[Show abstract][Hide abstract] ABSTRACT: Ant-aphid relationships provide excellent opportunities to study how changes in resource availability may affect the outcome of competitive interactions. Variations in soil fertility may affect host plant quality, with concomitant effects on aphid abundance and the amount/quality of aphid honeydew. This may determine the intensity at which tending ants defend aphids against natural enemies and competing ants. In a shrub-steppe of northern Patagonia, aphid-infested thistles naturally grow on contrasting fertility substrates: organic waste piles of leaf-cutting ants (refuse dumps) and nutrient-poor steppe soils. Thistles growing on refuse dumps have much larger aphid colonies than thistles growing on steppe soils. We took advantage of the co-occurrence in the field of plants with contrasting aphid density to study the effect of natural variation in food availability (aphid density) on aphid-tending ant species richness and agonistic interactions among them. Enhanced aphid density did not promote the coexistence of aphid-tending ant species. Although all ant species are potential colonizers of the study plants, thistles were often monopolized by a single ant species, regardless of aphid density. Field experiments showed that increased aphid density did not modify aggressiveness toward an intruder ant, nor the probability of coexistence between two rival ant species after the invasion of a host plant. We discuss several hypotheses to explain why increased resource availability does not necessarily reduce competitive interactions in ant-aphid relationships.
[Show abstract][Hide abstract] ABSTRACT: AimTo develop an integrative framework to evaluate variation in aboveground carbon storage (AGC). A model that can be applied to understand and predict how global-change drivers influence tropical carbon sinks.LocationOld-growth tropical forests world-wide.Methods
Using structural equation modelling (SEM), we propose an a priori model to evaluate the direct and indirect effects of climate, stand variables (basal area, tree diameter and wood density at plot level) and liana abundance on AGC. Our model indicated that stand variables increased AGC while liana abundance decreased AGC indirectly via negative effects on stand variables. We used a multigroup SEM to test the generality of our framework using a standardized dataset of 145 plots (0.1 ha) in dry, moist and wet tropical forests.ResultsOur model explained over 85% variation in AGC and showed a positive and consistent relationship between stand variables and AGC across forests types. The effects of climate on AGC were indirect rather than direct, with negative effects of temperature in all forests. Liana abundance reduced tree diameter and basal area in moist forests, but did not affect AGC in wet or dry forests.Main conclusionsOur results suggest that climate affects AGC indirectly, via its direct influence on stand variables and liana abundance. The effects of lianas on AGC result from reductions in stand variables and are as important as climate for moist forests, which harbour the greatest tropical carbon pools. Our model was consistent across forest types. This highlights the usefulness of an integrative framework to improve predictions of the effects of drivers of global change on tropical carbon sinks.
Global Ecology and Biogeography 04/2015; 24(8). DOI:10.1111/geb.12304 · 7.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: One of the central questions in evolutionary ecology is how different functional capacities impact fitness, and how it varies across populations. For instance, do phenotypic attributes influence fitness similarly across geographic gradients? Which traits (physiological, morphological and life history) are most likely to be targets of natural selection? Do particular combinations of traits maximize fitness? In a semi-natural experiment, we analysed introduced populations of an invasive species, the garden snail (Cornu aspersum) in Chile, which show low levels of genetic differentiation in spite of the distance. Specifically, we addressed whether the magnitude, sign and form of selection in snail populations could explain the differentiation (or its absence) among populations. A common garden/reciprocal transplant experiment was performed in three populations (La Serena, Constitución and Valdivia) that span a 1300-km latitudinal gradient and differ markedly in climate (semi-arid north to humid south). We released c. 450 individuals per population (two generations after field-captured snails) in replicated enclosures at the range extremes (La Serena and Valdivia). Morphological (size and shell darkness), physiological (standard metabolic rate and digestive efficiency) and life-history [growth rate (GR)] traits were measured in all snails before the release. Survival was recorded monthly during 1 year. Survival was significantly higher in snails from La Serena than in snails from Constitución and Valdivia, when raised at La Serena. However, at Valdivia, survival was not different among source populations. Interestingly, we found negative correlational selection in MB and SMRR at La Serena, whereas at Valdivia we only found directional selection on GR and MB, and stabilizing selection on SMRR. These results suggest that selection on physiological traits related with energy allocation is pervasive, irrespective of climate and distance.
[Show abstract][Hide abstract] ABSTRACT: Climbing plants require an external support to grow vertically and enhance light acquisition. Vines that find a suitable support have greater performance and fitness than those that remain prostrate. Therefore, the location of a suitable support is a key process in the life history of climbing plants. Numerous studies on climbing plant behaviour have elucidated mechanistic details of support searching and attachment. Much fewer studies have addressed the ecological significance of support finding behaviour and the factors that affect it. Without this knowledge, little progress can be made in the understanding of the evolution of support finding behaviour in climbers. I review studies addressing ecological causes and consequences of support finding and use by climbing plants. I also propose the use of behavioural ecology theoretical frameworks to study climbing plant behaviour. I show how host tree attributes may determine the probability of successful colonization for the different types of climbers, and examine the evidence of environmental and genetic control of circumnutation behaviour and phenotypic responses to support availability. Cases of oriented vine growth towards supports are highlighted. I discuss functional responses of vines to the interplay between herbivory and support availability under different abiotic environments, illustrating with one study case how results comply with a theoretical framework of behavioural ecology originally conceived for animals. I conclude stressing that climbing plants are suitable study subjects for the application of behavioural-ecological theory. Further research under this framework should aim at characterizing the different stages of the support finding process in terms of their fit with the different climbing modes and environmental settings. In particular, cost-benefit analysis of climbing plant behaviour should be helpful to infer the selective pressures that have operated to shape current climber ecological communities.
Published by Oxford University Press on behalf of the Annals of Botany Company.
[Show abstract][Hide abstract] ABSTRACT: 1.Interannual variability in climatic conditions should be taken into account in climate change studies in semiarid ecosystems. It may determine differentiation in phenotypic plasticity among populations, with populations experiencing higher environmental heterogeneity showing higher levels of plasticity.2.The ability of populations to evolve key functional traits and plasticity may determine the survival of plant populations under the drier and more variable climate expected for semiarid ecosystems.3.Working with populations of the semiarid Chilean shrub Senna candolleana along its entire distribution range, we assessed inter- and intra-population variation in functional traits as well as in their plasticity in response to water availability. We measured morphological and physiological traits related to drought resistance in both field conditions and in a greenhouse experiment, where drought response was evaluated under two water availability treatments.4.All populations responded plastically, but higher precipitation heterogeneity in dry-edge populations seemed to have selected for more plastic genotypes compared to populations growing at mesic sites and with more homogeneous environmental conditions.5.Synthesis: Our results suggest adaptive plasticity since higher levels of phenotypic plasticity were positively associated with plant performance. However, we did not find evidence for genetic variation for plasticity within populations. To the extent that phenotypic plasticity may play a key role in future persistence, populations at mesic sites may be more vulnerable to climate change due to their lower plasticity and their current limitations to evolve novel norms of reaction. Conversely, although Senna candolleana populations at the dry-edge are exposed to higher levels of stress, they may be less susceptible to climate change in view of their greater plasticity. We highlight the need to consider population differentiation in both mean traits and their plasticity to model realistic scenarios of species distribution under climate change.This article is protected by copyright. All rights reserved.
Journal of Ecology 02/2015; 103(2). DOI:10.1111/1365-2745.12372 · 5.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Dispersal is a major determinant of connectivity between communities that may modulate the importance of environmental and spatial processes on taxonomic composition. While wind is likely to influence transport distance, rate and direction for numerous species, its effects on community composition remain poorly understood.Using eigenvector-based spatial analyses, we investigated the influence of wind flows, estimated by mesoscale models, on the spatial structure of benthic macroinvertebrate assemblages with contrasting flying abilities in high Andean wetlands (26–32°S). We further quantified the relative importance of local and regional processes through a variation partitioning approach.The influence of environmental heterogeneity was prevalent and of relatively similar amplitude in both flying and non-flying assemblages. Significant spatial structure more strongly driven by wind flows than by Euclidean schemes was detected for both assemblages. As expected, the highest levels of spatial structure were observed for the flying macroinvertebrate assemblage and they occurred at a much larger spatial scale in this group, suggesting a greater dispersal aptitude of the flying taxa.Our results show that environmental effects are predominant in shaping the spatial structure of macroinvertebrate communities in high Andean wetlands, as generally found in other systems. They also demonstrate the significance of wind flows in regulating high-altitude wetland macroinvertebrate communities and illustrate the importance of considering adequate spatial models and biological characteristics of species to advance our understanding of community patterns.
[Show abstract][Hide abstract] ABSTRACT: This chapter discusses the evolutionary relevance of climbing plants from several lines of evidence based on bibliographic surveys, meta-analyses of published literature, and population genetics data. First, it provides an updated assessment of the prevalence and taxonomic distribution of climbing plant species, showing that over one-third of all seed plant families and three-quarters of all dicot orders have climbers. Next, the chapter discusses whether there is an association between specialized climbing mechanisms and species richness within families. It addresses whether the climbing habit is an evolutionary key innovation that has allowed climbing clades to become more species-rich than their non-climbing sister groups. The chapter further compares population differentiation in climbing vs. non-climbing species in temperate forests of southern South America and shows that temperate climbers have higher levels of genetic differentiation among populations than do non-climbers.
Ecology of Lianas, 10/2014: pages 239-250; , ISBN: 9781118392492
[Show abstract][Hide abstract] ABSTRACT: The effects of disturbance on diversity depend on the environmental conditions. Here, we assessed the role of natural disturbance by an endemic fossorial rodent (Spalacopus cyanus) on plant invasions and its consequence on ecological and phylogenetic community structure in an arid ecosystem. Exotic taxa tend to be associated with disturbed sites, affecting species composition and phylogenetic structure.
[Show abstract][Hide abstract] ABSTRACT: Species are the unit of analysis in many global change and conservation biology studies; however, species are not uniform entities but are composed of different, sometimes locally adapted, populations differing in plasticity. We examined how intraspecific variation in thermal niches and phenotypic plasticity will affect species distributions in a warming climate. We first developed a conceptual model linking plasticity and niche breadth, providing five alternative intraspecific scenarios that are consistent with existing literature. Secondly, we used ecological niche-modeling techniques to quantify the impact of each intraspecific scenario on the distribution of a virtual species across a geographically realistic setting. Finally, we performed an analogous modeling exercise using real data on the climatic niches of different tree provenances. We show that when population differentiation is accounted for and dispersal is restricted, forecasts of species range shifts under climate change are even more pessimistic than those using the conventional assumption of homogeneously high plasticity across a species' range. Suitable population-level data are not available for most species so identifying general patterns of population differentiation could fill this gap. However, the literature review revealed contrasting patterns among species, urging greater levels of integration among empirical, modeling and theoretical research on intraspecific phenotypic variation.
[Show abstract][Hide abstract] ABSTRACT: The knowledge derived from Antarctic ecology may be fundamental to 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.
[Show abstract][Hide abstract] ABSTRACT: The climbing habit is an evolutionary key innovation in plants because it is associated with enhanced clade diversification. We tested whether patterns of species divergence and variation of three ecophysiological traits that are fundamental for plant adaptation to light environments (maximum photosynthetic rate [Amax], dark respiration rate [Rd], and specific leaf area [SLA]) are consistent with this key innovation. Using data reported from four tropical forests and three temperate forests, we compared phylogenetic distance among species as well as the evolutionary rate, phylogenetic distance and phylogenetic signal of those traits in lianas and trees. Estimates of evolutionary rates showed that Rd evolved faster in lianas, while SLA evolved faster in trees. The mean phylogenetic distance was 1.2 times greater among liana species than among tree species. Likewise, estimates of phylogenetic distance indicated that lianas were less related than by chance alone (phylogenetic evenness across 63 species), and trees were more related than expected by chance (phylogenetic clustering across 71 species). Lianas showed evenness for Rd, while trees showed phylogenetic clustering for this trait. In contrast, for SLA, lianas exhibited phylogenetic clustering and trees showed phylogenetic evenness. Lianas and trees showed patterns of ecophysiological trait variation among species that were independent of phylogenetic relatedness. We found support for the expected pattern of greater species divergence in lianas, but did not find consistent patterns regarding ecophysiological trait evolution and divergence. Rd followed the species-level pattern, i.e., greater divergence/evolution in lianas compared to trees, while the opposite occurred for SLA and no pattern was detected for Amax. Rd may have driven lianas’ divergence across forest environments, and might contribute to diversification in climber clades.
PLoS ONE 06/2014; 9(6):e99871. DOI:10.1371/journal.pone.0099871 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: QuestionsHow do climbing species richness and composition change between subtropical and temperate areas of southern South America? How do growth form (lianas and vines) and climbing mechanisms change between subtropical and temperate areas of southern South America? How much of the diversity of species and traits of the extratropical climbing flora is derived from taxa shared with the tropical region?LocationSubtropical (23–30° S) and temperate (>30° S) areas of South America.Methods
An extensive literature search was carried out in the main databases concerning the flora of southern South America. Climbing species occurrence in subtropical and temperate areas and climbing traits were retrieved. Differences in the frequencies of both growth forms and climbing mechanisms between areas were evaluated using chi-square analyses. Trait frequencies in subtropical and temperate floras were analysed with and without considering species shared with the tropical region.ResultsClimbing species richness decreased from subtropical to temperate areas, and there were changes in the taxonomic composition. The frequency of growth forms and climbing mechanisms differed between subtropical and temperate areas. Herbaceous vines accounted for 85% of temperate-exclusive species. Twiners contributed less to climber richness in the temperate area, while tendril-bearers and leaf-climbers became more important; root-climbers were only found in temperate forests. Species shared with the tropical region increase the number of liana species in both subtropical and temperate floras, but alter the frequencies of climbing mechanisms in the subtropical flora only.Conclusions
Results call for a re-evaluation of the importance that is given to climbers in regions outside the tropics. Vines must be included in models of distribution and abundance of climbers in order to gain a better understanding of climbing plant ecology. The association between climbing mechanisms and the success of climbing plant species in different ecosystems must be further investigated.
[Show abstract][Hide abstract] ABSTRACT: 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  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.
Current biology: CB 04/2014; 24(9). DOI:10.1016/j.cub.2014.03.010 · 9.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Crassulacean acid metabolism (CAM) is a photosynthetic pathway found in many plant species from arid and semiarid environments. Few studies aiming to characterise plant species as CAM or C3 account for inter-population differences in photosynthetic pathway, often relying on samples taken from herbarium material and/or a single plant or population. This may be especially problematic for species growing under contrasting climate conditions, as is the case for species with a wide geographic range. We used Puya chilensis, a species previously reported as CAM and C3, to study among-population variation in expression of the CAM pathway within its distribution range, which spans a significant climate gradient. We carried out a wide sampling scheme, including five populations and a combination of analytical methods (quantification of nocturnal acidification and stable isotope measurements). The study populations of P. chilensis encompass the entire latitudinal distribution range, from semi-arid to temperate oceanic climates. Our results indicate that CAM decreased with latitude. However, even in the southern (wetter) populations, where δ13C values were indicative of C3 metabolism, we found some nocturnal acidification. We stress the value of using two methods along with the use of samples from different populations, as this allows more reliable conclusions on the photosynthetic pathway for ‘probable’ CAM species that face varying climate conditions within their distribution ranges.
[Show abstract][Hide abstract] ABSTRACT: In a current article in the Journal of Vegetation Science, Casanova-Katny et al. addressed a comment about an article by Molina-Montenegro et al., which demonstrated the climate modification induced by the macrolichen Usnea antarctica and its role as facilitator. They provided useful corrections concerning species identification and pointed out several issues that, in their view, weakened our study. They indicated that the role of U. antarctica as a facilitative species in the maritime Antarctica is merely philosophical and has no ecological relevance. In this commentary, we argue why these critiques are unsubstantial, and provide evidence that the macrolichen can modify the microclimate, ameliorating the harsh conditions prevailing in Antarctica, establishing positive interactions and eventually facilitating vascular species. Thus, the macrolichen U. antarctica would act as a ‘nurse species’, playing a key role in structuring the maritime Antarctic plant community.
[Show abstract][Hide abstract] ABSTRACT: Interspecific competition plays a key role in the organisation of ant communities. In ant–plant interactions, individual host plants are usually occupied by a single ant colony, and co-occurring ant species compete for hosts. Here indirect evidence of competition between three dominant ant species that tend aphids on two biennial thistles in northern Patagonia is described, and a novel defensive behaviour in temperate ant assemblages is reported.This study has found that: (i) dominant ant species were not spatially segregated, thus enhancing the probability of fights and invasions of host plants; (ii) ant species did not show preferences for a thistle species or for any plant characteristic, and thus all plants have similar chances of being colonised by all dominant ant species; (iii) the resident ant species remained on the same plant during the whole plant life cycle, monopolising plant resources (aphids); and (iv) all dominant species, whose nests are on the ground, assigned some ants to stay on the host plant during the night, when the low temperatures typical of this temperate environment greatly reduce foraging activities. When these ‘nocturnal guards’ were experimentally removed from the host plant, other ants from the same colony rapidly appeared showing aggressive behaviours.Taking all these findings together, it is suggested that interspecific competition influences the distribution of ants on their host plants and involves nocturnal defensive behaviours despite unfavourable thermal conditions. This illustrates how habitat features, such as the short life cycle of thistles and the low night-time temperatures that reduce ant foraging and thus make plants more vulnerable to invasion, might affect the distribution and behaviour of ants.
[Show abstract][Hide abstract] ABSTRACT: Antarctica is a highly interesting region for ecologists because of its extreme climatic conditions and the uniqueness of its species. In this article, we describe the trends in Antarctic ecological research participation by Latin American countries. In a survey of articles indexed by the ISI Web of Science, we searched under the categories ''Ecology'', ''Biodiversity Conservation'' and ''Evolutionary Biology'' and found a total of 254 research articles published by Latin American countries. We classified these articles according to the country of affiliation, kingdom of the study species, level of biological organization and environment. Our main finding is that there is a steady increase in the relative contribution of Latin American countries to Antarctic ecological research. Within each category, we found that marine studies are more common than terrestrial studies. Between the different kingdoms, most studies focus on animals and most studies use a community approach. The leading countries in terms of productivity were Argentina, Chile and Brazil, with Argentina showing the highest rate of increase.
Polar Research 09/2013; DOI:10.3402/polar.v32i0.19993 · 1.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Spatial variation in host plant availability may lead to specialization in host use and local host adaptation in herbivorous insects, which may involve a cost in performance on other hosts. We studied two geographically separated populations of the seed beetle Megacerus eulophus (Coleoptera: Bruchidae) in central Chile: a population from the host Convolvulus chilensis (in Aucó) and a population from C. bonariensis (in Algarrobo). In Aucó C. chilensis is the only host plant, while in Algarrobo both C. bonariensis and C. chilensis are available. We tested local adaptation to these native host plants and its influence on the use of another, exotic host plant. We hypothesized that local adaptation would be verified, particularly for the one-host population (Aucó), and that the Aucó population would be less able to use an alternative, high-quality host. We found evidence of local adaptation in the population from C. chilensis. Thus, when reared on C. chilensis, adults from the C. chilensis population were larger and lived longer than individuals from the C. bonariensis population, while bruchids from the two populations had the same body size and longevity when reared on C. bonariensis. Overall, bruchids from the C. chilensis population showed greater performance traits than those from the C. bonariensis population. There were no differences between the bruchid populations in their ability to use the alternative, exotic host Calystegia sepium, as shown by body size and longevity patterns. Results suggest that differences in local adaptation might be explained by differential host availability in the study populations.
PLoS ONE 09/2013; 8(1):e53892. DOI:10.1371/journal.pone.0053892 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Root climbers constitute a distinctive group within climbing plants and some evidence suggests that they are associated with high precipitation and low light availability at local scales, which is in contrast with general patterns of liana distribution in the tropics. The influence of precipitation and seasonality on the occurrence of root climbers was evaluated both globally and in the tropics. The presence/absence of root climbers was recorded in 174 sites of Alwyn H. Gentry Forest Transect Data Set. The effects of mean annual precipitation and dry-season length (and temperature) on their occurrence were analysed using logistic regressions. Root climbers were significantly more frequent in sites with greater precipitation and reduced seasonality. Increasing temperature reduced root-climber occurrence in tropical sites, but this effect was marginally significant at a global scale. Dry and open habitats appear unsuitable for root climbers. This can be explained by the susceptibility to desiccation of adventitious roots and/or the low acclimation ability of these climbers to high irradiance.