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Carrillo-Gavilan A.,CSIC - Doñana Biological Station | Moreira X.,Research Center Forestal Of Lourizan | Zas R.,Mision Biologica de Galicia MBG CSIC | Vila M.,CSIC - Doñana Biological Station | Sampedro L.,Research Center Forestal Of Lourizan
Functional Ecology | Year: 2012

The natural enemy hypothesis (NEH) predicts that alien plant species might receive less pressure from natural enemies than do related coexisting native plants. However, most studies to date are based on pairs of native and alien species, and the results remain inconclusive. The level of attack by native generalist herbivores can vary considerably between plant species, depending on defensive traits and strategies. Plant defences include preformed constitutive and induced defences that are activated as plastic responses to herbivore attack. However, the efficacy of induced defences could be altered when alien species entering an area are exposed to native enemies. We tested the NEH for several closely related alien and native pines to Europe by examining early anti-herbivore resistance to damage by two generalist native insect herbivores (Hylobius abietis and Thaumetopoea pityocampa); the differences in constitutive and inducible chemical defences (i.e. non-volatile resin and total phenolics in the stem and needles); and whether consumption preferences shift after induced defences have been triggered by real herbivory. We did not find alien pines to be less damaged by two generalist herbivores than native pines were. The constitutive concentration of chemical defences significantly differed among pine species. The concentration of constitutive total phenolics in the stem was greater in native than in alien pines. The opposite trend was found for constitutive total phenolics in the needles. The concentration of chemical defences (non-volatile resin and total phenolics) in the stem significantly increased after herbivory by H. abietis. Moreover, the induction of total phenolics by H. abietis damage was significantly greater in native pine species than in alien pines. On the other hand, only concentrations of non-volatile resin in needles significantly increased after herbivory by T. pityocampa, but without significant differences in inducibility between alien and native pines. In cafeteria bioassays, H. abietis consumed the twigs from alien more than those from native species irrespective of prior exposure to the insect. Meanwhile, no differences among range origin were found in the T. pityocampa cafeteria bioassays. Overall, we found no support for the NEH in alien pines to Europe. This suggests that alien pines, in regions where they coexist with native congeners, may be controlled by native generalist herbivores, this being one reason that invasion by alien pines is not frequent in Europe. © 2011 The Authors. Functional Ecology © 2011 British Ecological Society.

Moreira X.,University of California at Irvine | Mooney K.A.,University of California at Irvine | Zas R.,Mision Biologica de Galicia MBG CSIC | Sampedro L.,Research Center Forestal Of Lourizan
Proceedings of the Royal Society B: Biological Sciences | Year: 2012

While plant diversity is well known to increase primary productivity, whether these bottom-up effects are enhanced by reciprocal top-down effects from the third trophic level is unknown. We studied whether pine tree species diversity, aphid-tending ants and their interaction determined plant performance and arthropod community structure. Plant diversity had a positive effect on aphids, but only in the presence of mutualistic ants, leading to a threefold greater number of both groups in the tri-specific cultures than in monocultures. Plant diversity increased ant abundance not only by increasing aphid number, but also by increasing ant recruitment per aphid. The positive effect of diversity on ants in turn cascaded down to increase plant performance; diversity increased plant growth (but not biomass), and this effect was stronger in the presence of ants. Consequently, bottom-up effects of diversity within the same genus and guild of plants, and top-down effects from the third trophic level (predatory ants), interactively increased plant performance. © 2012 The Royal Society.

Moreira X.,Research Center Forestal Of Lourizan | Zas R.,Mision Biologica de Galicia MBG CSIC | Sampedro L.,Research Center Forestal Of Lourizan
Journal of Ecology | Year: 2012

Plant plastic responses to herbivore damage may include rapid, active reallocation of plant resources to reduce the impact of herbivory on future plant fitness. However, whether these inducible tolerance responses can be extended to pine trees and how these responses could be modulated by genetic and environmental factors remains unclear. Biomass allocation and phosphorus (P) and nitrogen (N) concentrations in above- and below-ground tissues were measured in Pinus pinaster juveniles belonging to 33 open-pollinated families grown under two P availabilities (P-deficient and complete fertilization). Measurements were taken 15days after half of the plants received a foliar spray treatment of 22mmolL -1 methyl jasmonate (MJ) to simulate above-ground herbivore attack. Simulated above-ground herbivory promoted a strong preferential allocation of biomass below ground in the form of fine roots, leading to an almost two-fold increase in fine root biomass in MJ-treated plants and a significant reduction in above-ground tissues and coarse roots. In addition, MJ signalling increased P and N concentrations in the shoots while reducing (P) or maintaining (N) concentrations in the roots. These results suggest that induced resource sequestration is not a generalized strategy in this pine species. Fine root biomass and concentration of N and P in plant tissues showed additive genetic variation, but responses to MJ signalling did not vary among families. Allocation of biomass to fine roots was not affected by P availability, whereas allocation of P to the shoot was more intense under complete fertilization. Synthesis: Two new putative tolerance mechanisms inducible by MJ signalling may help to minimize the impact of above-ground herbivore damage on the future fitness of young pine trees by (i) allocation of carbon to fine roots, this appeared to be a generalized strategy with weak environmental modulation and (ii) reallocation of P and N from roots to shoots, which was largely affected by P availability, and thus susceptible to greater phenotypic variation in heterogeneous environments. We provide evidence that changes in tolerance-related traits are rapidly inducible by herbivory cues in this pine species. These results should be integrated with induced resistance responses to fully understand the costs and benefits associated with induced responses to herbivory. © 2011 The Authors. Journal of Ecology © 2011 British Ecological Society.

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

Production of antiherbivore chemical defences is generally assumed to be costly in terms of fitness, although some studies have failed to detect such costs. A convincing explanation is that the expression of fitness costs depends on environmental conditions such as nutrient availability. We performed a greenhouse experiment with 33 half-sib families in order to study the phenotypic plasticity of constitutive and methyl jasmonate-induced chemical defences to soil phosphorus (P) availability, the existence of genetic trade-offs (costs) between growth and the production of those defences and the extent to which P availability may modulate the expression of those costs. We measured some proxies of vegetative fitness (primary growth, secondary growth and total biomass), plant reserves (soluble sugars and starch) and the concentration of quantitative chemical defences (diterpene content in the stem, total polyphenolics and condensed tannins in the needles). Phosphorus availability had a considerable effect, both on the allocation of resources to constitutive and induced defences and on the expression of vegetative costs associated with those chemical defences. Constitutive investment in chemical defences was greater under P-limited conditions for all studied traits. Inducibility of foliar phenolic compounds was greater under P-limited conditions, and it was strongly constrained under high P availability. Availability of P did not affect the inducibility of stem diterpenes. All defensive traits showed significant genetic variation, with different levels of genetic control in constitutive and induced modes, and genetic variation in their inducibility. We found significant negative genetic correlations (i.e. trade-offs) between growth and defensive investment, but costs of chemical defences emerged only in P-limited conditions. Vegetative costs of constitutive defences were detected for stem diterpenes but not for needle phenolics, while costs of induced defences were found for leaf phenolics but not for stem diterpenes. Synthesis. Our results indicate that P availability controls the production of chemical defences in this pine species, influencing the resource allocation to constitutive defences, the inducibility of those defences and the emergence of related vegetative costs. Phosphorus availability thus appears as a major driver in the evolution of pine resistance to insects and a potential factor in maintaining genetic variation in defences. © 2011 The Authors. Journal of Ecology © 2011 British Ecological Society.

Miguez-Soto B.,Research Center Forestal Of Lourizan | Fernandez-Lopez J.,Research Center Forestal Of Lourizan
Tree Genetics and Genomes | Year: 2012

Total height, diameter, index volume, stem straightness, apical dominance, and survival were assessed at 8 years from seed in an open-pollinated progeny test of 36 families of European chestnut (Castanea sativa Miller) established at two sites in the Atlantic area of Galicia, Spain. Iterative spatial analysis was applied to eliminate the effect of the spatial dependence in the original data and to estimate accurately genetic parameters for evaluating the potential for selection of the measured trees. Spatial analysis was very beneficial for growth traits and survival, but less so if at all for form traits. Estimated individual heritabilities ranged from moderate to high for growth traits (ĥ 2 i = 0.29 - 0.42%) and stem straightness (ĥ 2 i = 0.24 - 0.42%) High coefficients of additive genetic variance were obtained for volume (ĈV A = 36.5 - 41.5%) and straightness(ĈV A = 44.26 - 53.84%) Phenotypic and estimated genetic correlations between growth traits were very high, and correlations between sites indicated that there was no important family × site interaction. No adverse correlations between traits were evident. The results indicate the ample potential for selection in the current progeny trial, where responses to within-family and combined selection for growth traits may be high. Accordingly, three selection scenarios were addressed with the aim to initiate the selection of individuals for implementing the Forest Breeding Plan of Galicia for European chestnut. © 2011 Springer-Verlag.

The massive mortality of Castanea sativa in southwestern Europe, which was caused by different species of Phytophthora spp., led to the introduction of seeds of the Asiatic species Castanea crenata and Castanea mollissima and to hybridization to breed for resistance to Phytophthora spp. In Spain, two programmes were developed: one programme, focussed mainly on obtaining first generation hybrids by controlled pollinations, and the other programme, based on selection among open-pollinated progenies collected from first and second generation hybrids, in both cases between sweet and Japanese chestnut. A clone collection of 194 of the clones obtained is conserved at the Lourizán Forest Reseach Centre, and 32 of these were approved as basic material for forest reproduction. A sample of 356 individuals was genotyped using 13 isozyme loci, including the clone collection and several stands of Asiatic species. Only three loci were identified as being diagnostic among these species. The diversity of stands of both Asiatic species was reduced compared to that of C. sativa. Genotype inspection of diagnostic loci and two Bayesian procedures (STRUCTURE and NEWHYBRIDS) were used to classify all individuals into genealogical classes and, thus, reconstruct the history of chestnut hybridization in Spain.

Pestana M.,Research Center Forestal Of Lourizan | Santolamazza-Carbone S.,Research Center Forestal Of Lourizan
Agricultural and Forest Entomology | Year: 2010

1 Ecological interactions between banded pine weevil Pissodes castaneus and blue-stain fungus Leptographium serpens, when simultaneously sharing the same host plant (maritime pine Pinus pinaster) in winter and spring, were investigated. Temporal components of the interaction were taken into account by either introducing the weevils and the pathogen simultaneously or sequentially, with the weevils being introduced 1 month after the fungal inoculation. 2 We measured larval mortality, development time, offspring number, sex ratio and body size of P. castaneus. Phloem phosphorus and nitrogen concentrations were also assessed. Furthermore, we tested whether: (i) emerging offspring transported propagules of the fungus; (ii) artificially-contaminated weevils may transmit the disease to healthy trees; and (iii) field collected P. castaneus carry the fungus. 3 The fungus enhanced weevil colonization and brood production in both seasons. During winter and spring, adults from trees where the pathogen was inoculated prior to weevil introduction emerged earlier than weevils from trees where they had been introduced simultaneously with the fungus. During winter, weevils from pre-inoculated trees were also larger. Sex ratio and larval mortality were not affected. Leptographium serpens did not affect phloem nitrogen content but phosphorus content was greater in plants inoculated with the pathogen, which may explain the findings on weevil growth. 4 Sixty-five percent of the weevils that emerged from inoculated trees carried spores of L. serpens, although no successful isolation was made from field collected weevils. The fungus was recovered from 25% of the trees infested with artificially-contaminated weevils. 5 These results suggest that P. castaneus benefits from the presence of L. serpens and may contribute to its spread. © 2010 The Authors. Agricultural and Forest Entomology © 2010 The Royal Entomological Society.

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.

Pestana M.,Research Center Forestal Of Lourizan | Santolamazza-Carbone S.,Research Center Forestal Of Lourizan
Oecologia | Year: 2011

In this work, by artificially reproducing severe (75%) and moderate (25%) defoliation on maritime pines Pinus pinaster in NW Spain, we investigated, under natural conditions, the consequences of foliage loss on reproduction, abundance, diversity and richness of the fungal symbionts growing belowground and aboveground. The effect of defoliation on tree growth was also assessed. Mature needles were clipped during April 2007 and 2008. Root samples were collected in June-July 2007 and 2008. Collection of sporocarps was performed weekly from April 2007 to April 2009. Taxonomic identity of ectomycorrhizal fungi was assessed by using the internal transcribed spacer (ITS) regions of rDNA through the polymerase chain reaction (PCR) method, subsequent direct sequencing and BLAST search. Ectomycorrhizal colonization was significantly reduced (from 54 to 42%) in 2008 by 75% defoliation, accompanied with a decline in species richness and diversity. On the other hand, sporocarp abundance, richness and diversity were not affected by foliage loss. Some ECM fungal symbionts, which are assumed to have a higher carbon cost according to the morphotypes structure, were reduced due to severe (75%) defoliation. Furthermore, 75% foliage loss consistently depressed tree growth, which in turn affected the ectomycorrhizal growth pattern. Defoliation impact on ECM symbionts largely depends on the percentage of foliage removal and on the number of defoliation bouts. Severe defoliation (75%) in the short term (2 years) changed the composition of the ECM community likely because root biomass would be adjusted to lower levels in parallel with the depletion of the aboveground plant biomass, which probably promoted the competition among mycorrhizal types for host resources. The persistence of fungal biomass in mycorrhizal roots would be crucial for nutrient up-take and recovery from defoliation stress of the host plants. © 2010 Springer-Verlag.

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.

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