Phylogenetic position of Argentinian and Chilean endemic species of Senecio ser. Culcitium (Asteraceae) with an evolutionary analysis of morphological characters

LUCIANA SALOMON; SILVANA M. SEDE; SUSANA E. FREIRE

Phytotaxa

Magnolia Press

Año: 2019 p. 177 - 209

1179-3155

In its current circumscription, Senecio ser. Culcitium Cabrera, which includes ca. 40 South American species, is characterizedby discoid, sometimes nodding capitula, calycular bracts resembling a multiseriate involucre, and style branches apicallytruncate with a ring of penicillate collecting hairs. The phylogenetic relationships of Senecio ser. Culcitium were examinedbased on DNA sequences from ITS and trnK regions, focusing on seven endemic species of Argentina and Chile neverincluded in previous works. Likewise, 18 morphological characters were analyzed and mapped on the phylogeny in orderto discuss their importance in defining the group. Our results confirm the polyphyly of of S. ser. Culcitium as circumscribedby Cabrera because its members appeared in four different clades throughout Senecio. One clade contains the taxonomictype of the series and about a half of the species previously assigned to S. ser. Culcitium. Most of the Argentinean-Chileanendemic species are split into three different clades distantly related to the principal Culcitium clade: 1) Senecio candidansand S. gilliesii are nested within S. ser. Hualtatini; 2) S. aspleniifolius and S. jarae are nested within S. ser. Repentes; and 3)S. diemii, S. magellanicus, and S. martinensis appear within the informally named ?diemii group?. The nodding capitulum,which was traditionally used as a diagnostic character for Culcitium, could be used to define morphologically S. ser. Culcitiumin its revised circumscription. However, the other two characters traditionally used as diagnostic, i.e. development ofcalycular bracts and pubescence of style branches, are variable within the series: the calycular bracts range from scarcely towidely developed and the pubescence of the style branches ranges from a few short hairs poorly differentiated into a crownof hairs to numerous long hairs. As a result of the morphological study of the characters and the phylogenetic analysis, weinclude a key to differentiate S. ser. Culcitium s. str. from the other series and the informal diemii group, in which the Culcitiumspecies have been redistributed.