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

Capítulo 4
Within‐population variability: the role of maternal tree
It is known that maternal origin affects seedling performance by influencing
seed size (Leiva and Fernandez‐Alés, 1998; Castro, 1999; Merouani et al., 2001). To
tease apart these effects, maternal trees that produce seeds in the same range of size
variation might be chosen, in detriment of exploring the whole range of seed mass
present in the population. In this study we chose to cover the whole range of seed
mass and thus explore all maternal effects together in a complete ecological context
and not only in a subsample of it. Moreover, our analytical approach let us study seedmass
factor per se at each mother source, separating this effect from other maternal
influences. Our results also showed how maternal origin modulates environmental and
seed mass effects on different establishment phases. This within population variability
on responses across the resource gradients could be an adaptation to highly
heterogeneous and unpredictable environments (Castro, 1999; Sánchez‐Vilas and
Retuerto, 2007). In order to evaluate this hypothesis, it would be interesting to study
these effects on oak populations from less heterogeneous environments like
temperate or tropical forests.
Maternal effects could be caused either by environmental conditions during
seed development or by genetic variability (Wulff, 1986; Schmitt et al., 1992; Castro et
al., 2008). Woody perennials have more than 90% of their total genetic diversity within
populations rather than among them, thus being adapted to environmental variation
at small microhabitat scales (Campbell, 1979; Hamrick, 2004). In the context of rapid
climatic changes predicted for the Mediterranean region (IPCC, 2007), it is crucial to
understand whether sufficient genetic variation resides within populations to allow a
successfully recruitment and guarantee their persistence (Hamrick, 2004). In this
experiment we found that maternal source modifies seedling performance at different
stages of establishment, providing a first approach to the understanding of within
population variability patterns in relation to other environmental constraints.
Combining this kind of ecological studies of local adaptation with genetic approaches
using molecular techniques would provide useful knowledge that completes
conservation and restoration efforts (McKay et al., 2005).
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