PARENT SESSION
Poster Session 36: Genetics / Population Ecology
Thursday, August 11, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Relict islands of the temperate rainforest tree Aextoxicon punctatum (Aextoxicaceae) in semiarid Chile: Genetic differentiation and biogeographic history.
Núñez, Mariela*,1, 2, 3, 4, Armesto, Juan*,2, 3, 4, 1 FORECOS, Universidad Austral de Chile, Valdivia, Chile2 CASEB, Pontificia Universidad Católica de Chile, Santiago, CHile3 Facultad de Ciencias, Santiago, Chile4 Senda Darwin Foundation, Santiago, Chile
ABSTRACT- Aextoxicon punctatum (Olivillo), the only representative of the endemic and monotypic family Aextoxicaceae, has a biogeographic history that dates back to Gondwanan tropical forests, and a latitudinal distribution that extends over 1200 km, with disjunct populations in the Chilean semiarid region and southern temperate rainforests. This study explores how this biogeographic history has influenced the genetic diversity of present-day Olivillo populations. We sampled 16 populations distributed from the semiarid to the temperate forest zone (30°-43°S). Genetic diversity was estimated using 39 RAPD genetic phenotypes. Genetic differentiation was examined by AMOVA, UPGMA and Principal Coordinates analyses. Isolated outposts of Olivillo in semiarid Chile (30° -32°S) were genetically divergent from all other populations in central (34°-39°S) and southern (39°- 43°S) Chile, supporting the hypothesis that a long history of geographic isolation has restricted genetic exchange between relict Olivillo populations in semiarid Chile and the complex of populations in central and southern rain forests. Correlations between genetic and geographic distances were positive and significant for coastal populations of Olivillo from 39° to 42°S, while this relation was not significant for populations of the intermediate depression and Andean foothills at the same latitude. This pattern of genetic isolation by distance suggests that postglacial southward expansion of Olivillo along the Coastal Range occurred earlier in the Holocene than eastward expansion towards the intermediate depression and Andean foothills.
Key words: relict forests, genetic diversity, AMOVA, biogeographic history