Genetic variation in the widespread Embothrium coccineum (Proteaceae) endemic to Patagonia: effects of phylogeny and historical events

Allozyme electrophoresis was used to measure and compare, with other members of the Proteaceae, levels and distribution of genetic diversity in Embothrium coccineum J.R.Forst., a widespread outcrossing species endemic of Andean Patagonian forests. We analysed variation at the species level by sampling 34 populations along its entire range of similar to 20 degrees. latitude. We tested the hypothesis of multiple Pleistocene refugia by phylogeographic methods. We resolved 16 isozyme loci assayed in 934 adult trees. At the species level, total genetic diversity (H(T) = 0.220) was similar to that of other outcrossed and widespread plant species. Genetic parameters (N(A), P(SS), H(E)) were not statistically different from other outcrossed but mostly range-restricted Proteaceae, reflecting a strong phylogenetic imprinting for species sharing life-history traits. Populations are genetically divergent among each other (F(ST) = 0.202). The low correlation between geographic and genetic distances suggests separate histories, i.e. multiple glacial refugia for the cold-tolerant E. coccineum. Phylogeographic trees produced different topologies, although maximum likelihood and parsimony trees shared some elements. Both trees suggest a northern and central clade, and then a separate southern clade. Current processes such as gene flow and selection confound the historic signal. These results seem in contrast to many of the northern hemisphere post-glacial phylogeographic reconstructions which show clear historical tracks of northern range expansion from southern refugia. The present study highlights the importance of phylogenetic imprinting, life-history traits and historical events driving genetic diversity patterns in this widespread Proteaceae from southern South America.