphological and genetic variation was present in the studied populations. The nine primers generated 70 bands, of which 68 were polymorphic, with the primers A-08 and C-04 generating the highest number of polymorphic bands. The two populations differ principally in the pulp ratio and the proportion of total solids in the pulp (°Brix). RAPD markers used gave acceptable results and, to initiate the Federal University of Tocantins Active Mangaba Germplasm Bank, seven genotypes were sampled from the Canaã population and five from the São Judas Tadeu population.