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O impacto do Homem na estrutura de uma espécie: Portugal, um paradigma

Abstract : The Mediterranean basin is characterised by a traditional depletion of forest by man and the human impact has modified species’ genetic diversity. Maritime pine (Pinus pinaster Aiton) occurs naturally in fragmented populations in the western part of the Mediterranean basin. This distribution has been reshaped during the last two centuries by heavy afforestation, particularly in southwest France and in the Iberian Peninsula, and by invasive behaviour in disturbed areas. This presentation summarizes and discusses results of studies in which molecular markers were used to undercover the genetic diversity of this species, which further traced the human impact on its genetic structure, exemplary demonstrated for Portugal. The genetic parameters estimated from chloroplast microsatellites (cpSSR) data revealed that the level of genetic diversity in Pinus pinaster is very high. A clear and significant differentiation among groups of populations of different geographic origin (Portugal, France, Italy, Spain and Morocco) was observed. Conversely, the degree of population divergence within country is generally very low and close to zero, indicating a homogeneous distribution of the variation within groups. The presence of significant differentiation among groups of populations of different geographic areas seems to reflect the existence of different glacial refugia during the Quaternary, for this species. In France the observed haplotypic pattern suggest a genetic ‘melting pot’ of haplotypic diversity, derived from the mixture of material due to the artificial transfer from different regions. Using mitochondrial DNA, a maternally inherited marker, only three-mitochondrial haplotypes were found, which provided a clear picture of nonoverlapping areas colonized from different refugia, with no single population having a mixed composition. The phylogenetic analysis made with allozyme markers showed a high geographical structure in the Iberian Peninsula. The northwestern populations form a cluster and the southeastern populations another. Highest levels of diversity in the eastern and the southern populations and an important reduction of gene diversity in the northwestern range of the species in the Peninsula were observed. Nevertheless, a putative refugium in Portugal was not excluded, because P. pinaster could have survived during the last glaciation in sheltered areas at low altitude close to the Atlantic Ocean, also supported by pollen and charcoal fossil discoveries. The distribution of the genetic variation of P. pinaster in Portugal, as revealed by cpSSR, indicated that there are low levels of differentiation among populations and that the diversity is found mainly within populations. No discernible geographic pattern was found. Evidences of strong anthropogenic influence associated with extensive gene flow could explain these findings
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Submitted on : Thursday, June 4, 2020 - 7:57:04 AM
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  • HAL Id : hal-02764376, version 1
  • PRODINRA : 11658

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Maria Margarida Ribeiro, Santiago C. Gonzalez-Martinez, Christian Burban, Christophe Plomion, Giovanni Giuseppe Vendramin. O impacto do Homem na estrutura de uma espécie: Portugal, um paradigma. 5º Congresso Florestal Nacional : a Floresta e as Gentes, May 2005, Viseu, Portugal. ⟨hal-02764376⟩

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