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Hybridization as a dispersal mechanism
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An example from the genus Eucalyptus is used to argue that hybridization may be of
evolutionary significance as a means of gene dispersal where seed dispersal is limited. A previous
study of regeneration of E. risdonii and E. amygdalina indicated that the current selective regime
was favoring E. risdonii. However, the dispersal of E. risdonii by seeds is shown to be limited (S.
= 4.6 m). By comparison, the flow of E. risdoriii genes into the range of E.amygdalina by pollen
dispersal and F1 hybridization is widespread (r, = 82 m). While the actual level of hybridization
is low, interspecific hybridization effectively doubles the dispersal of E. risdonii genes into the
range of E. amygdalina. This pollen flow can have a significant genetic impact, since isolated
hybrids or patches of abnormal phenotypes have been found 200-300 m from the species boundary.
Based on lignotuber size, same of these patches appear to have been founded by F1 hybrids. The
frequency af E. risdonii types in the patches appears to increase with patch size suggesting that
there is selection for this phcenotype in subsequent generations. E. risdonii-like individuals were
recovered in the progeny from both intermediate and E. risdonii backcross phenotypes. These
results suggest that E. risdonii may invade suitable habitat islands within the E. amygdnlina forest,
independently of seed migration, by long-distance pollen migration followed by selection for the
gene combinations of the pollen parent.
|Journal or Publication Title:||Evolution|
|Page Range:||pp. 1245-1255|
|Date Deposited:||23 Sep 2008 03:25|
|Last Modified:||18 Nov 2014 03:49|
|Item Statistics:||View statistics for this item|
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