Phylogeographical studies in subgenus Nothofagus reflect past events occurred in Patagonia

MATHIASEN P., M.C. ACOSTA & A.C. PREMOLI

San Javier, Tucumán

Congreso; XXVII International Meeting of the Willi Hennig Society y VIII Reunión Argentina de Cladística y Biogeografía; 2008

Geological forces have modulated the geography of the continent as well as the distribution of plant populations and their genetic diversity. Patagonia has suffered the impact of ancient events such as plate tectonics, sea-level changes, and even more recent Pleistocene glaciations and volcanic eruptions. Phylogeographic structure of populations could be reflecting the response of plant species to those changes. The aim of this study is to examine the levels and distribution of chloroplast DNA variation in populations of widespread Nothofagus in relation to past events occurred in Patagonia. We sampled 190 populations of N. antarctica, N. betuloides, N. dombeyi, N. nitida and N. pumilio along their entire range of distribution, and 10 populations of N. nervosa and N. obliqua that were used as outgroup. Non-coding regions of chloroplast DNA were amplified by polymerase chain reaction (PCR) using 3 universal primer pairs: psbB-psbH, trnL-trnF and trnH-psbA. Relationships among haplotypes were analyzed by means of phylogenetic analyses of maximum parsimony using WINCLADA and NONA and Bayesian inference with Mr. Bayes. Finally, the haplotype median-joining network was constructed using Network. The matrix of aligned sequences of Nothofagus species contained 52 parsimony informative characters and yielded 17 different haplotypes. Parsimony analyses generated 6 most parsimonious trees (L= 69, CI=0.957, RI=0.965) and consensus tree showed two mayor clades separated latitudinally. Parsimony analyses and Bayesian inference yielded trees with same topologies. Greatest haplotype and nucleotide diversity was found towards the north of the distribution range. Our results suggest that populations of Nothofagus suffered disjunctions not only during the repeated glaciations that occurred in Patagonia, but also by other effects such as volcanism.