title: Genetic diversity and divergence at the Arbutus unedo L. (Ericaceae) westernmost distribution limit.
abstract: Mediterranean forests are fragile ecosystems vulnerable to recent global warming and reduction of precipitation, and a long-term negative effect is expected on vegetation with increasing drought and in areas burnt by fires. We investigated the spatial distribution of genetic variation of Arbutus unedo in the western Iberia Peninsula, using plastid markers with conservation and provenance regions design purposes. This species is currently undergoing an intense domestication process in the region, and, like other species, is increasingly under the threat from climate change, habitat fragmentation and wildfires. We sampled 451 trees from 15 natural populations from different ecological conditions spanning the whole species' distribution range in the region. We applied Bayesian analysis and identified four clusters (north, centre, south, and a single-population cluster). Hierarchical AMOVA showed higher differentiation among clusters than among populations within clusters. The relatively low within-clusters differentiation can be explained by a common postglacial history of nearby populations. The genetic structure found, supported by the few available palaeobotanical records, cannot exclude the hypothesis of two independent A. unedo refugia in western Iberia Peninsula during the Last Glacial Maximum. Based on the results we recommend a conservation strategy by selecting populations for conservation based on their allelic richness and diversity and careful seed transfer consistent with current species' genetic structure.
authors.affiliation: Departamento de Recursos Naturais e Desenvolvimento Sustentável, Instituto Politécnico de Castelo Branco, Escola Superior Agrária, Castelo Branco, Portugal.|Plant Ecology/ Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, Uppsala, Sweden.|Forest Research Centre, School of Agriculture, University of Lisbon, Tapada da Ajuda, Lisbon, Portugal.
authors.forename: Maria Margarida
authors.initials: MM
authors.lastname: Ribeiro
authors.affiliation: Institute of Biosciences and BioResources, National Research Council, Via Madonna del Piano 10, Sesto Fiorentino (Firenze), Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Piotti
authors.affiliation: Departamento de Recursos Naturais e Desenvolvimento Sustentável, Instituto Politécnico de Castelo Branco, Escola Superior Agrária, Castelo Branco, Portugal.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Ricardo
authors.affiliation: INIAV, Instituto Nacional de Investigação Agrária e Veterinária, I.P., Av. República, Quinta do Marquês Oeiras, Portugal.
authors.forename: Daniel
authors.initials: D
authors.lastname: Gaspar
authors.affiliation: Forest Research Centre, School of Agriculture, University of Lisbon, Tapada da Ajuda, Lisbon, Portugal.|INIAV, Instituto Nacional de Investigação Agrária e Veterinária, I.P., Av. República, Quinta do Marquês Oeiras, Portugal.
authors.forename: Rita
authors.initials: R
authors.lastname: Costa
authors.affiliation: Plant Ecology/ Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, Uppsala, Sweden.
authors.forename: Laura
authors.initials: L
authors.lastname: Parducci
authors.affiliation: Institute of Biosciences and BioResources, National Research Council, Via Madonna del Piano 10, Sesto Fiorentino (Firenze), Italy.
authors.forename: Giovanni Giuseppe
authors.initials: GG
authors.lastname: Vendramin
mesh_terms: D001499:Bayes Theorem; D029791:Ericaceae / Q000235:genetics*; D014644:Genetic Variation; D058974:Phylogeography; D013030:Spain