Isozyme differentiation betwen sympatric clones of Salix alba and Salix fragilis

1998

S.249-260

4 Abb., 9 Tab., zahlr. Lit.

Unselbständiges Werk

200055391

The allozyme variation in the progeny of controlled crosses within and between Salix alba and Salix fragilis was assessed for LAP, PGM, GOT and SkDH representing 12 alleles in 9 loci of which only 3 showed polymorphism. Lap-1 and Pgm-2 clearly followed the expected segregation and suggested that these polyploid willow species are functionally diploidized in the expression of these genes. Gene duplications have occured in PGM, GOT and ADH and most likely also in b-EST. Fixed heterozygosity was observed for Got-3 in the progeny of an intraspecific cross of S. fragilis. Based on the inferred genetic control of these allozymes, a survey of 239 clones of the morphological S. alba - S. fragilis complex indicated that there is rather a differentiation in allozyme frequencies at the level of the putative species than at the level of geographical hierarchies. The fixation index for Lap-1 indicated a lack of heterozygotes in all investigated S. alba locations. At the level of catchments, these values ranged from 0.457 to 0.617 and suggest that this might be a common situation. The lack of heterozygosity for Lap-1 was even more pronounced in the S. fragilis clones that were mainly homozygous or monomorphic. The hierarchical structuring of heterozygosity indicated that most of the differentiation occured at the level of locations or tributaries and that there is no further differentiation between the catchment level considered for each species.