Preliminary phylogenetic affinities of Microliabum within Liabeae (Asteraceae) inferred from ITS sequences

GUTIERREZ, D. G.; GARCIA-JACAS, N.; SUSANNA, A.

San Isidro, Buenos Aires

Congreso; VII Reunión Argentina de Cladística y Biogeografía; 2007

Instituto de Botánica Darwinion (IBODA-CONICET)

The Neotropical genus Microliabum Cabrera (Asteraceae, Liabeae) contains five or six species from southeastern Bolivia to central Argentina, with its centre of diversity in northwestern Argentina (Robinson, 1990; Cabrera et al., 1999; Gutiérrez et al., unpublished). As currently circumscribed, species of Microliabum are herbs with latex, trinerved leaves, heads solitary or grouped in corymbiform capitulescence, pale yellow anthers, pubescent style shaft with short branches, and double pappus with outer series of scales and inner series of bristles or scales. It is composed of two subgenus: Microliabum and Austroliabum. Originally Cabrera (1954, 1955) described the monotypic genus Microliabum and later Robinson (1990) expanded this concept adding species from the genus Liabum Adans. Firstly, Cabrera (1954) recognized the relationships of Microliabum and Liabum. Robinson (1983) suggested that Microliabum was closer to the Mexican and Central American genus Sinclairia Hook. & Arn. Phylogenetic analysis in Liabeae on the basis of morphological characters resulted in Microliabum being closer to Sinclaria but with weak support (Bremer, 1994; Funk et al., 1996). The goal of our present work was to identify the closest relative of Microliabum within Liabinae on the basis of molecular data. The more representative and widespread species of Microliabum, M. candidum (Griseb.) H. Rob. and M. polymnioides (R. E. Fr.) H. Rob., from subgenera Austroliabum and Microliabum (respectively), were used. In addition, species of the Liabean genera Dillandia Funk & H. Rob., Liabum, Oligactis (Kunth) Cass. and Sinclairia(from subtribe Liabinae), and Chrysactinium (Kunth) Wedd., Erato DC., Munnozia Ruiz & Pav., and Philoglossa DC. (from Munnoziinae), were chosen as outgroups. Two species belonging to Vernonia Schreb. (Vernonieae) were also included for rooting the analysis. The phylogenetic study was conducted using sequences of the internal transcribed spacers (ITS) 1 and 2 and the 5.8S gene. Parsimony analyses were performed. As a result of this preliminary analysis on molecular data, the genera of subtribe Munnoziinae were placed separated from the genera of Liabinae. Thus, Liabinae would constitute a monophyletic group. Within this subtribe, the analysis weakly supported Microliabum as a basal monophyletic genus, sister to a strongly supported Sinclairia-Oligactis-Dillandia-Liabum clade. Sinclairia was sister to the natural group formed by Dillandia, Liabum and Oligactis. This group (excepting Dillandia) had already been hypothesized in previous morphological works (Bremer, 1994; Funk et al., 1996; Gutiérrez, 2004). On the other hand, Dillandia, which had never been before included in a complete phylogenetic study of Liabeae, was sister close relative to Liabum with strong support. Finally, the evolutionary place of Microliabum resulting from our analyses disagree with Robinson (1983), Bremer (1994), and Funk et al. (1996) where Microliabum was understood as a derived Liabean genus. Contrarily, Microliabum could be considered an ancestral genus within Liabinae.