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1.
New Phytol ; 225(1): 488-498, 2020 01.
Artículo en Inglés | MEDLINE | ID: mdl-31412143

RESUMEN

Although tannins have been an important focus of studies of plant-animal interactions, traditional tannin analyses cannot differentiate between the diversity of structures present in plants. This has limited our understanding of how different mixtures of these widespread secondary metabolites contribute to variation in biological activity. We used UPLC-MS/MS to determine the concentration and broad composition of tannins and polyphenols in 628 eucalypt (Eucalyptus, Corymbia and Angophora) samples, and related these to three in vitro functional measures believed to influence herbivore defence: protein precipitation capacity, oxidative activity at high pH and capacity to reduce in vitro nitrogen (N) digestibility. Protein precipitation capacity was most strongly correlated with concentrations of procyanidin subunits in proanthocyanidins (PAs), and late-eluting ellagitannins. Capacity to reduce in vitro N digestibility was affected most by the subunit composition and mean degree of polymerisation (mDP) of PAs. Finally, concentrations of ellagitannins and prodelphinidin subunits of PAs were the strongest determinants of oxidative activity. The results illustrate why measures of total tannins rarely correlate with animal feeding responses. However, they also confirm that the analytical techniques utilised here could allow researchers to understand how variation in tannins influence the ecology of individuals and populations of herbivores, and, ultimately, other ecosystem processes.


Asunto(s)
Herbivoria/fisiología , Hojas de la Planta/metabolismo , Taninos/metabolismo , Modelos Estadísticos , Nitrógeno/metabolismo , Oxidación-Reducción , Polifenoles/metabolismo
2.
J Chem Ecol ; 44(1): 62-71, 2018 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-29209932

RESUMEN

Ecologists have long been interested in how the nutritional composition of leaves changes as they age, and whether this affects herbivore feeding preferences. As a consequence, the literature abounds with reports that younger leaves contain higher concentrations of nitrogen and plant secondary metabolites (PSMs) than do older leaves. Most of these studies, however, base their conclusions on average values that often mean little to herbivores. We examined this issue in the well-studied marsupial-eucalypt system, using Eucalyptus melliodora and captive common brushtail possums (Trichosurus vulpecula) offered branches from individual trees containing both young and mature leaves. Like many plants, the concentrations of N and PSMs differed among individual E. melliodora. Although young leaves were, on average, "better defended" by the PSM sideroxylonal than were mature leaves, some trees produced leaves that were relatively undefended at both ages. In response, possums chose different proportions of young and mature leaves depending on the chemistry of the individual tree. Possums did not always prefer leaves with lower concentrations of sideroxylonal (mature leaves) or those with higher concentrations of available N (young leaves). Instead, the sideroxylonal concentration of young leaves dictated their choice: possums preferred young leaves with low sideroxylonal concentrations, but not with high concentrations. By skewing their feeding toward trees producing young leaves with low concentrations of PSMs, possums may influence plant fitness. Researchers will detect these potentially important interactions only if they are aware that measuring variation among plants discloses more information than do average relationships.


Asunto(s)
Eucalyptus/química , Trichosurus/fisiología , Animales , Benzofuranos/análisis , Benzofuranos/farmacología , Cromatografía Líquida de Alta Presión , Eucalyptus/metabolismo , Conducta Alimentaria/efectos de los fármacos , Herbivoria , Masculino , Nitrógeno/análisis , Floroglucinol/análogos & derivados , Floroglucinol/análisis , Floroglucinol/farmacología , Hojas de la Planta/química , Hojas de la Planta/metabolismo , Factores de Tiempo
3.
Oecologia ; 174(3): 873-82, 2014 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-24253506

RESUMEN

Adequate nutrition is a fundamental requirement for the maintenance and growth of populations, but complex interactions between nutrients and plant toxins make it difficult to link variation in plant quality to the ecology of wild herbivores. We asked whether a 'foodscape' model of habitat that uses near-infrared spectroscopy to describe the palatability of individual trees in the landscape, predicted the foraging decisions of a mammalian browser, the koala (Phascolarctos cinereus). Specifically, we considered four behavioural decision points at which nutritional quality may influence an animal's decision. These were: which tree to enter, whether to feed from that tree, when to stop eating, and how long to remain in that tree. There were trends for koalas to feed in eucalypt trees that were more palatable than unvisited neighbouring conspecific trees, and than trees that they visited but did not eat. Koalas ate longer meals in more palatable trees, and stayed longer and spent more time feeding per visit to these trees. Using more traditional chemical analyses, we identified that an interaction between the concentrations of formylated phloroglucinol compounds (a group of plant secondary metabolites) and available N (an integrated measure of tannins, digestibility and N) influenced feeding. The study shows that foodscape models that combine spatial information with integrated measures of food quality are a powerful tool to predict the feeding behaviour of herbivores in a landscape.


Asunto(s)
Eucalyptus/química , Conducta Alimentaria , Phascolarctidae/psicología , Floroglucinol/análisis , Taninos/análisis , Animales , Ingestión de Alimentos , Ecología , Ecosistema , Femenino , Masculino , Valor Nutritivo , Espectroscopía Infrarroja Corta , Factores de Tiempo , Árboles/química
4.
Oecologia ; 176(1): 251-8, 2014 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-24974269

RESUMEN

The marsupials that eat Eucalyptus in south-eastern Australia provide an example of animals with similar niche requirements occurring sympatrically. They certainly differ in size, ranging from about 1 kg in the greater glider (Petauroides volans) and the closely related common ringtail possum (Pseudocheirus peregrinus), to 4 kg (common brushtail possum, Trichosurus vulpecula) and up to 15 kg in the koala (Phascolarctos cinereus). All species, however, may eat considerable amounts of eucalypt foliage, often favouring the same species, and thus appear to compete for food. In order to better understand the degree of competition for food, we measured feeding by the greater glider in response to increasing concentrations of a specific group of eucalypt plant secondary metabolites (PSM), the sideroxylonals, and then compared it to results published for the other species. The greater glider was more resilient than the other species to increasing concentrations of sideroxylonals. We suggest this allows gliders to feed on leaves from the eucalypt subgenus, Symphyomyrtus, while its small size and gliding ability allow it to feed where koalas cannot, on the young leaves on top of the canopy. In contrast, the common ringtail possum is well adapted to feeding from species of the subgenus Eucalyptus, which do not produce sideroxylonals but contain less available nitrogen (AvailN) than do the symphyomyrtles. These 'nutritional niches' segregate the forest and along with other factors, such as generalist and specialist feeding strategies and differences in body size and requirements for shelter, presumably minimise competition between the marsupial species.


Asunto(s)
Benzofuranos/toxicidad , Eucalyptus/química , Herbivoria/fisiología , Marsupiales/fisiología , Floroglucinol/análogos & derivados , Hojas de la Planta/química , Animales , Benzofuranos/análisis , Ingestión de Alimentos/efectos de los fármacos , Eucalyptus/metabolismo , Femenino , Masculino , Estructura Molecular , Nueva Gales del Sur , Nitrógeno/metabolismo , Floroglucinol/análisis , Floroglucinol/toxicidad , Hojas de la Planta/metabolismo
5.
New Phytol ; 198(1): 252-263, 2013 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-23316750

RESUMEN

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.


Asunto(s)
Plantas/química , Plantas/inmunología , Análisis por Conglomerados , Análisis de Componente Principal , Carácter Cuantitativo Heredable
6.
Oecologia ; 173(1): 203-12, 2013 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-23443356

RESUMEN

Estimating the nutritional value of a herbivore's diet is difficult because it requires knowing what the animal eats, the relative quality of each component and how these components interact in relation to animal physiology. Current methods are cumbersome and rely on many assumptions that are hard to evaluate. We describe a new method for estimating relative diet quality directly from faeces that avoids the problems inherent in other methods. We combine this method with near infrared reflectance spectroscopy (NIRS) to analyse many samples and thus provide a technique with immense value in ecological studies. The method stems from the correlation between the concentrations of dietary and faecal nitrogen in herbivores eating a tannin-free diet, but a weaker relationship in browsers that ingest substantial amounts of tannins, which form complexes with proteins. These complexes reduce the availability of nitrogen and may increase faecal nitrogen concentrations. Using the tannin-binding compound, polyethylene glycol, we showed that tannin-bound nitrogen is a significant and variable part of faecal nitrogen in wild common brushtail possums (Trichosurus vulpecula). We developed a technique to measure faecal available nitrogen and found that it predicted the reproductive success of female brushtail possums in northern Australia. Faecal available nitrogen combined with NIRS provides a powerful tool for estimating the relative nutritional value of the diets of browsing herbivores in many ecological systems. It is a better indicator of diet quality than other commonly used single-nutrient measures such as faecal nitrogen and foliage analysis paired with observed feeding behaviour.


Asunto(s)
Heces/química , Herbivoria , Valor Nutritivo , Reproducción/fisiología , Trichosurus/fisiología , Animales , Australia , Dieta , Femenino , Nitrógeno/análisis , Nitrógeno/química , Polietilenglicoles/química , Espectroscopía Infrarroja Corta/métodos , Taninos/química , Trichosurus/metabolismo
7.
Oecologia ; 169(2): 281-91, 2012 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-22246432

RESUMEN

Ecologists want to explain why populations of animals are not evenly distributed across landscapes and often turn to nutritional explanations. In seeking to link population attributes with food quality, they often contrast nutritionally positive traits, such as the concentration of nitrogen, against negative ones, such as fibre concentration, by using a ratio of these traits. This specific ratio has attracted attention because it sometimes correlates with the biomass of colobine primates across sites in Asia and Africa. Although empirically successful, we have identified problems with the ratio that may explain why it fails under some conditions to predict colobine biomass. First, available nitrogen, rather than total nitrogen, is nutritionally important, while the presence of tannins is the major factor reducing the availability of nitrogen in browse plant species. Second, tannin complexes inflate measures of fibre. Finally, simple ratios may be unsound statistically because they implicitly assume isometric relationships between variables. We used data on the chemical composition of plants from three continents to examine the relationships between the concentrations of nitrogen, available nitrogen, fibre and tannins in foliage and to evaluate the nitrogen to fibre ratio. Our results suggest that the ratio of the concentration of nitrogen to fibre in leaves does sometimes closely correlate with the concentration of available nitrogen. However, the ratio may give misleading results when leaves contain high concentrations of tannins. The concentration of available nitrogen, which incorporates measures of total nitrogen, dry matter digestibility and tannins, should give a better indication of the nutritional value of leaves for herbivorous mammals that can readily be extrapolated to habitats.


Asunto(s)
Fenómenos Fisiológicos Nutricionales de los Animales , Densidad de Población , África , Animales , Asia , Australia , Disponibilidad Biológica , Biomasa , Fibras de la Dieta/análisis , Ecosistema , Eucalyptus/química , Nitrógeno/análisis , Nitrógeno/farmacocinética , Valor Nutritivo , Hojas de la Planta/química , Taninos
8.
J Chem Ecol ; 38(7): 914-23, 2012 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-22661307

RESUMEN

Mosaic trees contain more than one phenotype. The two Eucalyptus mosaic trees studied here (E. melliodora and E. sideroxylon) are predominantly susceptible to insect herbivory, with the leaves on a single large branch on each tree resisting herbivory. We used gas chromatography-mass spectrometry and high-pressure liquid chromatography to analyze the chemical profile of leaves of the mosaic trees, as well as leaves of adjacent non-mosaic con-specifics. We show that the leaves of the two phenotypes are distinctly different. Compared to the susceptible (S) leaves on the same tree, the resistant (R) leaves on the mosaic trees had low concentrations of sesquiterpenes (E. melliodora: 2 vs. 24 mg·g(-1) dry matter; E. sideroxylon: 8 vs. 22 mg·g(-1) dry matter), high concentrations of FPCs (E. melliodora: 5.4 vs. 0.3 mg·g(-1) dry matter; E. sideroxylon: 9.8 vs. 0.2 mg·g(-1) dry matter) but similar concentrations of nitrogen (E. melliodora: 15.4 vs. 16.8 mg·g(-1) dry matter; E. sideroxylon: 13.1 vs. 14.0 mg·g(-1) dry matter). The only difference between the two mosaic trees was in the levels of monoterpenes. The R leaves from the mosaic E. melliodora contained higher concentrations of monoterpenes compared to the S leaves (12 vs. 6 mg·g(-1) dry matter). In contrast, the leaves from the E. sideroxylon mosaic contained much higher concentrations of monoterpenes with a reversed pattern (R: 26 vs. S: 45 mg·g(-1) dry matter). There were qualitative differences too on the mosaic trees. The R leaves of both species contained much higher concentrations of the monoterpene, 1,8-cineole, whereas the S chemotype of E. sideroxylon only had high concentrations of phellandrenes. Furthermore, the chemical differences between leaves on the R and S branches of the mosaic trees resembled those between the leaves of R and S con-specific trees in the same population. We use these data and knowledge of secondary metabolite biosynthesis to propose that high-level transcriptional differences may control the profile of specialized metabolites in eucalypts.


Asunto(s)
Eucalyptus/genética , Herbivoria , Monoterpenos/metabolismo , Mosaicismo , Sesquiterpenos/metabolismo , Eucalyptus/química , Eucalyptus/metabolismo , Redes y Vías Metabólicas , Floroglucinol/metabolismo , Hojas de la Planta/química , Hojas de la Planta/metabolismo , Sitios de Carácter Cuantitativo
9.
New Phytol ; 191(4): 1041-1053, 2011 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-21609332

RESUMEN

Eucalyptus is characterized by high foliar concentrations of plant secondary metabolites with marked qualitative and quantitative variation within a single species. Secondary metabolites in eucalypts are important mediators of a diverse community of herbivores. We used a candidate gene approach to investigate genetic associations between 195 single nucleotide polymorphisms (SNPs) from 24 candidate genes and 33 traits related to secondary metabolites in the Tasmanian Blue Gum (Eucalyptus globulus). We discovered 37 significant associations (false discovery rate (FDR) Q < 0.05) across 11 candidate genes and 19 traits. The effects of SNPs on phenotypic variation were within the expected range (0.018 < r(2) < 0.061) for forest trees. Whereas most marker effects were nonadditive, two alleles from two consecutive genes in the methylerythritol phosphate pathway (MEP) showed additive effects. This study successfully links allelic variants to ecologically important phenotypes which can have a large impact on the entire community. It is one of very few studies to identify the genetic variants of a foundation tree that influences ecosystem function.


Asunto(s)
Eucalyptus/genética , Genes de Plantas , Metaboloma , Hojas de la Planta/química , Transferasas Alquil y Aril/metabolismo , Alelos , Ciclohexanoles/metabolismo , Eucaliptol , Eucalyptus/química , Eucalyptus/metabolismo , Frecuencia de los Genes , Marcadores Genéticos , Genotipo , Desequilibrio de Ligamiento , Monoterpenos/metabolismo , Hojas de la Planta/metabolismo , Polimorfismo de Nucleótido Simple , Sitios de Carácter Cuantitativo , Especificidad de la Especie
10.
New Phytol ; 191(3): 777-788, 2011 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-21539574

RESUMEN

• It has long been believed that plant species from the tropics have higher levels of traits associated with resistance to herbivores than do species from higher latitudes. A meta-analysis recently showed that the published literature does not support this theory. However, the idea has never been tested using data gathered with consistent methods from a wide range of latitudes. • We quantified the relationship between latitude and a broad range of chemical and physical traits across 301 species from 75 sites world-wide. • Six putative resistance traits, including tannins, the concentration of lipids (an indicator of oils, waxes and resins), and leaf toughness were greater in high-latitude species. Six traits, including cyanide production and the presence of spines, were unrelated to latitude. Only ash content (an indicator of inorganic substances such as calcium oxalates and phytoliths) and the properties of species with delayed greening were higher in the tropics. • Our results do not support the hypothesis that tropical plants have higher levels of resistance traits than do plants from higher latitudes. If anything, plants have higher resistance toward the poles. The greater resistance traits of high-latitude species might be explained by the greater cost of losing a given amount of leaf tissue in low-productivity environments.


Asunto(s)
Enfermedades de las Plantas/inmunología , Hojas de la Planta/inmunología , Plantas/inmunología , Animales , Cianuros/análisis , Ambiente , Geografía , Lípidos/análisis , Fenotipo , Inmunidad de la Planta , Hojas de la Planta/anatomía & histología , Hojas de la Planta/química , Plantas/anatomía & histología , Plantas/química , Especificidad de la Especie , Taninos/análisis
11.
J Chem Ecol ; 37(1): 71-84, 2011 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-21161340

RESUMEN

The chemical quality of forage may determine landscape use and habitat quality for some herbivorous species. However, studies that investigate the relationship between foliar chemistry and foraging choices in wild vertebrates are rare. Petauroides volans (the greater glider) is unique among Australian marsupial folivores because it glides. It also frequently consumes foliage from both major Eucalyptus subgenera, Eucalyptus (common name "monocalypt") and Symphyomyrtus (common name "symphyomyrtle"), which differ markedly in their foliar chemistry. Such differences are thought to be a product of co-evolution that also led to guild-specific plant secondary metabolite (PSM) specialization among other marsupial eucalypt folivores. To explore whether foliar chemistry influences tree use, we analyzed foliage from eucalypt trees in which we observed P. volans during a radio tracking study and from eucalypt trees in which animals were never observed. We used a combination of chemical assays and near infrared spectrophotometry (NIRS) to determine concentrations of nitrogen (N), in vitro available nitrogen (AvailN), and in vitro digestible dry matter (DDM) from foliage sampled from the monocalypt and symphyomyrtle species, and total formylated phloroglucinol compounds (FPCs) and sideroxylonals (a class of FPCs) from the symphyomyrtle species (FPCs do not occur in monocalypts). Tree size and spatially-dependent, intraspecific variations in sideroxylonals and DDM concentrations in the symphyomyrtle foliage and of N, AvailN, and DDM in the monocalypt species were important indicators of tree use and habitat suitability for P. volans. The results i) demonstrate that guild-specific PSMs do not always lead to guild-specific foraging; ii) provide a compelling co-evolutionary case for the development of gliding in P. volans; and iii) have implications for the management and conservation of this and other folivorous species.


Asunto(s)
Conducta Alimentaria , Marsupiales/fisiología , Árboles , Animales , Australia , Espectroscopía Infrarroja Corta
12.
Ecology ; 91(11): 3165-76, 2010 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-21141178

RESUMEN

Ecologists trying to understand the value of habitat to animals must first describe the value of resources contained in the habitat to animals and, second, they must describe spatial variation in resource quality at a resolution relevant to individual animal foraging. We addressed these issues in a study of koalas (Phascolarctos cinereus) in a Eucalyptus woodland. We measured beneficial and deterrent chemical characteristics as well as the palatability of trees using a near-infrared spectroscopic model based on direct feeding experiments. Tree use by koalas was influenced by tree size and foliar quality but was also context-dependent: trees were more likely to be visited if they were surrounded by small, unpalatable trees or by large, palatable trees. Spatial autocorrelation analysis and several mapping approaches demonstrated that foliar quality is spatially structured in the woodland at a scale relevant to foraging decisions by koalas and that the spatial structure is an important component of habitat quality.


Asunto(s)
Ecosistema , Eucalyptus/fisiología , Conducta Alimentaria/fisiología , Phascolarctidae/fisiología , Animales , Demografía
13.
Ann Bot ; 105(5): 707-17, 2010 May.
Artículo en Inglés | MEDLINE | ID: mdl-20228089

RESUMEN

BACKGROUND AND AIMS: Both environmental and genetic effects contribute to phenotypic variation within and among populations. Genetic differentiation of quantitative traits among populations has been shown in many species, yet it can also be accompanied by other genetic changes, such as divergence in phenotypic plasticity and in genetic variance. Sideroxylonal (a formylated phloroglucinol compound or FPC) is an important chemical defence in eucalypts. The effect of environmental variation on its production is a critical gap in our understanding of its genetics and evolution. METHODS: The stability of genetic variation in sideroxylonal was assessed within and among populations of Eucalyptus tricarpa in three replicated provenance/progeny trials. The covariance structure of the data was also modelled to test whether genetic variances were consistent among populations and Fain's test was applied for major gene effects. KEY RESULTS: A significant genotype x environment interaction occurred at the level of population, and was related to temperature range and seasonality in source populations. Within-population genetic variation was not affected by genotype x environment effects or different sampling years. However, within-population genetic variance for sideroxylonal concentration differed significantly among source populations. Regression of family variance on family mean suggested that this trait is subject to major gene effects, which could explain the observed differences in genetic variances among populations. CONCLUSIONS: These results highlight the importance of replicated common-garden experiments for understanding the genetic basis of population differences. Genotype x environment interactions are unlikely to impede evolution or responses to artificial selection on sideroxylonal, but the lack of genetic variation in some populations may be a constraint. The results are broadly consistent with localized selection on foliar defence and illustrate that differentiation in population means, whether due to selection or to drift, can be accompanied by changes in other characteristics, such as plasticity and genetic variance.


Asunto(s)
Eucalyptus/genética , Eucalyptus/fisiología , Variación Genética/genética , Hojas de la Planta/genética , Hojas de la Planta/fisiología , Benzofuranos/metabolismo , Ambiente , Genotipo , Fenotipo , Floroglucinol/análogos & derivados , Floroglucinol/metabolismo
14.
Oecologia ; 161(3): 539-48, 2009 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-19585152

RESUMEN

Plant secondary metabolites (PSMs) strongly influence diet selection by mammalian herbivores. Concentrations of PSMs vary within and among plant species, and across landscapes. Therefore, local adaptations may cause different populations of herbivores to differ in their ability to tolerate PSMs. Here, we tested the food intake responses of three populations of a marsupial folivore, the common brushtail possum (Trichosurus vulpecula Kerr), from different latitudes and habitat types, to four types of PSMs. We found clear variation in the responses of northern and southern Australian possums to PSMs. Brushtail possums from southern Australia showed marked decreases in food intake in response to all four PSMs, while the two populations from northern Australia were not as sensitive and their responses did not differ from one another. These results were unexpected, based on our understanding of the experiences of these populations with PSMs in the wild. Our results suggest that geographically separated populations of possums may have evolved differing abilities to cope with PSMs, as a result of local adaptation to their natural environments. Our results provide the basis for future studies to investigate the mechanisms by which populations of mammalian species differ in their ability to tolerate PSMs.


Asunto(s)
Adaptación Fisiológica/fisiología , Dieta , Conducta Alimentaria/fisiología , Plantas/química , Trichosurus/fisiología , Animales , Masculino , Queensland
15.
Ecology ; 88(3): 716-28, 2007 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-17503599

RESUMEN

Exploring the spatial distribution of variation in plant secondary metabolites is critical for understanding the evolutionary ecology of biochemical diversity in wild organisms. In the present study, concentrations of foliar sideroxylonal, an important and highly heritable defense chemical of Eucalyptus melliodora, displayed strong, fine-scale spatial autocorrelation. The spatial patterns observed could promote associational effects on herbivore foraging decisions, which may influence the selection pressures exerted on sideroxylonal content. Multiple chemical traits have roles in certain eucalypt-herbivore interactions, and the spatial characteristics of the herbivore foraging environment are therefore determined by these different factors. We used a model of E. melliodora intake by common brushtail possums (Trichosurus vulpecula), based on the combined effects of two chemical traits, to explore this idea and found that the spatial patterns were different to those of sideroxylonal alone. Spatial genetic autocorrelation, examined using microsatellites, was strong and occurred at a fine scale, implying that restricted gene flow might allow genetic patches to respond to selection relatively independently. Local two-dimensional genetic autocorrelation, explored using a new heuristic method, was highly congruent with the pattern of local phenotypic variation observed for sideroxylonal, suggesting that the genetic variance underlying the sideroxylonal variation is similarly structured. Our results suggest that the spatial distribution of genetic and phenotypic variation could influence both the selective pressure imposed by herbivores on eucalypt defenses and the potential of populations to respond to natural selection. Spatial context should be considered in future studies of plant-herbivore interactions.


Asunto(s)
Demografía , Eucalyptus/química , Eucalyptus/fisiología , Modelos Biológicos , Fenotipo , Trichosurus/metabolismo , Animales , Territorio de la Capital Australiana , Benzofuranos/análisis , Benzofuranos/metabolismo , Ciclohexanoles/análisis , Ciclohexanoles/metabolismo , Eucaliptol , Eucalyptus/genética , Conducta Alimentaria/fisiología , Flujo Génico/genética , Funciones de Verosimilitud , Repeticiones de Microsatélite/genética , Monoterpenos/análisis , Monoterpenos/metabolismo , Nitrógeno/análisis , Hojas de la Planta/química , Polietilenglicoles/metabolismo , Espectroscopía Infrarroja Corta , Trichosurus/fisiología
16.
Phytochemistry ; 144: 197-207, 2017 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-28957714

RESUMEN

Many studies quantify total phenolics or total tannins, but understanding the ecological role of polyphenolic secondary metabolites requires at least an understanding of the diversity of phenolic groups present. We used UPLC-MS/MS to measure concentrations of different polyphenol groups - including the four most common tannin groups, the three most common flavonoid groups, and quinic acid derivatives - in foliage from 628 eucalypts from the genera Eucalyptus, Angophora and Corymbia. We also tested for phylogenetic signal in each of the phenolic groups. Many eucalypts contained high concentrations of polyphenols, particularly ellagitannins, which have been relatively poorly studied, but may possess strong oxidative activity. Because the biosynthetic pathways of many phenolic compounds share either precursors or enzymes, we found negative correlations between the concentrations of several of the constituents that we measured, including proanthocyanidins (PAs) and hydrolysable tannins (HTs), HTs and flavonol derivatives, and HTs and quinic acid derivatives. We observed moderate phylogenetic signal in all polyphenol constituents, apart from the concentration of the prodelphinidin subunit of PAs and the mean degree of polymerisation of PAs. These two traits, which have previously been shown to be important in determining plants' protein precipitation capacity, may have evolved under selection, perhaps in response to climate or herbivore pressure. Hence, the signature of evolutionary history appears to have been erased for these traits. This study is an important step in moving away from analysing "totals" to a better understanding of how phylogenetic effects influence phenolic composition, and how this in turn influences ecological processes.


Asunto(s)
Eucalyptus/química , Polifenoles/análisis , Estructura Molecular , Filogenia , Taninos/análisis
17.
Ecology ; 87(8): 2103-12, 2006 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-16937649

RESUMEN

Most herbivores eat more and survive better when they have access to a variety of foods. One explanation involves the detoxification of plant secondary metabolites (PSMs). By feeding from a variety of plants that contain different classes of PSMs, animals can use multiple detoxification pathways and presumably consume more food. Although popular, this theory is difficult to test because it requires knowledge of the detoxification pathways of each PSM in the diet. We established that common brushtail possums (Trichosurus vulpecula) use various combinations of oxidation, hydrolysis, and conjugation with glucuronic acid (GA) or glycine to detoxify six PSMs. Compared to their ingestion of a single PSM, possums ate more when offered a choice between two diets containing PSMs that require apparently independent detoxification pathways (benzoate and 1,8-cineole, benzoate and p-cymene, benzoate and orcinol, benzoate and salicin, or orcinol and 1,8-cineole). However, possums still did not eat as much of these diets as they did of a basal diet free of PSMs. This suggests that detoxification pathways are never independent, but are separated instead by degrees. In contrast, possums offered a choice of two PSMs that require competing detoxification pathways (1,8-cineole and p-cymene, 1,8-cineole and salicin, or orcinol and salicin) ate no more than when offered diets containing one of the compounds. There was an exception: even though both rutin and orcinol are detoxified via conjugation with GA, the feeding behavior of possums did not suggest competition for detoxification pathways. This implies that the supply of GA is not limiting. This study provides the first convincing evidence that herbivorous mammals can eat more by selecting mixed diets with a diversity of PSMs that make full use of their detoxification potential. It also emphasizes that other behavioral and physiological factors, such as transient food aversions, influence feeding behavior.


Asunto(s)
Conducta Alimentaria , Trichosurus/fisiología , Animales , Alcoholes Bencílicos/administración & dosificación , Alcoholes Bencílicos/farmacocinética , Ciclohexanoles/administración & dosificación , Ciclohexanoles/farmacocinética , Cimenos , Dieta , Ingestión de Alimentos , Eucaliptol , Glucósidos , Masculino , Monoterpenos/administración & dosificación , Monoterpenos/farmacocinética , Plantas/metabolismo , Resorcinoles/administración & dosificación , Resorcinoles/farmacocinética , Rutina/administración & dosificación , Rutina/farmacocinética , Benzoato de Sodio/administración & dosificación , Benzoato de Sodio/farmacocinética , Trichosurus/metabolismo
18.
PLoS One ; 10(5): e0121584, 2015.
Artículo en Inglés | MEDLINE | ID: mdl-25938422

RESUMEN

Although ecologists believe that vertebrate herbivores must select a diet that allows them to meet their nutritional requirements, while avoiding intoxication by plant secondary metabolites, this is remarkably difficult to show. A long series of field and laboratory experiments means that we have a good understanding of the factors that affect feeding by leaf-eating marsupials. This knowledge and the natural intraspecific variation in Eucalyptus chemistry allowed us to test the hypothesis that the feeding decisions of greater gliders (Petauroides volans) depend on the concentrations of available nitrogen (incorporating total nitrogen, dry matter digestibility and tannins) and of formylated phloroglucinol compounds (FPCs), potent antifeedants unique to Eucalyptus. We offered captive greater gliders foliage from two species of Eucalyptus, E. viminalis and E. melliodora, which vary naturally in their concentrations of available nitrogen and FPCs. We then measured the amount of foliage eaten by each glider and compared this with our laboratory analyses of foliar total nitrogen, available nitrogen and FPCs for each tree offered. The concentration of FPCs was the main factor that determined how much gliders ate of E. viminalis and E. melliodora, but in gliders fed E. viminalis the concentration of available nitrogen was also a significant influence. In other words, greater gliders ate E. viminalis leaves with a particular combination of FPCs and available nitrogen that maximised the nutritional gain but minimised their ingestion of toxins. In contrast, the concentration of total nitrogen was not correlated with feeding. This study is among the first to empirically show that browsing herbivores select a diet that balances the potential gain (available nutrients) and the potential costs (plant secondary chemicals) of eating leaves. The major implication of the study is that it is essential to identify the limiting nutrients and relevant toxins in a system in order to understand feeding behaviour.


Asunto(s)
Conducta Alimentaria , Alimentos , Marsupiales/fisiología , Toxinas Biológicas/análisis , Animales , Femenino , Masculino , Nitrógeno/análisis , Floroglucinol/análisis , Hojas de la Planta/química
19.
Oecologia ; 117(3): 365-373, 1998 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-28307915

RESUMEN

We used the doubly labeled water method to measure the field metabolic rates (FMRs, in kJ kg-1 day-1) and water flux rates (WIRs, in ml H2O kg-1 day-1) of adult desert tortoises (Gopherus agassizii) in three parts of the Mojave Desert in California over a 3.5-year period, in order to develop insights into the physiological responses of this threatened species to climate variation among sites and years. FMR, WIR, and the water economy index (WEI, in ml H2O kJ-1, an indicator of drinking of free water) differed extensively among seasons, among study sites, between sexes, and among years. In high-rainfall years, males had higher FMRs than females. Average daily rates of energy and water use by desert tortoises were extraordinarily variable: 28-fold differences in FMR and 237-fold differences in WIR were measured. Some of this variation was due to seasonal conditions, with rates being low during cold winter months and higher in the warm seasons. However, much of the variation was due to responses to year-to-year variation in rainfall. Annual spring peaks in FMR and WIR were higher in wet years than in drought years. Site differences in seasonal patterns were apparently due to geographic differences in rainfall patterns (more summer rain at eastern Mojave sites). In spring 1992, during an El Niño (ENSO) event, the WEI was greater than the maximal value obtainable from consuming succulent vegetation, indicating copious drinking of rainwater at that time. The physiological and behavioral flexibility of desert tortoises, evident in individuals living at all three study sites, appears central to their ability to survive droughts and benefit from periods of resource abundance. The strong effects of the El Niño (ENSO) weather pattern on tortoise physiology, reproduction, and survival elucidated in this and other studies suggest that local manifestations of global climate events could have a long-term influence on the tortoise populations in the Mojave Desert.

20.
PLoS One ; 9(12): e113930, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-25470599

RESUMEN

It is widely postulated that nutritional factors drive bottom-up, resource-based patterns in herbivore ecology and distribution. There is, however, much controversy over the roles of different plant constituents and how these influence individual herbivores and herbivore populations. The density of koala (Phascolarctos cinereus) populations varies widely and many attribute population trends to variation in the nutritional quality of the eucalypt leaves of their diet, but there is little evidence to support this hypothesis. We used a nested design that involved sampling of trees at two spatial scales to investigate how leaf chemistry influences free-living koalas from a low-density population in south east New South Wales, Australia. Using koala faecal pellets as a proxy for koala visitation to trees, we found an interaction between toxins and nutrients in leaves at a small spatial scale, whereby koalas preferred trees with leaves of higher concentrations of available nitrogen but lower concentrations of sideroxylonals (secondary metabolites found exclusively in eucalypts) compared to neighbouring trees of the same species. We argue that taxonomic and phenotypic diversity is likely to be important when foraging in habitats of low nutritional quality in providing diet choice to tradeoff nutrients and toxins and minimise movement costs. Our findings suggest that immediate nutritional concerns are an important priority of folivores in low-quality habitats and imply that nutritional limitations play an important role in constraining folivore populations. We show that, with a careful experimental design, it is possible to make inferences about populations of herbivores that exist at extremely low densities and thus achieve a better understanding about how plant composition influences herbivore ecology and persistence.


Asunto(s)
Fenómenos Fisiológicos Nutricionales de los Animales , Ecosistema , Phascolarctidae/fisiología , Hojas de la Planta/fisiología , Árboles/fisiología , Animales , Eucalyptus/química , Eucalyptus/fisiología , Heces/química , Herbivoria/fisiología , Modelos Teóricos , Nueva Gales del Sur , Hojas de la Planta/química , Densidad de Población , Árboles/química , Árboles/clasificación
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