Morphological and allozymic evidence of natural hybridization between two southern beeches (Nothofagus spp.) and its relation to heterozygosity and height growth
1997
Gallo, L.A. | Marchelli, P. | Breitembucher, A. (INTA, EEA Bariloche, San Carlos de Bariloche (Argentina). Forest Genetics Unit)
Seeds from 18 trees of Nothofagus nervosa (= N. alpina) were collected in the Lacar Lake basin, Neuquen Province, southwestern Argentina. During the first and second growing season, large morphological differences in the margins of the leaves from about 2000 individual seedlings were observed. Six families showed only individuals with the expected typical N. nervosa leaves. The other twelve families additionally showed individuals with leaves typical of the sympatric species N. obliqua in frequencies from 2 to 80 %. The hybridization of an isolated N. nervosa mother tree with pollen from the closely surrounding N. obliqua trees could be verified using an Adh-marker locus. The proportion of self-fertilization in this case was estimated as 6 %. Average degree of heterozygosity for three marker loci was higher in families with higher hybrid morphotypes frequencies. These families grew significantly faster than those without hybrids and a lower degree of heterozygosity. Putative hybrid individuals were also significantly taller within families. The possible manifestation of initial "heterosis effects" in the hybrids and of reproductive incompatibility is discussed. We concluded that interspecific hybridization can be very high in the case of isolated trees and can produce vigorous hybrid seedling. The main direction of the hybridization is apparently N. nervosa x N. obliqua
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