Because of the possibility that habitat shifts have led to the evolution of dimorphism, the Hawaiian Alsinoideae may provide information on causal mechanisms underlying the evolution of sexual dimorphism. Despite the importance of phylogenetic approaches for understanding the relationship of habitat and breeding system evolution, recent phylogenetic analyses have failed to identify the closest relatives of the Hawaiian clade, confounding questions of monophyly, character state polarization and ancestral breeding system state reconstruction. Relationships within the Hawaiian Alsinoideae have remained unresolved, due, in part, to low genetic divergences among closely related species, and extremely rapid radiation following colonization of the Hawaiian Islands.
Analyses based on nucleotide partitions alone support two separate origins of dimorphism.