Albertina De Lima - Academia.edu (original) (raw)
Papers by Albertina De Lima
International Review on Public and Nonprofit Marketing, 2009
This is a summary of the author’s PhD Thesis, supervised by Professor Clementina Galera Casquet a... more This is a summary of the author’s PhD Thesis, supervised by Professor Clementina Galera Casquet and defended on April 27th, 2009 at the Department of Management & Sociology of the Extremadura University (Spain). The thesis is written in portuguese and is available from the author upon request. This thesis examines social marketing techniques for propagating social ideas by public tax organizations with an education program on tax aimed at society in general. Not only can different ways be found in its content matter for improving the social marketing of tax institutions but also the introduction of a new term: “Tax marketing”.
Evolution, 2006
The efficacy of communication relies on detection of species-specific signals against the backgro... more The efficacy of communication relies on detection of species-specific signals against the background noise. Features affecting signal detection are thus expected to evolve under selective pressures represented by masking noise. Spectral partitioning between the auditory signals of co-occurring species has been interpreted as the outcome of the selective effects of masking interference. However, masking interference depends not only on signal's frequency but on receiver's range of frequency sensitivity; moreover, selection on signal frequency can be confounded by selection on body size, because these traits are often correlated. To know whether geographic variation in communication traits agrees with predictions about masking interference effects, we tested the hypothesis that variation in the male-male communication system of the Amazonian frog, Allobates femoralis, is correlated with the occurrence of a single species calling within an overlapping frequency range, Epipedobates trivittatus. We studied frogs at eight sites, four where both species co-occur and four where A. femoralis occurs but E. trivittatus does not. To study the sender component of the communication system of A. femoralis and to describe the use of the spectral range, we analyzed the signal's spectral features of all coactive species at each site. To study the receiver component, we derived frequency-response curves from playback experiments conducted on territorial males of A. femoralis under natural conditions. Most geographic variation in studied traits was correlated with either call frequency or with response frequency range. The occurrence of E. trivittatus significantly predicted narrower and asymmetric frequency-response curves in A. femoralis, without concomitant differences in the call or in body size. The number of acoustically coactive species did not significantly predict variation in any of the studied traits. Our results strongly support that the receiver but not the sender component of the communication system changed due to masking interference by a single species.
Biotropica, 2008
We studied patterns of call acoustics and external morphological differentiation in populations o... more We studied patterns of call acoustics and external morphological differentiation in populations of the dart-poison frog Allobates femoralis occurring in forested areas along a 250-km stretch of the upper Madeira River, Brazil. Multivariate analyses of variance using principal components representing shared acoustic and morphological parameters distinguished three groups in relation to call structure and external morphology: (1) populations belonging to a two-note call morphotype; (2) populations with four-note calls inhabiting the left riverbank; and (3) populations with four-note calls inhabiting the right riverbank. Our results report a case of Amazonian anuran diversity hidden by current taxonomy and provide evidence for the upper Madeira River being a boundary between distinct populations of A. femoralis, and suggest a new taxonomic interpretation for these groups. Samples that did not fit into the general differentiation pattern and the existence of a well-defined contact zone between two morphotypes on the left riverbank indicate that mechanisms complementary to river-barrier hypotheses are necessary to explain the phenotypic differentiation between populations. Our study shows that at least one anuran species shows congruence between population differentiation and separation by a large Amazonian river, as documented for birds and mammals. Conservation efforts should not consider the taxon now known as A. femoralis as a homogeneous entity. There is much within-taxon variability, which can be probably explained partly by the existence of cryptic species, partly by geological barriers and part of which currently has no obvious explanation.
Forest Ecology and Management, 2006
We used forest inventories, conducted in seventy-two 1-ha permanent plots to assess the variation... more We used forest inventories, conducted in seventy-two 1-ha permanent plots to assess the variation in tree and palm aboveground live biomass (AGLB), and its relation with soil gradients (texture and nutrients) and topography (altitude and slope). Our plots, located at Reserva Florestal Adolpho Ducke, a 10,000 ha reserve in central Amazonia, near the city of Manaus, were systematically spread over 64 km 2 . The plots were long (250 m) and narrow (up to 40 m), following elevational contours. Chemical and physical soil analyses were undertaken using topsoil samples, collected in each plot. The plots covered a soil textural gradient ranging from 8% to 98% percent of sand, slopes varying from 0.58 to 278, and the maximum difference of altitude among plots was 70 m, ranging from 39 to 109 m a.s.l. The mean total AGLB (palm + trees) for stems over 1 cm diameter breast height (dbh = 1.3 m), was 327.8 Mg/ha (ranging from 210.9 to 426.3) and was similar to other studies in the region. We found a two-fold variation in total AGLB estimates among plots, with soil or topography explaining around 20% of this variation. AGLB was positively related to either a soil textural gradient (represented by the percentage of clay) or altitude, but was insensitive to slope. Although slope had no detectable effect on the mean variation of AGLB per plot, it explained 14% of the AGLB in understory and emergent trees. On slopes, AGLB is concentrated mostly in tree classes of small size (1 dbh < 10 cm), whereas in flat areas, most of the biomass is concentrated in a few big trees. When considering palms and trees separately, we found that tree biomass tended to increase in clay-rich soils (mostly located in high areas), whereas palm biomass was higher in sandy soils (low slopes and bottomlands). This study shows that forests in central Amazonia grow in a heterogeneous environment in relation to soil and topography, and this heterogeneity seems to be in part responsible for differences in structure and AGLB accumulation. In the forest around Manaus, topography can be used to predict aboveground live biomass as an alternative to soil variables, with similar predictive power. Topographic variables can be easily assessed using satellite imagery and could improve current estimates of carbon stocks over large areas in the Amazon. #
Journal of Tropical Ecology, 2004
... 186 VIVIANE MARIA GUEDES LAYME, ALBERTINA PIMENTEL LIMA AND WILLIAM ERNEST MAGNUSSON ... with... more ... 186 VIVIANE MARIA GUEDES LAYME, ALBERTINA PIMENTEL LIMA AND WILLIAM ERNEST MAGNUSSON ... with more food (Bergallo &amp;amp; Magnusson 1999, Fitzgibbon 1997) and a correlation between ... of seeds has been shown for Mus musculus (Choquenot &amp;amp; Ruscoe 2000). ...
Amphibia-reptilia, 2000
We studied the distribution of anurans in savanna, regrowth and mature forest at the mouth of the... more We studied the distribution of anurans in savanna, regrowth and mature forest at the mouth of the Tapajós river in Brazilian Amazonia. We sampled 31 sites on the right bank of the Tapajós river and on the shores of lakes nearby, and recorded all acoustic and visual observations of frogs. We found 18 anuran species: Leptodactylidae (8), Hylidae , Bufonidae (2) and Pseudidae (1). The distribution of species indicated that some species are generalists and others are restricted to certain habitats. The species at Alter do Chão are a subset of those found in forested sites in Amazonia. Lakes and forested areas had the greatest anuran diversity, but are also the areas most disturbed by tourist development and agriculture. Reduction of anuran diversity in the area could be minimized by concentrating development along the main beaches of the Tapajós river.
Journal of Tropical Ecology, 2007
Abstract: Many studies suggest that edaphic variables are major determinants of frog distribution... more Abstract: Many studies suggest that edaphic variables are major determinants of frog distributions. However, leaf-litter depth and soil characteristics are influenced by distance from streams, so the apparent relationship between edaphic characteristics and species ...
Oecologia, 1999
We studied the energy flow from C3 and C4 plants to higher trophic levels in a central Amazonian ... more We studied the energy flow from C3 and C4 plants to higher trophic levels in a central Amazonian savanna by comparing the carbon stable-isotope ratios of potential food plants to the isotope ratios of species of different consumer groups. All C4 plants encountered in our study area were grasses and all C3 plants were bushes, shrubs or vines. Differences in δ13C ratios among bushes (x¯ = −30.8, SD = 1.2), vines (x¯ = −30.7, SD = 0.46) and trees (x¯ = −29.7, SD = 1.5) were small. However the mean δ13C ratio of dicotyledonous plants (x¯ = −30.4, SD = 1.3) was much more negative than that of the most common grasses (x¯ = −13.4, SD = 0.27). The insect primary consumers had δ13C ratios which ranged from a mean of −29.5 (SD = 0.47) for the grasshopper Tropidacris collaris to a mean of −14.7 (SD = 0.56) for a termite (Nasutitermes sp.), a range similar to that of the vegetation. However, the common insectivorous and omnivorous vertebrates had intermediate values for δ13C, indicating that carbon from different autotrophic sources mixes rapidly as it moves up the food chain. Despite this mixing, the frogs and lizards generally had higher values of δ13C (x¯ = −21.7, SD = 1.6; x¯ = −21.9, SD = 1.8, respectively) than the birds (x¯ = −24.8, SD = 1.8) and the only species of mammal resident in the savanna (x¯ = −25.4), indicating that they are generally more dependent on, or more able to utilise, food chains based on C4 grasses.
Journal of Mammalogy, 2005
We investigated the effects of food availability, fire, and habitat structure on population rates... more We investigated the effects of food availability, fire, and habitat structure on population rates of increase of the rodent Bolomys lasiurus in forty 4-ha plots distributed over an area of about 200 km 2 in Amazonian savannas near Alter do Chão, Pará, Brazil. Mean rodent density over the entire study area declined by about one-half during the study period, despite largely independent density fluctuations within plots. Fires had no detectable association with density and population growth rates. Both densities and population growth rates were significantly associated with availability of invertebrate prey and a multivariate index of habitat structure. Invertebrate availability varied temporally within plots, and was not predictable from knowledge of vegetation structure or fire events.
Forest Ecology and Management, 2000
Oecologia, 1999
We studied the energy¯ow from C 3 and C 4 plants to higher trophic levels in a central Amazonian ... more We studied the energy¯ow from C 3 and C 4 plants to higher trophic levels in a central Amazonian savanna by comparing the carbon stable-isotope ratios of potential food plants to the isotope ratios of species of dierent consumer groups. All C 4 plants encountered in our study area were grasses and all C 3 plants were bushes, shrubs or vines. Dierences in d 13 C ratios among bushes (" x = A30.8, SD = 1.2), vines (" x = A30.7, SD = 0.46) and trees (" x = A29.7, SD = 1.5) were small. However the mean d 13 C ratio of dicotyledonous plants (" x = A30.4, SD = 1.3) was much more negative than that of the most common grasses (" x = A13.4, SD = 0.27). The insect primary consumers had d 13 C ratios which ranged from a mean of A29.5 (SD = 0.47) for the grasshopper Tropidacris collaris to a mean of A14.7 (SD = 0.56) for a termite (Nasutitermes sp.), a range similar to that of the vegetation. However, the common insectivorous and omnivorous vertebrates had intermediate values for d 13 C, indicating that carbon from dierent autotrophic sources mixes rapidly as it moves up the food chain. Despite this mixing, the frogs and lizards generally had higher values of d 13 C (" x = A21.7, SD = 1.6; " x = A21.9, SD = 1.8, respectively) than the birds (" x = A24.8, SD = 1.8) and the only species of mammal resident in the savanna (" x = A25.4), indicating that they are generally more dependent on, or more able to utilise, food chains based on C 4 grasses.
Oecologia, 1998
This study investigates hypotheses about partitioning of food resources among all species and sev... more This study investigates hypotheses about partitioning of food resources among all species and several size classes in an assemblage of diurnal leaf-litter frogs in central Amazonia. All species in this assemblage change the type and size of prey as they grow. An ordination of diet composition was significantly associated with frog size and species-specific behaviour. However, a partial Mantel analysis indicated that species explained about 1.5 times more of the variation in diet overlap between individuals than frog size. Diet and foraging activity are correlated in juveniles, but not in adults, and this result holds whether species are considered as statistically independent observations or whether relationships are analysed using phylogenetically independent contrasts. This study showed that the partitioning of food resources between species changes with the population size structures. Thus, intraspecific and interspecific changes in diet, coupled with different patterns of juvenile recruitment, cause diet segregation among species due to temporal segregation of equivalent size classes.
Journal of Tropical Ecology, 1996
ABSTRACT
Ecology, 2001
We studied the effects of lizard size, and availability of C 3 and C 4 plants, on stable carbon-i... more We studied the effects of lizard size, and availability of C 3 and C 4 plants, on stable carbon-isotope (␦ 13 C) ratios of lizards in an Amazonian savanna. Availability of C 3 and C 4 plants was estimated from 500-point quadrats in each of 38 plots of 3.75 ha. Ratios of ␦ 13 C in muscle tissue were used to estimate the contributions of C 3 -and C 4 -based food chains to the diets of four species of lizards: Cnemidophorus lemniscatus, Kentropyx striata, Ameiva ameiva, and Anolis auratus. The relative contributions of C 3 and C 4 plants to the diets of the lizards were affected by the extent of shrub cover in C. lemniscatus, A. auratus, and possibly in K. striata. However, there was a strong effect of lizard size among and within lizard species. These results are at variance with a previous evaluation of diet overlap among size classes of these species that was based on overlap in prey taxonomic categories. This indicates that species and/or size classes of predators on arthropods may obtain their energy from food chains based on different autotrophic sources, despite high overlap in the taxonomic categories of prey.
In this study, we determined the floristic composition in 38 plots of 3.75 ha (250 m x 150 m) dis... more In this study, we determined the floristic composition in 38 plots of 3.75 ha (250 m x 150 m) distributed throughout 30.000 ha of savannas of " Alter do Chão" , Santarém Municipality. Our surveys revealed 130 species in 45 families. The only species of dicotoledons that covered 1% or more of the area in the herb-shrub layer were Dioclea bicolor Benth. and Lafoensia pacari A. St.-Hil. Most of the area was covered by the grasses Paspalum carinatum Humb. & Bonpl. ex Flügge (16%) and Trachypogon plumosus (Humb. & Bonpl. ex Willd.) Nees (22%). The grass Axonopus canescens (Nees ex Trin.) Pilg. and the sedge Rhyncospora hirsuta Vahl also covered slightly more than 1% of the area. Only eight species, Anacardium occidentale L., Himatanthus fallax (Müll. Arg.) M. M. Plumel, Lafoensia pacari A. St.-Hil., Byrsonima coccolobifolia Kunth, Byrsonima crassifolia (L.) Kunth, Pouteria ramiflora (Mart.) Radlk., Qualea grandiflora Mart. and Salvertia convallariodora A. St.-Hil. had canopies in the tree layer which projected over more than 1% of the area. Of these, only B. crassifolia (5.7%), S. convallariodora (6.0%) and P. ramiflora (2.1%) projected over more than 2% of the area. Most of the area (mean = 53%) did not have any grass, bush or sedge cover and 45% also had no tree-canopy cover. Grasses and sedges covered a mean of 39.2% of the plots, and shrubs 11.0%. The correlations between similarity matrices based on species in different vegetation strata and taxonomic groups were generally low and there was little correlation between matrices based on quantitative data and matrices based on presence/absence. Therefore, caution should be exercised in comparisons among savanna areas based on only one vegetative stratum or on only one taxonomic group.
Biota Neotropica, 2005
Our objectives were to develop a method that would be appropriate for long-term ecological studie... more Our objectives were to develop a method that would be appropriate for long-term ecological studies, but that would permit rapid surveys to evaluate biotic complementarity and land-use planning in Amazonia. The Amazon basin covers about 7 million km 2 . Therefore, even a sparse coverage, with one sample site per 10.000 km 2 , would require about 700 sampling sites. Financial considerations limit the number of sites and investment at each site, but incomplete coverage makes evaluation of biotic complementarity difficult or impossible . Our next challenge is to install similar systems throughout Amazonia. The cost, based on modification of Al Gentry's original design is moderate (less than US$ 50.000 per site if it is not necessary to immediately identify all vascular plants in plots) and we can obtain RAP results for most taxa in the short term at much lower cost. However, biological surveys will only be relevant if the local people participate and the surveys serve as much to teach the local communities about the value of their natural resources as they serve to teach the international community about biodiversity. Therefore, we want to see each site run as a long-term ecological research project by local people and institutions. Biological surveys are an important tool in land-use planning, but only the local people can implement those plans.
Austral Ecology, 2008
The savannas of South America support a relatively diverse ant fauna, but little is known about t... more The savannas of South America support a relatively diverse ant fauna, but little is known about the factors that influence the structure and dynamics of these assemblages. In 1998 and 2002, we surveyed the ground-dwelling ant fauna and the fauna associated with the woody vegetation (using baits and direct sampling) from an Amazonian savanna. The aim was to evaluate the influence of vegetation structure, disturbance by fire and dominant ants on patterns of ant species richness and composition. Variations in the incidence of fires among our 39 survey plots had no or only limited influence on these patterns. In contrast, spatial variations in tree cover and cover by tall grasses (mostly Trachypogon plumosus), significantly affected ant species composition. Part of the variation in species richness among the study plots correlated with variations in the incidence of a dominant species (Solenopsis substituta) at baits. Ant species richness and composition also varied through time, possibly as an indirect effect of changes in vegetation cover. In many plots, and independently of disturbance by fire, there was a major increase in cover by tall grasses, which occupied areas formerly devoid of vegetation. Temporal changes in vegetation did not directly explain the observed increase in the number of ant species per plot. However, the incidence of S. substituta at baits declined sharply in 2002, especially in plots where changes in vegetation cover were more dramatic, and that decline was correlated with an increase in the number of ground-dwelling species, a greater turnover of bait-recruiting species and the appearance of the little fire ant Wasmannia auropunctata. The extent to which these changes in fact resulted from the relaxation of dominance by S. substituta is not clear. However, our results strongly suggest that the ant fauna of Amazonian savannas is affected directly and indirectly by the structure of the vegetation.
International Review on Public and Nonprofit Marketing, 2009
This is a summary of the author’s PhD Thesis, supervised by Professor Clementina Galera Casquet a... more This is a summary of the author’s PhD Thesis, supervised by Professor Clementina Galera Casquet and defended on April 27th, 2009 at the Department of Management & Sociology of the Extremadura University (Spain). The thesis is written in portuguese and is available from the author upon request. This thesis examines social marketing techniques for propagating social ideas by public tax organizations with an education program on tax aimed at society in general. Not only can different ways be found in its content matter for improving the social marketing of tax institutions but also the introduction of a new term: “Tax marketing”.
Evolution, 2006
The efficacy of communication relies on detection of species-specific signals against the backgro... more The efficacy of communication relies on detection of species-specific signals against the background noise. Features affecting signal detection are thus expected to evolve under selective pressures represented by masking noise. Spectral partitioning between the auditory signals of co-occurring species has been interpreted as the outcome of the selective effects of masking interference. However, masking interference depends not only on signal's frequency but on receiver's range of frequency sensitivity; moreover, selection on signal frequency can be confounded by selection on body size, because these traits are often correlated. To know whether geographic variation in communication traits agrees with predictions about masking interference effects, we tested the hypothesis that variation in the male-male communication system of the Amazonian frog, Allobates femoralis, is correlated with the occurrence of a single species calling within an overlapping frequency range, Epipedobates trivittatus. We studied frogs at eight sites, four where both species co-occur and four where A. femoralis occurs but E. trivittatus does not. To study the sender component of the communication system of A. femoralis and to describe the use of the spectral range, we analyzed the signal's spectral features of all coactive species at each site. To study the receiver component, we derived frequency-response curves from playback experiments conducted on territorial males of A. femoralis under natural conditions. Most geographic variation in studied traits was correlated with either call frequency or with response frequency range. The occurrence of E. trivittatus significantly predicted narrower and asymmetric frequency-response curves in A. femoralis, without concomitant differences in the call or in body size. The number of acoustically coactive species did not significantly predict variation in any of the studied traits. Our results strongly support that the receiver but not the sender component of the communication system changed due to masking interference by a single species.
Biotropica, 2008
We studied patterns of call acoustics and external morphological differentiation in populations o... more We studied patterns of call acoustics and external morphological differentiation in populations of the dart-poison frog Allobates femoralis occurring in forested areas along a 250-km stretch of the upper Madeira River, Brazil. Multivariate analyses of variance using principal components representing shared acoustic and morphological parameters distinguished three groups in relation to call structure and external morphology: (1) populations belonging to a two-note call morphotype; (2) populations with four-note calls inhabiting the left riverbank; and (3) populations with four-note calls inhabiting the right riverbank. Our results report a case of Amazonian anuran diversity hidden by current taxonomy and provide evidence for the upper Madeira River being a boundary between distinct populations of A. femoralis, and suggest a new taxonomic interpretation for these groups. Samples that did not fit into the general differentiation pattern and the existence of a well-defined contact zone between two morphotypes on the left riverbank indicate that mechanisms complementary to river-barrier hypotheses are necessary to explain the phenotypic differentiation between populations. Our study shows that at least one anuran species shows congruence between population differentiation and separation by a large Amazonian river, as documented for birds and mammals. Conservation efforts should not consider the taxon now known as A. femoralis as a homogeneous entity. There is much within-taxon variability, which can be probably explained partly by the existence of cryptic species, partly by geological barriers and part of which currently has no obvious explanation.
Forest Ecology and Management, 2006
We used forest inventories, conducted in seventy-two 1-ha permanent plots to assess the variation... more We used forest inventories, conducted in seventy-two 1-ha permanent plots to assess the variation in tree and palm aboveground live biomass (AGLB), and its relation with soil gradients (texture and nutrients) and topography (altitude and slope). Our plots, located at Reserva Florestal Adolpho Ducke, a 10,000 ha reserve in central Amazonia, near the city of Manaus, were systematically spread over 64 km 2 . The plots were long (250 m) and narrow (up to 40 m), following elevational contours. Chemical and physical soil analyses were undertaken using topsoil samples, collected in each plot. The plots covered a soil textural gradient ranging from 8% to 98% percent of sand, slopes varying from 0.58 to 278, and the maximum difference of altitude among plots was 70 m, ranging from 39 to 109 m a.s.l. The mean total AGLB (palm + trees) for stems over 1 cm diameter breast height (dbh = 1.3 m), was 327.8 Mg/ha (ranging from 210.9 to 426.3) and was similar to other studies in the region. We found a two-fold variation in total AGLB estimates among plots, with soil or topography explaining around 20% of this variation. AGLB was positively related to either a soil textural gradient (represented by the percentage of clay) or altitude, but was insensitive to slope. Although slope had no detectable effect on the mean variation of AGLB per plot, it explained 14% of the AGLB in understory and emergent trees. On slopes, AGLB is concentrated mostly in tree classes of small size (1 dbh < 10 cm), whereas in flat areas, most of the biomass is concentrated in a few big trees. When considering palms and trees separately, we found that tree biomass tended to increase in clay-rich soils (mostly located in high areas), whereas palm biomass was higher in sandy soils (low slopes and bottomlands). This study shows that forests in central Amazonia grow in a heterogeneous environment in relation to soil and topography, and this heterogeneity seems to be in part responsible for differences in structure and AGLB accumulation. In the forest around Manaus, topography can be used to predict aboveground live biomass as an alternative to soil variables, with similar predictive power. Topographic variables can be easily assessed using satellite imagery and could improve current estimates of carbon stocks over large areas in the Amazon. #
Journal of Tropical Ecology, 2004
... 186 VIVIANE MARIA GUEDES LAYME, ALBERTINA PIMENTEL LIMA AND WILLIAM ERNEST MAGNUSSON ... with... more ... 186 VIVIANE MARIA GUEDES LAYME, ALBERTINA PIMENTEL LIMA AND WILLIAM ERNEST MAGNUSSON ... with more food (Bergallo &amp;amp; Magnusson 1999, Fitzgibbon 1997) and a correlation between ... of seeds has been shown for Mus musculus (Choquenot &amp;amp; Ruscoe 2000). ...
Amphibia-reptilia, 2000
We studied the distribution of anurans in savanna, regrowth and mature forest at the mouth of the... more We studied the distribution of anurans in savanna, regrowth and mature forest at the mouth of the Tapajós river in Brazilian Amazonia. We sampled 31 sites on the right bank of the Tapajós river and on the shores of lakes nearby, and recorded all acoustic and visual observations of frogs. We found 18 anuran species: Leptodactylidae (8), Hylidae , Bufonidae (2) and Pseudidae (1). The distribution of species indicated that some species are generalists and others are restricted to certain habitats. The species at Alter do Chão are a subset of those found in forested sites in Amazonia. Lakes and forested areas had the greatest anuran diversity, but are also the areas most disturbed by tourist development and agriculture. Reduction of anuran diversity in the area could be minimized by concentrating development along the main beaches of the Tapajós river.
Journal of Tropical Ecology, 2007
Abstract: Many studies suggest that edaphic variables are major determinants of frog distribution... more Abstract: Many studies suggest that edaphic variables are major determinants of frog distributions. However, leaf-litter depth and soil characteristics are influenced by distance from streams, so the apparent relationship between edaphic characteristics and species ...
Oecologia, 1999
We studied the energy flow from C3 and C4 plants to higher trophic levels in a central Amazonian ... more We studied the energy flow from C3 and C4 plants to higher trophic levels in a central Amazonian savanna by comparing the carbon stable-isotope ratios of potential food plants to the isotope ratios of species of different consumer groups. All C4 plants encountered in our study area were grasses and all C3 plants were bushes, shrubs or vines. Differences in δ13C ratios among bushes (x¯ = −30.8, SD = 1.2), vines (x¯ = −30.7, SD = 0.46) and trees (x¯ = −29.7, SD = 1.5) were small. However the mean δ13C ratio of dicotyledonous plants (x¯ = −30.4, SD = 1.3) was much more negative than that of the most common grasses (x¯ = −13.4, SD = 0.27). The insect primary consumers had δ13C ratios which ranged from a mean of −29.5 (SD = 0.47) for the grasshopper Tropidacris collaris to a mean of −14.7 (SD = 0.56) for a termite (Nasutitermes sp.), a range similar to that of the vegetation. However, the common insectivorous and omnivorous vertebrates had intermediate values for δ13C, indicating that carbon from different autotrophic sources mixes rapidly as it moves up the food chain. Despite this mixing, the frogs and lizards generally had higher values of δ13C (x¯ = −21.7, SD = 1.6; x¯ = −21.9, SD = 1.8, respectively) than the birds (x¯ = −24.8, SD = 1.8) and the only species of mammal resident in the savanna (x¯ = −25.4), indicating that they are generally more dependent on, or more able to utilise, food chains based on C4 grasses.
Journal of Mammalogy, 2005
We investigated the effects of food availability, fire, and habitat structure on population rates... more We investigated the effects of food availability, fire, and habitat structure on population rates of increase of the rodent Bolomys lasiurus in forty 4-ha plots distributed over an area of about 200 km 2 in Amazonian savannas near Alter do Chão, Pará, Brazil. Mean rodent density over the entire study area declined by about one-half during the study period, despite largely independent density fluctuations within plots. Fires had no detectable association with density and population growth rates. Both densities and population growth rates were significantly associated with availability of invertebrate prey and a multivariate index of habitat structure. Invertebrate availability varied temporally within plots, and was not predictable from knowledge of vegetation structure or fire events.
Forest Ecology and Management, 2000
Oecologia, 1999
We studied the energy¯ow from C 3 and C 4 plants to higher trophic levels in a central Amazonian ... more We studied the energy¯ow from C 3 and C 4 plants to higher trophic levels in a central Amazonian savanna by comparing the carbon stable-isotope ratios of potential food plants to the isotope ratios of species of dierent consumer groups. All C 4 plants encountered in our study area were grasses and all C 3 plants were bushes, shrubs or vines. Dierences in d 13 C ratios among bushes (" x = A30.8, SD = 1.2), vines (" x = A30.7, SD = 0.46) and trees (" x = A29.7, SD = 1.5) were small. However the mean d 13 C ratio of dicotyledonous plants (" x = A30.4, SD = 1.3) was much more negative than that of the most common grasses (" x = A13.4, SD = 0.27). The insect primary consumers had d 13 C ratios which ranged from a mean of A29.5 (SD = 0.47) for the grasshopper Tropidacris collaris to a mean of A14.7 (SD = 0.56) for a termite (Nasutitermes sp.), a range similar to that of the vegetation. However, the common insectivorous and omnivorous vertebrates had intermediate values for d 13 C, indicating that carbon from dierent autotrophic sources mixes rapidly as it moves up the food chain. Despite this mixing, the frogs and lizards generally had higher values of d 13 C (" x = A21.7, SD = 1.6; " x = A21.9, SD = 1.8, respectively) than the birds (" x = A24.8, SD = 1.8) and the only species of mammal resident in the savanna (" x = A25.4), indicating that they are generally more dependent on, or more able to utilise, food chains based on C 4 grasses.
Oecologia, 1998
This study investigates hypotheses about partitioning of food resources among all species and sev... more This study investigates hypotheses about partitioning of food resources among all species and several size classes in an assemblage of diurnal leaf-litter frogs in central Amazonia. All species in this assemblage change the type and size of prey as they grow. An ordination of diet composition was significantly associated with frog size and species-specific behaviour. However, a partial Mantel analysis indicated that species explained about 1.5 times more of the variation in diet overlap between individuals than frog size. Diet and foraging activity are correlated in juveniles, but not in adults, and this result holds whether species are considered as statistically independent observations or whether relationships are analysed using phylogenetically independent contrasts. This study showed that the partitioning of food resources between species changes with the population size structures. Thus, intraspecific and interspecific changes in diet, coupled with different patterns of juvenile recruitment, cause diet segregation among species due to temporal segregation of equivalent size classes.
Journal of Tropical Ecology, 1996
ABSTRACT
Ecology, 2001
We studied the effects of lizard size, and availability of C 3 and C 4 plants, on stable carbon-i... more We studied the effects of lizard size, and availability of C 3 and C 4 plants, on stable carbon-isotope (␦ 13 C) ratios of lizards in an Amazonian savanna. Availability of C 3 and C 4 plants was estimated from 500-point quadrats in each of 38 plots of 3.75 ha. Ratios of ␦ 13 C in muscle tissue were used to estimate the contributions of C 3 -and C 4 -based food chains to the diets of four species of lizards: Cnemidophorus lemniscatus, Kentropyx striata, Ameiva ameiva, and Anolis auratus. The relative contributions of C 3 and C 4 plants to the diets of the lizards were affected by the extent of shrub cover in C. lemniscatus, A. auratus, and possibly in K. striata. However, there was a strong effect of lizard size among and within lizard species. These results are at variance with a previous evaluation of diet overlap among size classes of these species that was based on overlap in prey taxonomic categories. This indicates that species and/or size classes of predators on arthropods may obtain their energy from food chains based on different autotrophic sources, despite high overlap in the taxonomic categories of prey.
In this study, we determined the floristic composition in 38 plots of 3.75 ha (250 m x 150 m) dis... more In this study, we determined the floristic composition in 38 plots of 3.75 ha (250 m x 150 m) distributed throughout 30.000 ha of savannas of " Alter do Chão" , Santarém Municipality. Our surveys revealed 130 species in 45 families. The only species of dicotoledons that covered 1% or more of the area in the herb-shrub layer were Dioclea bicolor Benth. and Lafoensia pacari A. St.-Hil. Most of the area was covered by the grasses Paspalum carinatum Humb. & Bonpl. ex Flügge (16%) and Trachypogon plumosus (Humb. & Bonpl. ex Willd.) Nees (22%). The grass Axonopus canescens (Nees ex Trin.) Pilg. and the sedge Rhyncospora hirsuta Vahl also covered slightly more than 1% of the area. Only eight species, Anacardium occidentale L., Himatanthus fallax (Müll. Arg.) M. M. Plumel, Lafoensia pacari A. St.-Hil., Byrsonima coccolobifolia Kunth, Byrsonima crassifolia (L.) Kunth, Pouteria ramiflora (Mart.) Radlk., Qualea grandiflora Mart. and Salvertia convallariodora A. St.-Hil. had canopies in the tree layer which projected over more than 1% of the area. Of these, only B. crassifolia (5.7%), S. convallariodora (6.0%) and P. ramiflora (2.1%) projected over more than 2% of the area. Most of the area (mean = 53%) did not have any grass, bush or sedge cover and 45% also had no tree-canopy cover. Grasses and sedges covered a mean of 39.2% of the plots, and shrubs 11.0%. The correlations between similarity matrices based on species in different vegetation strata and taxonomic groups were generally low and there was little correlation between matrices based on quantitative data and matrices based on presence/absence. Therefore, caution should be exercised in comparisons among savanna areas based on only one vegetative stratum or on only one taxonomic group.
Biota Neotropica, 2005
Our objectives were to develop a method that would be appropriate for long-term ecological studie... more Our objectives were to develop a method that would be appropriate for long-term ecological studies, but that would permit rapid surveys to evaluate biotic complementarity and land-use planning in Amazonia. The Amazon basin covers about 7 million km 2 . Therefore, even a sparse coverage, with one sample site per 10.000 km 2 , would require about 700 sampling sites. Financial considerations limit the number of sites and investment at each site, but incomplete coverage makes evaluation of biotic complementarity difficult or impossible . Our next challenge is to install similar systems throughout Amazonia. The cost, based on modification of Al Gentry's original design is moderate (less than US$ 50.000 per site if it is not necessary to immediately identify all vascular plants in plots) and we can obtain RAP results for most taxa in the short term at much lower cost. However, biological surveys will only be relevant if the local people participate and the surveys serve as much to teach the local communities about the value of their natural resources as they serve to teach the international community about biodiversity. Therefore, we want to see each site run as a long-term ecological research project by local people and institutions. Biological surveys are an important tool in land-use planning, but only the local people can implement those plans.
Austral Ecology, 2008
The savannas of South America support a relatively diverse ant fauna, but little is known about t... more The savannas of South America support a relatively diverse ant fauna, but little is known about the factors that influence the structure and dynamics of these assemblages. In 1998 and 2002, we surveyed the ground-dwelling ant fauna and the fauna associated with the woody vegetation (using baits and direct sampling) from an Amazonian savanna. The aim was to evaluate the influence of vegetation structure, disturbance by fire and dominant ants on patterns of ant species richness and composition. Variations in the incidence of fires among our 39 survey plots had no or only limited influence on these patterns. In contrast, spatial variations in tree cover and cover by tall grasses (mostly Trachypogon plumosus), significantly affected ant species composition. Part of the variation in species richness among the study plots correlated with variations in the incidence of a dominant species (Solenopsis substituta) at baits. Ant species richness and composition also varied through time, possibly as an indirect effect of changes in vegetation cover. In many plots, and independently of disturbance by fire, there was a major increase in cover by tall grasses, which occupied areas formerly devoid of vegetation. Temporal changes in vegetation did not directly explain the observed increase in the number of ant species per plot. However, the incidence of S. substituta at baits declined sharply in 2002, especially in plots where changes in vegetation cover were more dramatic, and that decline was correlated with an increase in the number of ground-dwelling species, a greater turnover of bait-recruiting species and the appearance of the little fire ant Wasmannia auropunctata. The extent to which these changes in fact resulted from the relaxation of dominance by S. substituta is not clear. However, our results strongly suggest that the ant fauna of Amazonian savannas is affected directly and indirectly by the structure of the vegetation.