Haplopappus Cass. (Astereae) sensu Hall: a polyphyletic conundrum revealed by plastid data

Marisa Szubryt

University of Oklahoma, Robert Bebb Herbarium, 770 Van Vleet Oval East #208, Norman, Oklahoma 73019, U.S.A.

https://orcid.org/0000-0001-5816-070X

DOI: http://dx.doi.org/10.53875/capitulum.02.2.03

ABSTRACT:  The genus Haplopappus Cass. has undergone drastic taxonomic changes since its inception in 1828 by Cassini. Initially based on a single species from Chile, H. glutinosus Cass., it was expanded to over 150 species by Hall and others to encompass cushion-like alpine herbs, caulescent perennials, low-elevation subshrubs, and sizeable shrubs, mostly indigenous to North America. Haplopappus means simple or single pappus consisting of scabrous capillary bristles, a feature seized upon by Hall, along with homochromous discoid or radiate capitula usually with yellow corollas, for uniting species in the genus. Various explanations were given to exclude other genera similar in this regard such as Solidago L. and Chrysothamnus Nutt. Hall’s treatment formed the basis for numerous subsequent taxonomic treatments and floras for decades. As cytological and other sorts of data emerged, however, its polyphyly became evident, and many researchers sought to define monophyletic lineages within this artificial group. Subsequently, Haplopappus sensu Hall has been disassembled into over thirty genera across several subtribes predominantly within a clade known as “North American Astereae”. Previously, limited phylogenetic resolution was achieved in this lineage with nuclear ribosomal data via Sanger Sequencing. In this study, high-throughput sequencing allowed the assembly of whole chloroplast genomes for phylogenetic analyses. The results from this work demonstrate that Haplopappus as circumscribed by Hall is deeply polyphyletic. 

Keywords: Asteraceae, Compositae, North America, Phylogenetics, Taxonomy.