AN OVERVIEW OF THE GENUS PYRRHOPAPPUS (ASTERACEAE: LACTUCEAE) WITH EMPHASIS ON CHLOROPLAST DNA RESTRICTION SITE DATA

Abstract

The genus Pyrrhopappus in recent systematic treatments has comprised five taxa (four species, one with two varieties), which have now been studied anew using morphogeographical and chloroplast DNA restriction site data. Eight populations, representing all of the recognized taxa of Pyrrhopappus, were digested with 17 restriction enzymes. Only three restriction site differences were found from among 750 restriction sites and no length variations were observed. This contrasts with similar studies, using these same enzymes, on the closely related genus Krigia in which 173 mutation sites and 20 length variations were found among the seven species concerned. Nucleotide sequence divergence values among the species of Pyrrhopappus were extremely low (0.0012) compared to much higher values found in the closely related genus Krigia (0.1270). Three species of Pyrrhopappus are herein recognized: two diploids with 2n = 12 chromosomes, P. carolinianus and P. pauciflorus (including P. multicaulis, P. geiseri and P. rothrockii), and a tetraploid (2n = 24), P. grandiflorus. The tetraploid is partially sympatric with both diploids but is readily recognized by its perennial roots, which bear tuber‐like enlargements. These three species presumably arose relatively recently, and the DNA data suggest that neither P. pauciflorus nor P. carolinianus gave rise to the tetraploid P. grandiflorus.