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

PREMOLI A.C & C.P. SOUTO

AUSTRALIAN JOURNAL OF BOTANY

CSIRO PUBLISHING

Año: 2007 p. 809 - 817

0067-1924

Abstract. 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 ∼20◦ 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 (HT =0.220) was similar to that of other outcrossed and widespread plant species. Genetic parameters (NA, PSS, HE) 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 (FST =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.