Juliana Chacon

From EESwiki

Evolutionary patterns of the family Alstroemeriaceae, an important clade of the Austral floristic realm

The Austral floristic realm comprises 16 families that are restricted to South America and Australasia. An important member of this realm is the Alstroemeriaceae, with 200 species in four genera, Alstroemeria and Bomarea in South America, and Drymophila and Luzuriaga in Australia, Tasmania, New Zealand as well as South America, since Luzuriaga also has species in South America. Evolutionary studies on the Alstroemeriaceae have included few species and have suffered from a lack of phylogenetic resolution due to limited signal in the DNA regions sequenced so far. The aim of this project is to test the hypothesis that the oldest divergence(s) in Alstroemeriaceae date(s) back to the break-up of East Gondwana, and to answer two questions: (i) What is the evolutionary relationship between Alstroemeria and Bomarea, and how was their divergence affected by the uplift phases of the Andes? And (ii) What is the history of the Alstroemeria subclades that appear to be restricted to the ancient Brazilian shield region and the relatively young Chilean and Peruvian/Ecuadorian chains of the Andes? A second goal of this project is to use the phylogeny to study the evolution of pollination modes in Alstroemerieae, which will be useful to understand the current distribution patterns of the species. By the moment the chloroplast DNA regions ndhF, rbcL, and the Internal Transcribed Spacer of nuclear ribosomal DNA (ITS) have been sequenced for 68 species of Alstroemeriaceae. Preliminary phylogenetic analyses have been performed including some members of the Colchicaceae family as outgroups. A pilot molecular clock run has been performed using the combined chloroplast matrices and the ages of some Smilax fossils as calibration points. Based on the results Alstroemeria and Bomarea are not mutually monophyletic and their divergence is dated to 17 Ma ago, which would imply that they diverged from each other more or less during the main Andean uplift. The topology of the trees also shows that Alstroemeriaceae entered South America twice (one event each in Luzuriageae and Alstroemerieae), each time from Antarctica, and then spread north to Mexico and northeast to Brazil and the Guianas.

Supervisor: Susanne Renner