Establecimiento de cuatro especies de Quercus en el sur de la ...

Capítulo 4
environmental constraints (McKay et al., 2005). Many studies focusing on the analysis
of the variability among populations, have found significant population‐associated
variations in physiological, structural and growth parameters (Sánchez‐Vilas and
Retuerto, 2007; Villar‐Salvador et al. 2008; Ramírez‐Valiente et al. 2009).
In the same sense, within‐population variability driven by maternal traits might
play a key role in the adaptation to local conditions. Seed mass is one of the traits
influenced by the maternal plant (Byers et al., 1997; Castro 1999; Merouani et al.,
2001) with a well‐recognised importance on regeneration, especially on large‐seeded
species growing in unfavourable environments (Leishman and Westoby, 1994;
Saverimuttu and Westoby, 1996). Seed mass is determined by maternal genotype,
maternal environment or both (Schmitt et al., 1992; Ramírez‐Valiente et al., 2009).
Plants from larger seeds could have some advantages, such as higher germination or
emergence rates higher biomass or a greater probability of survival (Gómez, 2004a;
Moles and Westoby, 2004; Quero et al. 2008b). The existence of inter‐individual
variation in acorn yield size has been studied for different oak species (Rice et al, 1993;
Gómez, 2004a) and seed mass has shown to be highly correlated to mother tree.
Therefore, the effect of seed mass can be confounded with other traits determined by
maternal source when experiments are conducted with seeds from different plants
(Castro, 1999).
Maternal source may also determine other traits that enhance seedling
establishment. The within‐population variability in leaf traits is well‐recognised
(González‐Rodríguez and Oyama, 2005; Ramírez‐Valiente et al., 2009). Rice et al.
(1993) suggested the possibility of genetic variation for plasticity in traits such as the
specific leaf area that can be especially important in heterogeneous environments
such as Mediterranean‐type areas. Seedling growth and other physiological traits
related to drought resistance seem as well to have a heritable component (Leiva and
Fernández‐Alés, 1998; Castro et al., 2008).
The preservation of adaptive genetic variation within and among populations
ensures that evolutionary potential is maintained and inbreeding avoided, determining
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