scholarly journals Polyploid evolution in arctic-alpine Draba (Brassicaceae)

Sommerfeltia ◽  
1992 ◽  
Vol 4 (s4) ◽  
pp. 1-44
Author(s):  
C. Brochmann
Keyword(s):  
Gene Flow ◽  
Phenotypic Expression ◽  
Phylogenetic Network ◽  
Ecological Niches ◽  
Mixed Mating ◽  
Enzyme Electrophoresis ◽  
Fixed Heterozygosity ◽  
Taxonomic Relationships ◽  
Disomic Inheritance ◽  
Wide Range

Abstract The mainly arctic-alpine genus Draba is well known for its complex morphological and chromosomal vanation. This paper reviews a larger study of Nordic Draba, aimed to provide insights into evolutionary processes that confound taxonomic relationships in the genus. The populations analyzed were referred to 16 currently recognized species of the sections Draba (petals white), Chrysodraba (petals yellow), andDrabella (petals yellow), and investigated using enzyme electrophoresis, restriction site analysis of cpDNA and rDNA, and analysis of chromosome numbers, artificial and natural hybrids, reproductive biology, habitat differentiation, and morphology. Section Draba comprises three diploids and seven polyploids (4x-10x) based on x = 8, sect. Chrysodraba comprises five polyploids (4x-16x) based on x = 8, and sect. Drabella comprises D. crassifolia, which probably is octoploid based on x = 5. Artificial F1 hybrids were obtained in 19 interspecific combinations. Later-generation hybrids were obtained in seven of these combinations. The genetic data suggest that 1) all polyploids are genetic allopolyploids, i.e., they show disomic inheritance and are highly fixed-heterozygous; 2) several of the polyploids have originated recurrently, some of them even polyphyletically; 3) some of the alloploid populations may have originated from cross-incompatible, sibling species that all belong to a single diploid taxonomic species; 4) interspecific gene flow across chromosome number barriers is possible and probably occurs in natural situations; 5) each of three of the polyploids represents an independent alloploid lineage, whereas sect. Draba and two species of sect. Chrysodraba form an intricate phylogenetic network; 6) some of the polyploids have originated locally, others have migrated repeatedly into the Nordic area; and 7) the phenotypic expression of genes encoding taxonomically important morphological characters does not follow consistent patterns in hybrids; this result may explain the discrepancies between genetic and taxonomic relationships in this highly reticulate genus. All species are sexual autogams, but there was large variation in autogamous seed set and traits promoting cross-pollination. The diploids are genetically depauperate, extremely inbreeding stress-tolerators occupying restricted ecological niches, whereas most of the polyploids have high levels of genetic variation, occupy a wide range of niches, and are either stress-tolerant competitors with a mixed mating system or primarily inbreeding ruderals. Mixed mating appears advantageous in the polyploids occurring in competitive habitats, although their fixed heterozygosity buffers the effect of selfing with respect to loss of variability. The ecological amplitude, heterozygosity, and biochemical diversity in the species were positively correlated and increased significantly with ploidal level. Two hypotheses are advanced to explain these correlations: 1) the general-purpose genotype hypothesis, which suggests that a high level of fixed heterozygosity in an allopolyploid genotype per se allows for exploitation of several different niches; and 2) the special-purpose genotype hypothesis, which suggests that repeated alloploidizations involving genetically divergent progenitors result in different fixed-heterozygous genotypes, each of which may exploit a particular niche. The evidence for multiple polyploid origins, differentiation into sibling diploids, and interploidal gene flow · in Draba add to a growing data base suggesting that polyploid complexes represent considerably more dynamic genetic systems than previously envisioned. In Draba, the principal evolutionary importance of these processes is probably that they serve as escapes from genetic and ecological depauperation caused by uniparental inbreeding at the diploid level. These processes inevitably result, however, in incongruities between taxonomic and evolutionary entities in the genus, supporting the use of a wide species concept.

scholarly journals Population genetics of Aedes albopictus (Diptera: Culicidae) in its native range in Lao People’s Democratic Republic

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Maysa Tiemi Motoki ◽  
Dina Madera Fonseca ◽  
Elliott Frederic Miot ◽  
Bruna Demari-Silva ◽  
Phoutmany Thammavong ◽  
...  
Keyword(s):  
Population Structure ◽  
Gene Flow ◽  
Aedes Albopictus ◽  
Isolation By Distance ◽  
Genetic Locus ◽  
Lao Pdr ◽  
Phylogenetic Network ◽  
Population Expansion ◽  
Recent Population Expansion ◽  
The Usa

Abstract Background The Asian tiger mosquito, Aedes (Stegomyia) albopictus (Skuse) is an important worldwide invasive species and can be a locally important vector of chikungunya, dengue and, potentially, Zika. This species is native to Southeast Asia where populations thrive in both temperate and tropical climates. A better understanding of the population structure of Ae. albopictus in Lao PDR is very important in order to support the implementation of strategies for diseases prevention and vector control. In the present study, we investigated the genetic variability of Ae. albopictus across a north-south transect in Lao PDR. Methods We used variability in a 1337-bp fragment of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1), to assess the population structure of Ae. albopictus in Lao PDR. For context, we also examined variability at the same genetic locus in samples of Ae. albopictus from Thailand, China, Taiwan, Japan, Singapore, Italy and the USA. Results We observed very high levels of genetic polymorphism with 46 novel haplotypes in Ae. albopictus from 9 localities in Lao PDR and Thailand populations. Significant differences were observed between the Luangnamtha population and other locations in Lao PDR. However, we found no evidence of isolation by distance. There was overall little genetic structure indicating ongoing and frequent gene flow among populations or a recent population expansion. Indeed, the neutrality test supported population expansion in Laotian Ae. albopictus and mismatch distribution analyses showed a lack of low frequency alleles, a pattern often seen in bottlenecked populations. When samples from Lao PDR were analyzed together with samples from Thailand, China, Taiwan, Japan, Singapore, Italy and the USA, phylogenetic network and Bayesian cluster analysis showed that most populations from tropical/subtropical regions are more genetically related to each other, than populations from temperate regions. Similarly, most populations from temperate regions are more genetically related to each other, than those from tropical/subtropical regions. Conclusions Aedes albopictus in Lao PDR are genetically related to populations from tropical/subtropical regions (i.e. Thailand, Singapore, and California and Texas in the USA). The extensive gene flow among locations in Lao PDR indicates that local control is undermined by repeated introductions from untreated sites.

scholarly journals Leeches as the intermediate host for strigeid trematodes: genetic diversity and taxonomy of the genera Australapatemon Sudarikov, 1959 and Cotylurus Szidat, 1928

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Ewa Pyrka ◽  
Gerard Kanarek ◽  
Grzegorz Zaleśny ◽  
Joanna Hildebrand
Keyword(s):  
Intermediate Host ◽  
Life Cycles ◽  
Coi Gene ◽  
Small Rivers ◽  
Ecological Niches ◽  
Its2 Region ◽  
28S Rrna ◽  
Intermediate Hosts ◽  
Internal Transcribed Spacer Region ◽  
Wide Range

Abstract Background Leeches (Hirudinida) play a significant role as intermediate hosts in the circulation of trematodes in the aquatic environment. However, species richness and the molecular diversity and phylogeny of larval stages of strigeid trematodes (tetracotyle) occurring in this group of aquatic invertebrates remain poorly understood. Here, we report our use of recently obtained sequences of several molecular markers to analyse some aspects of the ecology, taxonomy and phylogeny of the genera Australapatemon and Cotylurus, which utilise leeches as intermediate hosts. Methods From April 2017 to September 2018, 153 leeches were collected from several sampling stations in small rivers with slow-flowing waters and related drainage canals located in three regions of Poland. The distinctive forms of tetracotyle metacercariae collected from leeches supplemented with adult Strigeidae specimens sampled from a wide range of water birds were analysed using the 28S rDNA partial gene, the second internal transcribed spacer region (ITS2) region and the cytochrome c oxidase (COI) fragment. Results Among investigated leeches, metacercariae of the tetracotyle type were detected in the parenchyma and musculature of 62 specimens (prevalence 40.5%) with a mean intensity reaching 19.9 individuals. The taxonomic generic affiliation of metacercariae derived from the leeches revealed the occurrence of two strigeid genera: Australapatemon Sudarikov, 1959 and Cotylurus Szidat, 1928. Phylogenetic reconstructions based on the partial 28S rRNA gene, ITS2 region and partial COI gene confirmed the separation of the Australapatemon and Cotylurus clades. Taking currently available molecular data and our results into consideration, recently sequenced tetracotyle of Australapatemon represents most probably Au. minor; however, unclear phylogenetic relationships between Au. burti and Au. minor reduce the reliability of this conclusion. On the other hand, on the basis of the obtained sequences, supplemented with previously published data, the metacercariae of Cotylurus detected in leeches were identified as two species: C. strigeoides Dubois, 1958 and C. syrius Dubois, 1934. This is the first record of C. syrius from the intermediate host. Conclusions The results of this study suggest the separation of ecological niches and life cycles between C. cornutus (Rudolphi, 1808) and C. strigeoides/C. syrius, with potential serious evolutionary consequences for a wide range of host–parasite relationships. Moreover, phylogenetic analyses corroborated the polyphyletic character of C. syrius, the unclear status of C. cornutus and the separate position of Cotylurus raabei Bezubik, 1958 within Cotylurus. The data demonstrate the inconsistent taxonomic status of the sequenced tetracotyle of Australapatemon, resulting, in our opinion, from the limited availability of fully reliable, comparative sequences of related taxa in GenBank.

Congenital adrenal hyperplasia: molecular mechanisms resulting in 21-hydroxylase deficiency

1986 ◽  
Vol 113 (4_Suppl) ◽  
pp. S315-S320 ◽  
Author(s):  
Patricia A. Donohoue ◽  
Cornelis Van Dop ◽  
Nicholas Jospe ◽  
Claude J. Migeon
Keyword(s):  
Congenital Adrenal Hyperplasia ◽  
Molecular Mechanisms ◽  
Sequence Data ◽  
Phenotypic Expression ◽  
Restriction Pattern ◽  
Class Iii ◽  
Adrenal Hyperplasia ◽  
Hydroxylase Deficiency ◽  
Wide Range ◽  
21 Hydroxylase Deficiency

Abstract 21-Hydroxylase deficiency resulting in congenital adrenal hyperplasia (CAH) is a HLA-linked autosomal recessive disorder that has a wide range of phenotypic expression. Two homologous 21-hydroxylase genes (21-OHA and 21-OHB) occur within the Class III region of the major histocompatibility complex, but only one (21-OHB) appears to function in adrenal steroidogenesis. Our restriction maps, and initial sequence data from White et al. (Pediatr Res 20:274A (1986)) for the two human 21-OH genes reveal a high degree of homology between these genes and a reading frame shift mutation in the 21-OHA gene respectively. Among fourteen control subjects, the intragenic restriction patterns of the 21-OHA and 21-OHB genes are invariant. The few restriction fragment length polymorphisms (RFLPs) found in some controls result from polymorphic restriction sites outside the 21-OH genes. In patients with CAH, several different mechanisms for mutation of the 21-OHB gene have been described: 1) deletion of the unique sequences of the 21-OHB gene, 2) conversion of the unique sequences of the 21-OHB gene to those of 21-OHA, and 3) mutations of 21-OHB which do not result in a detectable alteration of restriction pattern (e.g., point mutations). Duplication of the 21-OHA gene has been found in some patients with attenuated CAH; however, the significance of this finding remains unclear.

scholarly journals Adaptation limits ecological diversification and promotes ecological tinkering during the competition for substitutable resources

2018 ◽  
Vol 115 (44) ◽  
pp. E10407-E10416 ◽  
Author(s):  
Benjamin H. Good ◽  
Stephen Martis ◽  
Oskar Hallatschek
Keyword(s):  
Evolutionary Dynamics ◽  
Competitive Exclusion ◽  
Directional Selection ◽  
Ecological Niches ◽  
Ecological Diversification ◽  
Effective Competition ◽  
Uptake Rates ◽  
Wide Range ◽  
Dynamical Features ◽  
Adaptation Limits

Microbial communities can evade competitive exclusion by diversifying into distinct ecological niches. This spontaneous diversification often occurs amid a backdrop of directional selection on other microbial traits, where competitive exclusion would normally apply. Yet despite their empirical relevance, little is known about how diversification and directional selection combine to determine the ecological and evolutionary dynamics within a community. To address this gap, we introduce a simple, empirically motivated model of eco-evolutionary feedback based on the competition for substitutable resources. Individuals acquire heritable mutations that alter resource uptake rates, either by shifting metabolic effort between resources or by increasing the overall growth rate. While these constitutively beneficial mutations are trivially favored to invade, we show that the accumulated fitness differences can dramatically influence the ecological structure and evolutionary dynamics that emerge within the community. Competition between ecological diversification and ongoing fitness evolution leads to a state of diversification–selection balance, in which the number of extant ecotypes can be pinned below the maximum capacity of the ecosystem, while the ecotype frequencies and genealogies are constantly in flux. Interestingly, we find that fitness differences generate emergent selection pressures to shift metabolic effort toward resources with lower effective competition, even in saturated ecosystems. We argue that similar dynamical features should emerge in a wide range of models with a mixture of directional and diversifying selection.

Taxonomic Relationships and Gene Flow in Four North American Quercus Species (Quercus section Lobatae)

2015 ◽  
Vol 40 (2) ◽  
pp. 510-521 ◽  
Author(s):  
Sandra A. Owusu ◽  
Alexis R. Sullivan ◽  
Jaime A. Weber ◽  
Andrew L. Hipp ◽  
Oliver Gailing
Keyword(s):  
Gene Flow ◽  
North American ◽  
Taxonomic Relationships

scholarly journals A test statistic to quantify treelikeness in phylogenetics

2021 ◽  
Author(s):  
Caitlin Cherryh ◽  
Bui Quang Minh ◽  
Rob Lanfear
Keyword(s):  
Evolutionary History ◽  
Incomplete Lineage Sorting ◽  
Phylogenetic Analyses ◽  
Phylogenetic Network ◽  
Parametric Bootstrap ◽  
Lineage Sorting ◽  
Test Statistic ◽  
Sequence Alignments ◽  
Wide Range ◽  
History Of

AbstractMost phylogenetic analyses assume that the evolutionary history of an alignment (either that of a single locus, or of multiple concatenated loci) can be described by a single bifurcating tree, the so-called the treelikeness assumption. Treelikeness can be violated by biological events such as recombination, introgression, or incomplete lineage sorting, and by systematic errors in phylogenetic analyses. The incorrect assumption of treelikeness may then mislead phylogenetic inferences. To quantify and test for treelikeness in alignments, we develop a test statistic which we call the tree proportion. This statistic quantifies the proportion of the edge weights in a phylogenetic network that are represented in a bifurcating phylogenetic tree of the same alignment. We extend this statistic to a statistical test of treelikeness using a parametric bootstrap. We use extensive simulations to compare tree proportion to a range of related approaches. We show that tree proportion successfully identifies non-treelikeness in a wide range of simulation scenarios, and discuss its strengths and weaknesses compared to other approaches. The power of the tree-proportion test to reject non-treelike alignments can be lower than some other approaches, but these approaches tend to be limited in their scope and/or the ease with which they can be interpreted. Our recommendation is to test treelikeness of sequence alignments with both tree proportion and mosaic methods such as 3Seq. The scripts necessary to replicate this study are available at https://github.com/caitlinch/treelikeness

scholarly journals Geography is more important than life history in the recent diversification of the tiger salamander complex

2021 ◽  
Vol 118 (17) ◽  
pp. e2014719118
Author(s):  
Kathryn M. Everson ◽  
Levi N. Gray ◽  
Angela G. Jones ◽  
Nicolette M. Lawrence ◽  
Mary E. Foley ◽  
...  
Keyword(s):  
Life History ◽  
Gene Flow ◽  
Genetic Differentiation ◽  
Population Genetic ◽  
Tiger Salamander ◽  
Life History Variation ◽  
Mexican Axolotl ◽  
Population Genetic Differentiation ◽  
Wide Range ◽  
Lineage Divergence

The North American tiger salamander species complex, including its best-known species, the Mexican axolotl, has long been a source of biological fascination. The complex exhibits a wide range of variation in developmental life history strategies, including populations and individuals that undergo metamorphosis; those able to forego metamorphosis and retain a larval, aquatic lifestyle (i.e., paedomorphosis); and those that do both. The evolution of a paedomorphic life history state is thought to lead to increased population genetic differentiation and ultimately reproductive isolation and speciation, but the degree to which it has shaped population- and species-level divergence is poorly understood. Using a large multilocus dataset from hundreds of samples across North America, we identified genetic clusters across the geographic range of the tiger salamander complex. These clusters often contain a mixture of paedomorphic and metamorphic taxa, indicating that geographic isolation has played a larger role in lineage divergence than paedomorphosis in this system. This conclusion is bolstered by geography-informed analyses indicating no effect of life history strategy on population genetic differentiation and by model-based population genetic analyses demonstrating gene flow between adjacent metamorphic and paedomorphic populations. This fine-scale genetic perspective on life history variation establishes a framework for understanding how plasticity, local adaptation, and gene flow contribute to lineage divergence. Many members of the tiger salamander complex are endangered, and the Mexican axolotl is an important model system in regenerative and biomedical research. Our results chart a course for more informed use of these taxa in experimental, ecological, and conservation research.

scholarly journals Population Genetics of the Red Rock Lobster,  Jasus edwardsii

2021 ◽  
Author(s):  
◽  
Luke Thomas
Keyword(s):  
Population Structure ◽  
Gene Flow ◽  
New Zealand ◽  
Genetic Differentiation ◽  
Microsatellite Markers ◽  
Rocky Reef ◽  
Rock Lobster ◽  
Wide Range ◽  
Jasus Edwardsii ◽  
Polymorphic Microsatellite

<p>Understanding patterns of gene flow across a species range is a vital component of an effective fisheries management strategy. The advent of highly polymorphic microsatellite markers has facilitated the detection of fine-scale patterns of genetic differentiation at levels below the resolving power of earlier techniques. This has triggered the wide-spread re-examination of population structure for a number of commercially targeted species. The aims of thesis were to re-investigate patterns of gene flow of the red rock lobster Jasus edwardsii throughout New Zealand and across the Tasman Sea using novel microsatellite markers. Jasus edwardsii is a keystone species of subtidal rocky reef system and supports lucrative export markets in both Australia and New Zealand. Eight highly polymorphic microsatellite markers were developed from 454 sequence data and screened across a Wellington south coast population to obtain basic diversity indices. All loci were polymorphic with the number of alleles per locus ranging from 6-39. Observed and expected heterozygosity ranged from 0.563-0.937 and 0.583-0.961, respectively. There were no significant deviations from Hardy-Weinberg equilibrium following standard Bonferroni corrections. The loci were used in a population analysis of J. edwardsii that spanned 10 degrees of latitude and stretched 3,500 km across the South Pacific. The analysis rejected the null-hypothesis of panmixia based on earlier mDNA analysis and revealed significant population structure (FST=0.011, RST=0.028) at a wide range of scales. Stewart Island was determined to have the highest levels of genetic differentiation of all populations sampled suggesting a high degree of reproductive isolation and self-recruitment. This study also identified high levels of asymmetric gene flow from Australia to New Zealand indicating a historical source-sink relationship between the two countries. Results from the genetic analysis were consistent with results from oceanographic dispersal models and it is likely that the genetic results reflect historical and contemporary patterns of Jasus edwardsii dispersal and recruitment throughout its range.</p>

The biology and ecology of hexaploid wheat (Triticum aestivum L.) and its implications for trait confinement

2008 ◽  
Vol 88 (5) ◽  
pp. 997-1013 ◽  
Author(s):  
C. J. Willenborg ◽  
R. C. Van Acker
Keyword(s):  
Triticum Aestivum ◽  
Gene Flow ◽  
Hexaploid Wheat ◽  
Triticum Turgidum ◽  
Cropping Systems ◽  
Pollen Viability ◽  
Triticum Aestivum L ◽  
Genetically Engineered ◽  
Wide Range ◽  
Trait Confinement

This review summarizes the biological and ecological factors of hexaploid wheat (Triticum aestivum L.) that contribute to trait movement including the ability to volunteer, germination and establishment characteristics, breeding system, pollen movement, and hybridization potential. Although wheat has a short-lived seedbank with a wide range of temperature and moisture requirements for germination and no evidence of secondary dormancy, volunteer wheat populations are increasing in relative abundance and some level of seed persistence in the soil has been observed. Hexaploid wheat is predominantly self-pollinating with cleistogamous flowers and pollen viability under optimal conditions of only 0.5 h, yet observations indicate that pollen-mediated gene flow can and will occur at distances up to 3 km and is highly dependent on prevailing wind patterns. Hybridization with wild relatives such as A. cylindrica Host., Secale cereale L., and Triticum turgidum L. is a serious concern in regions where these species grow in field margins and unmanaged lands, regardless of which genome the transgene is located on. More research is needed to determine the long-term population dynamics of volunteer wheat populations before conclusions can be drawn with regard to their role in trait movement. Seed movement has the potential to create adventitious presence (AP) on a larger scale than pollen, and studies tracing the movement of wheat seed in the grain handling system are needed. Finally, the development of mechanistic models that predict landscape-level trait movement are required to identify transgene escape routes and critical points for gene containment in various cropping systems. Key words: Triticum, coexistence, gene flow, genetically-engineered, herbicide-resistant, trait confinement

Botanical Identity of Seasonal Flowering Plants Available and Maintained in the Home Gardens of District Nainital, Uttarakhand

2016 ◽  
Vol 23 (2) ◽  
pp. 89-102
Author(s):  
Kuldeep Negi ◽  
Vandana Tiwari ◽  
Puran Mehta ◽  
Rajni Rawat ◽  
Saraswati Ojha ◽  
...  
Keyword(s):  
Economic Status ◽  
Plant Genetic Resources ◽  
Geographical Area ◽  
Flowering Plants ◽  
Home Gardens ◽  
Flowering Plant ◽  
Ecological Niches ◽  
Wide Range ◽  
Seasonal Flowering ◽  
Flowering Plant Species

Uttarakhand is a store house of plant genetic resources of several crop groups including ornamentals and seasonal flowering plant species. A wide range of seasonal flowering plants are being grown in the region because of its various and favourable agro-geo climatic zones. Ornamental plant enhances aesthetic value of our environment. There are 8 developmental blocks and 1082 villages in district Nainital of Uttarakhand. Nainital district, is a part of Kumaun region of Uttarakhand. It lies between 29?0.1' to 29?36' 21'' N latitude and 78?50' 53'' to 80?06' E longitude. More than 7.62 lakh population reside in 4064 km2 of geographical area of district Nainital. The district falls under sub-tropical to temperate zones. During the course of field survey (2013-2015), we came across wide range of seasonal flowering plants mostly belong to exotic origin being grown in the home gardens of natives of the region situated in different agro-ecological niches. The present study highlighted a total of 150 seasonal flowering plants with 120 genera belonging to 50 families. These were arranged alphabetically with botanical names followed by vernacular and trade name, family, origin or native place, nature, season with appropriate remarks of variation in shape, size and colour, method of propagation with economic status.

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