Reconstructing the biogeographical history of two plant genera with different dispersion capabilities

KATINAS, L.; CRISCI, J. V.

JOURNAL OF BIOGEOGRAPHY

Blackwell Publishing

Lugar: Oxford; Año: 2007 vol. 35 p. 1374 - 1384

0305-0270

Aim  The pappus is one of the most distinctive features of the genera belonging to the plant family Asteraceae (the sunflower family) and is an efficient mechanism for dispersion by wind. The role of the pappus in a historical context has not been analyzed yet. The pappose Holocheilus (seven species), and the epappose Panphalea (nine species) are two genera of the monophyletic subtribe Nassauviinae (Asteraceae, Mutisieae), which overlap in their areas of distribution and are ideal to develop this kind of study. This paper aims to reconstruct the biogeographic histories that shaped the distribution of these two phylogenetically and geographically related genera, but that differ in their means of dispersion. Location  Southeastern Brazil, Paraguay, Uruguay, and Argentina. Methods Two cladistic analyses, one for Holocheilus and one for Panphalea, based on morphological characters were performed and data matrices were analyzed with the Fitch parsimony algorithm of PAUP* version 4.0. The ancestral distributions were reconstructed using DIVA 1.1 according to the dispersal-vicariance optimization method; the number of ancestral areas was unconstrained. Results The Paranense-fields resulted as the most likely ancestral area of Holocheilus and Panphalea. The biogeographic reconstruction of Holocheilus shows several dispersal events from the Paranense-fields: two ancestral dispersal events to the Yungas followed by vicariance events (Paranense-fields/Yungas) and numerous terminal dispersals to the surrounding areas such as Chacoan, Pampean, and Espinal. DIVA´s reconstruction of Panphalea shows also frequent terminal dispersals from the Paranense-fields to the other areas:  Espinal, Pampean-Uruguayan, Pampean-oriental; Paranense-hills; Pampean-Uruguayan; and Paranense-pine lands, with no vicariant events. Main conclusions  The ancestor of both genera probably originated in the Paranense-fields area which was subject to the dry and humid cycles of the Quaternary glaciations. Dispersal was the predominating processes that shaped the distribution of Panphalea and Holocheilus, although DIVA showed differences in their respective biogeographic histories, differing in the range and the areas where they dispersed. The main barriers to dispersal were the dry Cerrado and Chaco, the latter promoting vicariance in Holocheilus.  The lack of a pappus in Panphalea was a limitation for dispersion and water and gravity may have played a major role in the distribution of this genus.