Phylogenetic and biogeographic approach to genus flourensia (asteraceae heliantheae)

Abstract

The Neotropical genus Flourensia DC. (Asteraceae, Heliantheae) comprises 32 taxa with two diversitycenters one in arid zones of southern South America and one in northern Mexico-southern USA. Thesame disjunction is found in several Angiosperm taxa (e,g., [Larrea (Zygophyllaceae), Prosopis,Prosopidastrum, Hoffmannseggia (Fabaceae), and Distichlis (Poaceae)] which has fuelled the discussionas to whether the flora of these biotas arose by vicariance or long distance dispersal. Phylogenetic studiesavailable for some of the groups support the latter and furthermore suggest that long distance dispersalmay have happened repeatedly in some of these. In Flourensia, the presence of several narrow endemicspecies in the northern Argentina suggests limited dispersal ability. Analyzing how and when Flourensiaobtained its disjunct distribution and diversified in arid regions of both southern and northern America isthe aim of the present study. In South America, Flourensia species mainly occupy environments of theinter-Andean dry valleys from the southern depression of Huancabamba in Peru to central Argentina, withmost of the species distributed in northern Argentina. Based on our parsimony analysis of Flourensiainferred from nuclear ITS and plastid trnL-F sequences, we study the geographical distributions of allspecies to determine whether the current disjunct distribution of the genus is due to one or several events.