Allozyme polymorphisms, outcrossing rates, and hybridization of three Nothofagus species

PREMOLI A. C.

GENETICA

SPRINGER

Año: 1996 p. 55 - 64

0016-6707

Electrophoretically detectable genetic variation was used to describe the genetic structure of three South American species of Nothofagus: the widespread N. betuloides and N. dombeyi, and the geographically restricted N. nitida. Although the widespread species possess higher levels of genetic variation, the three species have more genetic variation within than among populations. These results are consistent with the theoretical expectations for woody, presumably highly outcrossed species with wind-borne seeds. Estimates of outcrossing rates from progeny arrays yielded slightly higher average t-values for N. nitida (1.158) and N. dombeyi (range 0.873-1.045) than for N. betuloides (0.878). Hierarchical analysis of population structure revealed values of FIS and FIT that were positive and significantly different from zero at most loci and for each species. The levels of inbreeding detected by F-statistics indicate some degree of self-fertilization and/or population substructuring into discrete family groups. Reduced seed vagility and regeneration of natural stands after disturbance by a few remnant individuals would probably generate the recruitment of related seedlings underneath parent trees. The analysis of a putative hybrid population between N. nitida and N. betuloides indicated that individuals clearly segregated into nitida-like or betuloides-like individuals. The reduced outcrossing rate of betuloides-like individuals from the hybrid site (t = 0.585) is interpreted in concert with low pollen availability and the increased probability of selfing and/or hybridization in Nothofagus.