Microsatellite analysis of seed dispersal and parentage of saplings in bur oak, Quercus macrocarpa

Authors

  • B. D. DOW,

    Corresponding author
    1. Department of Biological Sciences (M/C 066), University of Illinois at Chicago, 845 West Taylor Street, Chicago, IL 60607, USA
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  • M. V. ASHLEY

    1. Department of Biological Sciences (M/C 066), University of Illinois at Chicago, 845 West Taylor Street, Chicago, IL 60607, USA
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  • Beverly Dow worked with Mary Ashley to develop microsatellite markers to study mating systems of trees while a doctoral student in the Ecology and Evolution program at University of Illinois at Chicago (UIC). Mary Ashley, an assistant professor at UIC, uses molecular genetic approaches to study population and evolutionary processes in a wide range of taxa. Beverly Dow is currently a tree research geneticist at the Northern Great Plains Research Laboratory (USDA-ARS) in Mandan, North Dakota.

USDA Agricultural Research Service Northern Great Plains Research Laboratory Highway 6 South, PO Box 459 Mandan, North Dakota 58554 Tel.: +1–701-667-3006 Fax: +1–701-667-3054. E-mail: dowb@ars.usda.gov

Abstract

Microsatellite analysis was used to examine parentage and spatial distributions of 62 adult bur oaks Quercus macrocarpa, and 100 saplings in a single stand. Using genotypes scored by PCR products at four microsatellite loci, we determined that 94 saplings matched at least one parent in the stand. Saplings often occur as dense clusters of half-sibs around the presumed maternal parent, and only four adults were seed parents to a large proportion of the saplings sampled. A stump apparently was the seed parent of the largest cluster of half-sibs, which occupied a sizeable light gap opened up by the death of their maternal tree. Approximately half of the saplings appeared to have grown from seeds that had not been removed after falling from the tree, and half from seeds that were dispersed beyond the crown of their maternal parent. Long-distance seed dispersal may be more common than has been previously reported. Extremely high levels of long-distance pollination were indicated, and pollen donors within the stand were generally distributed randomly around maternal trees. More than half of the saplings had paternal parents outside of the stand. This study demonstrates the utility of microsatellite analysis for studying mating systems, seed dispersal and seedling establishment in natural plant populations.

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