This study aims to analyse by isozymes the outcrossing rate in a Chorisia speciosa population. Thus, open-pollinated seeds from 28 trees and leaves from 53 adult trees were sampled in a C. speciosa population at the Bauru Ecological Station, São Paulo State, Brazil. Eighteen alleles were observed distributed in seven polymorphic loci. The fixation index (<img border=0 width=32 height=32 id="_x0000_i1030" src="../../../img/revistas/rbb/v26n1/a11let_f.gif" align=absmiddle>) was smaller in adult trees than in families, suggesting selection against homozygous. The multilocus outcrossing estimate (<img border=0 width=32 height=32 id="_x0000_i1031" src="../../../img/revistas/rbb/v26n1/a11let_tm.gif" align=absmiddle>) was 0.816, revealed that this species is a mixed mating system, predominantly alogamous. Heterogeneity of pollen pool was observed in outcrossing individual tree indicating that mating were not random. The paternity correlation (<img border=0 width=32 height=32 id="_x0000_i1032" src="../../../img/revistas/rbb/v26n1/a11let_rp.gif" align=absmiddle>) revealed that families are constituted of a high proportion of full sibs (71.4%). There was also detection of crossing among relatives in population (5.6%), indicating the possibility of family structure within population.
Chorisia speciosa; correlated matings; isozymes electrophoresis; outcrossing rate; population genetics
