Phylogeography of the subgenus Nothofagus from Patagonia

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

CLADISTICS (PRINT)

WILEY-BLACKWELL PUBLISHING, INC

Año: 2010 p. 216 - 216

0748-3007

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, sea-level 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 three 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 MrBayes. 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), the consensus of which showed the same topology as the tree obtained by Bayesian inference. Two major clades separated latitudinally were identified. The north clade (35 35¢ to 42 31¢S) includes one well defined subclade containing populations located south of 39 35¢S, and the rest of the terminals are located to the north of this latitude. The south clade includes populations located between 42 39¢S and 55 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 vulcanism and tectonism that occurred in Patagonia.