Family outcrossing rates and neighborhood floral density in natural populations of swamp milkweed (Asclepias incarnata): potential statistical artifacts

1999 ◽  
Vol 98 (6-7) ◽  
pp. 1063-1071 ◽  
Author(s):  
C. T. Ivey ◽  
R. Wyatt
Keyword(s):  
Natural Populations ◽  
Floral Density ◽  
Outcrossing Rates

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.

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.

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.

Outcrossing rates and male sterility in natural populations of Plantago coronopus

1988 ◽  
Vol 76 (2) ◽  
pp. 190-196 ◽  
Author(s):  
K. Wolff ◽  
B. Friso ◽  
J. M. M. van Damme
Keyword(s):  
Male Sterility ◽  
Natural Populations ◽  
Outcrossing Rates ◽  
Plantago Coronopus

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 Outcrossing rates and heterozygosity in natural populations of Hordeum spontaneum Koch in Israel

Heredity ◽  
1978 ◽  
Vol 41 (1) ◽  
pp. 49-62 ◽  
Author(s):  
A H D Brown ◽  
D Zohary ◽  
E Nevo
Keyword(s):  
Natural Populations ◽  
Hordeum Spontaneum ◽  
Outcrossing Rates

Outcrossing rates and organelle inheritance estimated from two natural populations of the Japanese endemic conifer Sciadopitys verticillata

2014 ◽  
Vol 127 (5) ◽  
pp. 617-626 ◽  
Author(s):  
James R. P. Worth ◽  
Masashi Yokogawa ◽  
Yuji Isagi
Keyword(s):  
Natural Populations ◽  
Organelle Inheritance ◽  
Outcrossing Rates ◽  
Sciadopitys Verticillata

Gametocyte sex ratios as indirect measures of outcrossing rates in malaria

Parasitology ◽  
1992 ◽  
Vol 104 (3) ◽  
pp. 387-395 ◽  
Author(s):  
A. F. Read ◽  
A. Narara ◽  
S. Nee ◽  
A. E. Keymer ◽  
K. P. Day
Keyword(s):  
Sex Ratio ◽  
Evolutionary Biology ◽  
Geometric Mean ◽  
Sex Ratios ◽  
Simple Game ◽  
Natural Populations ◽  
Theory Model ◽  
Indirect Measures ◽  
Epidemiological Surveys ◽  
Outcrossing Rates

The frequency of recombination between unlike genotypes is central to understanding the generation of genetic diversity in natural populations of malaria. Here we suggest a way of investigating the problem which could complement conventional biochemical approaches to the population genetics of malaria. Sex allocation theory is one of the most successful areas of evolutionary biology. A well-supported prediction is that progressively less female-biased sex ratios are favoured with more outcrossing; equal numbers of males and females being evolutionarily stable in randomly mating outbred populations. We present a simple game theory model to support the idea that outcrossing rates in malaria will be correlated with the sex ratio of gametocytes in the peripheral blood of vertebrate hosts. Blood films from epidemiological surveys and culture-adapted isolates from Madang Province, Papua New Guinea, were used to estimate average gametocyte sex ratio of Plasmodium falciparum in the area. The geometric mean proportion of males in the population was 0.18 (95% confidence limits: 0.15–0.22). From our model, we estimate that, on average, 36% of zygotes are the result of outcrossing. This estimate assumes that most microgametes released following exflagellation are capable of fertilization. If, on average, fewer than about 70% of microgametes are capable of fertilization (as is the case in at least one other species of Plasmodium), the observed sex ratio would be consistent with between zero and 36% of zygotes being the result of outcrossing. These estimates suggest that there is usually a numerically dominant genotype in the gametocyte population in a blood meal, and that a considerable amount of selfing is occurring in P. falciparum populations in the Madang region, even though it is an area of intense year-round transmission.

scholarly journals Intrapopulation fixation index dynamics in finite populations with variable outcrossing rates

2003 ◽  
Vol 60 (2) ◽  
pp. 305-313 ◽  
Author(s):  
Alexandre Siqueira Guedes Coelho ◽  
Roland Vencovsky
Keyword(s):  
Natural Populations ◽  
Finite Size ◽  
Simulated Data ◽  
Outcrossing Rate ◽  
Fixation Index ◽  
Data Sets ◽  
Mean Values ◽  
Outcrossing Rates ◽  
Size Condition ◽  
Simulated Data Sets

The intrapopulation fixation index ( f ) is inversely related to the outcrossing rate (t). Results obtained from data on molecular markers of natural populations have shown that these values are highly variable, even when measured in the same group of individuals. It is thus suggested that factors besides those described in Wright's genetic equilibrium must be operating. Using simulated data sets this study shows that the finite size condition of a population is sufficient to spread the estimated f values along a range at equilibrium, as opposed to keeping them at the theoretical equilibrium point. The variation in outcrossing rates can amplify this range considerably. Correlation between estimated f values obtained from different loci in this condition showed to be negatively related to the outcrossing rates, and positively related to the variance of these rates along generations. The finite size of populations associated to small fluctuations in t mean values over time may explain the usually reported high variation among estimated f values of different loci.

The mating system in natural populations of western redcedar (Thuja plicata)

2001 ◽  
Vol 79 (6) ◽  
pp. 753-756 ◽  
Author(s):  
Lisa M O'Connell ◽  
Frédérique Viard ◽  
John Russell ◽  
Kermit Ritland
Keyword(s):  
British Columbia ◽  
Mating System ◽  
Natural Populations ◽  
Seed Orchard ◽  
Outcrossing Rate ◽  
Thuja Plicata ◽  
Western Redcedar ◽  
Outcrossing Rates ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Thuja Plicata Donn

Outcrossing rates and the correlation of paternity were estimated in six natural populations of western redcedar (Thuja plicata Donn. ex D. Don) in southwestern British Columbia. Over 3000 offspring were assayed, as progeny arrays, for the only sufficiently polymorphic isozyme locus in this species, glucose-6-phosphate dehydrogenase. Estimates of population outcrossing rates ranged from 0.173 to 1.257 and averaged 0.715 ± 0.045 (mean ± SD). Estimates of the correlation of paternity generally did not differ from zero. Six of the seven outcrossing estimates (one population was surveyed in two consecutive years) were higher than a previous seed orchard study. However, these outcrossing rates are still lower than those estimated for most other species of conifers. Population outcrossing rates also showed wide variation, and this variation is discussed in terms of ecological and phenological differences among populations.Key words: Cupressaceae, conifers, isozymes, outcrossing rate, inbreeding.

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