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Hybridization in Betula Alleghaniensis Britt. and B. Lenta L.: A Comparative Analysis of Controlled Crosses

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Progenies of the crosses B. lenta X lenta, B. alleghaniensis X alleghaniensis, and B. lenta X alleghaniensis, at age 27, were compared using 47 morphological characters of leaves, fruit, bark, and pollen. Stepwise discriminant analysis indicated that number of cilia of bracts of fruiting catkins, length of bark exfoliation, and pollen diameter, in that order, gave the best separation of three taxa. B. lenta (2n = 28) was distinguished from B. alleghaniensis (2n = 84) and the hybrid by cilia alone. B. alleghaniensis and the hybrid were not completely separated until all three characters were considered. Principal components analysis using 25 morphological characters, and hybrid indices based on 47 characters, also indicated that the F1 hybrid was more similar to B. alleghaniensis than to B. lenta. Analyses based on leaf characters revealed considerable overlap between the hybrid and both parent taxa. Pollen abortion of the hybrid was low (3.3 percent) and not significantly different from B. alleghaniensis. Average height and diameter of the hybrid were significantly less than the parent taxa. Germination of open-pollinated seeds from the hybrids was only 10 percent. It was concluded that reduced vigor of F1 hybrids and low germination rates are postzygotic barriers strong enough to preclude or significantly reduce successive generation hybridization and gene flow between B. lenta and B. alleghaniensis in natural habitats. Forest Sci. 17:415-424.

Keywords: Pollen; discriminant analysis; germination; hybrid index; postzygotic barriers

Document Type: Journal Article

Affiliations: Research Associate and Professor of Forestry at the School of Natural Resources, University of Michigan, Ann Arbor 48104

Publication date: 1971-12-01

More about this publication?
  • Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.
    Forest Science is published bimonthly in February, April, June, August, October, and December.

    2015 Impact Factor: 1.702
    Ranking: 16 of 66 in forestry

    Average time from submission to first decision: 62.5 days*
    June 1, 2016 to Feb. 28, 2017

    Also published by SAF:
    Journal of Forestry
    Other SAF Publications
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