Quantitative and molecular genetic variation among botanical varieties and subpopulations of Hancornia speciosa Gomes (Apocynaceae)

Abstract

The comparison of inter-population quantitative variation and neutral variation based on molecular markers (QST − FST) has been extensively used to infer the influence of different selection forces on potentially adaptive traits. Only recently have studies focused on two levels of inter-population genetic structuring: among regions (or groups) and among subpopulations within groups. This work aimed to compare quantitative and molecular variation within these two hierarchical levels for Hancornia speciosa Gomes, a fruit tree species that is native to the Brazilian Cerrado. Six quantitative traits related to initial plant growth were evaluated in a common garden environment using samples from 57 maternal families (treatments) derived from 29 subpopulations within four botanical varieties. The quantitative divergence among the botanical varieties (QGT) and among the subpopulations within varieties (QSG) for each trait were compared with the corresponding neutral variation (FGT and FSG) obtained based on six microsatellite loci using a parametric bootstrap procedure. The molecular results revealed a low degree of divergence among the botanical varieties and significant structuring among the subpopulations within varieties. The estimates of the quantitative divergence among the varieties (QGT) tended to be greater than the divergence among the subpopulations within varieties (QSG) for five out of the six quantitative traits. The comparison between the quantitative and molecular parameters suggests that divergent selection shaped the genetic structure among the botanical varieties for some traits, while the variation among the subpopulations within varieties was influenced by genetic drift and uniform selection.