title: Halfway encounters: meeting points of colonization routes among the southern beeches Nothofagus pumilio and N. antarctica.
abstract: The Patagonian region is characterized by a complex biogeographic history, with evidence of deep phylogeographic breaks shared among species. Of particular interest to conservation is the nature of colonization and settlement patterns after the last glacial period, including the detection of secondary contact between different lineages and/or hybridization among related species around phylogeographic breaks. Here we studied population demography and past hybridization of two widespread tree species endemic to South America, Nothofagus pumilio and N. antarctica. Using 8 nuclear microsatellites we genotyped 41 populations of both species. Genetic variation and structure across the geographic region were evaluated within and among species and the past demographic history of hybridization between the two species was inferred using Approximate Bayesian Computation (ABC). Northern and southern lineages were identified in each species, and Bayesian clustering revealed their convergence at mid latitudes (42°S). Spatial genetic structure (SGS) also indicated the existence of a genetic discontinuity at these latitudes, which is in agreement with previous data from maternal DNA markers. Several populations around 42-44°S presented high levels of genetic diversity with a decrease toward southern populations. Even though the species are clearly differentiated (G'ST=0.335), admixed gene pools were observed in both species. Two independent runs of ABC suggested that inter species admixture-like patterns occurred within the timescale of the Last Glacial Maximum (around 20,000 BP). We also provide evidences of recent and bi-directional hybridization/introgression between the two Nothofagus species and describe features of the populationś demography in the past. The settlement of a secondary contact zone in Nothofagus species around 42-44°S coincides with the phylogeographic breaks and hotspots of genetic diversity found in other plant and animal species in Patagonia, highlighting its importance as reservoir of diversity. The characterization of the population history of native species can contribute substantially to long-term conservation and management policies.
authors: Instituto Nacional de Tecnología Agropecuaria - EEA Bariloche, Modesta Victoria 4450, 8400 Bariloche, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina. Electronic address: soliani.carolina@inta.gob.ar.
authors: Carolina
authors: C
authors: Soliani
authors: Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 75236 Uppsala, Sweden.
authors: Yoshiaki
authors: Y
authors: Tsuda
authors: Institute for Sustainable Plant Protection, National Research Council, Via Madonna del Piano 10, 50019 Sesto Fiorentino (Firenze), Italy.
authors: Francesca
authors: F
authors: Bagnoli
authors: Instituto Nacional de Tecnología Agropecuaria - EEA Bariloche, Modesta Victoria 4450, 8400 Bariloche, Argentina.
authors: Leonardo A
authors: LA
authors: Gallo
authors: Institute of Biosciences and Bioresources, National Research Council, Via Madonna del Piano 10, 50019 Sesto Fiorentino (Firenze), Italy.
authors: Giovanni G
authors: GG
authors: Vendramin
authors: Instituto Nacional de Tecnología Agropecuaria - EEA Bariloche, Modesta Victoria 4450, 8400 Bariloche, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.
authors: Paula
authors: P
authors: Marchelli
mesh_terms: D001499:Bayes Theorem; D005075:Biological Evolution; D018742:DNA, Chloroplast / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D029962:Fagaceae / Q000145:classification*; D005819:Genetic Markers; D014644:Genetic Variation; D005838:Genotype; D006239:Haplotypes; D006824:Hybridization, Genetic; D018895:Microsatellite Repeats; D010802:Phylogeny; D058974:Phylogeography; D017422:Sequence Analysis, DNA; D013020:South America
chemical_list: D018742:DNA, Chloroplast; D018744:DNA, Plant; D005819:Genetic Markers
keywords: ABC; Hybridization; Patagonian temperate forests; Phylogeography; Secondary contact zone; nSSRs