Pontevedra, Spain
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Moreira X.,Mision Biologica de Galicia | Zas R.,Mision Biologica de Galicia
PLoS ONE | Year: 2012

Optimal defense theory (ODT) predicts that the within-plant quantitative allocation of defenses is not random, but driven by the potential relative contribution of particular plant tissues to overall fitness. These predictions have been poorly tested on long-lived woody plants. We explored the allocation of constitutive and methyl-jasmonate (MJ) inducible chemical defenses in six half-sib families of Pinus radiata juveniles. Specifically, we studied the quantitative allocation of resin and polyphenolics (the two major secondary chemicals in pine trees) to tissues with contrasting fitness value (stem phloem, stem xylem and needles) across three parts of the plants (basal, middle and apical upper part), using nitrogen concentration as a proxy of tissue value. Concentration of nitrogen in the phloem, xylem and needles was found to be greater higher up the plant. As predicted by the ODT, the same pattern was found for the concentration of non-volatile resin in the stem. However, in leaf tissues the concentrations of both resin and total phenolics were greater towards the base of the plant. Two weeks after MJ application, the concentrations of nitrogen in the phloem, resin in the stem and total phenolics in the needles increased by roughly 25% compared with the control plants, inducibility was similar across all plant parts, and families differed in the inducibility of resin compounds in the stem. In contrast, no significant changes were observed either for phenolics in the stems, or for resin in the needles after MJ application. Concentration of resin in the phloem was double that in the xylem and MJ-inducible, with inducibility being greater towards the base of the stem. In contrast, resin in the xylem was not MJ-inducible and increased in concentration higher up the plant. The pattern of inducibility by MJ-signaling in juvenile P. radiata is tissue, chemical-defense and plant-part specific, and is genetically variable. © 2012 Moreira et al.

Olano J.M.,University of Valladolid | Arzac A.,University of the Basque Country | Garcia-Cervigon A.I.,University of Valladolid | von Arx G.,Swiss Federal Institute of forest | Rozas V.,Mision Biologica de Galicia
New Phytologist | Year: 2013

Tree-ring anatomy reflects the year-by-year impact of environmental factors on tree growth. Up to now, research in this field has mainly focused on the hydraulic architecture, with ray parenchyma neglected despite the growing recognition of its relevance for xylem function. Our aim was to address this gap by exploring the potential of the annual patterns of xylem parenchyma as a climate proxy. We constructed ring-width and ray-parenchyma chronologies from 1965 to 2004 for 20 Juniperus thurifera trees growing in a Mediterranean continental climate. Chronologies were related to climate records by means of correlation, multiple regression and partial correlation analyses. Ray parenchyma responded to climatic conditions at critical stages during the xylogenetic process; namely, at the end of the previous year's xylogenesis (October) and at the onset of earlywood (May) and latewood formation (August). Ray parenchyma-based chronologies have potential to complement ring-width chronologies as a tool for climate reconstructions. Furthermore, medium- and low-frequency signals in the variation of ray parenchyma may improve our understanding of how trees respond to environmental fluctuations and to global change. © 2013 New Phytologist Trust.

Vivas M.,University of Extremadura | Zas R.,Mision Biologica de Galicia | Solla A.,University of Extremadura
Forestry | Year: 2012

Pitch canker, caused by the fungus Fusarium circinatum, is an introduced non-native disease on pines in natural and planted stands of Europe. Research has not been conducted to test whether a European native pine species shows genetic variation in susceptibility to this disease. Half-sib families from 39 Pinus pinaster clones and seedlings from one unimproved seed source (control) were evaluated for resistance. Pitch canker resistance was not genetically related to tree growth, but seed weight and germination rates were predictive of time-to-death. Heritabilities and associated genetic gains calculated from the greenhouse experiment were consistent, h i 2 = 0.18 and 0.45 for time-to-death and for tree mortality, respectively. These heritabilities are high enough to allow pitch canker to be reduced through appropriate genetic strategies. Results indicated that selection for growth of P. pinaster trees in breeding programs would not necessarily imply an increase of susceptibility to F. circinatum. This research may allow the use of native pine individuals as breeding stock or as sources to produce seeds with moderate levels of tolerance to F. circinatum. © Institute of Chartered Foresters, 2011. All rights reserved.

Zas R.,Mision Biologica de Galicia | Moreira X.,Research Center Forestal Of Lourizan | Sampedro L.,Research Center Forestal Of Lourizan
Journal of Ecology | Year: 2011

1.Current hypotheses predict contrasting roles for natural enemies in determining the success or failure of plant invasions. Differences in plant-induced resistance and tolerance to native herbivores between native and exotic species might contribute to resolve this controversy. 2.We examined the differences between the native Pinus pinaster and the exotic P. radiata in constitutive resistance, inducibility of chemical defences, realized resistance and tolerance to the large pine weevil Hylobius abietis in NW Spain. In this region, both pine species closely coexist and are threatened by the weevil, a harmful phloem feeder that causes extensive mortality and growth reduction in young pine stands. 3.We performed two in vitro cafeteria bioassays, two induction experiments with direct exposure to the weevil and spraying methyl jasmonate and an exhaustive field study of the genetic variation in tolerance and resistance in forestry genetic trials. 4.The weevil significantly preferred the native to the exotic pine when twigs were offered as cut material in Petri dishes. However, the pattern in the field was the opposite, with greater damage on the exotic. Inducibility of stem oleoresin did not differ between species when elicited by the application of methyl jasmonate. However, after a 72-h experimental exposure to the weevil, stem resin content in the native pine was double that in the exotic pine, suggesting a lower capability of the exotic pine to respond to the insect damage. In the field, family relationships between early damage and several pine fitness correlates revealed a significantly greater tolerance of the native pine to the insect damage. Furthermore, only the native pine showed genetic variation in tolerance to the damage. 5.Synthesis. The preference of the herbivore for the native species was counterbalanced by a lower capability for expressing induced resistance to the weevil and reduced tolerance in the exotic species, resulting in no apparent fitness advantage of the exotic P. radiata over the native P. pinaster. Differences in inducibility by and tolerance to native enemies between exotic and native host congeners emerge as key traits for understanding how native enemies might contribute to preventing an introduced species from becoming invasive. © 2011 The Authors. Journal of Ecology © 2011 British Ecological Society.

de la Mata R.,Research Center Forestal Of Lourizan | Zas R.,Mision Biologica de Galicia
European Journal of Forest Research | Year: 2010

The inland region of Galicia (NW Spain) marks the boundary between the Atlantic climate of the coastal area and the typical Mediterranean climate of central Spain. Compared to the Atlantic coast, climate in this area has a pronounced summer drought, lower annual precipitation, and higher annual thermal oscillation. Despite the high productivity and ecological importance of maritime pine in inland Galicia, local forest reproductive material (FRM) of high genetic quality is not available for this area. Seed sources originating elsewhere and of unknown adaptation to this area are commonly used for reforestation. With the aim of finding new sources of FRM for this region and exploiting the genetic gains of existing breeding programmes, we analysed the performance in field conditions of improved families of the Coastal Galicia (CG) and Western Australia (WA) breeding programmes. Growth, stem characteristics and branch habit were evaluated in five progeny trials established following a coastal-to-inland gradient. Likelihood-based analyses were used to estimate genetic correlations between environments and to test statistically for causes and patterns of genotype × environment interaction. Because of the strong non-random spatial structures and heterogeneity of residual variances, the analyses were carried out using heterogeneous residual variance mixed models on spatially adjusted data. The results indicated that there is not sufficient evidence to subdivide Galicia into the two current deployment areas. Interaction patterns do not reveal significant differences between zones, and crossover interactions for height growth are present both between and within areas. On the inland sites, the Atlantic improved materials clearly outperformed unimproved seedlots tested in adjacent provenance trials, suggesting the feasibility of using both the CG and WA breeding materials as sources of FRM for reforestation in inland Galicia. Of the two, the WA material showed excellent results for all traits. The inclusion of this material into the Galician maritime pine breeding population should be strongly considered. © 2010 Springer-Verlag.

Santolamazza-Carbone S.,Mision Biologica de Galicia | Velasco P.,Mision Biologica de Galicia | Soengas P.,Mision Biologica de Galicia | Cartea M.E.,Mision Biologica de Galicia
Oecologia | Year: 2014

Quantitative differences in plant defence metabolites, such as glucosinolates, may directly affect herbivore preference and performance, and indirectly affect natural enemy pressure. By assessing insect abundance and leaf damage rate, we studied the responses of insect herbivores to six genotypes of Brassica oleracea var. acephala, selected from the same cultivar for having high or low foliar content of sinigrin, glucoiberin and glucobrassicin. We also investigated whether the natural parasitism rate was affected by glucosinolates. Finally, we assessed the relative importance of plant chemistry (bottom-up control) and natural enemy performance (top-down control) in shaping insect abundance, the ratio of generalist/specialist herbivores and levels of leaf damage. We found that high sinigrin content decreased the abundance of the generalist Mamestra brassicae (Lepidoptera, Noctuidae) and the specialist Plutella xylostella (Lepidoptera, Yponomeutidae), but increased the load of the specialist Eurydema ornatum (Hemiptera, Pentatomidae). Plants with high sinigrin content suffered less leaf injury. The specialist Brevicoryne brassicae (Hemiptera, Aphididae) increased in plants with low glucobrassicin content, whereas the specialists Pieris rapae (Lepidoptera, Pieridae), Aleyrodes brassicae (Hemiptera, Aleyrodidae) and Phyllotreta cruciferae (Coleoptera, Chrysomelidae) were not affected by the plant genotype. Parasitism rates of M. brassicae larvae and E. ornatum eggs were affected by plant genotype. The ratio of generalist/specialist herbivores was positively correlated with parasitism rate. Although both top-down and bottom-up forces were seen to be contributing, the key factor in shaping both herbivore performance and parasitism rate was the glucosinolate concentration, which highlights the impact of bottom-up forces on the trophic cascades in crop habitats. © 2013 Springer-Verlag Berlin Heidelberg.

Santalla M.,Mision Biologica de Galicia | de Ron A.M.,Mision Biologica de Galicia | de La Fuente M.,Mision Biologica de Galicia
Theoretical and Applied Genetics | Year: 2010

Southwestern Europe has been considered as a secondary centre of genetic diversity for the common bean. The dispersal of domesticated materials from their centres of origin provides an experimental system that reveals how human selection during cultivation and adaptation to novel environments affects the genetic composition. In this paper, our goal was to elucidate how distinct events could modify the structure and level of genetic diversity in the common bean. The genome-wide genetic composition was analysed at 42 microsatellite loci in individuals of 22 landraces of domesticated common bean from the Mesoamerican gene pool. The accessions were also characterised for phaseolin seed protein and for nine allozyme polymorphisms and phenotypic traits. One of this study's important findings was the complementary information obtained from all the polymorphisms examined. Most of the markers found to be potentially under the influence of selection were located in the proximity of previously mapped genes and quantitative trait loci (QTLs) related to important agronomic traits, which indicates that population genomics approaches are very efficient in detecting QTLs. As it was revealed by outlier simple sequence repeats, loci analysis with STRUCTURE software and multivariate analysis of phenotypic data, the landraces were grouped into three clusters according to seed size and shape, vegetative growth habit and genetic resistance. A total of 151 alleles were detected with an average of 4 alleles per locus and an average polymorphism information content of 0. 31. Using a model-based approach, on the basis of neutral markers implemented in the software STRUCTURE, three clusters were inferred, which were in good agreement with multivariate analysis. Geographic and genetic distances were congruent with the exception of a few putative hybrids identified in this study, suggesting a predominant effect of isolation by distance. Genomic scans using both markers linked to genes affected by selection (outlier) and neutral markers showed advantages relative to other approaches, since they help to create a more complete picture of how adaptation to environmental conditions has sculpted the common bean genomes in southern Europe. The use of outlier loci also gives a clue about what selective forces gave rise to the actual phenotypes of the analysed landraces. © 2010 Springer-Verlag.

Rozas V.,Mision Biologica de Galicia | Olano J.M.,University of Valladolid
Dendrochronologia | Year: 2013

Individual variation of tree-ring growth response to climate and heterogeneity of the local environment are usually neglected in dendrochronological research. Even if there is evidence showing that individual responsiveness to climate may depend on intrinsic traits such as tree age, size or sex, its modulation by the local heterogeneity of extrinsic factors has been less studied. Using an extensive, strictly regular sampling scheme across a 3300. ha woodland, we assessed the individual variation of tree-ring growth responses to climate in 100 Juniperus thurifera L. trees. The climatic response was evaluated by bootstrapped correlations of both population- and individual-based tree-ring chronologies with monthly records of precipitation, cloudiness, minimum and maximum temperatures. We studied also the influence of extrinsic abiotic (elevation, slope, heat load, tree location) and biotic (competition from neighbouring trees) factors on the individual growth variation and its climatic response. At a population level, growth was controlled by February-March precipitation, April minimum temperature, and June water stress. A significant proportion of individuals did not respond to those variables, but were sensitive to others not relevant at the population level. Inter-annual growth variation was strongly modulated by competition, whereas trees under lower competition levels, in eastern and warmer areas, were the most responsive to climate. The individual climatic response was, at least partially, modulated by the local heterogeneity of extrinsic factors. By considering environmental heterogeneity and neighbourhood interference we can identify the spectrum of site-dependent climatic responses in a population, which in turn will enable more realistic predictions of tree responses to ongoing climate change. © 2012 Elsevier GmbH.

Rozas V.,Mision Biologica de Galicia | Garcia-Gonzalez I.,University of Santiago de Compostela
Global and Planetary Change | Year: 2012

Forest dieback is usually triggered by climatic extremes, even if tree decline can be caused by diverse biotic and abiotic stressors acting synergistically on tree vitality. Many case studies worldwide illustrate the global importance of drought-induced forest dieback under a context of climate warming. However, forest decline is also occurring in regions that are not water-limited, but where increasing rainfall and exceptionally rainy events are observed. Here we assessed the influence of inter-tree competition, regional water availability, and large-scale climate variation on the decline and death of pedunculate oak (Quercus robur) in an Atlantic rainy forest in NW Spain. All healthy, declining, and dead trees in four replicated forest stands were mapped, and inter-tree competition was individually quantified with a distance-dependent competition index. Long-term variation of annual radial growth was analyzed on a selection of individuals per stand, and its dependence on climate variation was examined by correlation analysis with monthly climatic records. Trees under intense competition showed higher mortality risk. Increasing rainfall and the large-scale climatic pattern El Niño-Southern Oscillation (ENSO) have influenced tree growth during recent decades, acting as long-term stressors. A detrimental effect of water surplus during both the year preceding growth and spring of the current year has been noticed since 1980. Extremely rainy conditions in 2001 resulted in strong short-term stress that killed trees suffering from intense competition and wetness-induced stress. Our findings support that water excess is a relevant triggering factor for dieback of dominant forest trees in rainy temperate deciduous forest. This pattern is possible in regions where increasing precipitation and more frequent and intense rainfall extremes, associated with global climate warming, are happening. Since climate warming may lead to higher total annual rainfall, and to an increase in frequency and intensity of extreme precipitation events, forest dieback episodes associated with wetter conditions may become more common in the future. © 2012 Elsevier B.V.

Rozas V.,Mision Biologica de Galicia | Sampedro L.,Mision Biologica de Galicia
Plant and Soil | Year: 2013

Background and Aims: The dependence of oak decline on climatic stressors is fairly well documented, but little is known about the impact of soil properties on growth plasticity and as predisposing factors to decline. Here we investigate if oak dieback and individual responses to climatic stresses are related to soil nutrient availability. Methods: Chemical properties of surrounding soil and tree-ring series of healthy, declining, and dead oaks were analysed in four replicated forest stands under Atlantic wet climate conditions in NW Spain, where massive death has occurred. Results: Current nutrient availability significantly predicted oak death risk. Lower concentrations of macronutrients (N, Ca, Mg, and Na) were found in soil surrounding dead trees than living trees. Water excess before the growing season negatively affected growth, and trees showing declining symptoms were more responsive to climate. Trees with greater Ca availability in the surrounding soil were able to respond more plastically to the stress caused by water excess, while trees with lower Ca levels were less responsive to the stress and more predisposed to die. Conclusion: This work revealed that both climatically-induced dieback and the individual dendroclimatic response of oaks may be linked to the uneven distribution of soil resources in declining Atlantic forests. © 2013 Springer Science+Business Media Dordrecht.

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