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Premise of research. Herbivore damage is generally higher in the sun than in the shade. The influence of shade tolerance on herbivory has been mainly related to the fact that light-demanding plant species show lower defense investments—and hence higher herbivory—than shade-tolerant species. The pattern of increased herbivory with increasing light availability may take different forms, depending on the drivers of herbivore damage across the light gradient: (1) herbivory pressure alone, (2) herbivory pressure together with plant resistance associated with shade tolerance, or (3) the two drivers seen in scenario 2 added to a differential effect of light availability on plant resistance depending on shade tolerance. Elucidating the specific patterns behind the general pattern of increased herbivory with increasing light availability may contribute to understanding and aid prediction of herbivory patterns in forest communities under natural or anthropogenic disturbance. Methodology. In a field study with 15 tree species distributed across the light gradient in a temperate rainforest (1.6%–26.2% canopy openness), we evaluated the relationship between canopy openness and seedling herbivory, with 755 seedlings surveyed for herbivore damage. Specifically, we evaluated the consistency between the observed herbivory–canopy openness relationship and the three scenarios described above. Pivotal results. We found steeper slopes for the herbivory–canopy openness relationship in tree species with lower shade tolerance; that is, we verified scenario 3. Conclusions. Shade tolerance determined the slope of the herbivory–canopy openness relationship across the light gradient. This finding expands our understanding of the recognized influence of shade tolerance on the interplay between herbivory and the light environment. [ABSTRACT FROM AUTHOR]

Climate change is expected to promote biological invasions. Invasive species often undergo adaptive evolution, but whether invasive species show greater evolutionary potential than their native counterparts under climate change has rarely been evaluated. We conducted experimental evolution trials comparing the evolution of physiological performance (light‐saturated photosynthetic rate, Amax) of coexisting and closely related (1) invasive‐native species pairs from Arid, Alpine, and Antarctic ecosystems, and (2) an invasive‐naturalized species pair from a Mediterranean ecosystem differing in invasiveness. Experiments were conducted over three generations and under four environments of temperature and water availability resembling typical and climate change conditions in each ecosystem. Amax increased across generations for most species. Invasive species from Arid, Alpine, and Antarctic ecosystems showed similar, greater, and lesser evolution of Amax than their native counterparts, respectively. The Mediterranean invasive species showed greater evolution of Amax than its naturalized congener. Similar patterns were observed in all four experimental environments for each ecosystem, suggesting that comparable responses may be expected under climate change scenarios. All study species showed a positive association between Amax and reproductive output. Results suggest that invasive plants and their native (or naturalized) counterparts would show similar evolutionary responses of physiological performance to global warming and drought. [ABSTRACT FROM AUTHOR]

The mechanisms behind the unique capacity of the vine Boquila trifoliolata to mimic the leaves of several tree species remain unknown. A hypothesis in the original leaf mimicry report considered that microbial vectors from trees could carry genes or epigenetic factors that would alter the expression of leaf traits in Boquila. Here we evaluated whether leaf endophytic bacterial communities are associated with the mimicry pattern. Using 16S rRNA gene sequencing, we compared the endophytic bacterial communities in three groups of leaves collected in a temperate rainforest: (1) leaves from the model tree Rhaphithamnus spinosus (RS), (2) Boquila leaves mimicking the tree leaves (BR), and (3) Boquila leaves from the same individual vine but not mimicking the tree leaves (BT). We hypothesized that bacterial communities would be more similar in the BR–RS comparison than in the BT–RS comparison. We found significant differences in the endophytic bacterial communities among the three groups, verifying the hypothesis. Whereas non-mimetic Boquila leaves and tree leaves (BT–RS) showed clearly different bacterial communities, mimetic Boquila leaves and tree leaves (BR–RS) showed an overlap concerning their bacterial communities. The role of bacteria in this unique case of leaf mimicry should be studied further. [ABSTRACT FROM AUTHOR]

A key process determining community assembly is habitat filtering, which reduces the range of trait values and thus leads to trait convergence. Habitat filtering is often assumed to involve a reduction in species richness, but such trait convergence could also result from phenotypic plasticity. By allowing more species in the community to show the 'right' phenotype and pass the filter, phenotypic plasticity could maintain species richness despite trait convergence. If phenotypic plasticity plays this role, environmental changes should modify trait distribution but not species composition or richness. We tested this hypothesis in a forest edge community recently invaded by the alien shrub Rubus praecox. We measured functional traits beneath Rubus canopy (Rubus‐invaded community) and in adjacent microsites naturally free from Rubus (original community), comparing trait dispersion and community structure parameters. We also characterized the microenvironments to seek functional explanations for the observed phenotypic changes. The functional dispersion parameter FDis showed habitat filtering in the Rubus‐invaded community (trait convergence), while in the original community it did not differ from a null model. Species richness and composition did not differ between the two communities. Soil characteristics were similar in both communities but light availability was greatly reduced in the Rubus‐invaded community. A principal component analysis of community‐weighted means of functional traits showed that phenotypic changes between communities were mostly consistent with functional responses to shading, including an increase in specific leaf area and a reduction in flavonoid concentration in the Rubus‐invaded community. We verified the conditions necessary to infer that phenotypic plasticity mediates the outcome of habitat filtering driven by Rubus in the study system, i.e. plasticity would explain species persistence despite trait convergence. Phenotypic plasticity, often subsumed within intraspecific variation in community assembly studies, should be considered individually to improve our understanding of the causes and consequences of habitat filtering. [ABSTRACT FROM AUTHOR]

Maca (Lepidium meyenii) is a high-Andean crop whose subterranean storage organs (hypocotyls) show distinctive colors that are related to pharmacological properties. Little is known about seed color variation and its influence on germination performance, hypocotyl pigmentation and plant survival. Germination rate is critical for maca plants to survive frost events during early development. We evaluated the effect of germination promoters (gibberellic acid and sodium hypochlorite) and temperature regimes (constant and cold: 4°C; variable and moderate: 5–10°C; constant and warm: 16°C) on germination of seeds with different embryo color (yellow, reddish-purple and blue). We also assessed the association between seed color, hypocotyl color and plant survival under field conditions. Seeds with blue and yellow embryos had the lowest and highest germination rates, respectively, across cold and moderate temperature regimes. At warm temperature, germination was not affected by seed color. Germination promoters only enhanced seed germination at cold and moderate temperatures. In the field, black seeds (with blue embryos) showed the greatest survival. Seeds with reddish-purple embryos produced a higher proportion of pigmented hypocotyls – mainly purple – than other seed colors. Seed color should be taken into account in maca breeding programs, particularly in the context of climate change. [ABSTRACT FROM AUTHOR]

Summary: A trade‐off between growth and defence functions is commonly observed in plants. We propose that the association of plants with Epichloë fungal endophytes may eliminate this trade‐off. This would be a consequence of the double role of these endophytes in host plants: the stimulation of plant growth hormones (e.g. gibberellins) and the fungal production of antiherbivore alkaloids. We put forward a model that integrates this dual effect of endophytes on plant growth and defence and test its predictions by means of meta‐analysis of published literature. Our results support the notion that the enhanced plant resistance promoted by endophytes does not compromise plant growth. The limits and ecological benefits of this endophyte‐mediated lack of plant growth–defence trade‐off are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Aim: Crassulacean acid metabolism (CAM) is a widespread physiological adaptation to drought. CAM is common in plants distributed in arid regions, such as Bromeliaceae species. In Chile, latitude is an accurate predictor of climate, with increasing temperature and decreasing moisture towards north. Northern species of Chilean bromeliads mainly show CAM photosynthesis, while southern‐distributed species rely on the C3 pathway. We evaluated the influence of latitude and associated climatic variables on the adoption of photosynthetic pathways by Chilean bromeliads, accounting for phylogenetic relatedness. We expected a significant relation between photosynthetic pathway and the latitudinal limits of species’ distribution ranges, independent of phylogeny. Location: Data from Bromeliaceae species native to Chile (latitudinal distribution range: 15°S to 43°S). Methods: We gathered information on geographical ranges and isotopic discrimination data (δ13C, an indicator of photosynthetic pathway) of Chilean bromeliads. We evaluated whether δ13C values were related to latitude, temperature and precipitation using separate multiple linear regressions in northern and southern distribution limits of Chilean bromeliads. To account for phylogeny, we performed phylogenetically independent contrasts. Results: In the south, δ13C values were not significantly correlated with latitude, temperature or precipitation. In the north, δ13C values were significantly correlated with latitude and annual precipitation. After phylogenetic correction, both variables were still significantly associated with δ13C. Main conclusions: In Chilean bromeliads, for those taxa reaching northernmost latitudes both aridity and other factors associated with latitude are probably the main drivers of adaptive evolution of CAM photosynthesis while advancing towards their present limits in arid regions. Phylogenetic relatedness also influences CAM photosynthesis in this lineage. [ABSTRACT FROM AUTHOR]

Invasive species dominance in invaded communities may not be long-lasting due to regulatory processes, such as plant-soil feedbacks and neighboring species adaptation. Further, the change in species competitive ability may be contingent upon neighbor identity (i.e., specialized response) or consistent across neighbors (i.e., generalized response). Specialized responses can facilitate overall coexistence, while generalized responses may result in competitive exclusion. We set up a greenhouse experiment to test, in three species, the effect of soil conditions (non-invaded vs. invaded soil) and maternal experience (offspring of maternal plants from invaded vs. non-invaded areas) on species competitive ability against the invader Bromus inermis and conspecifics. If changes in species competitive ability against B. inermis were also evident when interacting with conspecifics, it would suggest a generalized increased/decreased competitive ability. Maternal experience resulted in reduced suppression of B. inermis in the three species and no change in tolerance. On the other hand, tolerance to B. inermis was enhanced when plants grew in soil from invaded areas, compared to non-brome soil. Importantly, both the decreased suppression due to maternal experience with B. inermis and the increased tolerance in invaded soil appear to be invader specific, as no such effects were observed when interacting with conspecifics. Specialized responses should facilitate coexistence, as no individual/species is a weaker or stronger competitor against all other neighbors or under all local soil conditions. Further, the negative plant-soil feedback for B. inermis should facilitate native species recovery in invaded areas and result in lower B. inermis performance and dominance over time. [ABSTRACT FROM AUTHOR]

Questions The impact of invasive species on community structure and function varies, yet it is difficult to predict. Different hypotheses have been proposed to predict invasive species establishment and impact on resident communities, based on characteristics of the resident community and/or environmental conditions. Invasive species, however, interact with both native and exotic species. The interaction with exotic species is important, as it can result in secondary invasion or greater impact on native species. Smooth brome ( Bromus inermis Leyss.) is a widely planted forage crop, but also a harmful invasive species in North American grasslands, yet little is known about the variability of its impact on resident communities. We ask (1) whether smooth brome has a consistent impact on community structure and function; (2) which biotic and abiotic conditions are associated with smooth brome's impact on resident communities; and (3) whether smooth brome has a similar impact on native and exotic species, and which biotic or abiotic conditions drive the interaction of smooth brome with native and exotic species. Location Eight grasslands throughout Alberta, Canada. Methods We used space-for-time substitutions to quantify smooth brome's impact on different aspects of community structure and function, and whether it varies depending on species richness, productivity, temperature, precipitation and variation in precipitation. Results Smooth brome had a consistent negative impact on community structure and function. However, the strength of the effect depended on aspects of the local community. Smooth brome impacts on species richness were higher in species-rich areas, while impact on resident species biomass was larger in productive, warmer and more variable sites. In most sites the negative effect of smooth brome on species richness was higher for native species, compared to exotics. Impact on native and exotic species richness was larger in species-rich and more variable sites, respectively. Conclusions Understanding and predicting smooth brome's impact on community structure and function can help managers prescribe management plans to reduce negative impacts of smooth brome on native communities. Predicting the interaction of smooth brome with exotic species may be just as important when planning management strategies, to avoid secondary invasion and/or the accumulation of exotic species. [ABSTRACT FROM AUTHOR]

ABSTRACT While average temperature is likely to increase in most locations on Earth, many places will simultaneously experience higher variability in temperature, precipitation, and other climate variables. Although ecologists and evolutionary biologists widely recognize the potential impacts of changes in average climatic conditions, relatively little attention has been paid to the potential impacts of changes in climatic variability and extremes. We review the evidence on the impacts of increased climatic variability and extremes on physiological, ecological and evolutionary processes at multiple levels of biological organization, from individuals to populations and communities. Our review indicates that climatic variability can have profound influences on biological processes at multiple scales of organization. Responses to increased climatic variability and extremes are likely to be complex and cannot always be generalized, although our conceptual and methodological toolboxes allow us to make informed predictions about the likely consequences of such climatic changes. We conclude that climatic variability represents an important component of climate that deserves further attention. [ABSTRACT FROM AUTHOR]

The climbing habit is a key innovation in plants: climbing taxa have higher species richness than nonclimbing sister groups. We evaluated the hypothesis that climbing plant species show greater among-population genetic differentiation than nonclimber species. We compared the among-population genetic distance in woody climbers (eight species, 30 populations) and trees (seven species, 29 populations) coexisting in nine communities in a temperate rainforest. We also compared within-population genetic diversity in co-occurring woody climbers and trees in two communities. Mean genetic distance between populations of climbers was twice that of trees. Isolation by distance (increase in genetic distance with geographic distance) was greater for climbers. Climbers and trees showed similar within-population genetic diversity. Our longevity estimate suggested that climbers had shorter generation times, while other biological features often associated with diversification (dispersal and pollination syndromes, mating system, size, and metabolic rate) did not show significant differences between groups. We hypothesize that the greater population differentiation in climbers could result from greater evolutionary responses to local selection acting on initially higher within-population genetic diversity, which could be driven by neutral processes associated with shorter generation times. Increased population genetic differentiation could be incorporated as another line of evidence when testing for key innovations. [ABSTRACT FROM AUTHOR]

Invasive plant species can have a strong negative impact on the resident native species, likely imposing new selective pressures on them. Altered selective pressures may result in evolutionary changes in some native species, reducing competitive exclusion and allowing for coexistence with the invader. Native genotypes that are able to coexist with strong invaders may represent a valuable resource for management efforts. A better understanding of the conditions under which native species are more, or less, likely to adapt to an invader is necessary to incorporate these eco-evolutionary dynamics into management strategies. We propose that the spatial structure of invasion, in particular the size and isolation of invaded patches, is one factor which can influence the evolutionary responses of native species through modifying gene flow and the strength of selection. We present a conceptual model in which large, dense, and well-connected patches result in a greater likelihood of native species adaptation. We also identify characteristics of the interacting species that may influence the evolutionary response of native species to invasion and outline potential management implications. Identifying areas of rapid evolutionary change may offer one additional tool to managers in their effort to conserve biodiversity in the face of invasion. [ABSTRACT FROM AUTHOR]

The knowledge derived from Antarctic ecology may be fundamental for facing the complex environmental future of the world. As an early-warning system, a deep understanding of Antarctic ecosystems is therefore needed, but Antarctic ecology as a field is still very young and currently under consolidation. Around the world, 55 nations are involved in this task through their research programs, and, considering the importance of this joint effort, we evaluate some basic trends of their publications through a wide bibliographical review of Antarctic ecology. All ecology-related Antarctic papers published for 106 years (1904–2010) were reviewed. A lack of population and ecosystem research was observed, even in Animalia, the most studied kingdom. The publications originated mainly in developed countries; however, emerging countries have increased their participation in recent years. The current trends of Antarctic ecology as a field show a constant but low representation in both Antarctic science and ecology. [ABSTRACT FROM PUBLISHER]

Summary: Mimicry refers to adaptive similarity between a mimic organism and a model. Mimicry in animals is rather common, whereas documented cases in plants are rare, and the associated benefits are seldom elucidated [1, 2]. We show the occurrence of leaf mimicry in a climbing plant endemic to a temperate rainforest. The woody vine Boquila trifoliolata mimics the leaves of its supporting trees in terms of size, shape, color, orientation, petiole length, and/or tip spininess. Moreover, sequential leaf mimicry occurs when a single individual vine is associated with different tree species. Leaves of unsupported vines differed from leaves of climbing plants closely associated with tree foliage but did not differ from those of vines climbing onto leafless trunks. Consistent with an herbivory-avoidance hypothesis, leaf herbivory on unsupported vines was greater than that on vines climbing on trees but was greatest on vines climbing onto leafless trunks. Thus, B. trifoliolata gains protection against herbivory not merely by climbing and thus avoiding ground herbivores [3] but also by climbing onto trees whose leaves are mimicked. Unlike earlier cases of plant mimicry or crypsis, in which the plant roughly resembles a background or color pattern [4–7] or mimics a single host [8, 9], B. trifoliolata is able to mimic several hosts. [ABSTRACT FROM AUTHOR]

Several studies across species have linked leaf functional traits with shade tolerance. Because evolution by natural selection occurs within populations, in order to explain those interspecific patterns it is crucial to examine variation of traits associated with shade tolerance and plant fitness at an intraspecific scale. In a southern temperate rainforest, two climbing plant species coexist but differ in shade tolerance. Whereas Luzuriaga radicans is most abundant in the shaded understory, L. polyphylla typically occurs in intermediate light environments. We carried out an intraspecific approach to test the hypothesis of differential selection patterns in relation to shade tolerance in these congeneric species. The probability of showing reproductive structures increased with specific leaf area (SLA) in L. polyphylla, and decreased with dark respiration in L. radicans. When reproductive output of fertile individuals was the fitness variable, we detected positive directional selection on SLA in L. polyphylla, and negative directional selection on dark respiration and positive directional selection on leaf size in L. radicans. Total light radiation differed between the microsites where the Luzuriaga species were sampled in the old-growth forest understory. Accordingly, L. radicans had a lower minimum light requirement and showed fertile individuals in darker microsites. L. radicans showed lower dark respiration, higher chlorophyll content, and greater leaf size and SLA than L. polyphylla. Results suggest that in more shade-tolerant species, established in the darker microsites, selection would favor functional traits minimizing carbon losses, while in less shade-tolerant species, plants displaying leaf traits enhancing light capture would be selected. [ABSTRACT FROM AUTHOR]

Background:InAristolochiaspecies the pollination process involves temporary imprisonment of pollinators. Floral longevity is an essential trait for pollination biology, influencing the total number of pollinator visits. Floral longevity should balance costs of flower maintenance and time to fulfil reproduction. ForAristolochiaspecies there is an extra factor: survival of trapped insects. Environmental conditions may affect floral longevity because pollinator visits are likely to be less frequent in stressful habitats. Aims:Our aim was to study the pollination biology ofA. chilensisin an arid ecosystem and to determine the relationship between floral longevity inAristolochiaand aridity. Methods:We measured floral longevity, pollinator quantity and identity and tested the viability of self-fertilisation inA. chilensis. We also compiled information on floral longevity and habitat characteristics ofAristolochiaspecies using published literature. Results: Dipterans were the only effective pollinators ofA. chilensis, which required pollinators to set fruit.A. chilensishad the greatest floral longevity recorded for the genus and the study population was located in the most arid and least productive environment reported for anyAristolochiaspecies. When data from nineAristolochiaspecies were analysed, floral longevity increased with habitat aridity and decreased with habitat productivity. Conclusions:Floral longevity varies consistently with habitat aridity and productivity inAristolochia. Further research should determine the relative importance of biotic and abiotic factors in the evolution of floral longevity inAristolochia. [ABSTRACT FROM AUTHOR]

There is limited evidence regarding the adaptive value of plant functional traits in contrasting light environments. It has been suggested that changes in these traits in response to light availability can increase herbivore susceptibility. We tested the adaptive value of plant functional traits linked with carbon gain in contrasting light environments and also evaluated whether herbivores can modify selection on these traits in each light environment. In a temperate rainforest, we examined phenotypic selection on functional traits in seedlings of the pioneer tree Aristotelia chilensis growing in sun (canopy gap) and shade (forest understory) and subjected to either natural herbivory or herbivore exclusion. We found differential selection on functional traits depending on light environment. In sun, there was positive directional selection on photosynthetic rate and relative growth rate (RGR), indicating that selection favors competitive ability in a high-resource environment. Seedlings with high specific leaf area (SLA) and intermediate RGR were selected in shade, suggesting that light capture and conservative resource use are favored in the understory. Herbivores reduced the strength of positive directional selection acting on SLA in shade. We provide the first demonstration that natural herbivory rates can change the strength of selection on plant ecophysiological traits, that is, attributes whose main function is resource uptake. Research addressing the evolution of shade tolerance should incorporate the selective role of herbivores. [ABSTRACT FROM AUTHOR]

Climbing plants are a key component of rainforests, but mechanistic approaches to their distribution and abundance are scarce. In a southern temperate rainforest, we addressed whether the dominance of climbing plants across light environments is associated with the expression of ecophysiological traits. In mature forest and canopy gaps, we measured leaf size, specific leaf area, photosynthetic rate, and dark respiration in six of the most abundant woody vines. Mean values of traits and their phenotypic change (%) between mature forest and canopy gaps were predictor variables. Leaf size and specific leaf area were not significantly associated with climbing plant dominance. Variation in gas-exchange traits between mature forest and canopy gaps explained, at least partly, the dominance of climbers in this forest. A greater increase in photosynthetic rate and a lower increase in dark respiration rate when canopy openings occur were related to the success of climbing plant species. Dominant climbers showed a strategy of maximizing exploitation of resource availability but minimizing metabolic costs. Results may reflect phenotypic plasticity or genetic differentiation in ecophysiological traits between light environments. It is suggested that the dominant climbers in this temperate rainforest would be able to cope with forest clearings due to human activities. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity is traditionally defined as the capacity of a given genotype to render alternative phenotypes under different environmental conditions. Some studies focus on the individual genotype to study 'true' phenotypic plasticity, regardless of the level of ecological organization involved in each particular study. We argue that, depending on the research question and the scale, there are advantages of looking beyond the genetic identity of each individual phenotype when addressing phenotypic plasticity. This broad approach may simplify experimental designs, increase their statistical power, and allow a more inclusive estimation of the extent of phenotypic plasticity in natural populations. We also posit that when the focus is on the ecological significance of a given phenotype, the final ontogenetic stage and size of the experimental individuals whose plastic responses are compared should not be necessarily considered as confounding factors. A broad approach to the genotypic basis of phenotypic responses, focusing on the representativeness of the genotypic sample, together with the recognition that any environmentally-induced phenotypic change is legitimate plasticity (and potential target of natural selection), may contribute to the understanding of the ecological significance of phenotypic plasticity. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 1-7. [ABSTRACT FROM AUTHOR]

Crassulacean acid metabolism (CAM) is a photosynthetic pathway that significantly increases water use efficiency in plants. It has been proposed that CAM photosynthesis, which evolved from the ancestral C3 pathway, has played a role in the diversification of some prominent plant groups because it may have allowed them to colonize and successfully spread into arid or semi-arid environments. However, the hypothesis that CAM photosynthesis constitutes an evolutionary key innovation, thereby enhancing diversification rates of the clades possessing it, has not been evaluated quantitatively. We tested whether CAM photosynthesis is a key innovation in the Bromeliaceae, a large and highly diversified plant family that has successfully colonized arid environments. We identified five pairs of sister groups with and without the CAM feature, including 31 genera and over 2000 species. In all five cases, the clades with CAM photosynthesis were more diverse than their C3 counterparts. We provide quantitative evidence that the evolution of CAM photosynthesis is significantly associated with increased diversification in Bromeliaceae and thus constitutes an evolutionary key innovation. We also found preliminary evidence of an association between the CAM pathway and growth habit in bromeliads, with terrestrial species being more likely to show CAM photosynthesis than epiphytic species. To our knowledge, this is the first case of a physiological attribute shown to be a key innovation in plants. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104, 480-486. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity is commonly considered as a trait associated with invasiveness in alien plants because it may enhance the ability of plants to occupy a wide range of environments. Although the evidence of greater phenotypic plasticity in invasive plants is considerable, it is not yet conclusive. We used a meta-analysis approach to evaluate whether invasive plant species show greater phenotypic plasticity than their native or non-invasive counterparts. The outcome of such interspecific comparisons may be biased when phylogenetic relatedness is not taken into account. Consequently, species pairs belonged to the same genus, tribe or family. The meta-analysis included 93 records from 35 studies reporting plastic responses to light, nutrients, water, CO2, herbivory and support availability. Contrary to what is often assumed, overall, phenotypic plasticity was similar between invasive plants and native or non-invasive closely related species. The same result was found when separate analyses were conducted for trait plasticity to nutrients, light and water availability. Thus, invasive plant species and their native or non-invasive counterparts are equally capable of displaying functional responses to environmental heterogeneity. The colonization of a wide range of environments by invasive plants could be due to their capacity to undergo adaptive ecotypic differentiation rather than to their ability to display plastic responses. Alternatively, phenotypic plasticity might play a role in plant invasion, but only during the initial phases, when tolerance of the novel environment is essential for plant survival. Afterwards, once alien plants are identified as invaders, the magnitude of phenotypic plasticity might be reduced after selection of the optimum phenotypes in each habitat. The identification of plant traits that consistently predict invasiveness might be a futile task because different traits favor invasiveness in different environments. Approaches at the local scale, focusing on the ecology of specific invasive plants, could be more fruitful than global macro-analyses. [ABSTRACT FROM AUTHOR]

Background and Aims While the climbing habit allows vines to reach well-lit canopy areas with a minimum investment in support biomass, many of them have to survive under the dim understorey light during certain stages of their life cycle. But, if the growth/survival trade-off widely reported for trees hold for climbing plants, they cannot maximize both light-interception efficiency and shade avoidance (i.e. escaping from the understorey). The seven most important woody climbers occurring in a Chilean temperate evergreen rainforest were studied with the hypothesis that light-capture efficiency of climbers would be positively associated with their abundance in the understorey. Methods Species abundance in the understorey was quantified from their relative frequency and density in field plots, the light environment was quantified by hemispherical photography, the photosynthetic response to light was measured with portable gas-exchange analyser, and the whole shoot light-interception efficiency and carbon gain was estimated with the 3-D computer model Y-plant. Key Results Species differed in specific leaf area, leaf mass fraction, above ground leaf area ratio, light-interception efficiency and potential carbon gain. Abundance of species in the understorey was related to whole shoot features but not to leaf level features such as specific leaf area. Potential carbon gain was inversely related to light-interception efficiency. Mutual shading among leaves within a shoot was very low (<20 %). Conclusions The abundance of climbing plants in this southern rainforest understorey was directly related to their capacity to intercept light efficiently but not to their potential carbon gain. The most abundant climbers in this ecosystem match well with a shade-tolerance syndrome in contrast to the pioneer-like nature of climbers observed in tropical studies. The climbers studied seem to sacrifice high-light searching for coping with the dim understorey light. [ABSTRACT FROM AUTHOR]

The ability to display functional responses to shading, i.e. phenotypic changes that enhance plant performance in low light, is fundamental for plant success in forest communities. Herbivory may constrain plant functional responses to shading and this could explain the often observed lower plant tolerance of herbivore damage in the shade. We carried out a field trial and a greenhouse experiment to evaluate whether simulated herbivory (i) causes greater fitness losses in the shade, and (ii) modifies plant functional responses to shading. Changes in functional traits were measured at the biochemical, leaf, shoot and whole-plant levels, in seedlings of the light-demanding evergreen tree Aristotelia chilensis (Elaeocarpaceae), which is endemic to South American austral forests. We hypothesized that plant responses to shade would be constrained by herbivory due to within-plant limitations in resource availability and/or antagonistic interactions between responses to shade and herbivory. We further expected that this limitation would result in a greater field mortality of damaged plants in forest understory as compared to open sites. Simulated herbivory (50% defoliation) on field seedlings decreased 8-month plant survival in the shade (forest understory) but not in the sun (canopy gaps) in a temperate rainforest. Likewise, simulated herbivory in the greenhouse decreased plant growth rate and final biomass in the shade treatment but not in the sun treatment. The phenotypic responses to shading of seven traits were constrained by simulated herbivory: chlorophyll, leaf shape, leaf blade angle, petiole angle, SLA (specific leaf area), internodes length and total leaf area. A path-analysis showed that most of these constrained responses were uncorrelated to each other. Some of these results might be explained by antagonistic interactions between molecules or pathways involved in plant responses to shading and herbivory. Four functional traits exhibited greater responses to shading in damaged plants: A (Photosynthetic rate), foliar carbon, shoot : root ratio and LMR (leaf mass ratio); but most of them resulted from correlated changes in SLA. The present study undertook a mechanistic approach to the often observed pattern of greater impact of herbivore damage on plant performance in low light environments. The central finding of this study is that the unraveling of herbivory-constrained plant functional responses to shading may explain the often observed greater fitness losses due to herbivory in the shade. It is also suggested that herbivory pressure is an underestimated factor in pioneer species distribution along the light gradient. [ABSTRACT FROM AUTHOR]

Global change drivers create new environmental scenarios and selective pressures, affecting plant species in various interacting ways. Plants respond with changes in phenology, physiology, and reproduction, with consequences for biotic interactions and community composition. We review information on phenotypic plasticity, a primary means by which plants cope with global change scenarios, recommending promising approaches for investigating the evolution of plasticity and describing constraints to its evolution. We discuss the important but largely ignored role of phenotypic plasticity in range shifts and review the extensive literature on invasive species as models of evolutionary change in novel environments. Plasticity can play a role both in the short-term response of plant populations to global change as well as in their long-term fate through the maintenance of genetic variation. In new environmental conditions, plasticity of certain functional traits may be beneficial (i.e., the plastic response is accompanied by a fitness advantage) and thus selected for. Plasticity can also be relevant in the establishment and persistence of plants in novel environments that are crucial for populations at the colonizing edge in range shifts induced by climate change. Experimental studies show taxonomically widespread plastic responses to global change drivers in many functional traits, though there is a lack of empirical support for many theoretical models on the evolution of phenotypic plasticity. Future studies should assess the adaptive value and evolutionary potential of plasticity under complex, realistic global change scenarios. Promising tools include resurrection protocols and artificial selection experiments. [ABSTRACT FROM AUTHOR]

Herbivory and water shortage are key ecological factors affecting plant performance. While plant compensatory responses to herbivory include reallocation of biomass from below-ground to above-ground structures, plant responses to reduced soil moisture involve increased biomass allocation to roots and a reduction in the number and size of leaves. In a greenhouse study we evaluated the effects of experimental drought and leaf damage on biomass allocation in Convolvulus demissus (Convolvulaceae), a perennial herb distributed in central Chile, where it experiences summer drought typical of Mediterranean ecosystems and defoliation by leaf beetles and livestock. The number of leaves and internode length were unaffected by the experimental treatments. The rest of plant traits showed interaction of effects. We detected that drought counteracted some plant responses to damage. Thus, only in the control watering environment was it observed that damaged plants produced more stems, even after correcting for main stem length (index of architecture). In the cases of shoot : root ratio, relative shoot biomass and relative root biomass we found that the damage treatment counteracted plant responses to drought. Thus, while undamaged plants under water shortage showed a significant increase in root relative biomass and a significant reduction in both shoot : root ratio and relative shoot biomass, none of these responses to drought was observed in damaged plants. Total plant biomass increased in response to simulated herbivory, apparently due to greater shoot size, and in response to drought, presumably due to greater root size. However, damaged plants under experimental drought had the same total biomass as control plants. Overall, our results showed counteractive biomass allocation responses to drought and damage in C. demissus. Further research must address the fitness consequences under field conditions of the patterns found. This would be of particular importance because both current and expected climatic trends for central Chile indicate increased aridity. [ABSTRACT FROM AUTHOR]

Differential herbivory and/or differential plant resistance or tolerance in sun and shade environments may influence plant distribution along the light gradient. Embothrium coccineum is one of the few light-demanding tree species in the temperate rainforest of southern South America, and seedlings are frequently attacked by insects and snails. Herbivory may contribute to the exclusion of E. coccineum from the shade if 1) herbivory pressure is greater in the shade, which in turn can result from shade plants being less resistant or from habitat preferences of herbivores, and/or 2) consequences of damage are more detrimental in the shade, i.e., shade plants are less tolerant. We tested this in a field study with naturally established seedlings in treefall gaps (sun) and forest understory (shade) in a temperate rainforest of southern Chile. Seedlings growing in the sun sustained nearly 40% more herbivore damage and displayed half of the specific leaf area than those growing in the shade. A palatability test showed that a generalist snail consumed ten times more leaf area when fed on shade leaves compared to sun leaves, i.e., plant resistance was greater in sun-grown seedlings. Herbivore abundance (total biomass) was two-fold greater in treefall gaps compared to the forest understory. Undamaged seedlings survived better and showed a slightly higher growth rate in the sun. Whereas simulated herbivory in the shade decreased seedling survival and growth by 34% and 19%, respectively, damaged and undamaged seedlings showed similar survival and growth in the sun. Leaf tissue lost to herbivores in the shade appears to be too expensive to replace under the limiting light conditions of forest understory. Following evaluations of herbivore abundance and plant resistance and tolerance in contrasting light environments, we have shown how herbivory on a light-demanding tree species may contribute to its exclusion from shade sites. Thus, in the shaded forest understory, where the seedlings of some tree species are close to their physiological tolerance limit, herbivory could play an important role in plant establishment. [ABSTRACT FROM AUTHOR]

Question: Are vines light-demanding species? Location: Temperate evergreen rain forest of southern Chile (40°39′S, 72°11′W). Methods: In 45 plots of 25 m2 distributed in treefall canopy gaps, secondary forest stands and old-growth forest (15 plots per light environment), all climbing and non-supported vines were counted and identified to species level, and canopy openness was quantified using hemispherical photographs. Vine abundance and diversity (species richness and Simpson's index) were compared in the three light environments and similarity between vine communities was estimated using Jaccard's similarity coefficient. We also determined the relationship between light niche breadth and local dominance at the species level. Results: In total there were 2510 vine individuals of 14 species. Canopy openness was significantly different in the three light environments. Species richness, diversity, community composition and density of vines were similar in treefall gaps, secondary and old-growth forest. Of the seven more common vine species, which accounted for 91% of all vines, three had even distribution, two were more abundant in the shaded understorey, and two had higher density in well-lit sites. Local dominance of vine species and niche breadth were not significantly associated. Conclusions: Our study in a temperate rain forest questions the widespread notion of vines as pioneer-like species, which may be a consequence of the abundance of some lianas in disturbed sites of tropical forests. Functional arguments are needed to justify a general hypothesis on light requirements of vines, which constitute a vast group of species. [ABSTRACT FROM AUTHOR]

Question: In a southern temperate rain forest, we addressed three questions: (1) Does the abundance of climbing plants increase with light availability? (2) Do host tree species differ in their susceptibility to vine infestation? (3) How does the relationship between host tree trunk diameter and relative abundance of vines vary with their climbing mechanism? Location: Two sites in the temperate evergreen rain forest of southern Chile: Puyehue (40°39′S, 72°09′W; 350 m a.s.l.) and Pastahue (42°22′S, 73°49′W; 285 m a.s.l.). Methods: We sampled vines in 60 25-m2 plots, with 20 plots in each of three light environments: mature forest, forest edges and canopy gaps. In each plot, for every tree ≥1.50-m tall of any diameter we counted and identified all climbing plant individuals at a height of 1.30 m. We also counted, measured (trunk diameter at 1.30 m) and identified all these trees, and determined prevalence of vine infestation for each tree species. Results: Light availability in forest plots did not affect vine abundance when the number and size of host trees was taken into account. Overall, vine abundance increased with host tree trunk diameter. Tree species did not differ in the prevalence of vine infestation. The relative abundance of stem twiners and adhesive climbers decreased and increased with trunk diameter, respectively. The densities of stem twiners and adhesive climbers were negatively correlated across the forest. Conclusion: We provide further evidence that the pattern of vine abundance is independent of light availability in southern temperate rain forests, in contrast to results commonly reported for tropical rain forests. We also show that support suitability across the forest varies with the mechanism by which vines climb, probably due in part to biomechanical constraints and in part to vine interspecific competition, a virtually unexplored ecological factor. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity is essential for plant adaptation to changing environments but some factors limit its expression, causing plants to fail in producing the best phenotype for a given environment. Phenotypic integration refers to the pattern and magnitude of character correlations and it might play a role as an internal constraint to phenotypic plasticity. We tested the hypothesis that phenotypic integration – estimated as the number of significant phenotypic correlations between traits – constrains phenotypic plasticity of plants. The rationale is that, for any phenotypic trait, the more linked with other traits it is, the more limited is its range of variation. In the perennial species Convolvulus chilensis (Convolvulaceae) and Lippia alba (Verbenaceae) we determined the relationship between phenotypic plasticity to relevant environmental factors – shading for C. chilensis and drought for L. alba– and the magnitude of phenotypic integration of morphological and biomass allocation traits. In C. chilensis plants, plasticity to shading of a given trait decreased with the number of significant correlations that it had with the other traits. Likewise, the characters that showed greater plasticity to experimental drought in L. alba plants had fewer significant phenotypic correlations with other characters. We report a novel limit to phenotypic plasticity of plants by showing that the phenotypic trait architecture may constrain their plastic, functional responses to the environment. [ABSTRACT FROM AUTHOR]

Abstract: Mediterranean-type ecosystems are increasingly prone to drought stress. Herbivory might limit plant functional responses to water shortage. This may occur as a result of plant resource depletion or due to the fact that leaf damage and drought may elicit opposite phenotypic responses. We evaluated the impact of herbivory on plant fitness in the field, and the effects of leaf damage on phenotypic plasticity to reduced soil moisture in a greenhouse. The study species was Convolvulus demissus, a perennial herb endemic to central Chile, which has a Mediterranean-type climate. Controlled herbivory by chrysomelid beetles (natural herbivores) in the field had a negative impact on plant fitness, estimated as number of fruits. Whereas reduced soil moisture alone did not affect seedling survival, damaged seedlings (simulated herbivory) had greater mortality when growing under water shortage. The hypothesis that herbivory would constrain phenotypic plasticity was supported by significant statistical interactions between leaf damage and soil moisture, followed by inspections of reaction norms. This was verified both overall (all phenotypic traits taken together, MANOVA) and in four of the six traits evaluated (ANOVAs). When plants were damaged, the reaction norms in response to low soil moisture of water use efficiency, root:shoot ratio and xylem water potential showed reduced slopes. While undamaged plants increased root biomass in response to low moisture, the opposite trend was found for damaged plants. The simultaneous occurrence of herbivory and drought events might curtail recruitment in plant populations of central Chile and other Mediterranean-type ecosystems due to the inability of damaged seedlings to show functional responses to low soil moisture. This finding is of ecological significance in view of current and projected trends of increased aridity in these ecosystems. [Copyright &y& Elsevier]

Abstract: Resource availability may limit plant tolerance of herbivory. To predict the effect of differential resource availability on plant tolerance, the limiting resource model (LRM) considers which resource limits plant fitness and which resource is mostly affected by herbivore damage. We tested the effect of experimental drought on tolerance of leaf damage in Ipomoea purpurea, which is naturally exposed to both leaf damage and summer drought. To seek mechanistic explanations, we also measured several morphological, allocation and gas exchange traits. In this case, LRM predicts that tolerance would be the same in both water treatments. Plants were assigned to a combination of two water treatments (control and low water) and two damage treatments (50% defoliation and undamaged). Plants showed tolerance of leaf damage, i.e., a similar number of fruits were produced by damaged and undamaged plants, only in control water. Whereas experimental drought affected all plant traits, leaf damage caused plants to show a greater leaf trichome density and reduced shoot biomass, but only in low water. It is suggested that the reduced fitness (number of fruits) of damaged plants in low water was mediated by the differential reduction of shoot biomass, because the number of fruits per shoot biomass was similar in damaged and undamaged plants. Alternative but less likely explanations include the opposing direction of functional responses to drought and defoliation, and resource costs of the damage-induced leaf trichome density. Our results somewhat challenge the LRM predictions, but further research including field experiments is needed to validate some of the preliminary conclusions drawn. [Copyright &y& Elsevier]

Small-scale disturbances caused by animals often modify soil resource availability and may also affect plant attributes. Changes in the phenotype of plants growing on disturbed, nutrient-enriched microsites may influence the distribution and abundance of associated insects. We evaluated how the high nutrient availability generated by leaf-cutting ant nests in a Patagonian desert steppe may spread along the trophic chain, affecting the phenotype of two thistle species, the abundance of a specialist aphid and the composition of the associated assemblage of tending ants. Plants of the thistle species Carduus nutans and Onopordum acanthium growing in piles of waste material generated by leaf-cutting ant nests (i.e., refuse dumps) had more leaves, inflorescences and higher foliar nitrogen content than those in non-nest soils. Overall, plants in refuse dumps showed higher abundance of aphids than plants in non-nest soils, and aphid colonies were of greater size on O. acanthium plants than on C. nutans plants. However, only C. nutans plants showed an increase in aphid abundance when growing on refuse dumps. This resulted in a similar aphid load in both thistle species when growing on refuse dumps. Accordingly, only C. nutans showed an increase in the number of ant species attending aphids when growing on refuse dumps. The increase of soil fertility generated by leaf-cutting ant nests can affect aphid abundance and their tending ant assemblage through its effect on plant size and quality. However, the propagation of small-scale soil disturbances through the trophic chain may depend on the identity of the species involved. [ABSTRACT FROM AUTHOR]

Optimal defence theory (ODT) predicts that, whereas high risk of herbivory should select for high constitutive levels of defence, induced defences should be more advantageous in environments with a low probability of herbivory. In the present field study, conducted on the Azteca– Cecropia ant–plant system in a Neotropical rainforest, we evaluated whether the constitutive and induced ant defence of leaves are directly and inversely related to an estimate of herbivory risk, respectively. To assess the constitutive level of Azteca defence in Cecropia obtusifolia trees, we recorded the number of ants patrolling undamaged leaves. To evaluate the induced level of Azteca defence, the same leaves were subjected to simulated herbivory by punching circular holes in them. We recorded the maximum number of ants patrolling the damaged leaves from 2 to 15 min after damage. Past herbivory (% defoliation of old leaves) was assumed to indicate a risk of herbivory. Regression analyses showed that, whereas the constitutive level of ant patrolling was positively associated with the magnitude of herbivory on old leaves, there was a negative association between the magnitude of induced ant defence and past herbivory. These preliminary results lend support to ODT. [ABSTRACT FROM AUTHOR]

1. Associational resistance occurs when one plant species gains protection from its consumers by association with a defended species. In semi-arid ecosystems of Chile, the perennial herb Convolvulus chilensis (Convolvulaceae) suffers heavy herbivory by small mammals when growing prostrate but plants seem to be protected when they are climbing onto cacti or thorny shrubs (nurse species). 2. Field observations suggest that damaged main stems have a greater number of small lateral stems, which greatly enhance climbing success. In this field study we addressed whether C. chilensis shows associational resistance by climbing onto nurse species, and evaluated whether damage and also shade (a cue for neighbour presence) elicit architectural responses that enhance climbing probability. 3. We documented associational resistance for C. chilensis: climbing individuals growing associated with cacti and thorny shrubs suffered less herbivory (percentage of damaged stems: 35 vs. 98) and had greater reproductive output (number of reproductive structures at the end of the season: 150 vs. 0) than prostrate individuals growing in isolation. Experimental clipping of the main stem caused plants to produce a greater number of lateral stems both in sun (70% increase) and in shade (66% increase) treatments. Moreover, stem damage caused a 50% increase in the number of stems actually climbing on a support, but only in shade. 4. Synthesis. We show for the first time that phenotypic responses to herbivory of the potentially protected species may enhance association with the defended nurse species, thereby promoting associational resistance. This finding adds a new perspective for mechanistic studies of positive interactions among plants, suggesting that behavioural responses of the protégée may mediate the magnitude of nurse effects. [ABSTRACT FROM AUTHOR]

Contents Phenotypic plasticity is considered the major means by which plants cope with environmental heterogeneity. Although ubiquitous in nature, actual phenotypic plasticity is far from being maximal. This has been explained by the existence of internal limits to its expression. However, phenotypic plasticity takes place within an ecological context and plants are generally exposed to multifactor environments and to simultaneous interactions with many species. These external, ecological factors may limit phenotypic plasticity or curtail its adaptive value, but seldom have they been considered because limits to plasticity have typically addressed factors internal to the plant. We show that plastic responses to abiotic factors are reduced under situations of conservative resource use in stressful and unpredictable habitats, and that extreme levels in a given abiotic factor can negatively influence plastic responses to another factor. We illustrate how herbivory may limit plant phenotypic plasticity because damaged plants can only rarely attain the optimal phenotype in the challenging environment. Finally, it is examined how phenotypic changes involved in trait-mediated interactions can entail costs for the plant in further interactions with other species in the community. Ecological limits to plasticity must be included in any realistic approach to understand the evolution of plasticity in complex environments and to predict plant responses to global change. [ABSTRACT FROM AUTHOR]

Despite important advances in ecological knowledge of Mediterranean-type ecosystems, advances in restoration ecology have not seen a parallel increase in these systems. Although some concepts such as positive plant–plant interaction (facilitation) have received attention in the restoration ecology community, others such as phenotypic plasticity have not. Some concepts (e.g., environmental heterogeneity) are mature enough for a wide use in restoration, whereas available knowledge on others (e.g., facilitation, plasticity) is less conclusive. However, the scientific knowledge is in general enough to significantly improve the guidelines for restoration of Mediterranean ecosystems. Our review suggests that (1) the extent of facilitation in dry ecosystems is partially understood, with supporting, but somewhat contradictory empirical evidence for its potential use in restoration; (2) the influence of habitat heterogeneity on plant performance and plasticity is only beginning to be understood, with a strong bias toward patterns of structural heterogeneity and negligible information on functional heterogeneity; and (3) sound evaluations of phenotypic plasticity might be useful to increase the success of restoration practices in patchy Mediterranean environments. Future global change scenarios involving temperature rise, reduced precipitation, increased frequency of extreme climatic events, and important land use changes and fragmentation must be particularly considered when restoring Mediterranean ecosystems. Further research on how to incorporate results on facilitation, environmental heterogeneity, and plasticity within a global change framework is clearly needed. [ABSTRACT FROM AUTHOR]

Abstract: Tolerance to damage allows plants to endure herbivory without major fitness consequences and may be associated with changes in plant morphology. We evaluated in a greenhouse experiment the tolerance to damage (clipping of 25% of aboveground biomass) and phenotypic changes after damage in plants from two populations of the endemic Chilean species Convolvulus chilensis (Convolvulaceae). The populations differ, among several environmental features, in the type of damage experienced by plants: clipping by humans vs. mammal herbivory. We also evaluated whether the effect of damage in plants is affected by light availability. Both populations were equally tolerant to damage in terms of survival and plant growth, and tolerance was not different under sun and shade. Damage significantly affected plant architecture (an increase in number of stems/plant height), and there was no differential effect of damage according to population of origin. The light environment did not influence the effect of damage on plant architecture. The latter finding contrasts with similar work on other species and might be related to the reported remarkable ability of C. chilensis to cope with shading conditions. Results preliminary suggest that the occurrence of tolerance in C. chilensis might be a generalized response to repeated damage regardless of the particular type of damage. [Copyright &y& Elsevier]

We studied the effect of larval host (two Convolvulus L. species, Convolvulaceae) on sexual size dimorphism and on the fitness consequences of adult feeding in the bruchid beetle Megacerus eulophus (Erichson) (Coleoptera: Bruchidae). Whereas Convolvulus chilensis Pers. occurs in low density in semiarid habitats, Convolvulus bonariensis Cav. occurs in less stressful environments and exhibits higher population density. Host plants neither differ in seed mass nor in seed nitrogen content, and there were no consistent host-associated differences in female fitness. Consequently, host quality was considered to be similar. Sexual size dimorphism, expressed as the female:male ratio of body size, was significantly greater in C. chilensis than in C. bonariensis. A greater female size in the C. chilensis population could be selectively advantageous due to higher survival during host-plant search in stressful environments. Female longevity was affected by food availability (starvation vs. honey-pollen solution) and by the interaction between food availability and larval host. Fed females lived longer than starved females. This trend was found in both hosts, but it was of greater magnitude in C. chilensis than in C. bonariensis. Fecundity was significantly affected by adult feeding and larval host, and marginally affected by their interaction. Fed females laid more eggs than starved females. However, the increase in fitness of fed females was greater in C. chilensis. Results might be explained by differential selection on plasticity in life-history traits in contrasting environments. Females in stressful environments should take a greater advantage of the transient availability of resources. [ABSTRACT FROM AUTHOR]

In the Urubamba Valley, Peruvian Andes, we evaluated the abundance of insect pests and natural enemies in experimental plots where maize was grown either as monoculture, intercropped with beans, or intercropped with beans plus associated weeds. We also assessed the consequences of the cropping system for maize yield. The main insect pests recorded were Diabrotica spp. (Coleoptera: Chrysomelidae), Carpophilus sp. (Coleoptera: Nitidulidae) and Pagiocerus frontalis (Coleoptera: Scolytidae), and their overall abundance did not differ among crop diversity treatments. However, there was a significant adverse effect of crop diversity on the maximum abundance of both Carpophilus and Pagiocerus. The main beneficial arthropods were Paratriphleps sp. (Hemiptera: Anthocoridae), ladybirds and spiders, and their density did not differ among treatments. Maize yield did not decrease with increasing plant diversity. The reported benefits of intercropping, together with the associated efficiency in land use, make this traditional agricultural practice a valuable alternative to the use of pesticides, particularly for resource-poor Andean farmers. [ABSTRACT FROM AUTHOR]

• Successful climbing by vines not only prevents shading by neighbouring vegetation, but also may place the vines beyond ground herbivores. Here we tested the hypothesis that herbivory might enhance climbing in a vine species, and that such induced climbing should be greater in the shade. • We assessed field herbivory in climbing and prostrate ramets of the twining vine Convolvulus arvensis. We evaluated plant climbing after mechanical damage in a glasshouse under both sun and shade conditions, and determined whether control and damaged plants differed in growth rate or photosynthetic capacity. • Plants experienced greater herbivory when growing prostrate than when climbing onto companion plants, in both an open habitat and a shaded understorey. Experimental plants increased their twining rate on a stake after suffering leaf damage, in both high- and low-light conditions, and this induced climbing was not coupled to an increase in growth rate. Increased photosynthesis was associated with enhanced twining rate only in the shade. • Herbivory may be an ecological factor promoting the evolution of a climbing habit in plants. New Phytologist (2005) doi: 10.1111/j.1469-8137.2005.01484.x © New Phytologist (2005) [ABSTRACT FROM AUTHOR]

We evaluated in common-garden experiments the morphological plasticity to shading of three Convolvulus species that occur in Chile and differ in ecological breadth. Convolvulus arvensis L. is a world weed distributed along the country, and is found in open as well as in shaded habitats. Convolvulus chilensis Pers. is a Chilean endemic species typical of coastal habitats, and is found in open to partially open sites. C. demissus choisy occurs only on slopes of the Andes of Chile and Argentina, habitats with high incidence of solar radiation. We hypothesized that the magnitude of phenotypic plasticity to shading of these species would correlate with their ecological breadth. Shading had a significant effect on internode length, petiole length, stem diameter, stem length, number of branches, leaf area, leaf shape, leaf biomass, and specific leaf area. Species differed in all the morphological traits except leaf biomass. A significant Shading × Species interaction in the two-way ANOVA, i.e. differential plasticity to shading of Convolvulus species, was found for petiole length, stem length, number of branches, leaf shape, and specific leaf area. Contrary to our hypothesis, tests of parallelism showed that, in general, the plasticity to shading of C. chilensis (the species of intermediate ecological breadth) was the greatest, and that of C. arvensis (the weed) and C. demissus (the species of narrow distribution) was similar. Issues of ecotype differentiation, in the case of C. arvensis, and the role of life history traits are raised to explain the observed lack of association between ecological breadth and magnitude of phenotypic plasticity. [Copyright &y& Elsevier]

Ecological theory predicts that a generalist strategy should be more favored in changing environments than in stable environments. I tested whether phenotypic plasticity is greater in plants from a temporally heterogeneous habitat than in plants from a more homogeneous habitat. In addition, I evaluated whether the environmental heterogeneity of the original habitat influences the relationship between environmental stress and phenotypic integration, i.e., the degree of correlation among phenotypic traits. The perennial weed Convolvulus arvensis L. was used as a model species. Plants were collected in agrestal (oat field) and ruderal (wasteland) populations located in the same area of central Chile. In situ measurements during the growing season determined that the agrestal habitat was heterogeneous and the ruderal habitat homogeneous for soil moisture, but both habitats were heterogeneous for light intensity. Phenotypic plasticity to light and moisture was evaluated in a common garden, with two light levels (100% and 20% full sunlight) and two moisture treatments (control and low watering). Although the magnitude of phenotypic plasticity to light was very similar in plants coming from the agrestal and ruderal habitats, plastic response to moisture was greater in plants from the agrestal habitat. These results agree with the determination of habitat temporal heterogeneity for light and moisture availability, and hence support the tenet of predominance of a generalist strategy in changing environments. A positive relationship between environmental stress and phenotypic integration was verified. This relationship was stronger in plants from the ruderal habitat. These results contribute to the elucidation of the ecological significance of phenotypic integration in plants. [ABSTRACT FROM AUTHOR]

The preference-performance hypothesis predicts that insect preference should correspond to host suitability for offspring development. We studied the pattern of within-plant preference in the aphid Sipha flava and its consequences for offspring performance on the host-plant Sorghum halepense, regarding the role of induced responses of plants to aphid feeding. The consequences of within-plant preference on aphid population growth and host-plant traits were also evaluated. Our results showed that winged and wingless aphids preferred to settle on mature rather than young leaves. In contrast, aphid individual growth rate was higher on young leaves when compared with mature leaves, suggesting that the outcome of this test rejected the preference-performance hypothesis. However, the inclusion of the factor ‘previous aphid infestation’ changed the outcome from a maladaptive choice to a neutral one. Thus, individual growth rates of S. flava increased when aphids developed on leaves that had been previously infested. Interestingly, aphid growth rate on previously infested leaves did not differ between young and mature leaves. On the other hand, aphid population reproductive rate was higher and the percentage of winged aphids lower when infestation occurred on mature rather than young leaves. Aphid infestation reduced plant and shoot biomass, and increased leaf mortality. These negative effects on plant traits related to plant fitness were greater when aphid infestation occurred on young leaves. Likewise, whereas infestation on mature leaves did not cause a significant reduction in the number of flowering plants compared with control plants, aphid infestation on young leaves did reduce the number of plants at the flowering stage. Consequently, if both the reproductive rate of aphids in the mid-term, and host-plant fitness are taken into account, the results indicate that aphid preference for mature leaves may be an adaptive choice, thus supporting the preference-performance hypothesis. [ABSTRACT FROM AUTHOR]

The presence of physical support elicits a number of morphological changes in the shoot of the common morning glory Ipomoea purpurea, including a shortening of internodes and petioles and a thickening of the main stem. Working with experimentally supported and non-supported plants of I. purpurea, I tested the existence of maternal environmental effects of physical support in this twining vine. I evaluated whether the offspring of supported plants differed from the offspring of non-supported plants in a number of morphological and reproductive characters. Stem diameter was the only shoot trait that showed a significant effect of the maternal environment (support). The stems of the progeny of supported mother plants were thicker than the steins of the progeny of non-supported mother plants. This was true for both supported and non-supported progeny. Stem diameter, however, was not significantly related to plant fitness (seed number) in supported or non-supported progeny plants. The maternaI environment did not affect the magnitude of the phenotypic responses to support of shoot traits in the progeny plants. There were no maternal environmental effects of physical support on the proportion of flowering plants at week 10 in both non-supported and supported progeny. Likewise, the presence of physical support in the maternal environment did not affect reproductive traits (seed number, seed size, percentage of reproductive biomass in supported and non-supported progeny plants. Finally, the relationship between seed size and seed number was affected by the maternal support environment. The progeny of supported mother plants showed a significantly negative association (trade-off) between seed size and number, whereas such a trade-off was not observed in the progeny of non-supported plants. This was true for both supported and non-supported progeny. [ABSTRACT FROM AUTHOR]

It has been postulated that the plasticity to shading of spacing organs in plants of different growth habit is more likely related to the analogy of organs than to their homology. Accordingly, vertical spacers (internodes in erect species, petioles in prostrate species) should be more plastic than horizontal spacers (petioles in erect species, internodes in prostrate species). This hypothesis was tested in the climbing plant Convolvulus arvensis. Given their facultative erect or prostrate habit, depending on support availability, climbing plants may be model species to test the relationship between growth habit and spacer plasticity in the absence of the confounding factors that are typical of interspecific comparisons. The phenotypic correlations among traits were also addressed. Three shading treatments (100%, 20%, and 5% of sunlight) and two support conditions (with and without a stake on which plants could twine) provided the experimental setting. Traits evaluated included internode length, petiole length, stem thickness, and biomass as well as area, shape, and specific area of leaves. The hypothesis was not supported. Internodes were more plastic than petioles in supported ("erect") as well as in nonsupported ("prostrate") plants, thereby supporting homology, and not analogy, of organs as a factor in explaining plasticity patterns. Most traits were significantly correlated both in supported and nonsupported plants. Internode and petiole length showed a highly significant positive correlation. This is discussed, and trait correlations are considered as possible constraints on the expected pattern of differential spacer plasticity to shading. [ABSTRACT FROM AUTHOR]

Summary 1 Colonies of the aphid Rhopalosiphum maidis on Johnsongrass, Sorghum halepense, usually occur inside the whorl. The present work assessed the role of two biotic factors, plant quality and parasitism by Lysiphlebus testaceipes, in determining within-plant distribution and performance of R. maidis. The mean relative growth rate of aphids inside the whorl and on a mature leaf was compared, and the concentration of hydroxamic acids in those tissues determined as an indicator of plant quality. Parasitism effectiveness and parasitoid behaviour were evaluated using three treatments: aphid colonies placed (1) wholly inside the whorl, (2) on the inner and outer surfaces of the whorl, and (3) on a mature leaf. 2 The mean relative growth rate of aphids was lower on the whorl than on the mature leaf, and hydroxamic acid concentration in the whorl was higher than in the mature leaf. 3 The number of parasitized dead aphids (mummies) inside the whorl was considerably lower than in the other two treatments. Mummies were present in 80% of the replicates in the whorl, whereas mummies were present in all replicates of the other treatments. 4 Host location time of the parasitoid was increased on the mature leaf compared with the other treatments. No significant differences in the residence time of the parasitoid in the aphid colony occurred between treatments. 5 Host location time showed a negative correlation, and residence time of the parasitoid a positive correlation with the number of aphids on the outer surface of the whorl. [ABSTRACT FROM AUTHOR]

Plasticity of leaf traits of Solanum incanum was evaluated by comparing its expression in three sites differing in soil moisture (dry, intermediate, humid) in Nguruman, SW Kenya. Leaf size and shape, and leaf traits related to defence against herbivores, varied significantly among sites. The relationship between leaf traits showing among-site variation and insect herbivory was evaluated at a within-site scale. Leaf thickness was correlated with the level of foliar herbivory by a flea beetle (Epitrix sp.). This correlation was negative at the dry site and positive at the humid site. No relationship was found at the intermediate site. Interestingly, leaf thickness and toughness were positively and significantly correlated at the dry site, but not elsewhere. Finally, overall patterns of herbivory by the flea beetle and unidentified defoliators differed among sites. The importance of scale when evaluating plant plasticity is discussed. [ABSTRACT FROM AUTHOR]

Group living in gregarious caterpillars may shorten the larval stage, which is thought to reduce predation exposure. In the gregarious caterpillar Battus polydamas archidamas (Papilionidae) we addressed the effects of simulated predation threat on the duration of the larval stage in solitary and gregarious caterpillars. We further evaluated the consequences of group rearing and predation stimuli for pupal mass.We reared caterpillars singly and in groups of ten individuals. Caterpillars were subjected to simulated predation threats (prodding with a paintbrush) and control larvae were untouched. We determined larval stage duration and pupal mass. We also recorded in solitary and gregarious caterpillars the proportion of individuals reacting to predation threats with distinct behavioural responses.Caterpillars in the group completed larval development earlier than solitary caterpillars. This pattern of accelerated development was already evident in the first instar. Simulated predation reduced the duration of both the entire larval stage and the first instar, but only for caterpillars in the group. Pupal mass was not affected by the predation treatment in either solitary or gregarious caterpillars. Solitary caterpillars showed thrashing and osmeterium display + thrashing more frequently than gregarious caterpillars, while individuals in the group reacted with osmeterium display to a greater extent.Accelerated larval development in response to predation risk has been predicted by theoretical models, but–to our knowledge–this is the first report on gregarious caterpillars. This putative adaptive response did not entail a fitness cost in terms of pupal mass. [ABSTRACT FROM AUTHOR]

We analyze the publication output of 119 Chilean ecologists and find strong evidence that self-citations significantly affect the h-index increase. Furthermore, we show that the relationship between the increase in the h-index and the proportion of self-citations differs between high and low h-index researchers. In particular, our results show that it is in the low h-index group where self-citations cause the greater impact. [ABSTRACT FROM AUTHOR]

Solar activity has a significant influence on Earth's climate and may drive many biological processes. Here, we measured growth in 11 tree species distributed along an ≈600‐km latitudinal gradient in South‐Central Chile, recording the width of their growth‐rings among periods of maximum (highest number of sunspots) and minimum (lowest number of sunspots) solar activity. In one of these species, Quillaja saponaria, we experimentally assessed three ecophysiological traits (CO2 fixation through photosynthesis [Amax], growth and leaf production) as well as the expression of five genes related to cell wall elongation and expansion following exposure to high and low levels of UV‐B radiation, simulating scenarios of maximum and minimum solar activity, respectively. We found lower tree growth during the periods of maximum solar activity, with this trend being more evident at lower latitudes, where UV‐B radiation is higher. Exposure of Q. saponaria to higher levels of UV‐B affected the ecophysiological parameters, revealing a decrease in Amax, growth and leaf production. In addition, higher levels of UV‐B led to repression in four of the five genes studied. Our results may help foresee environmental scenarios for different plant species associated with solar activity. [ABSTRACT FROM AUTHOR]