scholarly journals Taxonomic Differentiation of Iberian Knapweeds (Centaurea sects. Jacea and Lepteranthus, Asteraceae) and Genetic Isolation of Infraspecific Floral Morphotypes

2020 ◽  
Vol 105 (4) ◽  
pp. 481-501
Author(s):  
Itziar Arnelas ◽  
Ernesto Pérez-Collazos ◽  
Juan A. Devesa ◽  
Antonio J. Manzaneda ◽  
Pilar Catalan
Keyword(s):  
Genetic Diversity ◽  
Isolation By Distance ◽  
Population Level ◽  
Potential Effect ◽  
Genetic Distances ◽  
Fixation Index ◽  
Genetic Isolation ◽  
Related Factors ◽  
Genetic Diversity And Structure ◽  
The Impact

The taxonomic boundaries of Centaurea L. species and infraspecific taxa are often blurred by hybridizations. However, counterbalancing genetic isolation contributes to maintaining taxonomic limits and fostering rapid speciation processes. Radiant (R) and non-radiant (NR) capitula are two major floral morphs present in Centaurea. However, it is unclear how gene flow affects the distribution of floral morphotypes across populations and taxa. We have investigated the taxonomic differentiation and potential effect of genetic isolation in R and NR populations of Iberian Centaurea sects. Jacea (Mill.) Pers. ex Dumort. and Lepteranthus (Neck. ex DC.) Dumort. A total of 510 individuals from 58 populations (12 taxa) were analyzed using 165 amplified fragment length polymorphism (AFLP) markers. Genetic diversity and structure parameters were estimated at the taxon, population, and floral morphotypic levels. We tested whether there was correlation between population pairwise fixation index (Fst) genetic distances and the inbreeding coefficient (Fis), taken as a surrogate of reproductive isolation between the R and NR morphotypes of each group, and also taking into account geographic distances, using distance-based redundancy analysis (dbRDA). We also performed isolation by distance (IBD) tests between different floral morphotypes, aiming to infer the impact of genetic isolation on evolutionary and taxonomic divergence of the individuals. The taxa of Centaurea sects. Jacea and Lepteranthus constitute independent evolutionary lineages. Most of the detected genetic clusters match the taxonomic circumscription proposed in our most recent treatments. Genetic diversity was highest in C. debeauxii Godr. & Gren. subsp. debeauxii and subsp. grandiflora (Gaudin ex Schübl. & G. Martens) Devesa & Arnelas and in C. jacea L. subsp. angustifolia (DC.) Gremli (R) and lowest in C. nevadensis Boiss. & Reut. (NR) within the Centaurea sect. Jacea clade, whereas it was highest in C. linifolia L. within the Centaurea sect. Lepteranthus clade. Population-level dbRDA tests did not detect a significant correlation of R versus NR genetic distances and Fis values in any of the studied cases; by contrast, they detected significant correlation with longitude (C. jacea subsp. angustifolia, C. debeauxii, C. linifolia–C. stuessyi Arnelas, Devesa & E. López) or latitude (C. nigra L.). IBD analysis at the individual level showed that, in addition to geography, other morphotype-related factors may affect the genetic differentiation of R versus NR morphs in C. nigra, C. debeauxii, and C. linifolia–C. stuessyi. These results suggest that the fixation of the different morphs within the same taxon or group may be explained by geographic isolation, though we could not discount other potential unknown factors that could have contributed to microspeciation in these recently divergent populations, which originated only several thousands of years ago.

scholarly journals Population level genetic differentiation among temperate Neoconocephalus katydids

2017 ◽  
Author(s):  
◽  
Gideon Ney
Keyword(s):  
Genetic Differentiation ◽  
Gulf Coast ◽  
Isolation By Distance ◽  
Population Level ◽  
Genetic Isolation ◽  
Continental Scale ◽  
Pattern Of Variation ◽  
Habitat Generalist ◽  
Species Specific ◽  
The Impact

Recent work indicates that radiation events may play a significant role in shaping species diversity across entire continents. Here we quantify population level genetic differentiation in several species of Neoconocephalus katydids in order to determine the mechanisms of genetic isolation across a continental scale. Patterns of genetic isolation can be generalized into four types: isolation by resistance (IBR), isolation by barrier (IBB), isolation by distance (IBD), and epigenetic incompatibility. N. melanorhinus is a salt marsh specialist restricted to a narrow corridor along the Atlantic and Gulf coasts. IBD was the predominant pattern of variation across their range. In addition, we saw evidence of two possible biogeographic barriers to gene flow (IBB), one at the Atlantic-Gulf divide and the other along the Gulf coast. We investigated the impact of IBR by comparing genetic differentiation between a habitat specialist, N. bivocatus, and a habitat generalist, N. robustus. Similar levels of genetic diversity and genetic differentiation were present within populations of both species. Genetic variation and epigenetic changes can diverge between populations in isolation. We found significant variation in total methylation levels between N. bivocatus and N. robustus. Genetic differentiation did a better job of explaining species-specific phenotypes than epigenetic differentiation. Epigenetic differentiation, although present between species, is likely the result of an interaction between genetic and epigenetic loci.

scholarly journals Genetic Diversity and Structure of Walnut Populations in Central and Southwestern China Revealed by Microsatellite Markers

2008 ◽  
Vol 133 (2) ◽  
pp. 197-203 ◽  
Author(s):  
Hua Wang ◽  
Dong Pei ◽  
Rui-sheng Gu ◽  
Bao-qing Wang
Keyword(s):  
Genetic Diversity ◽  
Juglans Regia ◽  
Central Area ◽  
Population Level ◽  
Genetic Distances ◽  
Mantel Test ◽  
Southwestern China ◽  
Group Method ◽  
Pair Group ◽  
Genetic Diversity And Structure

Molecular markers were used to study the genetic diversity, structure, and relationship of Juglans L. with nine populations (five from Juglans regia L. and four from Juglans sigillata Dode) in central and southwestern China. A moderate level of genetic diversity was observed at the population level with the number of effect alleles per locus (A E) ranging from 1.75 to 3.35 (average 2.39) and the proportion of polymorphic loci (P) equaling 100.0%. The expected heterozygosity (H E) within populations ranged from 0.389 to 0.687, and the average was 0.525. The proportion of genetic variation presented among populations accounted for 18.6% of the total genetic diversity. The overall gene flow (N m) among populations equaled 1.10. The unweighted pair-group method using arithmetic averages (UPGMA) clustering and the Mantel test showed that genetic distances among the nine populations are in a good agreement with their geographic distribution, supporting the viewpoint that J. regia and J. sigillata belong to one species. We suggest that the central area of the southwestern mountain regions of China could be considered as a priority for walnut genetic resource conservation.

scholarly journals Contrasting effects of local environment and grazing pressure on the genetic diversity and structure of Artemisia frigida

2021 ◽  
Author(s):  
Khurelpurev Oyundelger ◽  
Veit Herklotz ◽  
Dörte Harpke ◽  
Batlai Oyuntsetseg ◽  
Karsten Wesche ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Isolation By Distance ◽  
Grazing Intensity ◽  
Population Level ◽  
Local Environment ◽  
Grazing Pressure ◽  
Climatic Gradient ◽  
Genetic Structuring ◽  
Artemisia Frigida ◽  
Genetic Diversity And Structure

AbstractDrylands count among the most globally extensive biomes, and while many desert and dry rangeland ecosystems are under threat, genetic structures of dryland species are still rarely studied. Artemisia frigida is one of the most widely distributed plant species in the temperate rangelands of Eurasia and North America, and it also dominates in many habitats of Mongolia due to its tolerance to low temperatures, drought and disturbance. Local environmental conditions and grazing pressure can influence species performance and affect spatial patterns of genetic diversity in contrasting ways, and our study set out to evaluate such effects on the genetic diversity and structure of A. frigida. We first developed new species-specific Simple Sequence Repeats (SSRs) markers using whole genome sequencing. We then analysed 11 populations of A. frigida that had been sampled along a large climatic gradient in Mongolia, which were sub-structured according to three levels of grazing intensity. Estimates of genetic diversity at the population level were high (HO = 0.56, HE = 0.73) and tended to increase with higher precipitation and soil nutrient availability. Grazing had no effect on genetic diversity, however, a high number of grazing-specific indicator alleles was found at grazed sites. Genetic differentiation among populations was extremely low (global GST = 0.034). Analysis of Molecular Variance revealed 5% variance between populations along the climatic gradient, with 3% of the variance being partitioned among different grazing intensity levels. We found no relationship between geographic and genetic distances, and thus no isolation by distance in this widely distributed species. The relatively low genetic structuring suggests that considerable gene flow exists among A. frigida populations across the rangelands of Mongolia, in spite of the pervasive grazing in the region.

scholarly journals Genetic Diversity and Population Divergence of a Rare, Endemic Grass (Elymus breviaristatus) in the Southeastern Qinghai-Tibetan Plateau

2019 ◽  
Vol 11 (20) ◽  
pp. 5863 ◽  
Author(s):  
Qingqing Yu ◽  
Qian Liu ◽  
Yi Xiong ◽  
Yanli Xiong ◽  
Zhixiao Dong ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Tibetan Plateau ◽  
Isolation By Distance ◽  
Genetic Distances ◽  
Conservation Strategy ◽  
Conservation Strategies ◽  
Grass Species ◽  
Population Divergence ◽  
High Genetic Diversity ◽  
Widespread Species

Elymus breviaristatus is a grass species only distributed in the southeast of Qinghai-Tibetan Plateau (QTP), which has suffered from serious habitat fragmentation. Therefore, understanding patterns of genetic diversity within and among natural E. breviaristatus populations could provide insight for future conservation strategies. In this study, sequence-related amplified polymorphism markers were employed to investigate the genetic diversity and hierarchical structure of seven E. breviaristatus populations from QTP, China. Multiple measures of genetic diversity indicated that there is low to moderate genetic variation within E. breviaristatus populations, consistent with its presumed mating system. In spite of its rarity, E. breviaristatus presented high genetic diversity that was equivalent to or even higher than that of widespread species. Bayesian clustering approaches, along with clustering analysis and principal coordinate analysis partitioned the studied populations of E. breviaristatus into five genetic clusters. Differentiation coefficients (Fst, GST, etc.) and AMOVA analysis revealed considerable genetic divergence among different populations. BARRIER analyses indicated that there were two potential barriers to gene flow among the E. breviaristatus populations. Despite these patterns of differentiation, genetic distances between populations were independent of geographic distances (r = 0.2197, p = 0.2534), indicating little isolation by distance. Moreover, despite detecting a common outlier by two methods, bioclimatic factors (altitude, annual mean temperature, and annual mean precipitation) were not related to diversity parameters, indicating little evidence for isolation caused by the environment. These patterns of diversity within and between populations are used to propose a conservation strategy for E. breviaristatus.

scholarly journals Genotyping-by-Sequencing Reveals Molecular Genetic Diversity in Italian Common Bean Landraces

Diversity ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 154 ◽  
Author(s):  
Lucia Lioi ◽  
Diana L. Zuluaga ◽  
Stefano Pavan ◽  
Gabriella Sonnante
Keyword(s):  
Genetic Diversity ◽  
Common Bean ◽  
Genotyping By Sequencing ◽  
Fixation Index ◽  
Most Probable Number ◽  
Probable Number ◽  
Individual Snps ◽  
Starting Point ◽  
Genetic Diversity And Structure ◽  
The Common

The common bean (Phaseolus vulgaris L.) is one of the main legumes worldwide and represents a valuable source of nutrients. Independent domestication events in the Americas led to the formation of two cultivated genepools, namely Mesoamerican and Andean, to which European material has been brought back. In this study, Italian common bean landraces were analyzed for their genetic diversity and structure, using single nucleotide polymorphism (SNP) markers derived from genotyping-by-sequencing (GBS) technology. After filtering, 11,866 SNPs were obtained and 798 markers, pruned for linkage disequilibrium, were used for structure analysis. The most probable number of subpopulations (K) was two, consistent with the presence of the two genepools, identified through the phaseolin diagnostic marker. Some landraces were admixed, suggesting probable hybridization events between Mesoamerican and Andean material. When increasing the number of possible Ks, the Andean germplasm appeared to be structured in two or three subgroups. The subdivision within the Andean material was also observed in a principal coordinate analysis (PCoA) plot and a dendrogram based on genetic distances. The Mesoamerican landraces showed a higher level of genetic diversity compared to the Andean landraces. Calculation of the fixation index (FST) at individual SNPs between the Mesoamerican and Andean genepools and within the Andean genepool evidenced clusters of highly divergent loci in specific chromosomal regions. This work may help to preserve landraces of the common bean from genetic erosion, and could represent a starting point for the identification of interesting traits that determine plant adaptation.

Genetic diversity and structure of Jatropha curcas L. in its centre of origin

2014 ◽  
Vol 13 (1) ◽  
pp. 9-17 ◽  
Author(s):  
M. Salvador-Figueroa ◽  
J. Magaña-Ramos ◽  
J. A. Vázquez-Ovando ◽  
M. L. Adriano-Anaya ◽  
I. Ovando-Medina
Keyword(s):  
Genetic Diversity ◽  
Jatropha Curcas ◽  
Isolation By Distance ◽  
Random Mating ◽  
Mantel Test ◽  
Reproductive Pattern ◽  
Chain Reactions ◽  
Polymerase Chain Reactions ◽  
Centre Of Origin ◽  
Genetic Diversity And Structure

To investigate the genetic diversity and structure of Jatropha curcas L. oilseed plant, in this study, native populations from Chiapas, Mexico, were evaluated, using microsatellite DNA markers. A total of 93 representative samples were selected from seven sites in two regions in the state of Chiapas grouped by geographical proximity, where leaf samples were collected to isolate the genomic DNA. Individual polymerase chain reactions were carried out with ten pairs of specific oligonucleotides for the microsatellites of J. curcas, separating the products of amplification by acrylamide electrophoresis. Twenty-seven fragments were detected (77% polymorphic) with which heterozygous individuals were distinguished. The most informative microsatellite was Jcps20 (nine alleles, polymorphic index content 0.354). The average polymorphism per population was 58%. The Hardy–Weinberg tests revealed a reproductive pattern of non-random mating. The diversity descriptors and the analysis of molecular variance revealed that the populations were structured and moderately differentiated (FST 0.087) and that this differentiation was not due to isolation by distance, as the Mantel test was not significant (P= 0.137), but rather due to allopatry. Bayesian analysis revealed that the accessions belonged to only four genetic groups and confirmed the differentiation between the regions. Because some loci were in Hardy–Weinberg disequilibrium, it is proposed that differentiation is due to the clonal reproduction of J. curcas practised by farmers in Chiapas, along with the anthropogenic dispersion at regional levels. The results of this study reveal that J. curcas in Chiapas has genetic diversity that is greater than that reported in other parts of the world, which represents a potential germplasm pool for the selection of genotypes.

scholarly journals Assessment of genetic diversity and population structure of oil palm (Elaeis guineensis Jacq.) field genebank: A step towards molecular-assisted germplasm conservation

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0255418
Author(s):  
Siou Ting Gan ◽  
Chin Jit Teo ◽  
Shobana Manirasa ◽  
Wei Chee Wong ◽  
Choo Kien Wong
Keyword(s):  
Genetic Diversity ◽  
Genetic Distance ◽  
Oil Palm ◽  
Core Collection ◽  
Elaeis Guineensis ◽  
Germplasm Conservation ◽  
Ex Situ ◽  
Fixation Index ◽  
Core Set ◽  
Genetic Diversity And Structure

Oil palm (Elaeis guineensis) germplasm is exclusively maintained as ex situ living collections in the field for genetic conservation and evaluation. However, this is not for long term and the maintenance of field genebanks is expensive and challenging. Large area of land is required and the germplasms are exposed to extreme weather conditions and casualty from pests and diseases. By using 107 SSR markers, this study aimed to examine the genetic diversity and relatedness of 186 palms from a Nigerian-based oil palm germplasm and to identify core collection for conservation. On average, 8.67 alleles per SSR locus were scored with average effective number of alleles per population ranging from 1.96 to 3.34 and private alleles were detected in all populations. Mean expected heterozygosity was 0.576 ranging from 0.437 to 0.661 and the Wright’s fixation index calculated was -0.110. Overall moderate genetic differentiation among populations was detected (mean pairwise population FST = 0.120, gene flow Nm = 1.117 and Nei’s genetic distance = 0.466) and this was further confirmed by AMOVA analysis. UPGMA dendogram and Bayesian structure analysis concomitantly clustered the 12 populations into eight genetic groups. The best core collection assembled by Core Hunter ver. 3.2.1 consisted of 58 palms accounting for 31.2% of the original population, which was a smaller core set than using PowerCore 1.0. This core set attained perfect allelic coverage with good representation, high genetic distance between entries, and maintained genetic diversity and structure of the germplasm. This study reported the first molecular characterization and validation of core collections for oil palm field genebank. The established core collection via molecular approach, which captures maximum genetic diversity with minimum redundancy, would allow effective use of genetic resources for introgression and for sustainable oil palm germplasm conservation. The way forward to efficiently conserve the field genebanks into next generation without losing their diversity was further discussed.

scholarly journals Does silvoagropecuary landscape fragmentation affect the genetic diversity of the sigmodontine rodent Oligoryzomys longicaudatus?

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3842 ◽  
Author(s):  
Daniela Lazo-Cancino ◽  
Selim S. Musleh ◽  
Cristian E. Hernandez ◽  
Eduardo Palma ◽  
Enrique Rodriguez-Serrano
Keyword(s):  
Genetic Diversity ◽  
Genetic Distance ◽  
Isolation By Distance ◽  
Landscape Fragmentation ◽  
Native Forest ◽  
Least Cost Path ◽  
Natural Habitats ◽  
Forest Patches ◽  
Genetic Diversity And Structure ◽  
Oligoryzomys Longicaudatus

Background Fragmentation of native forests is a highly visible result of human land-use throughout the world. In this study, we evaluated the effects of landscape fragmentation and matrix features on the genetic diversity and structure of Oligoryzomys longicaudatus, the natural reservoir of Hantavirus in southern South America. We focused our work in the Valdivian Rainforest where human activities have produced strong change of natural habitats, with an important number of human cases of Hantavirus. Methods We sampled specimens of O. longicaudatus from five native forest patches surrounded by silvoagropecuary matrix from Panguipulli, Los Rios Region, Chile. Using the hypervariable domain I (mtDNA), we characterized the genetic diversity and evaluated the effect of fragmentation and landscape matrix on the genetic structure of O. longicaudatus. For the latter, we used three approaches: (i) Isolation by Distance (IBD) as null model, (ii) Least-cost Path (LCP) where genetic distances between patch pairs increase with cost-weighted distances, and (iii) Isolation by Resistance (IBR) where the resistance distance is the average number of steps that is needed to commute between the patches during a random walk. Results We found low values of nucleotide diversity (π) for the five patches surveyed, ranging from 0.012 to 0.015, revealing that the 73 sampled specimens of this study belong to two populations but with low values of genetic distance (γST) ranging from 0.022 to 0.099. Likewise, we found that there are no significant associations between genetic distance and geographic distance for IBD and IBR. However, we found for the LCP approach, a significant positive relationship (r = 0.737, p = 0.05), with shortest least-cost paths traced through native forest and arborescent shrublands. Discussion In this work we found that, at this reduced geographical scale, Oligoryzomys longicaudatus shows genetic signs of fragmentation. In addition, we found that connectivity between full growth native forest remnants is mediated by the presence of dense shrublands and native forest corridors. In this sense, our results are important because they show how native forest patches and associated routes act as source of vector species in silvoagropecuary landscape, increasing the infection risk on human population. This study is the first approach to understand the epidemiological spatial context of silvoagropecuary risk of Hantavirus emergence. Further studies are needed to elucidate the effects of landscape fragmentation in order to generate new predictive models based on vector intrinsic attributes and landscape features.

Genetic diversity and population structure of disjunct Newfoundland and central Ontario populations of eastern white pine (Pinus strobus)

1998 ◽  
Vol 76 (3) ◽  
pp. 500-508 ◽  
Author(s):  
Om P Rajora ◽  
Linda DeVerno ◽  
Alex Mosseler ◽  
David J Innes
Keyword(s):  
Genetic Diversity ◽  
Population Structure ◽  
Pinus Strobus ◽  
Population Bottleneck ◽  
Genetic Distances ◽  
Population Variation ◽  
White Pine ◽  
Eastern White Pine ◽  
Genetic Diversity And Structure ◽  
Allozyme Loci

The dramatic decline of eastern white pine (Pinus strobus L.) populations in Newfoundland over the past 100 years presents an opportunity to determine and monitor population bottleneck effects on genetic diversity in trees. To provide benchmarks and indicators for monitoring genetic changes due to recent and future bottleneck events and to assist development of conservation strategies, we assessed genetic diversity and structure of six small, isolated white pine populations from two regions at the limits of its geographical range in Newfoundland for comparison with three populations from its central range in Ontario for 20 allozyme loci coding for 12 enzymes. On average, 47.8% of the loci were polymorphic, the number of alleles per locus was 1.75, and the observed and expected heterozygosities were 0.215 and 0.195, respectively. Although most of the alleles were widespread, unique alleles were found in three of the nine populations examined. The Newfoundland populations were as genetically variable as those from Ontario. Generally, all populations exhibited slight excess of heterozygotes at most loci. Only 6.1% of the detected genetic variation was among populations, and the remainder among individuals within populations. The genetic distances among the populations within a province or region were as great as those among populations between the provinces or regions. Canonical discriminant functions and cluster analysis from genetic distances separated nine populations into the same four groups. Neither provincial nor regional or geographic gradient-related patterns of population variation and differentiation were apparent. It appears that 8000 years of postglacial geographic isolation and recent population decline have had little or no detectable effect on genetic diversity or differentiation of disjunct Newfoundland white pine populations from their ancestral mainland populations. Assuming their adaptability, the Ontario seed sources may be acceptable for white pine restoration in Newfoundland.Key words : Pinus strobus, allozymes, gene conservation, genetic diversity and population structure, genetic drift, population bottleneck.

Molecular systematics reveals multiple lineages and cryptic speciation in the freshwater crayfish Parastacus brasiliensis (von Martens, 1869) (Crustacea : Decapoda : Parastacidae)

2018 ◽  
Vol 32 (6) ◽  
pp. 1265 ◽  
Author(s):  
Ivana Miranda ◽  
Kelly M. Gomes ◽  
Felipe B. Ribeiro ◽  
Paula B. Araujo ◽  
Catherine Souty-Grosset ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Isolation By Distance ◽  
Conservation Status ◽  
Sensu Stricto ◽  
Genetic Distances ◽  
Distribution Data ◽  
Lake Basin ◽  
Gene Pools ◽  
Freshwater Crayfish ◽  
Isolated Populations

The characterisation of intraspecific genetic diversity in representatives of the South American crayfish genus Parastacus Huxley, 1879 is here carried out for the first time by comparing populations of Parastacus brasiliensis (von Martens, 1869) as currently defined. Phylogenetic reconstructions based on mitochondrial and nuclear markers indicate the existence of multiple lineages, of which only one can be considered as P. brasiliensis sensu stricto. In addition, there are seven other lineages, one of which is the subspecies Parastacus brasiliensis promatensis Fontoura & Conter, 2008, which is here elevated to species level. We thereby increase to 14 the number of recognised species within Parastacus in South America. Genetic distances among P. brasiliensis sensu stricto and the lineages ‘A’, ‘B’ and ‘C’ increase with geographical distances, suggesting isolation by distance as an important driver of diversification, and eventually speciation, in these burrowing crayfishes. Parastacus brasiliensis occurs mainly in the Guaíba Lake basin and studied populations show limited connectivity and gene flow, probably due to habitat fragmentation. On the basis of genetic and distribution data, the conservation status of P. brasiliensis sensu stricto is confirmed as Near Threatened (NT). These findings lead us to encourage the establishment of preservation areas for isolated populations. The importance of preserving the newly recognised distinct gene pools in order to maintain overall genetic diversity is emphasised.

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