Phylogenetic relationships in Helichrysum (Compositae: Gnaphalieae) and related genera: Incongruence between nuclear and plastid phylogenies, biogeographic and morphological patterns, and implications for generic delimitation

The Helichrysum‐Anaphalis‐Pseudognaphalium (HAP) clade is a major component of the tribe Gnaphalieae (Compositae) and includes the genera Helichrysum, Anaphalis, Achyrocline and Pseudognaphalium. Allopolyploid origins for at least two clades within the HAP clade have previously been suggested, one involving the genus Anaphalis and the Mediterranean‐Asian Helichrysum species, and a second one involving part of Pseudognaphalium. In the present paper, with the use of two nuclear ribosomal and two plastid DNA markers and an extensive sampling of the HAP clade, further evidence relevant to the origin, composition and closest relatives of these clades is provided, and additional cases of incongruence are discussed. The superposition of distribution areas on the phylogeny suggests that the HAP clade originated in the Cape region of southern Africa and subsequently dispersed to and diversified in the Afromontane regions of east southern Africa, mainly the Drakensberg, before spreading northward and giving rise to several lineages in Afromontane and Afroalpine areas of central tropical Africa and in Madagascar. Allopolyploidy may have preceded the dispersal and diversification of the HAP lineage out of Africa to the Mediterranean area, and to the Americas and Asia. Finally, discussion on the distribution of several morphological characters in the phylogeny and their taxonomic relevance is also provided, with views on the need for a new generic delimitation.