SAMUEL, ROSABELLE* AND FRIEDRICH EHRENDORFER. Department of Higher Plant Systematics and Evolution, Institute of Botany, University of Vienna, Rennweg 14, A-1030 Vienna, Austria. - Interspecific hybridization and phylogenetic relationships in eastern European Quercus as revealed by Isozymes, RAPDs, chloroplast (trnl) and nuclear rDNA (ITS) Molecular Markers.
Quercus is well known
for weak crossing barriers between species. Species of oaks are
interfertile in many combinations, and natural hybrids may be
formed between pairs of species that are very different from one
another both morphologically and ecologically. Allozyme variation
at 14 loci in 19 populations of Quercus cerris,
Q. pubescens, Q. petraea
and Q. robur showed that Q. cerris
(sect. Cerris) is clearly separated from the
other three species (sect. Quercus). The degree
of genetic differentiation based on isozyme data among Q.
pubescens, Q. petraea and Q.
robur falls into a range found among conspecific populations.
RAPD results are consistent with allozyme data obtained for the
GOT-2 locus and with a phenotypic classification
(petraea-like, hybrids and robur-like) in samples from hybrid
populations. Sequences of the highly conserved chloroplast tRNALeu
intron show a single nucleotide mutation (T to C) in SE.European
Q. pubescens, Q. petraea
and Q. robur, which suggests Pleistocene hybrid
chloroplast capture among these species. ITS sequences from nuclear
rDNA of these and other Euro-Mediterranean, East Asiatic and North
American Quercus taxa reveal two clearly
divergent clades and suggest unexpected phylogenetic relationships.
Study on the chloroplast DNA trnL(UAA) - trnF (GAA) intergenic
spacer sequences is in progress.
Key words: chloroplast (trnl), isozymes, Quercus, RAPDs, rDNA (ITS)