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Factors affecting effective population size estimation in a seed orchard: a case study of Pinus sylvestris Du š an Gömöry 1 , Roman Longauer 2 , Ladislav Paule 1 , Rudolf Bruch ánik 3. 1 Department of Phytology, Technical University in Zvolen, Zvolen, Slovakia

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1 Department of Phytology, Technical University in Zvolen, Zvolen, Slovakia

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Factors affecting effective

population size estimation

in a seed orchard: a case study

of Pinus sylvestris

Dušan Gömöry1, Roman Longauer2,

Ladislav Paule1, Rudolf Bruchánik3

1Department of Phytology, Technical University in Zvolen, Zvolen, Slovakia

2National Forestry Centre, Forestry Research Institute , Zvolen, Slovakia

3State Forests of the Slovak Republic, General Directorate, Banská Bystrica, Slovakia


Ideal seed orchard:

Randomly mating Mendelian population

Contribution of genotypes to male and

female gamete pools proportionate

to their frequencies

No change of allelic frequencies over

generations


Real clonal seed orchards of European

conifers:

Marker studies:

Generally no or small deviations of genotypic

frequencies from HWE expectations

Low levels of self-fertilization

but (1)

Sometimes significant differences in allelic

frequencies between seed orchard and the

crop

but (2)

Marker studies cannot easily be done everywhere


  • Ideal clonal seed orchard:

  • Equal contribution of parental clones

  • to the gene pool of the seed crop

  • Reality:

  • Deviations from equal contribution because of:

  • unequal female gamete contributions

  • unequal male gamete contributions

  • phenological isolation

  • pollen dispersal in space (distribution of clones –

  • distance-dependent dispersal, wind direction,

  • turbulences)

  • genetic incompatibilities


  • Consequences:

  • loss of genetic diversity in seed orchard crops

  • increased coancestry (potentially higher

  • inbreeding in the following generation)

  • Monitoring the genetic diversity in seed

  • orchard crops:

  • Effective population size (e.g. effective number

  • of clones)

  • Status number (Lindgren et al. 1996:

  • Silvae Genet. 45: 52–59).

  • NS= 0.5/Θ

  • = number of unrelated non-inbred genotypes

  • having the same average coancestry as

  • the considered population


Case study: three Scots pine seed orchards


Assessed characteristics (for each ramet):

Female gamete contribution – cone weighting

Male gamete contribution – counting and size

assessment of male strobili

Flowering phenology: 3 dates in Háj and Sýkorová,

5 dates in Kolkáreň, 5 developmental stages for

male strobili, 6 stages for female strobili

Spatial dispersal of pollen: negative exponential

dispersal function (Adams & Birkes 1991)


  • Alien genotypes present in all three seed orchards (rootstocks with aborted scions,

  • unregistered clones, …) as proved by allozyme genotyping

  • Three situations considered:

  • Alien material removed

  • Alien ramets not removed but not

  • harvested

  • (3) Cones harvested from all ramets


Effective number, status number

and coancestry estimates

F – female contributions assessed, M –male contributions assessed,

P – phenology assessed, D – pollen flow considered


Effective number, status number

and coancestry estimatesHáj


Effective number, status number

and coancestry estimates

F – female contributions assessed, M –male contributions assessed,

P – phenology assessed, D – pollen flow considered


Effective number, status number

and coancestry estimatesSýkorová


Effective number, status number

and coancestry estimates

F – female contributions assessed, M –male contributions assessed,

P – phenology assessed, D – pollen flow considered


Effective number, status number

and coancestry estimatesKolkáreň


  • Conclusions

  • In old, fully fructificating seed orchards of Scots pine in Central Europe, effective number of clones is a sufficient estimator of the effective population size

  • Phenology and spatially-dependent pollen dispersal do not considerably affect NS estimates and need not be assessed for practical purposes

  • Young seed orchard are unbalanced and phenologically not synchronized, consequently, effective number of clones is a poor estimator of effective size and status number is affected by all factors (male + female fertility, phenology, spatial design)


Thank you for your attention


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