—Missouri and Indiana have markedly different histories of glaciation and recolonization by forest trees. These states also differ in land use patterns and degree of anthropogenic landscape change such as forest fragmentation. To determine the overall effects of these and other demographic differences on the levels of genetic diversity and structure in black walnut (Juglans nigra L.) more than 550 total black walnut trees from nine populations in Indiana and 10 in Missouri were sampled and analyzed using 12 nuclear microsatellite loci. Although genetic diversity parameters such as allelic richness and expected heterozygosity were high overall, they varied little among populations and their mean values for the two states were not significantly different. Pairwise genetic distance values between all population pairs ranged from 0.012-0.159, but no significant pattern of isolation by distance was detected. The estimate of the degree of genetic differentiation between states (FPT = 0.0009) was very small and not significant, indicating that differences between states explained an inconsequential portion of the total variance. The observed low levels of local and regional genetic structure indicate that high levels of pollen flow have buffered black walnut from the genetic consequences of founder effects and genetic drift in both geologic and recent time scales.


Victory, E.R., J.C. Glaubitz, J. Fike, O.E. Rhodes, Jr., and K.E. Woeste. 2008. Different Histories but Similar Genetic Diversity and Structure for Black Walnut in Indiana and Missouri. p. 436-445. IN: D. Jacobs and C. Michler et al. (eds) Proceedings of 16th Central Hardwood Forestry Conference, April 8 – 9, West Lafayette, IN, Gen. Tech. Rept. NRS-P-24, U.S.D.A. Forest Service, Northern Research Station, Newtown Square, PA (refereed)

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