Phylogeography of subgenus Nothofagus from Patagonia

MATHIASEN, PAULA; ACOSTA, M. CRISTINA; PREMOLI, ANDREA C.

S. M. de Tucumán, Argentina

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

Geological forces have affected the geography of the austral continents as well as the distribution of plant populations and their genetic patterns. Patagonia has suffered the impact of ancient events such as plate tectonics, sealevel changes, and even more recent Pleistocene glaciations and volcanic eruptions. We hypothesize that these historical factors will be reflected in the phylogeographic structure of plant populations of old angiosperm lineages inhabiting austral latitudes. 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 that 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 trnHpsbA. 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 65 parsimony informative characters and yielded 20 different haplotypes. Parsimony analyses generated 68 most parsimonious trees (L= 121, CI=71, RI=80) and consensus tree showed the same topology as the tree obtained by Bayesian inference. Two major clades separated latitudinally were identified. The north clade (35o 35’ to 42o 31’ S) includes one well defined subclade containing populations located south of 39o 35’ S, and the rest of the terminals are located to the north of this latitude. The south clade includes populations located between 42o 39’ S and 55o 3’ S. Greatest haplotype and nucleotide diversity was found towards the north of the distribution range. Our results suggest that populations of Nothofagus suffered significant latitudinal disjunctions due to repeated glaciations, as it was widely discussed in previous studies, and also to other processes such as volcanism and tectonism that occurred in Patagonia.Nothofagus in relation to past events that 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 trnHpsbA. 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 65 parsimony informative characters and yielded 20 different haplotypes. Parsimony analyses generated 68 most parsimonious trees (L= 121, CI=71, RI=80) and consensus tree showed the same topology as the tree obtained by Bayesian inference. Two major clades separated latitudinally were identified. The north clade (35o 35’ to 42o 31’ S) includes one well defined subclade containing populations located south of 39o 35’ S, and the rest of the terminals are located to the north of this latitude. The south clade includes populations located between 42o 39’ S and 55o 3’ S. Greatest haplotype and nucleotide diversity was found towards the north of the distribution range. Our results suggest that populations of Nothofagus suffered significant latitudinal disjunctions due to repeated glaciations, as it was widely discussed in previous studies, and also to other processes such as volcanism and tectonism that occurred in Patagonia.