Distribution patterns of genetic variation in the widespread Embothrium coccineum echoes geographic heterogeneity in Patagonia

SOUTO C. P.; PREMOLI A. C.

AUSTRALIAN JOURNAL OF BOTANY

CSIRO Publishing

Lugar: Sydney; Año: 2007 vol. 55 p. 1 - 2

0067-1924

Allozyme electrophoresis was used to measure and compare, with other members of the Proteaceae, levels and distribution of genetic diversity in Embothrium coccineum Forst., a widespread outcrossing species endemic of Andean Patagonic forests. We analysed variation at the species level by sampling 34 populations along its entire range of c. 20º latitude. We tested the hypothesis of multiple Plesitocene refugia using 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 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 north 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. This 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.