Authors:
Abstract
DNA sequence data have confirmed that Helenieae s. lat. is not monophyletic; lineages corresponding to “core Heliantheae” and Eupatorieae are nested among clades of helenioid taxa, as previously suggested. Clades coordinate with one or more helenioid subtribe(s) demonstrate,
however, that major components of diversity within Helenieae s. lat. are natural groups warranting taxonomic recognition. Continued treatment of Eupatorieae at tribal rank while adhering to a criterion ofmonophyly for tribal classification requires that (1) Helenieae be recognized in a narrow sense [corresponding in membership to subtribe Gaillardiinae sensu Robinson (1981) +
Marshallia and Pelucha], (2) Madieae and Tageteaebe recognized in expanded senses [Madieae including Madiinae sensu Carlquist (1959), Baeriinae in a new sense, and Arnica and x = 1 9 relatives; Tageteae including Pectidinae sensu Robinson ( 1 98 1 ), Flaveriinae sensu Turner and Powell (1977), and genera historically aligned with Flaveriinae (Clappla, Coulterella, Pseudoclappia, Varilla), among others] and (3) three new tribes be erected – Bahieae, for Bahiinae in a new sense; Chaenactideae, for Chaenactis, Dimeresia, and Orochaenactis; and Perityleae, for Peritylinae sensu Robinson (1981) and, provisionally, Lycapsinae sensu Robinson (1981). Only one of the epaleate taxa referable to Helenieae s. lat. that we sampled (Jrichocoryne) was robustly placed within a clade of principally paleate taxa belonging to “core Hehantheae” in the traditional sense; loss of receptacular bracts appears to have occurred rarely during radiation of Heliantheae s. lat. We conclude that expression of receptacular bracts in “core Heliantheae” in the traditional sense and the tarweed Comp. Newsl. 40, 2003 subtribe, Madiinae, is homoplasious; Madiinae is most closely related to Arnica and is nested among epaleate lineages. We also conclude that pappi of bristles or bristlelike elements have evolved in various lineages ofHelenieae s. lat. and generally have received too much weight in circumscriptions of suprageneric taxa. Multiple examples of extreme descending dysploidy from high (putatively polyploid) ancestral chromosome numbers in Helenieae s. lat. are evident from the phylogenetic data. Bidirectional ecological shifts between annual and perennial habits and repeated origins of woodiness from herbaceous ancestors must be concluded for Helenieae s. lat. Based on modern distributions of taxa and evident phylogenetic patterns, the most recent common ancestor of Heliantheae s. lat. and Eupatorieae probably occurred in southwestern North America (including northern Mexico). Baeriinae, Madiinae, and the X = 1 9 “amicoid” taxa may share a common Califomian ancestry.