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Moreira X.,University of California at Irvine | Zas R.,Mision Biologica de Galicia MBG CSIC
Heredity | Year: 2013

The apparent failure of invasions by alien pines in Europe has been explained by the co-occurrence of native pine congeners supporting herbivores that might easily recognize the new plants as hosts. Previous studies have reported that exotic pines show reduced tolerance and capacity to induce resistance to those native herbivores. We hypothesize that limited genetic variation in resistance to native herbivores and the existence of evolutionary trade-offs between growth and resistance could represent additional potential constraints on the evolution of invasiveness of exotic pines outside their natural range. In this paper, we examined genetic variation for constitutive and induced chemical defences (measured as non-volatile resin in the stem and total phenolics in the needles) and resistance to two major native generalist herbivores of pines in cafeteria bioassays (the phloem-feeder Hylobius abietis and the defoliator Thaumetopoea pityocampa) using half-sib families drawn from a sample of the population of Pinus radiata introduced to Spain in the mid-19th century. We found (i) significant genetic variation, with moderate-to-high narrow-sense heritabilities for both the production of constitutive non-volatile resin and induced total phenolics, and for constitutive resistance against T. pityocampa in bioassays, (ii) no evolutionary trade-offs between plant resistance and growth traits or between the production of different quantitative chemical defences and (iii) a positive genetic correlation between constitutive resistance to the two studied herbivores. Overall, results of our study indicate that the exotic pine P. radiata has limited genetic constraints on the evolution of resistance against herbivores in its introduced range, suggesting that, at least in terms of interactions with these enemies, this pine species has potential to become invasive in the future. © 2013 Macmillan Publishers Limited All rights reserved 0018-067X/13.


Cendan C.,Mision Biologica de Galicia MBG CSIC | Zas R.,Mision Biologica de Galicia MBG CSIC
Environmental and Experimental Botany | Year: 2013

Optimizing the germination timing is crucial for the establishment of new generations. We hypothesized that environmental maternal effects may be relevant in the fine tuning of this trait in a long-lived Mediterranean model tree. We analyzed the influence of maternal genotype, maternal environment and their interaction on the germination success and germination phenology of 8725 Pinus pinaster seeds collected from genotypes clonally replicated in two contrasting environments. Besides maternal genetic effects, the maternal environment significantly affected both the percentage and the timing of germination. Seeds from the more favourable environment germinated 7.5 days earlier and showed higher germination rate (0.93. ±. 0.01 vs 0.85. ±. 0.03). Seed weight significantly influenced germination time, but seed weight differences between maternal environments were not enough to explain this form of transgenerational plasticity. The effect of the maternal environment varied depending on the genotype, indicating that genetic variation in the sensitivity to the maternal environment in this pine species does exist. © 2011 Elsevier B.V.


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 | Rasmann S.,University of California at Irvine | Petry W.K.,University of California at Irvine | And 3 more authors.
Ecology Letters | Year: 2014

There is increasing evidence that geographic and climatic clines drive the patterns of plant defence allocation and defensive strategies. We quantified early growth rate and both constitutive and inducible chemical defences of 18 Pinaceae species in a common greenhouse environment and assessed their defensive allocation with respect to each species' range across climatic gradients spanning 31o latitude and 2300 m elevation. Constitutive defences traded-off with induced defences, and these defensive strategies were associated with growth rate such that slow-growing species invested more in constitutive defence, whereas fast-growing species invested more in inducible defence. The position of each pine species along this trade-off axis was in turn associated with geography; moving poleward and to higher elevations, growth rate and inducible defences decreased, while constitutive defence increased. These geographic patterns in plant defence were most strongly associated with variation in temperature. Climatic and geographical clines thus act as drivers of defence profiles by mediating the constraints imposed by trade-offs, and this dynamic underlays global patterns of defence allocation. © 2014 John Wiley & Sons Ltd/CNRS.


Zas R.,Mision Biologica de Galicia MBG CSIC | Sampedro L.,Mision Biologica de Galicia MBG CSIC
Heredity | Year: 2015

Quantitative seed provisioning is an important life-history trait with strong effects on offspring phenotype and fitness. As for any other trait, heritability estimates are vital for understanding its evolutionary dynamics. However, being a trait in between two generations, estimating additive genetic variation of seed provisioning requires complex quantitative genetic approaches for distinguishing between true genetic and environmental maternal effects. Here, using Maritime pine as a long-lived plant model, we quantified additive genetic variation of cone and seed weight (SW) mean and SW within-individual variation. We used a powerful approach combining both half-sib analysis and parent-offspring regression using several common garden tests established in contrasting environments to separate G, E and G × E effects. Both cone weight and SW mean showed significant genetic variation but were also influenced by the maternal environment. Most of the large variation in SW mean was attributable to additive genetic effects (h 2 =0.55-0.74). SW showed no apparent G × E interaction, particularly when accounting for cone weight covariation, suggesting that the maternal genotypes actively control the SW mean irrespective of the amount of resources allocated to cones. Within-individual variation in SW was low (12%) relative to between-individual variation (88%), and showed no genetic variation but was largely affected by the maternal environment, with greater variation in the less favourable sites for pine growth. In summary, results were very consistent between the parental and the offspring common garden tests, and clearly indicated heritable genetic variation for SW mean but not for within-individual variation in SW. © 2015 Macmillan Publishers Limited All rights reserved.


Quantitative seed provisioning is an important life-history trait with strong effects on offspring phenotype and fitness. As for any other trait, heritability estimates are vital for understanding its evolutionary dynamics. However, being a trait in between two generations, estimating additive genetic variation of seed provisioning requires complex quantitative genetic approaches for distinguishing between true genetic and environmental maternal effects. Here, using Maritime pine as a long-lived plant model, we quantified additive genetic variation of cone and seed weight (SW) mean and SW within-individual variation. We used a powerful approach combining both half-sib analysis and parent-offspring regression using several common garden tests established in contrasting environments to separate G, E and G × E effects. Both cone weight and SW mean showed significant genetic variation but were also influenced by the maternal environment. Most of the large variation in SW mean was attributable to additive genetic effects (h2=0.55-0.74). SW showed no apparent G × E interaction, particularly when accounting for cone weight covariation, suggesting that the maternal genotypes actively control the SW mean irrespective of the amount of resources allocated to cones. Within-individual variation in SW was low (12%) relative to between-individual variation (88%), and showed no genetic variation but was largely affected by the maternal environment, with greater variation in the less favourable sites for pine growth. In summary, results were very consistent between the parental and the offspring common garden tests, and clearly indicated heritable genetic variation for SW mean but not for within-individual variation in SW.Heredity advance online publication, 27 August 2014; doi:10.1038/hdy.2014.76.


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.


Zas R.,Mision Biologica de Galicia MBG CSIC | Cendan C.,Mision Biologica de Galicia MBG CSIC | Sampedro L.,Mision Biologica de Galicia MBG CSIC
Heredity | Year: 2013

Although maternal environmental effects are increasingly recognized as an important source of phenotypic variation with relevant impacts in evolutionary processes, their relevance in long-lived plants such as pine trees is largely unknown. Here, we used a powerful sample size and a strong quantitative genetic approach to analyse the sources of variation of early seedling performance and to identify seed mass (SM)-dependent and -independent maternal environmental effects in Maritime pine. We measured SM of 8924 individual seeds collected from 10 genotypes clonally replicated in two environments of contrasting quality (favourable and stressful), and we measured seedling growth rate and biomass allocation to roots and shoots. SM was extremely variable (up to 14-fold) and strongly determined by the maternal environment and the genotype of the mother tree. The favourable maternal environment led to larger cones, larger seeds and reduced SM variability. The maternal environment also determined the offspring phenotype, with seedlings coming from the favourable environment being 35% larger and with greater root/shoot ratio. Transgenerational plasticity appears, thus, to be a relevant source of phenotypic variation in the early performance of this pine species. Seed provisioning explained most of the effect of the maternal environment on seedling total biomass. Environmental maternal effects on seedling biomass allocation were, however, determined through SM-independent mechanisms, suggesting that other epigenetic regulation channels may be involved. © 2013 Macmillan Publishers Limited All rights reserved.

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