Evolution of flower morphology and a natural re-arrangement of Calyceraceae

Abstract

Calyceraceae is a small South American family sister to Asteraceae. Previous phylogenetic analyses revealed that Calyceraceae genera are para- or polyphyletic. Fruit and inflorescence characters used historically as diagnostic in Calyceraceae taxonomy have proven unreliable in defining natural groups. Surprisingly, flower morphology does not appear in diagnoses of Calyceraceae genera, and its diversity and evolution has remained unstudied before now. Based on phylogenetic analyses using six molecular markers and an almost complete sampling of the family (43 of 46 species), we propose a taxonomic re-arrangement of Calyceraceae. In the search for diagnostic morphological characters, we studied flower structure diversity and optimized 12 discrete characters by maximum parsimony and maximum likelihood to reconstruct floral evolution in the family. Calyceraceae species are arranged in eight genera (three monotypic, five with 6 to 13 species). Two genera are new (Anachoretes, Asynthema), one is reinstated (Leucocera), with the remaining five emended (Acicarpha, Boopis, Calycera, Gamocarpha, Moschopsis). Flower morphology is notably diverse but provides only a few diagnostic features. Many floral attributes likely reflect selection for pollination or fruit dispersal rather than phylogenetic affinity. In the context of this taxonomic revision, we include a key to genera, new and emended diagnoses, and new combinations.