Phenotypic plasticity blurs ecotypic divergence in the response of <Emphasis Type="Italic">Quercus coccifera</Emphasis> and <Emphasis Type="Italic">Pinus halepensis</Emphasis> to water stress |
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Authors: | Francisco J Baquedano Fernando Valladares Federico J Castillo |
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Institution: | (1) Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, 31006 Pamplona, Spain;(2) Instituto de Recursos Naturales, Centro de Ciencias Medioambientales, CSIC, Serrano 115, 28006 Madrid, Spain;(3) Departamento de Biología y Geología. Escuela Superior de Ciencias Experimentales y Tecnológicas, Universidad Rey Juan Carlos, c/Tulipán s/n, 28933 Móstoles, Spain;(4) Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, 31006 Pamplona, Spain |
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Abstract: | The Mediterranean evergreen woody plants Quercus coccifera and Pinus halepensis grow in a range of environments where selection by drought, heat and high irradiance can drive genetic and phenotypic differentiation
of populations. However, the role of these stresses in filtering out maladaptive genotypes remains unknown. We hypothesize
that this filtering is an important process for woody Mediterranean species due to their low phenotypic plasticity reported
in previous studies. We have studied the response of saplings of Q. coccifera and P. halepensis, originating from two contrasting populations (a rock outcrop and a garrigue formation), to water stress. Isozyme characterization
of genetic diversity was done to determine whether populations were genetically distinct. Water response analysis was based
on water relations, gas exchange, chlorophyll a fluorescence, pigment content, antioxidant status and morphological and structural parameters. Ecotypic differentiation was
found for both Q. coccifera and P. halepensis populations, with a higher population isozyme similarity and a higher frequency of dominance of a few genotypes at the rock
outcrop in both the species. P. halepensis exhibited small but significant differences between populations for plastic responses to water, with lower phenotypic plasticity
in saplings from the rock outcrop. Although it was not found in Q. coccifera, this pattern suggests that ecotypic differentiation rendering stress-tolerant ecotypes involves a decreased plasticity. Phenotypic
plasticity was not high but it explained over 75% of the total variability among individual plants. Thus, and although evidence
for ecotypic divergence was found in both the species, saplings were plastic enough to blur ecotypic differentiation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Drought Ecotype Genetic variability Mediterranean species Phenotypic plasticity |
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