Strong effects of hydrologic environment and weak effects of elevated CO<Subscript>2</Subscript> on the invasive weed <Emphasis Type="Italic">Alternanthera philoxeroides</Emphasis> and the biocontrol beetle <Emphasis Type="Italic">Agasicles hygrophila</Emphasis>

Global change, such as elevated CO₂, may alter interactions between invasive plants and biocontrol agents, impacting biocontrol efficacy. Here, we conducted four experiments in Texas, USA to test how elevated CO₂ influences an invasive plant (Alternanthera philoxeroides) and its interactions with an introduced biocontrol beetle (Agasicles hygrophila) in terrestrial (well-watered) and flooded environments. We grew plants for 9 months in ambient or elevated CO₂ (800 ppm) chambers in continuously flooded or well-watered conditions. In no-choice trials, flooding increased leaf toughness and decreased beetle consumption but beetles only oviposited on ambient CO₂ leaves. In choice trials, beetles preferred to feed and oviposit on terrestrial plants but were also less likely to damage elevated CO₂ leaves. Caged beetle populations were larger in terrestrial conditions than aquatic conditions for a second set of plants grown in the chambers. With a third set of plants grown in the ambient or elevated CO₂ chambers, damage for plants placed in the field (aquatic setting) was higher for plants grown in terrestrial conditions vs. flooded conditions at ambient CO₂. Our results suggest that elevated CO₂ will have minor effects on the efficacy of this biocontrol agent by decreasing oviposition and number of leaves damaged, and hydrologic environment may affect invasive plant performance by altering herbivore oviposition and feeding preferences. A broader understanding of the effects of global change on biocontrol will help prevent and manage future spread of invasive plants.     

Stomatal distribution patterns change according to leaf development and leaf water status in <Emphasis Type="Italic">Salix miyabeana</Emphasis>

Salix is a pioneer woody plant genus characterized by a strong plasticity in leaf morphology. The aims of this paper were to determine stomatal distribution (1) in mature leaves in response to environmental conditions, and (2) during leaf development. Stomata of abaxial and adaxial faces of mature leaves of Salix miyabeana SX67 (cultivated in short rotation coppice) were analyzed at the end of summer 2012 and 2013 at six locations in Quebec, Canada. Within each site and across the two growing seasons, stomatal density of abaxial faces was diluted by an increase in area of mature leaves due to higher rainfall. For shrubs with more than one growing season, stomatal density of abaxial faces was affected by annual rainfall, independently of site, whereas leaf area was predominantly influenced by site but was also modulated in part by rainfall. The number of stomata per leaf was site-specific, independently of rainfall. These leaves were mainly hypostomatic, although those collected on shrubs during their first growing season after coppicing (i.e. with a high root:shoot ratio) were amphistomatic. Similarly, at early development stages (surface area <2.8 cm²), leaves were amphistomatic, whereas stomata on adaxial faces of larger leaves were occluded. Nevertheless, stomatal conductance of abaxial faces increased with leaf area, whereas stomatal density was best described by a quadratic relationship. This strategy allows for a maximum uptake of carbon while limiting water loss during leaf development and to adapt the morphology of mature leaves depending on moisture and site conditions.     

Increased nitrogen deposition alleviated the adverse effects of drought stress on <Emphasis Type="Italic">Quercus variabilis</Emphasis> and <Emphasis Type="Italic">Quercus mongolica</Emphasis> seedlings

The plasticity response of Quercus variabilis and Quercus mongolica seedlings to combined nitrogen (N) deposition and drought stress was evaluated, and their performance in natural niche overlaps was predicted. Seedlings in a greenhouse were exposed to four N deposition levels (0, 4, 8, and 20 g N m^?2 year^?1) and two water levels (80 and 50 % field-water capacity). Plant traits associated with growth, biomass production, leaf physiology, and morphology were determined. Results showed that drought stress inhibited seedling performance, altered leaf morphology, and decreased fluorescence parameters in both species. By contrast increased N supply had beneficial effects on the nutritional status and activity of the PSII complex. The two species showed similar responses to drought stress. Contrary to the effects in Q. mongolica, N deposition promoted leaf N concentration, PSII activity, leaf chlorophyll contents, and final growth of Q. variabilis under well-watered conditions. Thus, Q. variabilis was more sensitive to N deposition than Q. mongolica. However, excessive N supply (20 g N m^?2 year^?1) did not exert any positive effects on the two species. Among the observed plasticity of the plant traits, plant growth was the most plastic, and leaf morphology was the least plastic. Therefore, drought stress played a primary role at the whole-plant level, but N supply significantly alleviated the adverse effects of drought stress on plant physiology. A critical N deposition load around 20 g N m^?2 year^?1 may exist for oak seedlings, which may more adversely affect Q. variabilis than Q. mongolica.     

Aquaporin gene expression and physiological responses of <Emphasis Type="Italic">Robinia pseudoacacia</Emphasis> L. to the mycorrhizal fungus <Emphasis Type="Italic">Rhizophagus irregularis</Emphasis> and drought stress

The influence of arbuscular mycorrhiza (AM) and drought stress on aquaporin (AQP) gene expression, water status, and photosynthesis was investigated in black locust (Robinia pseudoacacia L.). Seedlings were grown in potted soil inoculated without or with the AM fungus Rhizophagus irregularis, under well-watered and drought stress conditions. Six full-length AQP complementary DNAs (cDNAs) were isolated from Robinia pseudoacacia, named RpTIP1;1, RpTIP1;3, RpTIP2;1, RpPIP1;1, RpPIP1;3, and RpPIP2;1. A phylogenetic analysis of deduced amino acid sequences demonstrated that putative proteins coded by these RpAQP genes belong to the water channel protein family. Expression analysis revealed higher RpPIP expression in roots while RpTIP expression was higher in leaves, except for RpTIP1;3. AM symbiosis regulated host plant AQPs, and the expression of RpAQP genes in mycorrhizal plants depended on soil water condition and plant tissue. Positive effects were observed for plant physiological parameters in AM plants, which had higher dry mass and lower water saturation deficit and electrolyte leakage than non-AM plants. Rhizophagus irregularis inoculation also slightly increased leaf net photosynthetic rate and stomatal conductance under well-watered and drought stress conditions. These findings suggest that AM symbiosis can enhance the drought tolerance in Robinia pseudoacacia plants by regulating the expression of RpAQP genes, and by improving plant biomass, tissue water status, and leaf photosynthesis in host seedlings.     

Shifts in the abundance and distribution of shallow water fish fauna on the southeastern Brazilian coast: a response to climate change

Myriophyllum aquaticum is a semi-submerged exotic macrophyte that was introduced to China for many years. This species may be found in an emergent form in aquatic environments or in an amphibious form under drained conditions. Nuisance growth of this species has often been attributed to excessive amounts of nutrients. Therefore, we tested the following hypotheses: (1) high nutrient availability facilitates the establishment of M. aquaticum and (2) fragment type interacts with nutrient availability to determine the colonization and regeneration capacities of M. aquaticum. Two types of fragments were grown in water solutions with two levels of phosphorous. After 3 weeks, the survival rates showed no significant difference between the phosphorous treatments. However, emergent fragments showed higher RGR in the low and high phosphorous treatments than amphibious fragments. In addition, emergent fragments also showed higher regeneration capacities, indicating higher invasiveness in emergent fragments compared to amphibious fragments. Moreover, the high phosphorous concentration caused emergent fragments to produce more branches, indicating that nutrient availability may increase M. aquaticum propagule pressure. Our study highlights that nutrient supply increased emergent fragment establishment and shaped the invasion dynamics of macrophytes, which could help predict the spread and potential impact of exotic macrophytes in natural aquatic ecosystems.     

Distinct diversity patterns of <Emphasis Type="Italic">Planctomycetes</Emphasis> associated with the freshwater macrophyte <Emphasis Type="Italic">Nuphar lutea</Emphasis> (L.) Smith

Members of the phylum Planctomycetes were originally described as freshwater bacteria. Most recent studies, however, address planctomycete diversity in other environments colonized by these microorganisms, including marine and terrestrial ecosystems. This study was initiated in order to revisit the specific patterns of planctomycete diversity in freshwater habitats using cultivation-independent approaches. The specific focus was made on planctomycetes associated with Nuphar lutea (L.) Smith, an emergent macrophyte with floating leaves, which is widespread in the Holarctic. As revealed by Illumina pair-end sequencing of 16S rRNA gene fragments, the bacterial assemblages colonizing floating leaf blades of waterlilies sampled from two different boreal lakes displayed similar composition but were distinct from the planktonic bacterial communities. 16S rRNA gene fragments from the Planctomycetes comprised 0.1–1 and 1–2.2% of total 16S rRNA gene reads retrieved from water samples and plant leaves, respectively. Planktonic planctomycetes were mostly affiliated with the class Planctomycetaceae (77–97%), while members of the Phycisphaerae were less abundant (3–22%). The relative proportion of the latter group, however, increased by 13–45% on leaves of N. lutea. The Phycisphaera-related group WD2101, Pirellula-like planctomycetes, as well as Gemmata, Zavarzinella and Planctopirus species were the most abundant groups of planctomycetes associated with plant leaves, which may suggest their involvement in the degradation of plant-derived organic matter.     

Adaptive phenotypic plasticity and competitive ability deployed under a climate change scenario may promote the invasion of <Emphasis Type="Italic">Poa annua</Emphasis> in Antarctica

Antarctica is one of the less prone environments for plant invasions, nevertheless a growing number of non-native species have been registered in the last decades with negative effects on native flora. Here we assessed adaptive phenotypic plasticity in three photoprotective traits (non-photochemical quenching, total soluble sugars, and de-epoxidation state of xanthophylls cycle), and fitness-related traits (maximum quantum yield, photosynthetic rate and total biomass) in the invasive species Poa annua and Deschampsia antarctica under current conditions of water availability and those projected by climate change models. In addition, two manipulative experiments in controlled and field conditions were conducted to evaluate the competitive ability and survival of both species under current and climate change conditions. Moreover, we performed an experiment with different water availabilities to assess cell damage as a potential mechanism involved in the competitive ability deployed in both species. Finally, was assessed the plasticity and biomass of both species subject to factorial abiotic scenarios (water × temperature, and water × nutrients) ranging from current to climate change condition. Overall, results showed that P. annua had greater phenotypic plasticity in photoprotective strategies, higher performance, and greater competitive ability and survival than D. antarctica under current and climate change conditions. Also, cell damage, assessed by lipid peroxidation, was significantly greater in D. antarctica when grown in presence of P. annua compared when grown alone. Finally, P. annua showed a greater plasticity and biomass than D. antarctica under the factorial abiotic scenarios, being more evident under a climate change scenario (i.e., higher soil moisture). Our study suggests that the high adaptive plasticity and competitive ability deployed by P. annua under current and climate change conditions allows it to cope with harsh abiotic conditions and could help explain its successful invasion in the Antarctica.     

Fungi from leaves of lotus (<Emphasis Type="Italic">Nelumbo nucifera</Emphasis>)

In spite of the self-cleaning property of its leaves called the lotus effect, leaves of lotus (Nelumbo nucifera) provide a habitat for an unknown fungal diversity. The aim of this study was to detect and identify fungi from leaves of N. nucifera, including ectophytic, parasitic and endophytic fungi, in Taiwan using different collection strategies, as well as morphological and diverse molecular markers established in the different systematic groups of fungi. Among ectophytic and parasitic fungi, a new species of Dissoconium and of Pseudocercospora are described, respectively. Phyllosticta nelumbonis Sawada is transferred to Diaporthe. Among plant parasitic fungi, Erysiphe takamatsui and Ps. nymphaeacea are recorded in Taiwan for the first time. Euryale is recorded as a new host genus for Ps. nymphaeacea. The basidiomycetous yeast Fereydounia khargensis is recorded for the first time from living plants and in East Asia. Endophytic fungi from lotus were studied for the first time. From 1002 plant segments, 476 endophytic isolates were produced in culture, comprising 33 typical terrestrial species mainly belonging to the genera Colletotrichum (mainly C. siamense), Diaporthe (D. tulliensis and D. ueckerae) and Fusarium (F. solani species 6, hitherto known from clinical samples), as well as to Xylariaceae, but no Ingoldian fungi. Most isolates were from leaf laminas (71%) compared to those from petioles (29%). From this observation, we conclude that the fungi of the aquatic lotus plant appear to have terrestrial origin and, after dispersal by wind and in spite of the lotus effect, may enter the plant from the lamina. Only three species isolated as endophytes were also found as ectophytic or parasitic fungi.     

CAUSAL MECHANISMS OF LEAF DIMORPHISM IN THE AQUATIC ANGIOSPERM CALLITRICHE HETEROPHYLLA

This report investigates the physiological basis for the production of dimorphic leaves on the aquatic angiosperm Callitriche heterophylla. In nature, the leaf morphology of this plant depends on whether the shoot apex is submerged in or emergent from water. The water-form leaves that develop on submerged apices assume a long, linear shape in contrast to the short, obovate appearance of land forms on emergent apices. The parameters of length/width ratio and stomatal density were used as developmental indices to characterize how natural conditions, fluctuating water levels and other experimental treatments affect leaf shape. Transferring submerged and emergent shoots to the alternative culture conditions caused immature leaves to assume the characteristics appropriate to their new environment. Moreover, the treatments of 0.24 mol mannitol, high temperature (30 C) and 10^−-5 m abscisic acid induced submerged shoots to produce land-form leaves whereas 10^−-5 m gibberellic acid mediated the development of water-form leaves on emergent shoots. Water, osmotic and pressure potentials of immature leaves in the control and experimental treatments were determined by thermocouple psychrometry. Under natural conditions, growing water forms exhibited high turgors (3–5 bars) while developing land forms showed much lower turgors (0–1 bar). Similar correlations between turgor pressure and leaf morphology were observed in the case of the gibberellic acid and mannitol treatments. However, abscisic acid and high temperature caused the developing land-form leaves to exhibit high turgors without a concomitant change to the water-form morphology. Microscopic measurements of epidermal cells established that irrespective of the experimental conditions, water-form leaves had longer and narrower epidermal cells with less convoluted anticlinal walls than land forms. Cell counts indicated that the numbers of epidermal cells did not account for the observed differences in leaf morphology. The results are interpreted in terms of how cell expansion might regulate leaf morphology in aquatic angiosperms.     

The <Emphasis Type="Italic">trans</Emphasis> and <Emphasis Type="Italic">cis</Emphasis> zeatin isomers play different roles in regulating growth inhibition induced by high nitrate concentrations in maize

Abscisic acid (ABA), auxins, and cytokinins (CKs) are known to be closely linked to nitrogen signaling. In particular, CKs control the effects of nitrate availability on plant growth. Our group has shown that treatment with high nitrate concentrations limits root growth and leaf development in maize, and conditions the development of younger roots and leaves. CKs also affect source-sink relationships in plants. Based on these results, we hypothesized that CKs regulate the source-sink relationship in maize via a mechanism involving complex crosstalk with the main auxin indole-3-acetic acid (IAA) and ABA. To evaluate this hypothesis, various CK metabolites, IAA, and ABA were quantified in the roots and in source and sink leaves of maize plants treated with high and normal nitrate concentrations. The data obtained suggest that the cis and trans isomers of zeatin play completely distinct roles in maize growth regulation by a complex crosstalk with IAA and ABA. We demonstrate that while trans-zeatin (tZ) and isopentenyladenine (iP) regulate nitrate uptake and thus control final leaf sizes, cis-zeatin (cZ) regulates source and sink strength, and thus controls leaf development. The implications of these findings relating to the roles of ABA and IAA in plants’ responses to varying nitrate concentrations are also discussed.     

Influence of grapevine cultivars on the leafhopper <Emphasis Type="Italic">Empoasca vitis</Emphasis> and its egg parasitoids

The leafhopper Empoasca vitis (Göthe) (Homoptera: Cicadellidae) can cause economic damage in European vineyards. Egg parasitoids, in particular Anagrus atomus (Linnaeus) (Hymenoptera: Mymaridae), are the most important natural enemies of the leafhopper. In four different years, leaves of ten grapevine cultivars, which were grown in a vineyard of north-eastern Italy, were collected at the end of the leafhopper 2nd generation to determine the total number of E. vitis eggs per leaf and the percentage of the E. vitis eggs parasitized. These data were analysed for correlation with leaf density and foliar pubescence. The E. vitis eggs per leaf and the percentage of eggs parasitized by Anagrus spp. were significantly influenced by the cultivar. The number of E. vitis eggs per leaf was positively correlated to leaf density, but it was not influenced by leaf hair density. The parasitization rate by Anagrus spp. was affected by foliar pubescence, especially by erect hairs on the veins. These findings could be used for integrated pest management. In particular, (1) the more susceptible cultivars can be used as early indicators of leafhopper infestation, (2) agronomic practices, that reduce leaf density, could decrease the E. vitis population level and (3) clones with glabrous leaves would favour egg parasitoid activity.     

Bi-directional acclimation of <Emphasis Type="Italic">Cycas micronesica</Emphasis> leaves to abrupt changes in incident light in understory and open habitats

Leaf gas-exchange responses to shadefleck–sunfleck and sun–cloud transitions were determined for in situ Cycas micronesica K.D. Hill plants on the island of Guam to add cycads to the published gymnosperm data. Sequential sunfleck–shadefleck transitions indicated understory leaves primed rapidly but open field leaves primed slowly. Time needed to reach 90% induction of net CO₂ assimilation (P_N) was 2.9 min for understory leaves and 13.9 min for open field leaves. Leaf responses to sun–cloud transitions exhibited minimal adjustment of stomatal conductance, so P_N rapidly returned to precloud values following cloud–sun transitions. Results indicate bi-directional leaf acclimation behavior enables mature C. micronesica trees to thrive in deep understory conditions in some habitats and as emergent canopy trees in other habitats. These data are the first nonconifer gymnosperm data; the speed of gas-exchange responses to rapid light transitions was similar to some of the most rapid angiosperm species described in the literature.     

The ecology of aero-aquatic hyphomycetes

We observed 35 species of aero-aquatic hyphomycetes belonging to 21 genera and 4 unidentified taxa of the Clavariopsis, Dactilella, Helicoon, and Tetracladium genera. Substrate preferences were detected in some species. Species such as Anguillospora longissima, Tetracladium marchalianum, and Fusarium aqueductum were found on different types of substrata. Only 11 species are developed on pine needles, while 20 species were observed on leaves. Eight species of aquatic hyphomycetes (Alatospora acuminata, Angullospora aquatica, Lemonniera aquatica, Tetracladium setigerum, Tricladium angulatum, Tripospermum campelopardus, Septonema secedens, and Spermospora sp.) were revealed on leaves taken from water habitats, whereas 15 species were found in litter. The jointly grown species did not demonstrate any inhibiting effects on each other except for Tripospermum campelopardus, which inhibited the growth of other species (Table 3). The microcyclic development of a Dactilella sp. was detected for the first time while being incubated on leaves in the laboratory. The frequency of appearance changes, and the diversity of the species of aquatic hyphomycetes appears to be higher on intact leaves than on skeletonized ones. The seasonal dynamics of aquatic hyphomycetes with two peaks of mass conidia development (vernal and sharper autumnal) were described. Some species were observed throughout the entire vegetation season. The conidial development in the leaf samples incubated in the laboratory lasted for 30–40 days. Therefore, the method of incubation for 7–10 days recommended in the literature did not allow for the complete investigation of species diversity in aquatic hyphomycetes.     

Ecological Plasticity of the Photosynthetic Apparatus of <Emphasis Type="Italic">Hibiscus syriacus</Emphasis> L. under Pressure of High Temperature,Insolation, and Air Pollution

This paper describes the integrated effect of high summer temperature, intensive insolation, gas pollution, and dust in the air on the pigment content and net oxygen production (apparent photosynthesis) and dark respiration rates of common hibiscus (Hibiscus syriacus L.) leaves. The study included three observation sites: Tashkent Botanical Garden (Academy of Sciences, the Republic of Uzbekistan), the public garden in the central part of the city of Tashkent, and a mountain holiday camp. The research was carried out in 2017 during the period of active vegetation. The results of experiments showed a high adaptive potential of H. syriacus L., as well as its adaptiveness to stress environmental factors of the semiarid zone, provided a sufficient level of its irrigation. The ecological plasticity of the photosynthetic apparatus of hibiscus plays a key role in species adaptation to environmental conditions. It has been revealed that the growth of the plants of the Tashkent Botanical Garden under shading conditions leads to the formation of large, wide, thin, shade leaf blades, which can be considered as the manifestation of sciomorphosis. Heliomorphosis features of hibiscus leaves were identified in mountains, where sun leaves with significantly smaller, thickened, and compacted blades are formed under high insolation. The adaptive significance of these structural leaf modifications is to strengthen photosynthetic capacity for compensating the deficiency in sunlight (in the case of sciomorphosis), and, on the contrary, to provide mutual shading for photosynthetic elements as a measure of protection against the damaging effect of redundant solar radiation (in the case of heliomorphosis). This provides carbon dioxide assimilation and organic matter production for maintaining the constant energy balance for the plant under different environmental conditions. The study of the temperature correlation of dark respiration and net oxygen production rates has shown that these processes are more resistant to temperature injuries under more extreme environmental conditions. In addition, mature H. syriacus leaves have a higher resistance than young leaves; i.e., the plant adapts to possible temperature drops in the process of its ontogenesis. Taking into account the optimal measuring conditions, the net oxygen production rate of H. syriacus during the period of active vegetation is approximately at the same level under different growing conditions (0.20 ± 0.05 μmol of O₂/(dm² s)); this is considered a norm of reaction of the net production (apparent photosynthesis) rate of H. syriacus and determines the specific features of its photosynthetic apparatus.     

Environmental conditions modulate plasticity in the physiological responses of three plant species of the Neotropical savannah

Plasticity in plants could be changed due to abiotic factors, tending to increase fitness across environments. In the Neotropical savannah, a strong water deficit during the dry season is one of the main factors limiting the plasticity in physiological responses of plants. The present study aims to assess the plasticity in physiological responses and vegetative phenology of three plant species of the Neotropical savannah (Cerrado in Brazil) during the dry and the rainy seasons. The three species, Byrsonima verbascifolia, Roupala montana, and Solanum lycocarpum, occur in Serra do Cipó in the state of Minas Gerais, Brazil. The development and vegetative phenology of individuals of these three species were evaluated over the course of 1 year. In February 2012 (rainy season) and August 2012 (dry season), stomatal conductance (g _s), water potential (Ψ), photosynthetic quantum yield, and concentration of leaf photosynthetic pigments were measured. The relative distance among the physiological parameters of all individuals within each season was measured using the relative distance plasticity index. B. verbascifolia has pronounced senescence in July and lost leaves completely by the early September, while R. montana and S. lycocarpum have green leaves throughout the year. The three studied species had greater control of stomatal opening during the dry season. S. lycocarpum and R. montana had negative water potential values in the dry season and in the middle of the day in both seasons. In the dry season, the three species exhibited a decrease in F _v/F _m, with values between 0.7 and 0.75. The relative distance plasticity index varied from 0 to 1. R. montana demonstrated the greatest plasticity and S. lycocarpum had lower plasticity. Then, a seasonal effect on physiological response was observed in all three model-species, with lower values for leaf water potential and stomatal conductance, and increased photoinhibition, in the dry season. Ecophysiological traits, such as stomatal conductance and leaf water potential, exhibited the greatest plasticity. In addition, there was a seasonal effect on the plasticity in physiological responses of the three plants species of the Neotropical savannah. The results are contradicting the idea that water restriction in the dry season would reduce the plasticity in most species of the Neotropical savannah.     

Changes in leaf epicuticular wax,gas exchange and biochemistry metabolism between <Emphasis Type="Italic">Jatropha mollissima</Emphasis> and <Emphasis Type="Italic">Jatropha curcas</Emphasis> under semi-arid conditions

Jatropha curcas and Jatropha mollissima plants were evaluated under conditions of high (HSM) and low (LSM) soil moisture in a semi-arid environment, as changes in the content and concentration of epicuticular wax and the leaf metabolism which could have a relationship with drought tolerance. Besides epicuticular wax, gas exchange, antioxidant system and biochemical parameters of the photosynthetic metabolism were measured. The epicuticular wax content increased only in J. mollissima leaves 95 % under LSM, when compared with HSM conditions. Therefore, J. curcas invested less in the production of long-chain n-alkanes than did J. mollissima under LSM conditions. J. mollissima plants showed the highest CO₂ assimilation rate during the HSM period compared to J. curcas. Both species showed high stability in some leaf biochemistry products, highlighting the highest sugar content, free amino acids, total soluble protein, and photosynthetic pigments in the leaves of J. mollissima plants under both of the soil moisture conditions. Moreover, the stability and performance of the different parameters, such as morphologic variables, seem to allow J. mollissima plants to tolerate semi-arid conditions.     

Genetic determination of tannins and herbivore resistance in <Emphasis Type="Italic">Quercus ilex</Emphasis>

Genetic variability of trees influences the chemical composition of tissues. This determines herbivore impact and, consequently, herbivore performance. We evaluated the independent effects of plant genotype and provenance on the tannin content of holm oak (Quercus ilex) and their consequences for herbivory and performance of gypsy moth (Lymantria dispar) larvae. Oak seedlings of 48 open-pollinated families from six populations were grown in a common garden in central Spain. Half the plants were subjected to defoliation by gypsy moth larvae and the other half were destructively sampled for chemical analysis. Tannin content of leaves did not differ significantly among populations but differed significantly among families. Estimates of heritability (h ²) and quantitative genetic differentiation among populations for tannin content (Q _ST) were 0.83 and 0.12, respectively. Defoliation was not related to the tannin content of plants nor to spine and trichome densities of leaves, although positive family–mean associations were observed between defoliation and both seed weight and plant height (P < 0.003). Among the oak populations, differential increase in larval weight gain with defoliation was observed. Leaf tannin content in Q. ilex is genetically controlled but does not influence defoliation or predict performance of the larvae. Different efficiencies of food utilisation depending on the oak genotypes indicate that other plant traits are influencing the feeding patterns and fitness of L. dispar and consequent population dynamics.