Defense syndromes against herbivory in a cerrado plant community
TL;DR: It is argued that herbivory exerts significant selection pressure on these plant defense traits, and grouped the species into defense syndromes according to their traits.
Abstract: Plants have traits against herbivory that may occur together and increase defense efficiency. We tested whether there are defense syndromes in a cerrado community and, if so, whether there is a phylogenetic signal in them. We measured nine defense traits from a woodland cerrado community in southeastern Brazil. We tested the correlation between all pairs of traits and grouped the species into defense syndromes according to their traits. Most pairwise correlations of traits were complementary. Plants with lower specific leaf area also presented tougher leaves, with low nitrogen, more trichomes, and tannins. We found five syndromes: two with low defenses and high nutritional quality, two with high defenses and low nutritional quality, and one with traits compensating each other. There were two predominant strategies against herbivory in cerrado: “tolerance” and “low nutritional quality” syndromes. Phylogeny did not determine the suite of traits species presented. We argue that herbivory exerts significant selection pressure on these plant defense traits.
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TL;DR: Progress is reviewed in understanding of how megafauna affect ecosystem physical and trophic structure, species composition, biogeochemistry, and climate, drawing on special features of PNAS and Ecography that have been published as a result of an international workshop held in Oxford in 2014.
Abstract: Large herbivores and carnivores (the megafauna) have been in a state of decline and extinction since the Late Pleistocene, both on land and more recently in the oceans. Much has been written on the timing and causes of these declines, but only recently has scientific attention focused on the consequences of these declines for ecosystem function. Here, we review progress in our understanding of how megafauna affect ecosystem physical and trophic structure, species composition, biogeochemistry, and climate, drawing on special features of PNAS and Ecography that have been published as a result of an international workshop on this topic held in Oxford in 2014. Insights emerging from this work have consequences for our understanding of changes in biosphere function since the Late Pleistocene and of the functioning of contemporary ecosystems, as well as offering a rationale and framework for scientifically informed restoration of megafaunal function where possible and appropriate.
319 citations
TL;DR: A conceptual model is developed to predict litter breakdown dynamics in low order streams, explaining variations in leaf litter breakdown rates and shredder abundance across large geographic areas, allowing the formulation of predictions of how anthropogenic pressures may affect litter breakdown rate.
Abstract: The detrital-based food web of many streams and rivers plays a fundamental role in the cycling and retention of carbon and nutrients. However, we still need to understand which global mechanisms underlie the biogeochemical pathways that control energy transfer from the detrital pool through local food webs into nutrient and energy cycles and storage. Previous attempts to understand the variability in litter breakdown rates have included the search for latitudinal variation patterns and analysis of the influence of different factors. Here we complement those studies by developing a conceptual model to predict litter breakdown dynamics in low order streams. According to the model, litter breakdown rates and the relative role of microbial decomposers and shredder detritivores on this process are hierarchically governed by interactions between climate/hydrology and geology acting upon plant traits, nutrient and leaf availability to decomposers, and metabolism of microbial decomposers and shredders. The model explains variations in leaf litter breakdown rates and shredder abundance across large geographic areas, allowing the formulation of predictions of how anthropogenic pressures may affect litter breakdown rates.
167 citations
University of New South Wales1, Autonomous University of Madrid2, Australian National University3, University of Minnesota4, University of Melbourne5, National Scientific and Technical Research Council6, Woods Hole Research Center7, Stanford University8, VU University Amsterdam9, James Cook University10, Aarhus University11, National University of Saint Anthony the Abbot in Cuzco12, Umeå University13, Norwegian University of Science and Technology14, University of Adelaide15, University of Zambia16, Victoria University of Wellington17, University of Western Sydney18, National University of Austral Patagonia19, Pacific Northwest National Laboratory20, Stellenbosch University21, Mid Sweden University22, University of New England (Australia)23, Griffith University24, University of Alaska Fairbanks25, University of Southern Queensland26, National Autonomous University of Mexico27, University of Zululand28, Xishuangbanna Tropical Botanical Garden29, National University of Tucumán30, University of Arizona31, Washington University in St. Louis32, Curtin University33, University of Tasmania34
TL;DR: It is suggested that a lack of consistent defence syndromes may be adaptive, resulting from selective pressure to deploy a different combination of defences to coexisting species.
Abstract: Most plant species have a range of traits that deter herbivores. However, understanding of how different defences are related to one another is surprisingly weak. Many authors argue that defence traits trade off against one another, while others argue that they form coordinated defence syndromes. We collected a dataset of unprecedented taxonomic and geographic scope (261 species spanning 80 families, from 75 sites across the globe) to investigate relationships among four chemical and six physical defences. Five of the 45 pairwise correlations between defence traits were significant and three of these were tradeoffs. The relationship between species' overall chemical and physical defence levels was marginally nonsignificant (P = 0.08), and remained nonsignificant after accounting for phylogeny, growth form and abundance. Neither categorical principal component analysis (PCA) nor hierarchical cluster analysis supported the idea that species displayed defence syndromes. Our results do not support arguments for tradeoffs or for coordinated defence syndromes. Rather, plants display a range of combinations of defence traits. We suggest this lack of consistent defence syndromes may be adaptive, resulting from selective pressure to deploy a different combination of defences to coexisting species.
130 citations
TL;DR: This study highlighted the validity of the CSR classification outside the temperate region where it was originally developed and corroborated in a tropical plant community.
Abstract: The classification of plant species according to the CSR ecological strategy scheme has been proposed as a common language that allows comparison among species, communities, and floras. Although several studies on European continent have demonstrated a consistent association between CSR strategies and key ecosystem processes, studies of this type are still lacking in other ecoregions worldwide. For the first time, the CSR strategy scheme is applied in a tropical plant community. In a Brazilian mountain grassland ecosystem characterized by both high biodiversity and environmental stress, we sampled various functional traits of 48 herbaceous species in stony and sandy grasslands, and evaluated the relationship between CSR strategies and functional traits with several environmental parameters. The extremely infertile soils in the two studied habitats may have acted as a major environmental filter leading to a clear predominance of the stress-tolerant strategy in both communities. However, fine-scale environmental differences between the two communities resulted in the filtering of distinct functional trait values. The sites with coarser soil texture, lower percentage of plant cover and (paradoxically) higher mineral nutrient concentrations favored plants with narrower leaves, higher stress tolerance, lower competitiveness, and higher sclerophylly (i.e., lower specific leaf area and higher leaf dry matter content). The comparison between the functional character of stony and sandy communities evidenced the influence of soil texture and water availability in the environmental filtering. This study highlighted the validity of the CSR classification outside the temperate region where it was originally developed and corroborated.
94 citations
Cites methods from "Defense syndromes against herbivory..."
...The leaf toughness was measured using a digital penetrometer (Chatillon model DFE-010, Largo, Florida, USA) coupled to a cone-shaped tip (model SPK-FMG-009A), according to Silva and Batalha (2011)....
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TL;DR: This study evaluated the habitat preference of 284 woody species using data collected in six paired seasonal forest and savanna habitats throughout the Brazilian Cerrado and found that acquisitive traits were associated with species occurring in forests, whereas conservative traits wereassociated with species recorded in savannas.
Abstract: Seasonal forests and savannas often occur side by side in Neotropical landscapes, so it is possible to find plant species in both or in just one of these two contrasting habitats. But, what adaptations to the prevailing environmental conditions explain species occurrence in these habitats? In this study, we tested the hypotheses that (i) distinct ecological strategies explain the occurrence of woody species in forests, savannas, or in both habitats, and that (ii) such strategies appear at both inter- and intraspecific levels. We evaluated the habitat preference of 284 woody species using data collected in six paired seasonal forest and savanna habitats throughout the Brazilian Cerrado. To investigate the ecological strategies of forest-specialist, savanna-specialist or generalist species, we used data on functional traits at the inter- and intraspecific levels. We found that acquisitive traits were associated with species occurring in forests, whereas conservative traits were associated with species recorded in savannas. Additionally, our findings indicate that intraspecific variability underlies the ability of species to persist in these contrasting ecosystems. Our results demonstrate how environmental filters select plant species with distinct traits and ecological strategies. Acquisitive traits indicate higher competitive ability and faster resource acquisition for forest species that occur in light-limited environments. On the other hand, conservative traits promote resistance of savanna species to environmental stressors such as fire, drought and low soil fertility. Generalist species matched the strategy of the habitat where they were sampled, which could be explained by high intraspecific trait variability in plant maximum height, leaf thickness, SLA, leaf nitrogen and magnesium contents. Therefore, these are likely to be key traits for adaptation of populations and species in forest and savannas.
51 citations
References
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TL;DR: A method of correcting for the phylogeny has been proposed, which specifies a set of contrasts among species, contrasts that are statistically independent and can be used in regression or correlation studies.
Abstract: Recent years have seen a growth in numerical studies using the comparative method. The method usually involves a comparison of two phenotypes across a range of species or higher taxa, or a comparison of one phenotype with an environmental variable. Objectives of such studies vary, and include assessing whether one variable is correlated with another and assessing whether the regression of one variable on another differs significantly from some expected value. Notable recent studies using statistical methods of this type include Pilbeam and Gould's (1974) regressions of tooth area on several size measurements in mammals; Sherman's (1979) test of the relation between insect chromosome numbers and social behavior; Damuth's (1981) investigation of population density and body size in mammals; Martin's (1981) regression of brain weight in mammals on body weight; Givnish's (1982) examination of traits associated with dioecy across the families of angiosperms; and Armstrong's (1983) regressions of brain weight on body weight and basal metabolism rate in mammals. My intention is to point out a serious statistical problem with this approach, a problem that affects all of these studies. It arises from the fact that species are part of a hierarchically structured phylogeny, and thus cannot be regarded for statistical purposes as if drawn independently from the same distribution. This problem has been noticed before, and previous suggestions of ways of coping with it are briefly discussed. The nonindependence can be circumvented in principle if adequate information on the phylogeny is available. The information needed to do so and the limitations on its use will be discussed. The problem will be discussed and illustrated with reference to continuous variables, but the same statistical issues arise when one or both of the variables are discrete, in which case the statistical methods involve contingency tables rather than regressions and correlations.
8,833 citations
"Defense syndromes against herbivory..." refers methods in this paper
...We also constructed a matrix with the phylogenetically independent contrasts (PICs) of traits, which corrects each variable for phylogenetic dependence by scaling the contrasts by their standard deviation related to phylogenetic distances, assuming a Brownian model of evolution (Felsenstein 1985)....
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TL;DR: In this article, a text designed to make multivariate techniques available to behavioural, social, biological and medical students is presented, which includes an approach to multivariate inference based on the union-intersection and generalized likelihood ratio principles.
Abstract: A text designed to make multivariate techniques available to behavioural, social, biological and medical students. Special features include an approach to multivariate inference based on the union-intersection and generalized likelihood ratio principles.
6,488 citations
TL;DR: A method for identifying clusters of points in a multidimensional Euclidean space is described and its application to taxonomy considered and an informal indicator of the "best number" of clusters is suggested.
Abstract: A method for identifying clusters of points in a multidimensional Euclidean space is described and its application to taxonomy considered. It reconciles, in a sense, two different approaches to the investigation of the spatial relationships between the points, viz., the agglomerative and the divisive methods. A graph, the shortest dendrite of Florek etal. (1951a), is constructed on a nearest neighbour basis and then divided into clusters by applying the criterion of minimum within cluster sum of squares. This procedure ensures an effective reduction of the number of possible splits. The method may be applied to a dichotomous division, but is perfectly suitable also for a global division into any number of clusters. An informal indicator of the "best number" of clusters is suggested. It is a"variance ratio criterion" giving some insight into the structure of the points. The method is illustrated by three examples, one of which is original. The results obtained by the dendrite method are compared with those...
5,772 citations
"Defense syndromes against herbivory..." refers methods in this paper
...The number of groups varied from two to five, and we selected the best clustering number with the pseudo F-statistic (Calinski and Harabasz 1974)....
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...The number of groups varied from two to five, and we selected the best clustering number with the pseudo F-statistic ( Calinski and Harabasz 1974 )....
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TL;DR: A common pattern of phylogenetic conservatism in ecological character is recognized and the challenges of using phylogenies of partial lineages are highlighted and phylogenetic approaches to three emergent properties of communities: species diversity, relative abundance distributions, and range sizes are reviewed.
Abstract: ▪ Abstract As better phylogenetic hypotheses become available for many groups of organisms, studies in community ecology can be informed by knowledge of the evolutionary relationships among coexisting species. We note three primary approaches to integrating phylogenetic information into studies of community organization: 1. examining the phylogenetic structure of community assemblages, 2. exploring the phylogenetic basis of community niche structure, and 3. adding a community context to studies of trait evolution and biogeography. We recognize a common pattern of phylogenetic conservatism in ecological character and highlight the challenges of using phylogenies of partial lineages. We also review phylogenetic approaches to three emergent properties of communities: species diversity, relative abundance distributions, and range sizes. Methodological advances in phylogenetic supertree construction, character reconstruction, null models for community assembly and character evolution, and metrics of community ...
3,615 citations
"Defense syndromes against herbivory..." refers background in this paper
...However, strong selection pressure can lead to adaptive convergence in two distantly related species such that they respond similarly to the selection pressure (Webb et al. 2002; Núñez-Farfán et al. 2007)....
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...However, strong selection pressure can lead to adaptive convergence in two distantly related species such that they respond similarly to the selection pressure ( Webb et al. 2002 ; N u´n ˜ez-Farfa ´ ne t al. 2007)....
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...If so, phylogenetic proximity of two species and the traits inherited from common ancestry should reveal similar responses to environmental processes ( Webb et al. 2002 ; N u´n ˜ez-Farfa ´ ne t al. 2007)....
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...If so, phylogenetic proximity of two species and the traits inherited from common ancestry should reveal similar responses to environmental processes (Webb et al. 2002; Núñez-Farfán et al. 2007)....
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TL;DR: This paper provides an international methodological protocol aimed at standardising this research effort, based on consensus among a broad group of scientists in this field, and features a practical handbook with step-by-step recipes, for 28 functional traits recognised as critical for tackling large-scale ecological questions.
Abstract: There is growing recognition that classifying terrestrial plant species on the basis of their function (into 'functional types') rather than their higher taxonomic identity, is a promising way forward for tackling important ecological questions at the scale of ecosystems, landscapes or biomes. These questions include those on vegetation responses to and vegetation effects on, environmental changes (e.g. changes in climate, atmospheric chemistry, land use or other disturbances). There is also growing consensus about a shortlist of plant traits that should underlie such functional plant classifications, because they have strong predictive power of important ecosystem responses to environmental change and/or they themselves have strong impacts on ecosystem processes. The most favoured traits are those that are also relatively easy and inexpensive to measure for large numbers of plant species. Large international research efforts, promoted by the IGBP–GCTE Programme, are underway to screen predominant plant species in various ecosystems and biomes worldwide for such traits. This paper provides an international methodological protocol aimed at standardising this research effort, based on consensus among a broad group of scientists in this field. It features a practical handbook with step-by-step recipes, with relatively brief information about the ecological context, for 28 functional traits recognised as critical for tackling large-scale ecological questions.
3,288 citations
"Defense syndromes against herbivory..." refers background or methods in this paper
...For each species in the sample, we randomly selected 10 individuals to measure the traits (Cornelissen et al. 2003)....
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...Low specific leaf areas represent high investment in structural defenses, whereas high specific leaf areas indicate greater palatability (Weiher et al. 1999; Cornelissen et al. 2003)....
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...In addition, plants with more structural defenses, such as cell wall toughness, have more mass per leaf area and consequently low specific leaf areas (Weiher et al. 1999; Cornelissen et al. 2003)....
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...We oven-dried the leaves at 75 C over 72 h to obtain dry mass. Dividing leaf area by dry mass, we obtained specific leaf area (Cornelissen et al. 2003)....
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