Aeschynomene sp. prope villosa (a dalbergioid legume) represents a group of populations with morphological characteristics similar to those of Aeschynomene villosa, but without complete overlap, and whose cytogenetic characteristics subtly differ from both the latter and other related taxa. In this study, conventional surface spread and air-drying techniques, along with Giemsa staining, were used to analyze metaphase chromosome complements and karyotypes of individuals belonging to a population of A. sp. prope villosa, a taxon included in the Americanae series of Aeschynomene. The results confirm a previously obtained karyotypic formula. Differences observed in chromosome sizes do not modify the karyotype or its symmetry. They are interpreted here as a loss of gene flow between populations or adaptations to different ecogeographic conditions. The presence of chromosome stickiness in 7.4% of the nuclei analyzed is noteworthy. This aberration, not previously observed in Aeschynomene, primarily involves areas near the telomeres of apparently homologous and non-homologous chromosomes. This phenomenon, observed mainly in meiosis, has been linked to the tendency of chromosomes to clump together during cellular divisions following plant hybridization events. The same criterion of chromosomal interaction after hybridization could explain the changes in the number and position of satellites recorded in a previous study. Although unexpected, these results should not be surprising, since intergradation between A. villosa and A. americana, species with which it overlaps in its distribution area, has been suspected for at least 70 years. Furthermore, hybridization and allopolyploidy have already been demonstrated in other morphological series of Aeschynomene.
Fernando Tapia-Pastrana (Wed,) studied this question.