RIBOSOMAL RNA GENE DIVERSITY, EFFECTIVE POPULATION SIZE, AND EVOLUTIONARY LONGEVITY IN ASEXUAL GLOMEROMYCOTA

Abstract Fertility and gene diversity were estimated in three second generation (F2) seed stands (SPA 1-3) and two clone trials (CSO 1&2) of Eucalyptus camaldulensis to assess the impact on seed crop. F2 seedlots were evaluated in comparison to native provenances, ten commercial clones and interspecific hybrids at diverse sites. SPA 1&2 were genetic gain trials of five first generation (F1) orchard seedlots, SPA 3 a plantation of one F1 orchard seedlot, and CSOs were clone trials of 21 commercial clones established at two contrasting sites. Fertility variation, as indicated by sibling coefficient, was high (Ψ, 9-14) in the SPAs as only about 26 % trees were fertile compared to 81 % trees in CSOs. Effective population size was higher in SPA 1 and 2 (Ns, 95 and 74, respectively) than SPA 3 (Ns = 39). Fertility was highly skewed in CSO 2 resulting in low effective population size (Ns = 2) compared to CSO 1 (Ns = 11). Constant seed collection enabled 3-fold increase in relative population size and 22 % higher predicted gene diversity in CSO 2. Genetic diversity (He) estimated using SSR markers was higher in SPA 1&2 and native provenances (NAT), compared to SPA 3 and CSO 1, whereas CSO 2 and clones had lower values. There was a high positive correlation between estimated He and predicted gene diversity values of SPAs and CSOs. He was positively correlated to mean field survival and negatively correlated to kraft pulp yield (KPY), evaluated at three years in progeny trials across three locations. Number of alleles per locus was higher in SPAs and native provenances compared to CSOs and clones. Discriminant principal component analysis clustered CSO, NAT and SPA seedlots in different groups while commercial E. camaldulensis clones clustered close to NAT. Multilocus outcrossing rate was generally high (tm, 91-100 %), though selfing was observed in two families of SPA 3 and CSO 2. Selected interspecific hybrid families of commercial E. camaldulensis clones (with E. urophylla and E. pellita) evaluated at two of the sites had higher He and KPY than clones at three years.

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Influence of gene flow and breeding tactics on gene diversity within populations.

Genetics ◽

10.1093/genetics/129.2.573 ◽

1991 ◽

Vol 129 (2) ◽

pp. 573-583 ◽

Cited By ~ 7

Author(s):

R K Chesser

Keyword(s):

Genetic Variation ◽

Gene Flow ◽

Population Size ◽

Effective Population Size ◽

Gene Diversity ◽

Island Model ◽

Effective Population ◽

Migration Rates ◽

Asymptotic Values ◽

Fixation Indices

Abstract Expressions describing the accumulation of gene correlations within and among lineages and individuals of a population are derived. The model permits different migration rates by males and females and accounts for various breeding tactics within lineages. The resultant equations enable calculation of the probabilistic quantities for the fixation indices, rates of loss of genetic variation, accumulation of inbreeding, and coefficients of relationship for the population at any generation. All fixation indices were found to attain asymptotic values rapidly despite the consistent loss of genetic variation and accumulation of inbreeding within the population. The time required to attain asymptotic values, however, was prolonged when gene flow among lineages was relatively low (less than 20%). The degree of genetic differentiation among breeding groups, inbreeding coefficients, and gene correlations within lineages were found to be primarily functions of breeding tactics within groups rather than gene flow among groups. Thus, the asymptotic value of S. Wright's island model is not appropriate for describing genetic differences among groups within populations. An alternative solution is provided that under limited conditions will reduce to the original island model. The evolution of polygynous breeding tactics appears to be more favorable for promoting intragroup gene correlations than modification of migration rates. Inbreeding and variance effective sizes are derived for populations that are structured by different migration and breeding tactics. Processes that reduce the inbreeding effective population size result in a concomitant increase in variance effective population size.

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Intraspecific variation in population gene diversity and effective population size correlates with the mating system in plants.

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.88.10.4494 ◽

1991 ◽

Vol 88 (10) ◽

pp. 4494-4497 ◽

Cited By ~ 256

Author(s):

D. J. Schoen ◽

A. H. Brown

Keyword(s):

Mating System ◽

Population Size ◽

Effective Population Size ◽

Intraspecific Variation ◽

Gene Diversity ◽

Effective Population

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Inconsistent effects of urbanization on amphibian genetic diversity

10.1101/2020.08.16.253104 ◽

2020 ◽

Author(s):

Chloé Schmidt ◽

Colin J Garroway

Keyword(s):

Genetic Diversity ◽

Population Size ◽

Effective Population Size ◽

Habitat Loss ◽

Gene Diversity ◽

Amphibian Declines ◽

Population Declines ◽

Effective Population ◽

Negative Effects ◽

Amphibian Species

AbstractHabitat loss and fragmentation are leading causes of vertebrate population declines. These declines are thought to be partly due to decreased connectivity and habitat loss reducing population sizes in human transformed habitats. With time this can lead to reduced effective population size and genetic diversity which restricts the ability of wildlife to cope with environmental change through genetic adaptation. However, it is not well understood whether these effects are generally applicable across taxa. Here, we repurposed and synthesized raw microsatellite data from online repositories from 19 amphibian species sampled at 554 sites in North America. For each site, we estimated gene diversity, allelic richness, effective population size, and population differentiation. Using binary urban-rural census designations, and continuous measures of human population density and the Human Footprint Index, we tested for generalizable effects of human land use on amphibian genetic diversity. We found no consistent relationships for any of our genetic metrics. While we did not detect directional effects for most species, a few generalist species responded positively to urbanization. These results contrast with consistent negative effects of urbanization in mammals and species specific positive and negative effects in birds. In the context of widespread amphibian declines, our results suggest that habitat loss in human transformed habitats is a more immediate concern than declining genetic diversity in populations that persist.

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Clonal fertility variation and its effects on the effective population size in the seed orchard of dioecious species, Fraxinus rhynchophylla

Silvae Genetica ◽

10.1515/sg-2012-0010 ◽

2012 ◽

Vol 61 (1-6) ◽

pp. 79-84

Author(s):

Kyu-Suk Kang ◽

Chang-Soo Kim

Keyword(s):

Population Size ◽

Effective Population Size ◽

Gene Pool ◽

Gene Diversity ◽

Seed Orchard ◽

Effective Population ◽

Dioecious Species ◽

Theoretical Approaches ◽

Fertility Variation ◽

Male Flowers

Abstract The numbers of female and male flowers were assessed in a clonal seed orchard of Fraxinus rhynchophylla for four consecutive years from 2004 through 2007. The female and male flowers of the grafts from 48 clones were counted individually over the crown. Fertility variation was calculated by sibling coefficient that is related to the coefficient of variation in parental flower assessment. Estimated maternal and paternal fertilities were not constant but varied from year to year, and they were also found to be weakly correlated. The effective numbers of clones serving as male and female parents were calculated from the sibling coefficients of maternity and paternity. We applied two theoretical approaches to estimate the clonal effective population sizes based on 1) fertility variation (i.e., effective number of parents, N(c)) and 2) gender balance (effective population size, Nee) among parental genotypes. The values of Ne(c) were higher in the years with abundant flowering and seed production, while sibling coefficients were lower. On average (pooled), the maternal, paternal and clonal values of Ne(c) were calculated to be 17.3, 21.0 and 38.1 respectively. The Ne(c) for maternal gamete gene pool was ranged from 9.8 to 16.7. The values of Ne for paternal gamete gene pool were generally higher (ranged from 14.9 to 21.9) than those for maternal. When pooled, the Ne was 47.2 and the values of Ne were higher when the gender ratio was more balanced. An option of equal seed harvest might be good to mitigate fertility variation and to improve gene diversity of seeds.

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