Low levels of outcrossing in Pinus leucodermis: further evidence in artificial stands

1994 ◽  
Vol 72 (9) ◽  
pp. 1289-1293 ◽  
Author(s):  
M. Morgante ◽  
P. Rossi ◽  
G. G. Vendramin ◽  
G. Boscherini
Keyword(s):  
Natural Populations ◽  
Selective Advantage ◽  
Minimum Variance ◽  
Outcrossing Rates ◽  
Self Fertilization ◽  
Low Levels ◽  
High Level ◽  
Germinating Seeds ◽  
Neighbourhood Structure ◽  
Key Words Mating System

Outcrossing rates were estimated in two artificial stands of Pinus leucodermis, a wind pollinated conifer characterized by a relatively high level of selfing. Multilocus outcrossing rates, estimated by assaying five enzyme loci, were lower than 86% in the two stands, using both dormant and germinating seeds, and not different from those observed in two natural populations located in the same area. The lack of relevant differences between single-locus minimum variance means and the multilocus outcrossing rate estimates observed in both the artificial stands indicates that most of the apparent selfing is probably caused by actual self-fertilization. The presence of a high level of self-fertilization in this species seems confirmed also in artificial stands, where the density is higher and neighbourhood structure should be less pronounced. The high level of self-fertilization found in P. leucodermis, which is probably due to the presence of a reduced number of recessive embryonic lethals as a consequence of genetic drift, could represent a selective advantage for this pioneering and precocius species. Key words: mating system, outcrossing rates, artificial stands, Pinus leucodermis.

Evidence of high self-fertilization in natural populations of eastern white cedar (Thuja occidentalis)

1990 ◽  
Vol 68 (3) ◽  
pp. 663-668 ◽  
Author(s):  
Daniel J. Perry ◽  
Peggy Knowles
Keyword(s):  
Natural Populations ◽  
Outcrossing Rate ◽  
Significant Heterogeneity ◽  
Embryo Survival ◽  
Thuja Occidentalis ◽  
White Cedar ◽  
Northwestern Ontario ◽  
Outcrossing Rates ◽  
Self Fertilization ◽  
Eastern White Cedar

Arrays of open-pollinated seeds were assayed for allozyme polymorphisms at four loci (Mdh-1, Me, 6Pg-2, and Pgm) to obtain estimates of outcrossing rates for three eastern white cedar populations in northwestern Ontario, Canada. Multilocus population outcrossing rate estimates were low, ranging from 0.507 to 0.745, with significant heterogeneity among populations. Low stand densities and relatively high selfed embryo survival may have contributed to the low effective outcrossing rates observed. Single-tree multilocus outcrossing rate estimates were obtained for nine trees from one population. When estimated jointly with outcross pollen pool allele frequencies, these outcrossing rate estimates ranged from 0.253 to 1.023 with significant heterogeneity among trees. Key words: mating system, outcrossing rate, Thuja occidentalis L.

Regional divergence and inbreeding in Eucalyptus cladocalyx (Myrtaceae)

2003 ◽  
Vol 51 (4) ◽  
pp. 393 ◽  
Author(s):  
M. W. McDonald ◽  
M. Rawlings ◽  
P. A. Butcher ◽  
J. C. Bell
Keyword(s):  
Genetic Diversity ◽  
Natural Populations ◽  
South Australia ◽  
Natural Distribution ◽  
Flinders Ranges ◽  
Outcrossing Rates ◽  
Low Levels ◽  
Western Victoria ◽  
Ornamental Species ◽  
Regional Divergence

Eucalyptus cladocalyx F.Muell. is a widely cultivated tree in dryland southern Australia. It is grown for firewood, timber production and as a windbreak and ornamental species. Natural populations of E. cladocalyx are endemic to South Australia where they occur in three disjunct regions. This study assessed the mating system and patterns of genetic diversity in natural populations of E. cladocalyx by using allozymes. Populations had relatively low levels of genetic diversity (HE = 0.148) and high levels of genetic divergence (θ = 0.26) among populations, similar to other regionally distributed eucalypts. Populations clustered into three distinct groups, which corresponded to its disjunct natural distribution. Genetic differentiation among populations and between regions was highly significant. Relatively high levels of inbreeding (tm = 0.57) were detected in natural populations of E.�cladocalyx. Outcrossing rates were highly variable among families, ranging from 0 to 100%. One-third of families from four populations had outcrossing rates that were not significantly different from zero. The origins of three commercially significant, cultivated stands of E. cladocalyx were also assessed. Allozyme profiles of cultivated stands from Wail and Lismore in western Victoria suggested origins in the Wirrabara region of the southern Flinders Ranges, while a cultivated stand of E. cladocalyx var. nana Hort. ex Yates had an allozyme profile consistent with origins in the Eyre Peninsula region. The results are discussed in relation to the species' morphological variation, biogeography and the implications for its domestication and conservation.

scholarly journals Outcrossing rates in an experimentally admixed population of self-compatible and self-incompatible Arabidopsis lyrata

Heredity ◽  
2021 ◽  
Author(s):  
Christina Steinecke ◽  
Courtney E. Gorman ◽  
Marc Stift ◽  
Marcel E. Dorken
Keyword(s):  
Gene Flow ◽  
Natural Populations ◽  
Secondary Contact ◽  
Uniform Density ◽  
Evolutionary Divergence ◽  
Arabidopsis Lyrata ◽  
Multiple Origins ◽  
Outcrossing Rates ◽  
Self Fertilization ◽  
Self Compatibility

AbstractThe transition to self-compatibility from self-incompatibility is often associated with high rates of self-fertilization, which can restrict gene flow among populations and cause reproductive isolation of self-compatible (SC) lineages. Secondary contact between SC and self-incompatible (SI) lineages might re-establish gene flow if SC lineages remain capable of outcrossing. By contrast, intrinsic features of SC plants that reinforce high rates of self-fertilization could maintain evolutionary divergence between lineages. Arabidopsis lyrata subsp. lyrata is characterized by multiple origins of self-compatibility and high rates of self-fertilization in SC-dominated populations. It is unclear whether these high rates of selfing by SC plants have intrinsic or extrinsic causes. We estimated outcrossing rates and examined patterns of pollinator movement for 38 SC and 40 SI maternal parents sampled from an admixed array of 1509 plants sourced from six SC and six SI populations grown under uniform density. Although plants from SI populations had higher outcrossing rates (mean tm = 0.78 ± 0.05 SE) than plants from SC populations (mean tm = 0.56 ± 0.06 SE), outcrossing rates among SC plants were substantially higher than previous estimates from natural populations. Patterns of pollinator movement appeared to contribute to lower outcrossing rates for SC plants; we estimated that 40% of floral visits were geitonogamous (between flowers of the same plant). The relatively high rates of outcrossing for SC plants under standardized conditions indicate that selfing rates in natural SC populations of A. lyrata are facultative and driven by extrinsic features of A. lyrata, including patterns of pollinator movement.

scholarly journals Genetic evaluation of seeds of highly endangered Pinus uliginosa Neumann from Węgliniec reserve for ex-situ conservation program

2011 ◽  
Vol 74 (3) ◽  
pp. 237-242 ◽  
Author(s):  
Andrzej Lewandowski ◽  
Jarosław Burczyk ◽  
Witold Wachowiak ◽  
Adam Boratyński ◽  
Wiesław Prus-Głowacki
Keyword(s):  
Genetic Variation ◽  
Genetic Erosion ◽  
Minimum Variance ◽  
Ex Situ ◽  
The Mean ◽  
Low Levels ◽  
Species Specific ◽  
High Level ◽  
Individual Trees ◽  
Pinus Uliginosa

Peat-bog pine <em>Pinus uliginosa</em> Neumann has become extinct or rare in many parts of Europe. We have investigated the levels of genetic variation and inbreeding in seeds collected from a highly endangered reserve of this species in Poland, using allozymes as genetic markers. Generally, a high level of genetic variation was observed. The mean expected heterozygosity was 0.376, while average (Na) and effective (Ne) numbers of alleles per locus were 2.45 and 1.67, respectively. Nevertheless, we have detected relatively low levels of outcrossing, and potential biparental inbreeding. The population-wide multilocus outcrossing rate was estimated to be 0.706 (±0.091), while the minimum variance mean of single-locus estimates was distinctly lower (ts=0.611). The estimates of outcrossing calculated for individual trees ranged widely from 0.051 to 1.017, indicating the complexity of outcrossing patterns. The investigated population of <em>P. uliginasa</em> from Węgliniec is small and surrounded by extensive forest stands of <em>P. sylvestris</em>. Our three-year records of phenological observations demonstrated that flowering periods for <em>P. uliginosa</em> and <em>P. sylvestris</em> overlap, allowing for cross-pollination. The possibility of <em>P. uliginosa</em> pollination by <em>P. sylvestris</em> creates a potential danger of genetic erosion of the <em>P. uliginosa</em> gene pool. Nonetheless, based on a species specific cpDNA marker we have found that among 533 seedlings of <em>P. uliginosa</em> there were only six seedlings carrying cpDNA marker specific for <em>P. sylvestris</em>, indicating that such hybridization seems to be rare.

scholarly journals Predicting insecticide resistance: mutagenesis, selection and response

1998 ◽  
Vol 353 (1376) ◽  
pp. 1729-1734 ◽  
Author(s):  
J. A. McKenzie ◽  
P. Batterham
Keyword(s):  
Single Gene ◽  
Natural Populations ◽  
Selective Advantage ◽  
Resistance Mechanisms ◽  
Predictive Capacity ◽  
Evolution Of Resistance ◽  
Australian Sheep ◽  
Delivery Strategies ◽  
Low Levels ◽  
Molecular Bases

Strategies to manage resistance to a particular insecticide have usually been devised after resistance has evolved. If it were possible to predict likely resistance mechanisms to novel insecticides before they evolved in the field, it might be feasible to have programmes that manage susceptibility. With this approach in mind, single–gene variants of the Australian sheep blowfly, Lucilia cuprina , resistant to dieldrin, diazinon and malathion, were selected in the laboratory after mutagenesis of susceptible strains. The genetic and molecular bases of resistance in these variants were identical to those that had previously evolved in natural populations. Given this predictive capacity for known resistances, the approach was extended to anticipate possible mechanisms of resistance to cyromazine, an insecticide to which L. cuprina populations remain susceptible after almost 20 years of exposure. Analysis of the laboratory–generated resistant variants provides an explanation for this observation. The variants show low levels of resistance and a selective advantage over susceptibles for only a limited concentration range. These results are discussed in the context of the choice of insecticides for control purposes and of delivery strategies to minimize the evolution of resistance.

Pollination biology of yellow starthistle (Centaurea solstitialis) in California

1996 ◽  
Vol 74 (2) ◽  
pp. 262-267 ◽  
Author(s):  
D. M. Maddox ◽  
A. Mayfield ◽  
D. B. Joley ◽  
D. M. Supkoff
Keyword(s):  
Pollination Biology ◽  
Centaurea Solstitialis ◽  
Yellow Starthistle ◽  
Pollen Presentation ◽  
Self Fertilization ◽  
Low Levels ◽  
High Level ◽  
Insect Visitors ◽  
Achene Production ◽  
European Honeybee

Various facets of the pollination biology affecting achene production of Centaurea solstitialis L. were examined. Production of viable achenes commenced in capitula bagged or excised in the late flowering stage (F-2 midstage). In all studies in which capitula were prevented from crossing, only one plant had a high level of achene production, all others producing either a few achenes or none at all. Achene production in plants allowed to cross was high and significantly greater than in plants prevented from crossing. Persistent low levels of self-fertilization in most plants indicated that there was selection against inbreeding. The pollen presentation mechanism for C. solstitialis was similar to that of other Centaurea spp. described previously. The most commonly observed insect visitors of yellow starthistle capitula were Hymenoptera spp., especially the European honeybee. Keywords: Centaurea, pollination, yellow starthistle.

High world sugar prices: is Asia’s production cycle to blame?

2010 ◽  
pp. 169-173
Author(s):  
Martin Todd
Keyword(s):  
Supply Chain ◽  
Supply And Demand ◽  
Production Cycle ◽  
Low Levels ◽  
High Level ◽  
High World

The current high world sugar prices reflect a major imbalance between global supply and demand, which has reduced stocks to very low levels. Although it remains to be seen whether prices will rise much above current values, it is clear that the supply chain will remain stretched throughout 2010 and this will help to maintain prices at a high level.

scholarly journals POPULATION GENETICS OF ALLOZYME VARIATION IN NEUROSPORA INTERMEDIA

Genetics ◽  
1975 ◽  
Vol 80 (4) ◽  
pp. 785-805
Author(s):  
P T Spieth
Keyword(s):  
Genetic Variation ◽  
Vegetative Reproduction ◽  
Vascular Plant ◽  
Natural Populations ◽  
Allozyme Variation ◽  
Regular Feature ◽  
Local Populations ◽  
Neurospora Intermedia ◽  
Pattern Of Variation ◽  
High Level

ABSTRACT Electrophoretically detectable variation in the fungus Neurospora intermedia has been surveyed among isolates from natural populations in Malaya, Papua, Australia and Florida. The principal result is a pattern of genetic variation within and between populations that is qualitatively no different than the well documented patterns for Drosophila and humans. In particular, there is a high level of genetic variation, the majority of which occurs at the level of local populations. Evidence is presented which argues that N. intermedia has a population structure analogous to that of an annual vascular plant with a high level of vegetative reproduction. Sexual reproduction appears to be a regular feature in the biology of the species. Substantial heterokaryon function seems unlikely in natural populations of N. intermedia. Theoretical considerations concerning the mechanisms underlying the observed pattern of variation most likely should be consistent with haploid selection theory. The implications of this constraint upon the theory are discussed in detail, leading to the presentation of a model based upon the concept of environmental heterogeneity. The essence of the model, which is equally applicable to haploid and diploid situations, is a shifting distribution of multiple adaptive niches among local populations such that a given population has a small net selective pressure in favor of one allele or another, depending upon its particular distribution of niches. Gene flow among neighboring populations with differing net selective pressures is postulated as the principal factor underlying intrapopulational allozyme variation.

scholarly journals Testing Todd: family types and development

2021 ◽  
pp. 1-18
Author(s):  
Jerg Gutmann ◽  
Stefan Voigt
Keyword(s):  
Rule Of Law ◽  
Civil Society Organizations ◽  
The Rule Of Law ◽  
State Fragility ◽  
Family Types ◽  
Low Levels ◽  
Parsimonious Model ◽  
The One ◽  
High Level

Abstract Many years ago, Emmanuel Todd came up with a classification of family types and argued that the historically prevalent family types in a society have important consequences for its economic, political, and social development. Here, we evaluate Todd's most important predictions empirically. Relying on a parsimonious model with exogenous covariates, we find mixed results. On the one hand, authoritarian family types are, in stark contrast to Todd's predictions, associated with increased levels of the rule of law and innovation. On the other hand, and in line with Todd's expectations, communitarian family types are linked to racism, low levels of the rule of law, and late industrialization. Countries in which endogamy is frequently practiced also display an expectedly high level of state fragility and weak civil society organizations.

Flavonoids and UV Photoprotection in Arabidopsis Mutants

2001 ◽  
Vol 56 (9-10) ◽  
pp. 745-754 ◽  
Author(s):  
Ken G Ryan ◽  
Ewald E Swinny ◽  
Chris Winefield ◽  
Kenneth R Markham
Keyword(s):  
Crucial Role ◽  
Hydroxycinnamic Acid ◽  
Ultraviolet B ◽  
Uvb Radiation ◽  
Wild Type ◽  
Hydroxycinnamic Acid Derivatives ◽  
Quercetin Glycosides ◽  
Kaempferol Glycosides ◽  
Low Levels ◽  
High Level

AbstractWild-type Arabidopsis L. leaves exposed to low ultraviolet-B (U V B ) conditions contained predominantly kaempferol glycosides, with low levels of quercetin glycosides. The flavonoid level doubled on treatment with UVB and an increase in the ratio of quercetin: kaempferol was observed. These results suggest that flavonols protect Arabidopsis plants from UVB damage, and indicate that the flavonoid 3’-hydroxylase (F3’H) enzyme, which converts dihydrokaempferol to dihydroquercetin, may play a crucial role. The tt7 mutant lacks this gene and, after treatment with sub-ambient UVB, contained kaempferol glycosides exclusively, to a level of total flavonols similar to that in wild-type Arabidopsis. Total flavonols after enhanced UVB treatment were higher in tt7 than in similarly treated wild-type plants, and only kaempferol glycosides were detected. Despite this high level, tt7 plants were less tolerant of UVB radiation than wild-type plants. These observations suggests that kaempferol is a less effective photoprotectant than quercetin. The chalcone isomerase (CHI) mutant (tt5) surprisingly did not accumulate naringenin chalcone, and this suggests that the mutation may not be restricted to the CHI gene alone. The concentration of hydroxycinnamic acid derivatives did not change with UVB treatment in most varieties indicating that their role in UV photoprotection may be subordinate to that of the flavonoids.

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