Abstract
The diversity of forest ecosystems depends on the species richness, but also on the genetic variability at the intraspecific level. In this work, we investigate the contrasting patterns of genetic diversity among Spanish tree species, illustrated by means of four case studies. Combining molecular, palaeobotanical and historical information, we identify the main factors that explain the observed genetic variability of some representative taxa: (1) isolation of relict tree populations in island ecosystems of Balearic evergreen oaks and Canary Island Pine; (2) existence of glacial refugia for Pinus sylvestris, Quercus petraea and Q. pyrenaica; and (3) domestication and spread of Ulmus minor by Romans throughout Western Europe. These situations represent a gradient in the observed values of genetic diversity: Pinus canariensis and the evergreen oaks show high levels of genetic diversity in the Canary Islands and the Balearics, respectively; P. sylvestris, Q. petraea and Q. pyrenaica have also maintained high levels of genetic diversity, even under intensive, longstanding human management. Finally, U. minor genetic variability has been greatly affected by human activities, Dutch elm disease, and the interaction between the two. Understanding how the genetic diversity is maintained and how it is geographically distributed is basic to develop sound conservation policies and sustainable forest management strategies.
Highlights
Since Neolithic times, the interaction between the human being and the forests has been essential for the development of civilizations, as tree species provide a renewable supply of valuable basic materials and indirect environmental benefits
Several studies using a common set of chloroplast microsatellite markers have shown that the genetic diversity differences with P. pinea and P. halepensis, the most thermophilic species of the genus in the region, are substantial: the population haplotypic diversity for Scots pine is significantly much larger than those of P. pinea and P. halepensis, while Pinus pinaster, a species with a high ecological plasticity, shows diversity values only slightly smaller than those of P. sylvestris
Scots pine neutral genetic diversity level appears to be resilient to long-term demographic dynamics caused by climatic changes, we can wonder whether contemporary anthropogenic disturbances may be producing a significant impact on the natural evolutionary processes of the species
Summary
Since Neolithic times, the interaction between the human being and the forests has been essential for the development of civilizations, as tree species provide a renewable supply of valuable basic materials and indirect environmental benefits. We present an overview of the genetic diversity levels of representative species of the main tree genera distributed through the Iberian Peninsula and the Balearic and Canary Islands.
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