Genetic variation in the widespread Embothrium coccineum (Proteaceae) endemic to Patagonia: effects of phylogeny and historical events
Cintia P. Souto A B and Andrea C. Premoli AA Laboratorio Ecotono, Universidad Nacional del Comahue, Quintral 1250, Bariloche (8400), Río Negro, Argentina.
B Corresponding author. Email: csouto@crub.uncoma.edu.ar
Australian Journal of Botany 55(8) 809-817 https://doi.org/10.1071/BT06183
Submitted: 30 August 2006 Accepted: 27 August 2007 Published: 14 December 2007
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.
Acknowledgements
Field work was supported by a Field Grant from the British Genetic Society. This research was also funded by the European Commission under Framework IV of DGXII, as part of the BIOCORES project (PL ICA4–2000–10029). We thank National Park authorities of Argentina and Chile for logistical support and for facilitating access to protected areas. We thank A. Boi, F. Boi, S. Boi, P. Quiroga and A. Rovere for help during the field work. P. Mathiasen provided valuable assistance in the laboratory. A. Ruggiero and R. Vidal helped with figures. E. Gonzales and M. Rossetto made helpful suggestions on early versions of this manuscript. We also thank two anonymous reviewers for their suggestions that greatly improved the clarity and the science of our manuscript. C.P.S. and A.C.P. are members of CONICET.
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