Phenotypic variation among natural populations of pines. Implications for the management and conservation of genetic resources

Resumo

The study of variation at different levels is a constant topic of research. In the field of genetics, it is necessary to know the causes and the effects of variation in traits that influence traits of individuals in their natural habitats. Genetic variation is considered the most basic level of biological diversity and a prerequisite for the variability of species, populations, and ecosystems. Populations that lose genetic variation cannot evolve since evolution cannot proceed without genetic variation and populations that are unable to adapt to changing conditions will go extinct. Forest genetics studies have shown that environmental heterogeneity influences the genetic differentiation among tree populations, creating geographic genetic patterns that are consistent with phenotypic traits. One can look at this association to detect climate variables that are shaping the genetic structure of populations or even identify which genes are under pronounced natural selection. Genetic conservation aims to protect and preserve genetic variation, vital for the maintenance of adaptive potential within populations and species. Conserving forest genetic resources (FGR) constitute a unique and irreplaceable resource for the future, including for sustainable economic growth and progress and environmental adaption. The aim of this thesis is to investigate the phenotypic variation among natural population of pines at local and regional scales, and define its implications in the use and conservation of genetic resources. At first step, we analyzed the relationship between within-population variance in fitness-related phenotypic traits (survival, height and diameter), phenotypic plasticity of these traits, and environmental (climatic) heterogeneity in the region surrounding provenances of Pinus sylvestris, P. pinaster and P. halepensis. We used multi-site tree provenance tests of Iberian pine species and a model selection approach to infer the relationship between them. It was found that climatic heterogeneity at different spatial scale can explain a significant part of the intrapopulation phenotypic variation in different traits, but the relationships depend on the species and traits considered. Second, we assessed the inter- and intraspecific genetic variation in seedling drought tolerance in Pinus oocarpa, P. patula and P. pseudostrobus from the Trans-Mexican Volcanic Belt, a relevant genetic resource management scale. It was evaluated the growth and biomass fractions of pine seedlings in a greenhouse with two highly contrasted watering regimes. We found that even at reduced geographical scales, Mexican pines present differences in the response to water stress. The responses differed among species, including the allometric phenotypic changes in biomass allocation (plasticity), the genetic differences among populations, and the differences in phenotypic plasticity among populations. 10 Third, we identified areas for gene conservation and proposing measures for the conservation and sustainable use of forest genetic resources for four pines species: P. greggii, P. oocarpa, P. patula and P. pseudostrobus. It was obtained the most relevant information related to the identification and characterization of forest genetic resources of these species. We used the distribution range of the species, and information for conservation of forest genetic resources and for the sustainable use of forest genetic resources. It was checked gaps considering the distribution area and the genetic zones of the species. We propose recommendations to improve the status of conservation and sustainable use of forest genetic resources in the evaluated species.