Reconstructing the Phylogeny of Calliandra sect. Androcallis (Fabaceae): Inclusion of Colombian Species, with a Focus on the Enigmatic Taxon Calliandra medellinensis

Abstract

Abstract— Until now, phylogenetic relationships for the genus Calliandra section Androcallis (Fabaceae) were unresolved. We reconstructed the phylogeny of the section, including previously sequenced species from Central and South America and unexamined species from Colombia. Here, we generated 80 novel DNA sequences of Calliandra species from Colombia for the nuclear internal transcribed spacer (ITS) and the chloroplast trnL and trnL-F intergenic spacer. By incorporating a broader taxonomic sampling, the relationships among main clades in C. sect. Androcallis were clarified, providing a systematics framework in which to test evolutionary hypotheses. Phylogenetic analysis recovered four well-supported clades within C. sect. Androcallis. Relationships among the four to five major clades, contingent upon the inclusion of C. sect. microcallis, are strongly supported for the first time. Most species within each clade had similar geographical distributions. However, core C. sect. Androcallis relationships, including most species from Colombia sequenced here, remain unclear. A second goal of this study was to determine the taxonomic status of Calliandra medellinensis. This enigmatic taxon emblematic of Medellín, Colombia, is found in limited numbers within the Aburrá Valley and no populations have been found in the field. For that reason, it has been proposed to be a hybrid taxon. Here, C. magdalenae and C. haematocephala were not monophyletic within the core C. sect. Androcallis clade, while results concerning the monophyly of C. medellinensis are not conclusive. More informative molecular markers should be used in future studies to the determine the status of species for these taxa. Specifically, genomic studies should assess interspecific hybridization demographic models. Such insights can illuminate the C. medellinensis origin, guiding conservation strategies and providing valuable evolutionary overviews.