Dubreuil M., Riba M., González-Martínez S.C., Vendramin G.G., Sebastiani F., Mayol M. (2010) Genetic effects of chronic habitat fragmentation revisited: Strong genetic structure in a temperate tree, Taxus baccata (Taxaceae), with great dispersal capability. American Journal of Botany. 97: 303-310.EnllaçDoi: 10.3732/ajb.0900148
Tree species are thought to be relatively resistant to habitat fragmentation because of their longevity and their aptitude for extensive gene flow, although recent empirical studies have reported negative genetic consequences, in particular after long-term habitat fragmentation in European temperate regions. Yet the response of each species to habitat loss may differ greatly depending on their biological attributes, in particular seed dispersal ability. In this study, we used demographic and molecular data to investigate the genetic consequences of chronic habitat fragmentation in remnant populations of Taxus baccata in the Montseny Mountains, northeast Spain. The age structure of populations revealed demographic bottlenecks and recruitment events associated with exploitation and management practices. We found a strong genetic structure, both at the landscape and within-population levels. We also detected high levels of inbreeding for a strictly outcrossing species. Chronic forest fragmentation resulting from long-term exploitation in the Montseny Mountains seems the most plausible explanation for the strong genetic structure observed. Our results support the view that, contrary to some predictions, tree species are not buffered from the adverse effects of habitat fragmentation, even in the case of species with a high dispersal potential.
González-Martínez S.C., Dubreuil M., Riba M., Vendramin G.G., Sebastiani F., Mayol M. (2010) Spatial genetic structure of Taxus baccata L. in the western Mediterranean Basin: Past and present limits to gene movement over a broad geographic scale. Molecular Phylogenetics and Evolution. 55: 805-815.EnllaçDoi: 10.1016/j.ympev.2010.03.001
English yew (Taxus baccata L., Taxaceae), a Tertiary relict, provides a seminal example of a widespread albeit locally endangered (often close to extinction) tree species. In order to gain detailed insights into the evolutionary dynamics of the species on a broad geographical scale, over 1000 trees from 91 populations of English yew in the western Mediterranean were analyzed using seven nuclear microsatellite markers. Our results revealed contrasting patterns of genetic structure at different spatial scales: genetic variation was highly structured at the local scale, while only a low proportion of the observed variation was attributed to regional differences. We also found a geographic gradient of decreasing diversity and increasing population divergence from northwest (central Europe and northern Iberian Peninsula) to southeast (Mediterranean Iberia and North Africa). The patterns revealed in this study probably reflect the combined effects of Quaternary climatic changes and recent impact of human activities, and potentially also more ancient events dating back to the Tertiary. Both climatic and anthropogenic factors seem to have conducted to a long history of population isolation, which may have contributed significantly to enhance population divergence through restricted gene flow and genetic drift. © 2010 Elsevier Inc. All rights reserved.
González-Martínez SC, Dubreuil M, Riba M, Vendramin GG, Sebastiani F, Mayol M (2010) Spatial genetic structure of Taxus baccata L. in the western Mediterranean Basin: Past and present limits to gene movement over a broad geographic scale. Molecular Phylogenetics and Evolution 55: 805-815.
Dubreuil M, Riba M, González-Martínez SC, Vendramin GG, Sebastiani F, Mayol M (2010) Genetic effects of chronic habitat fragmentation revisited: Strong genetic structure in a temperate tree, Taxus baccata L. (Taxaceae), with great dispersal capability. American Journal of Botany 97: 303-310.
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