Natural hybridisation between a deciduous (Nothofagus antarctica, Nothofagaceae) and an evergreen (N. dombeyi) forest tree species as evidenced by morphological and isoenzymatic traits.

STECCONI MARINA; MARCHELLI PAULA; PUNTIERI JAVIER; PICCA PABLO; GALLO LEONARDO

ANNALS OF BOTANY

American Press

Lugar: Londres; Año: 2004 vol. 94 p. 775 - 786

0305-7364

·        Trees with a partial leaf-shedding pattern and other morphological features a priori considered intermediate between those of the deciduous Nothofagus antarctica (G. Forster) Oersted and the evergreen N. dombeyi (Mirb.) Oersted (Nothofagaceae) were found in natural stands. The hybridisation between a deciduous and an evergreen species of Nothofagus has not been reported so far in natural communities. ·         The putative hybrids and the two presumed parental species were compared using fourteen enzyme systems as well as shoot, leaf and reproductive morphology. ·        Six enzyme systems showed good resolution (MDH, IDH, SKDH, 6-PGDH, GOT and PGI) and in four of them (PGI, MDH-B, SKDH and 6-PGDH) the putative hybrids showed intermediate zymogram patterns between N. antarctica and N. dombeyi. Both Principal Coordinates Analysis on isozyme data and Principal Components Analysis on quantitative morphological traits of shoots and leaves, separated both parental species and located the putative hybrids closer to N. antarctica than to N. dombeyi. In the PCA, the number of basal cataphylls and the length/width ratio of leaves were the variables most discriminating among shoots of the three entities. The putative hybrids were intermediate between both species regarding leaf vernation, outline and venation, variation in leaf shape (length/width) with position on the parent shoot and in staminate inflorescence and cupule morphology. For other morphological traits, the putative hybrids resembled one of the parental species or differed from both species (e.g. valve morphology). ·        Isoenzymatic and morphological data sets support the idea of the hybrid nature (probably F1 generation) of the semi-deciduous trees found. Nothofagus antarctica and N. dombeyi are probably more closely related than previously assumed. The use of leaf-shedding patterns should be avoided in infrageneric classifications of Nothofagus.