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Last Updated 16. September 2018

Genetic structures and mating pattern were studied in a typically small stand of Taxus baccata L. in Germany using six variable allozyme loci (Adh-A, Pgi-B, Aat-B, Pgm-A, Idh-B and Skdh-B) as genetic markers. The stand exhibits a high level of genetic variation. The effective number of alleles was 1.58 in the totality of the stand, 1.64 in the group of male trees, 1.50 in the female trees and 1.66 in the progeny.

Since gymnosperm seeds provide access to haploid tissue of maternal origin, it is possible to recognize gametic sex of the embryo alleles. Methods of paternity analysis were applied to determine the pollen contributions to the progeny of female trees using multilocus genotypes. Besides exclusion techniques and maximum-likelihood estimates, multilocus gametic segregation ratios among the potential pollen contributions of potential pollen parents and linkage relationships between gene loci were considered. Immigrant pollen flow is postulated for all male gametes that contain alleles or multilocus combinations of alleles that could not originate from the study stand. The detectable and thus minimum total proportion of immigrant pollen amounted to 28%. Mean and maximum pollen dispersal distances within the stand were estimated with 143 m and 320 m, respectively. Extreme differences among individual mating patterns were observed as quantified by a mean differentiation of 24% among single pollen clouds. Three pollen clouds are dominated by contributions of the nearest male neighbor amounting up to 100%. It thus appears that the breeding structure consists of a considerable proportion of pollination between neighboring males and females coupled with substantial long-distance pollen movement.

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