Professor of Ecology at Universidade Federal do Rio de JaneiroWork with mammalogy, evolution, population biology, conservation biology and sometimes with public policies and health issues.
The restinga de Maricá has twelve species of mammals identified. All species are in common with t... more The restinga de Maricá has twelve species of mammals identified. All species are in common with the Atlantic Forest. The ones we studied the water balance had no adaptation to salt concentration. The restinga has four major type of macrohabitat that are determined by the interaction between soil and microclimate. There some variation in mammal distribution and abundance due to habitat variation at both meso and micro scales. The variation was the cause in the variance in mammal density at each collecting place with no discernible border effect: where humidity is higher there was higher mammal diversity and populations. A population study was carried out during five years showing an increase in abundance in an La Niña year. Only one in seven species showed no microhabitat preferences. This one had its distribution determined by abundance of alimentary resources. Some methodological problems are discussed.
The biotic communities of the sandy coastal plains of Eastern Brazil are called restingas. Their ... more The biotic communities of the sandy coastal plains of Eastern Brazil are called restingas. Their biotas are composed chiefly by that occur in the nearby biomes, the Atlantic Forest and the Caatingas. This similarity is due to the Pleistocene origin of these plains. Some species are endemic. Such endemism is linked to Quaternary sea level variation.
Nutritional requirements of 12 species of Neotropical opossums (Didelphidae) were inferred throug... more Nutritional requirements of 12 species of Neotropical opossums (Didelphidae) were inferred through a laboratory food preference experiment. Nutritional contents of experimental diets follow predictions based on field diet data, with more frugivorous species showing high non-structural carbohydrate proportions and more carnivorous species high protein contents in their selected diets. Mouse opossums selected nutritional and fibre proportions that suggested that they may be more frugivorous and less strictly insectivorous than previously thought. The species form a gradient of differential food specialisation from frugivory to car-nivory, and significant differences are found only between extremes of this gradient. Nutritional contents established here are consistent with natural diet patterns and can be used as important complementary data to field diet studies and to prepare diets for captive maintenance of the species.
The reproduction, development and growth in Akodon lindberghi were studied in captivity. The col... more The reproduction, development and growth in Akodon lindberghi were studied in captivity. The colony was derived from animals captured in Simão Pereira, Minas Gerais State, which represents a new area of geographical distribution known for this species. Twelve males and twelve females were crossed, producing 144 young in 53 litters. Post-partum oestrus was observed and gestation length was estimated in 23 days. Litter size ranged from 1 to 4 with a mean of 2.72 (SD=0.97, n=53) and modal size of 3. Sexual dimorphism was neither present at body mass at birth nor at weaning. There was a significant negative correlation between litter size and mass at birth or weaning. Permanent emergence of adult external appearance occurred at 15 days. Puberty for males and females was 43 and 42 days, respectively, and the first fecundation event for two females was recorded at 47 and 54 days of age. The weight growth was described fitting a Gompertz model. No significant difference was found in any parameter of growth curves for males and females. Measurements (head-body, tail, hind foot and internal and external ear lengths) obtained for adult individuals did not also reveal the presence of sexual dimorphism.
Space and diet are frequently considered the two most important dimensions of an organism niche, ... more Space and diet are frequently considered the two most important dimensions of an organism niche, but in tropical forests these two dimensions are associated, with fruits more accessible in the canopy and upper strata of the forest, and arthropods more abundant in the forest litter. This constitutes a genuine macroecological pattern, potentially common to all tropical forests. We tested the existence of this trade-off between frugivory-insectivory in the vertical strata, and if it results from feeding specializations, using didelphid marsupials as a model group. We compared nine species, representing different lineages, that differ in diet and use of the forest strata, using phylogenetically independent contrasts. Species were classified according to their use of the vertical strata into four categories based on the literature (terrestrial-semiaquatic, terrestrial-understory, underestory-subcanopy-canopy, and canopy only). Diet was analyzed by the proportion of nutrients (carbohydrates, fibers, proteins and lipids) in a cafeteria food preference experiment: more frugivorous diets have higher carbohydrate and fiber content, whereas more carnivorous and insectivorous diets have higher protein and lipid content. Along the phylogeny, increases in use of the vertical strata were significantly associated with increases in carbohydrate and fiber contents, and reductions in lipid content. Levels of protein content also reduced with increasing use of the vertical strata, but this association was not significant. The macroecological pattern of increasing frugivory with use of the upper strata is supported by the results for didelphid marsupials, which also indicate specialization is a mechanism involved. The contribution of didelphid marsupials to the ecosystem process of frugivory and seed dispersal is performed by a subset of species, despite being broadly described as omnivorous. Future studies should evaluate this macroecological pattern in more specialized taxonomic groups that vary in the use of the vertical strata, and if specialization is the general mechanism involved.
Schistosomiasis is a health problem in Brazil and the role of rodents in maintaining the ... more Schistosomiasis is a health problem in Brazil and the role of rodents in maintaining the schistosome life-cycle requires further clarification. The influence of Schistosoma mansoni on a population of Nectomys squamipes was studied by capture-recapture (1st phase, from June 1991 to November 1995) and removal (2nd phase, from April 1997 to March 1999) studies at Sumidouro, Rio de Janeiro, Brazil. During both phases coproscopic examinations were performed. At the 2nd phase the rodents were perfused and worms were counted. The population dynamics of parasites was studied. During the 1st phase, female reproductive parameters, longevity, recruitment and survivorship rates and migration patterns were studied in relation to schistosome prevalence. Water contamination (source of miracidia), abundance intermediate host and rodent migration were related to prevalence. The N. squamipes population was not obviously influenced by the infection, as shown by the high number of reproductive infected females, high longevity of infected individuals and the absence of a relationship between recruitment or survivorship rates and the intensity of schistosome infection. The data indicate that N. squamipes can increase transmission of S. mansoni in endemic areas and carry it to non-infected areas. Furthermore, this rodent can be used as an indicator of a transmission focus.
Brazilian Private Natural Heritage Reserves (RPPN, the Portuguese acronym), which are established... more Brazilian Private Natural Heritage Reserves (RPPN, the Portuguese acronym), which are established on private lands must be considered when total protected areas are surveyd
The role of Victor Ernest Shelford and Charles Christopher Adams in the origins of Ecology as sc... more The role of Victor Ernest Shelford and Charles Christopher Adams in the origins of Ecology as science
OPINIÃO Uma atividade básica em Zoologia é a coleta de dados no campo. Se um país pretende ter o ... more OPINIÃO Uma atividade básica em Zoologia é a coleta de dados no campo. Se um país pretende ter o controle efetivo sobre seus recursos naturais assim como cuidar da saúde pública e da proteção à biodiversidade, as atividades básicas de coleta de dados devem ser incentivadas e não se pode conceber que exista uma política que, de fato, obstaculize o colecionamento. Os dados coletados pelos mastozoóogos (e pelos zoólogos, em geral) podem ser sobre os animais em estudo ou sobre as condições ambientais do local onde constatamos sua presença. Dados sobre os animais podem, grosso modo, serem de dois tipos:
Karyotypic analysis was performed in two male specimens of Sphiggurus villosus collected in the A... more Karyotypic analysis was performed in two male specimens of Sphiggurus villosus collected in the Atlantic forest of Rio de Janeiro State, Brazil. The observed 2n = 42 / FN = 76 karyotype was similar to those of other Erethizontidae such as Erethizon dorsatum and Sphiggurus vestitus pruinosus and to those of other histricomorph rodents as Myocastor coypus and Agouti taczanowskii. Our data support the proposition that 2n = 42 is an ancestral condition of the Erethizontidae.
RESUMO: Pequenos mamíferos (roedores e marsupiais) neotropicais do leste do Brasil foram estudado... more RESUMO: Pequenos mamíferos (roedores e marsupiais) neotropicais do leste do Brasil foram estudados em relação aos fatores responsáveis pelo início da estação reprodutora. Os primeiros estudos utilizaram os dados de espécies depositados no Museu Nacional e, posteriormente, trabalhos de campo e de laboratório. Dois modos de reprodução foram concebidos. Constatou-se que os marsupiais têm o início da estação reprodutora determinado pela variação do fotoperíodo. Os roedores Sigmodontini no Nordeste do Brasil têm sua reprodução iniciada pela chegada da estação chuvosa. O modo de reprodução dos marsupiais é, portanto, marcadamente estacional e relativamente independente das condições ambientais com solstícios e equinócios funcionando como fatores próximos. O modo de reprodução dos Sigmodontini é determinado pela possibilidade das fêmeas acumularem reservas e está ligado diretamente aos fatores primários. Palavras-chave: Marsupiais, roedores, fatores ambientais, reprodução, estação reprodutiva, ecologia da reprodução, chuva, duração do dia. ABSTRACT: Environmental factors and the reproduction of eastern Brazilian marsupials and rodents. Small neotropical mammals were studied in relation to factors determining the onset of the breeding season. The first studies were based on data from specimens housed at the Museu Nacional, Rio de Janeiro, and were followed by field and laboratory studies. Two modes of reproduction were first proposed. Later, it was found that marsupials have the onset of the breeding season determined by the variation of photoperiod. The Sigmodontini rodents in Northeastern Brazil have their reproduction set by the beginning of the rainy season. Therefore, the marsupial mode of reproduction is markedly climatically seasonal, being somewhat independent of environmental conditions, solstices and equinoxes functioning as proximal factors. The Sigmodontini mode of reproduction has the onset of the breeding season determined by the storage of reserves by the females being linked directly to primary factors.
La reproduction de Didelphis albiventris a etc etudiee dans trois regions du nord-est du Bresil. ... more La reproduction de Didelphis albiventris a etc etudiee dans trois regions du nord-est du Bresil. On n'a pas observe de variations du pelage. La croissance des femelles est plus rapide que celle des males apres l'adolescence (au-delä de la classe 5). Le commencement de la saison de reproduction semble en rapport avec la distribution des preci-pitations. II n'y a pas de taille minimale des femelles qui commencent ä se reproduire, mais seulement un age minimal. II y a des males fertiles toute 1'annee. Les implications ecologiques de ces faits sont discutees.
The Neotropical black-eared opossums comprise two allopatric species that are restricted to fores... more The Neotropical black-eared opossums comprise two allopatric species that are restricted to forested habitats : Didelphis aurita occurring from northern Argentina to the Northeast of Brazil, mostly along the Atlantic rainforest but also at Araucaria highlands, and D. mar-supialis which occurs mostly within the Amazonian rainforest. Their status as separate species or allopatric subspecies has been a matter of debate. We provide an analysis of the morphometric differences between D. aurita and D. marsupialis based on eigheteen cranium measurements. An ANOVA between sexes showed sexual dimorphism with males consistently larger than females in both species. Hence, sexes were treated separately. ANOVA between D. aurita and D. marsu-pialis showed that they are significantly different for 14 and eight characters of females and males, respectively. D. aurita and D. marsupialis were also readily separated by discriminant analysis that correctly classified more than SO % of the specimens. The squared Mahalanobis distances were slightly higher than five at both sexes. Despite the lack of obvious qualitative morphological characters distinguishing D. aurita and D. marsupialis, our results show that they are morphometrically diagnosable and should be considered separate species. Resume.-Les opossums ä oreilles noires neotropicaux sont represented par deux especes allopatriques limitees a des habitats de foret: Didelphis aurita, repartie depuis le nord de Argentine jusqu'au nord-est du Bresil, surtout le long de la foret atlantique, mais aussi sur les plateaux a Araucarias ; D. marsupialis qui se trouve surtout dans la foret d'Amazonie. Leur Statut d'especes ou de sous-especes allopatriques a ete le sujet de debats. Dans ce travail nous donnons une analyse des differences morphometriques entre D. aurita et D. marsupialis en utilisant 18 mensurations du crane. Une ANOVA entre sexes a mis en evidence 1'existence d'un dimor-phisme sexuel, les males etant plus grands que les femelles dans les deux formes. Les sexes ont done ete traites separement. Une ANOVA entre D. aurita et D. marsupialis a montre que les deux especes sont significativement differentes pour 14 caracteres de femelles et 8 caracteres de males. D. aurita et D. marsupialis sont aussi immediatement separees par une analyse discrimi-nante qui a permis de reconnaitre correctement plus de 80 % des specimens. Les carres des distances de Mahalanobis ont ete legerement superieurs ä cinq pour les deux sexes. Malgre Fabsence de caracteres morphologiques qualitatifs qui distinguent D. aurita de D. marsupialis, nos resultats montrent qu'ils sont morphometriquement identifiables et doivent etre considered comme deux especes distinctes.
The variables in habitat studies are usually transformed in such a way that they become abstracti... more The variables in habitat studies are usually transformed in such a way that they become abstractions and intuition is lost. We tested a new method for the analysis of habitat using data collected in a grid laid at the " restinga de Maricá " , in Rio de Janeiro State, Brazil. Thirty-seven microhabitat variables were measured at each trap station. We assume that these variables characterize the microhabitat structure at the moment when measurements were taken. The data are transformed in 3 ways: (1) the averages of the measured variables were calculated, as usual in habitat studies; (2) the data are transformed in densities per area in square meters without reduction in the number of variables; and (3) we calculated the natural logarithms of the data thus transformed. The 3 sets were analised through discriminant analysis. The logarithms of densities were the most efficient kind of transformation. This transformation resulted in a significance of p = 0.0001 with 39.72% of variance in the 1 st discrimi-nant function and of p = 0.0426 with 31.45% of variance in the 2 nd function, and 84.62% of groups correctly classified. We obtained better classification results than previous similar works and we kept the intuition through the data analysis. RESUMO Um novo método de estudo da estrutura de microhábitat de pequenos mamíferos As variáveis utilizadas em estudos de hábitat são transformadas de tal maneira que se tornam abstrações e se perde a intuição. Testamos um novo método para esse tipo de análise usando dados coletados em uma grade na restinga de Maricá, Rio de Janeiro. Em cada ponto de captura foram medidas 37 variáveis de microhábitat. Consideramos que tais variáveis caracterizam a estrutura dos microhábitats no momento em que são tomadas. Os dados foram transformados de 3 maneiras: (1) as médias das variáveis foram calculadas, como é usual em estudos de hábitat; (2) os dados foram transformados em suas densidades por área em metros quadrados, sem redução no número de variáveis; e (3) calculamos os logaritimos naturais dos dados transformados em densidades. Os 3 conjuntos foram submetidos à análise discri-minante. O logaritimo das densidades foi o tipo de transformação mais eficiente. Esta transformação resultou na obtenção de p = 0,0001, com 39,72% da variância na 1 a função e um p = 0,0426 com 31,45% da variância na 2 a função, com um acerto de 84,62% na classificação dos grupos. Os resultados obtidos foram melhores do que em trabalhos similares anteriores, mantendo-se a intuição.
The restinga de Maricá has twelve species of mammals identified. All species are in common with t... more The restinga de Maricá has twelve species of mammals identified. All species are in common with the Atlantic Forest. The ones we studied the water balance had no adaptation to salt concentration. The restinga has four major type of macrohabitat that are determined by the interaction between soil and microclimate. There some variation in mammal distribution and abundance due to habitat variation at both meso and micro scales. The variation was the cause in the variance in mammal density at each collecting place with no discernible border effect: where humidity is higher there was higher mammal diversity and populations. A population study was carried out during five years showing an increase in abundance in an La Niña year. Only one in seven species showed no microhabitat preferences. This one had its distribution determined by abundance of alimentary resources. Some methodological problems are discussed.
The biotic communities of the sandy coastal plains of Eastern Brazil are called restingas. Their ... more The biotic communities of the sandy coastal plains of Eastern Brazil are called restingas. Their biotas are composed chiefly by that occur in the nearby biomes, the Atlantic Forest and the Caatingas. This similarity is due to the Pleistocene origin of these plains. Some species are endemic. Such endemism is linked to Quaternary sea level variation.
Nutritional requirements of 12 species of Neotropical opossums (Didelphidae) were inferred throug... more Nutritional requirements of 12 species of Neotropical opossums (Didelphidae) were inferred through a laboratory food preference experiment. Nutritional contents of experimental diets follow predictions based on field diet data, with more frugivorous species showing high non-structural carbohydrate proportions and more carnivorous species high protein contents in their selected diets. Mouse opossums selected nutritional and fibre proportions that suggested that they may be more frugivorous and less strictly insectivorous than previously thought. The species form a gradient of differential food specialisation from frugivory to car-nivory, and significant differences are found only between extremes of this gradient. Nutritional contents established here are consistent with natural diet patterns and can be used as important complementary data to field diet studies and to prepare diets for captive maintenance of the species.
The reproduction, development and growth in Akodon lindberghi were studied in captivity. The col... more The reproduction, development and growth in Akodon lindberghi were studied in captivity. The colony was derived from animals captured in Simão Pereira, Minas Gerais State, which represents a new area of geographical distribution known for this species. Twelve males and twelve females were crossed, producing 144 young in 53 litters. Post-partum oestrus was observed and gestation length was estimated in 23 days. Litter size ranged from 1 to 4 with a mean of 2.72 (SD=0.97, n=53) and modal size of 3. Sexual dimorphism was neither present at body mass at birth nor at weaning. There was a significant negative correlation between litter size and mass at birth or weaning. Permanent emergence of adult external appearance occurred at 15 days. Puberty for males and females was 43 and 42 days, respectively, and the first fecundation event for two females was recorded at 47 and 54 days of age. The weight growth was described fitting a Gompertz model. No significant difference was found in any parameter of growth curves for males and females. Measurements (head-body, tail, hind foot and internal and external ear lengths) obtained for adult individuals did not also reveal the presence of sexual dimorphism.
Space and diet are frequently considered the two most important dimensions of an organism niche, ... more Space and diet are frequently considered the two most important dimensions of an organism niche, but in tropical forests these two dimensions are associated, with fruits more accessible in the canopy and upper strata of the forest, and arthropods more abundant in the forest litter. This constitutes a genuine macroecological pattern, potentially common to all tropical forests. We tested the existence of this trade-off between frugivory-insectivory in the vertical strata, and if it results from feeding specializations, using didelphid marsupials as a model group. We compared nine species, representing different lineages, that differ in diet and use of the forest strata, using phylogenetically independent contrasts. Species were classified according to their use of the vertical strata into four categories based on the literature (terrestrial-semiaquatic, terrestrial-understory, underestory-subcanopy-canopy, and canopy only). Diet was analyzed by the proportion of nutrients (carbohydrates, fibers, proteins and lipids) in a cafeteria food preference experiment: more frugivorous diets have higher carbohydrate and fiber content, whereas more carnivorous and insectivorous diets have higher protein and lipid content. Along the phylogeny, increases in use of the vertical strata were significantly associated with increases in carbohydrate and fiber contents, and reductions in lipid content. Levels of protein content also reduced with increasing use of the vertical strata, but this association was not significant. The macroecological pattern of increasing frugivory with use of the upper strata is supported by the results for didelphid marsupials, which also indicate specialization is a mechanism involved. The contribution of didelphid marsupials to the ecosystem process of frugivory and seed dispersal is performed by a subset of species, despite being broadly described as omnivorous. Future studies should evaluate this macroecological pattern in more specialized taxonomic groups that vary in the use of the vertical strata, and if specialization is the general mechanism involved.
Schistosomiasis is a health problem in Brazil and the role of rodents in maintaining the ... more Schistosomiasis is a health problem in Brazil and the role of rodents in maintaining the schistosome life-cycle requires further clarification. The influence of Schistosoma mansoni on a population of Nectomys squamipes was studied by capture-recapture (1st phase, from June 1991 to November 1995) and removal (2nd phase, from April 1997 to March 1999) studies at Sumidouro, Rio de Janeiro, Brazil. During both phases coproscopic examinations were performed. At the 2nd phase the rodents were perfused and worms were counted. The population dynamics of parasites was studied. During the 1st phase, female reproductive parameters, longevity, recruitment and survivorship rates and migration patterns were studied in relation to schistosome prevalence. Water contamination (source of miracidia), abundance intermediate host and rodent migration were related to prevalence. The N. squamipes population was not obviously influenced by the infection, as shown by the high number of reproductive infected females, high longevity of infected individuals and the absence of a relationship between recruitment or survivorship rates and the intensity of schistosome infection. The data indicate that N. squamipes can increase transmission of S. mansoni in endemic areas and carry it to non-infected areas. Furthermore, this rodent can be used as an indicator of a transmission focus.
Brazilian Private Natural Heritage Reserves (RPPN, the Portuguese acronym), which are established... more Brazilian Private Natural Heritage Reserves (RPPN, the Portuguese acronym), which are established on private lands must be considered when total protected areas are surveyd
The role of Victor Ernest Shelford and Charles Christopher Adams in the origins of Ecology as sc... more The role of Victor Ernest Shelford and Charles Christopher Adams in the origins of Ecology as science
OPINIÃO Uma atividade básica em Zoologia é a coleta de dados no campo. Se um país pretende ter o ... more OPINIÃO Uma atividade básica em Zoologia é a coleta de dados no campo. Se um país pretende ter o controle efetivo sobre seus recursos naturais assim como cuidar da saúde pública e da proteção à biodiversidade, as atividades básicas de coleta de dados devem ser incentivadas e não se pode conceber que exista uma política que, de fato, obstaculize o colecionamento. Os dados coletados pelos mastozoóogos (e pelos zoólogos, em geral) podem ser sobre os animais em estudo ou sobre as condições ambientais do local onde constatamos sua presença. Dados sobre os animais podem, grosso modo, serem de dois tipos:
Karyotypic analysis was performed in two male specimens of Sphiggurus villosus collected in the A... more Karyotypic analysis was performed in two male specimens of Sphiggurus villosus collected in the Atlantic forest of Rio de Janeiro State, Brazil. The observed 2n = 42 / FN = 76 karyotype was similar to those of other Erethizontidae such as Erethizon dorsatum and Sphiggurus vestitus pruinosus and to those of other histricomorph rodents as Myocastor coypus and Agouti taczanowskii. Our data support the proposition that 2n = 42 is an ancestral condition of the Erethizontidae.
RESUMO: Pequenos mamíferos (roedores e marsupiais) neotropicais do leste do Brasil foram estudado... more RESUMO: Pequenos mamíferos (roedores e marsupiais) neotropicais do leste do Brasil foram estudados em relação aos fatores responsáveis pelo início da estação reprodutora. Os primeiros estudos utilizaram os dados de espécies depositados no Museu Nacional e, posteriormente, trabalhos de campo e de laboratório. Dois modos de reprodução foram concebidos. Constatou-se que os marsupiais têm o início da estação reprodutora determinado pela variação do fotoperíodo. Os roedores Sigmodontini no Nordeste do Brasil têm sua reprodução iniciada pela chegada da estação chuvosa. O modo de reprodução dos marsupiais é, portanto, marcadamente estacional e relativamente independente das condições ambientais com solstícios e equinócios funcionando como fatores próximos. O modo de reprodução dos Sigmodontini é determinado pela possibilidade das fêmeas acumularem reservas e está ligado diretamente aos fatores primários. Palavras-chave: Marsupiais, roedores, fatores ambientais, reprodução, estação reprodutiva, ecologia da reprodução, chuva, duração do dia. ABSTRACT: Environmental factors and the reproduction of eastern Brazilian marsupials and rodents. Small neotropical mammals were studied in relation to factors determining the onset of the breeding season. The first studies were based on data from specimens housed at the Museu Nacional, Rio de Janeiro, and were followed by field and laboratory studies. Two modes of reproduction were first proposed. Later, it was found that marsupials have the onset of the breeding season determined by the variation of photoperiod. The Sigmodontini rodents in Northeastern Brazil have their reproduction set by the beginning of the rainy season. Therefore, the marsupial mode of reproduction is markedly climatically seasonal, being somewhat independent of environmental conditions, solstices and equinoxes functioning as proximal factors. The Sigmodontini mode of reproduction has the onset of the breeding season determined by the storage of reserves by the females being linked directly to primary factors.
La reproduction de Didelphis albiventris a etc etudiee dans trois regions du nord-est du Bresil. ... more La reproduction de Didelphis albiventris a etc etudiee dans trois regions du nord-est du Bresil. On n'a pas observe de variations du pelage. La croissance des femelles est plus rapide que celle des males apres l'adolescence (au-delä de la classe 5). Le commencement de la saison de reproduction semble en rapport avec la distribution des preci-pitations. II n'y a pas de taille minimale des femelles qui commencent ä se reproduire, mais seulement un age minimal. II y a des males fertiles toute 1'annee. Les implications ecologiques de ces faits sont discutees.
The Neotropical black-eared opossums comprise two allopatric species that are restricted to fores... more The Neotropical black-eared opossums comprise two allopatric species that are restricted to forested habitats : Didelphis aurita occurring from northern Argentina to the Northeast of Brazil, mostly along the Atlantic rainforest but also at Araucaria highlands, and D. mar-supialis which occurs mostly within the Amazonian rainforest. Their status as separate species or allopatric subspecies has been a matter of debate. We provide an analysis of the morphometric differences between D. aurita and D. marsupialis based on eigheteen cranium measurements. An ANOVA between sexes showed sexual dimorphism with males consistently larger than females in both species. Hence, sexes were treated separately. ANOVA between D. aurita and D. marsu-pialis showed that they are significantly different for 14 and eight characters of females and males, respectively. D. aurita and D. marsupialis were also readily separated by discriminant analysis that correctly classified more than SO % of the specimens. The squared Mahalanobis distances were slightly higher than five at both sexes. Despite the lack of obvious qualitative morphological characters distinguishing D. aurita and D. marsupialis, our results show that they are morphometrically diagnosable and should be considered separate species. Resume.-Les opossums ä oreilles noires neotropicaux sont represented par deux especes allopatriques limitees a des habitats de foret: Didelphis aurita, repartie depuis le nord de Argentine jusqu'au nord-est du Bresil, surtout le long de la foret atlantique, mais aussi sur les plateaux a Araucarias ; D. marsupialis qui se trouve surtout dans la foret d'Amazonie. Leur Statut d'especes ou de sous-especes allopatriques a ete le sujet de debats. Dans ce travail nous donnons une analyse des differences morphometriques entre D. aurita et D. marsupialis en utilisant 18 mensurations du crane. Une ANOVA entre sexes a mis en evidence 1'existence d'un dimor-phisme sexuel, les males etant plus grands que les femelles dans les deux formes. Les sexes ont done ete traites separement. Une ANOVA entre D. aurita et D. marsupialis a montre que les deux especes sont significativement differentes pour 14 caracteres de femelles et 8 caracteres de males. D. aurita et D. marsupialis sont aussi immediatement separees par une analyse discrimi-nante qui a permis de reconnaitre correctement plus de 80 % des specimens. Les carres des distances de Mahalanobis ont ete legerement superieurs ä cinq pour les deux sexes. Malgre Fabsence de caracteres morphologiques qualitatifs qui distinguent D. aurita de D. marsupialis, nos resultats montrent qu'ils sont morphometriquement identifiables et doivent etre considered comme deux especes distinctes.
The variables in habitat studies are usually transformed in such a way that they become abstracti... more The variables in habitat studies are usually transformed in such a way that they become abstractions and intuition is lost. We tested a new method for the analysis of habitat using data collected in a grid laid at the " restinga de Maricá " , in Rio de Janeiro State, Brazil. Thirty-seven microhabitat variables were measured at each trap station. We assume that these variables characterize the microhabitat structure at the moment when measurements were taken. The data are transformed in 3 ways: (1) the averages of the measured variables were calculated, as usual in habitat studies; (2) the data are transformed in densities per area in square meters without reduction in the number of variables; and (3) we calculated the natural logarithms of the data thus transformed. The 3 sets were analised through discriminant analysis. The logarithms of densities were the most efficient kind of transformation. This transformation resulted in a significance of p = 0.0001 with 39.72% of variance in the 1 st discrimi-nant function and of p = 0.0426 with 31.45% of variance in the 2 nd function, and 84.62% of groups correctly classified. We obtained better classification results than previous similar works and we kept the intuition through the data analysis. RESUMO Um novo método de estudo da estrutura de microhábitat de pequenos mamíferos As variáveis utilizadas em estudos de hábitat são transformadas de tal maneira que se tornam abstrações e se perde a intuição. Testamos um novo método para esse tipo de análise usando dados coletados em uma grade na restinga de Maricá, Rio de Janeiro. Em cada ponto de captura foram medidas 37 variáveis de microhábitat. Consideramos que tais variáveis caracterizam a estrutura dos microhábitats no momento em que são tomadas. Os dados foram transformados de 3 maneiras: (1) as médias das variáveis foram calculadas, como é usual em estudos de hábitat; (2) os dados foram transformados em suas densidades por área em metros quadrados, sem redução no número de variáveis; e (3) calculamos os logaritimos naturais dos dados transformados em densidades. Os 3 conjuntos foram submetidos à análise discri-minante. O logaritimo das densidades foi o tipo de transformação mais eficiente. Esta transformação resultou na obtenção de p = 0,0001, com 39,72% da variância na 1 a função e um p = 0,0426 com 31,45% da variância na 2 a função, com um acerto de 84,62% na classificação dos grupos. Os resultados obtidos foram melhores do que em trabalhos similares anteriores, mantendo-se a intuição.
We suggest here that the onset of the breeding season of Monodelphis domestica may be controled ... more We suggest here that the onset of the breeding season of Monodelphis domestica may be controled by photoperiod. This phenomenon is well known in Australian marsupials, but it is the first time that such factor can be interpreted as influencing the breeding season of a Neotropical marsupial.
The characterization of the different taxa of the highly diverse genus Monodelphis is poorly unde... more The characterization of the different taxa of the highly diverse genus Monodelphis is poorly understood, as is the case of their distribution. Historically, taxonomic studies of Monodelphis have been restricted to a few or single species, whereas molecular approaches have been used for estimating phylogenetic relationships between species. We carried out phylogenetic analyses of 14 Monodelphis species, including Monodelphis domestica, based on cytochrome b mitochondrial DNA sequences. Forty-five complete (1149 bp) sequences of this gene were obtained from 39 specimens of M. domestica collected in 23 localities of the Brazilian Cerrado, Pantanal, and Caatinga morphoclimatic domains; one of Monodelphis umbristriata, two of Monodelphis americana, and two of Monodelphis dimidiata. A total of 72 haplotypes were analyzed, 48 only in M. domestica. Analyses were carried out in conjunction with 46 other sequences retrieved from GenBank, including M. domestica, Monodelphis brevicaudata, Monodelphis adusta, with six other different didelphid species used as outgroups. Maximum likelihood and Bayesian inference were similar in depicting phylogenetic relationships of different Monodelphis taxa. Two clades of M. domestica were defined on the basis of these results. Genetic distance estimates ranged from 3.2% to 6.2% between these clades of M. domestica. Population analyses were carried out to infer the likely demographic scenarios and the relationship between M. domestica haplotypes. Median-joining and spatial analyses showed two populations related to different morphoclimatic domains (Cerrado/Pantanal and Caatinga). These results indicate a population structure in M. domestica and the possibility that this taxon might represent a species complex.
We study the population size time series of a Neotropical small mammal with the intent of detecti... more We study the population size time series of a Neotropical small mammal with the intent of detecting and modelling population regulation processes generated by density-dependent factors and their possible delayed effects. The application of analysis tools based on principles of statistical generality are nowadays a common practice for describing these phenomena, but, in general, they are more capable of generating clear diagnosis rather than granting valuable modelling. For this reason, in our approach, we detect the principal temporal structures on the bases of different correlation measures, and from these results we build an ad-hoc minimalist autoregressive model that incorporates the main drivers of the dynamics. Surprisingly our model is capable of reproducing very well the time patterns of the empirical series and, for the first time, clearly outlines the importance of the time of attaining sexual maturity as a central temporal scale for the dynamics of this species. In fact, an important advantage of this analysis scheme is that all the model parameters are directly biologically interpretable and potentially measurable, allowing a consistency check between model outputs and independent measurements. One of the main objectives in the field of population dynamics is to determine the extent of deterministic vs. stochastic forces in time series of abundance and population parameters. The deterministic share of the observed fluctuations is usually assigned to nonlinear density-dependent processes, which create regulatory and stabilising forces 1. Different theoretical and modelling frameworks have been used through the history of population dynamics , but time series analysis and autoregressive models are a frequent and natural choice, as the population size in the future is related to the population size in the past 2–4. A variety of time series analysis methods have been used in population dynamics to diagnose their structure and density dependence 5 , particularly successful in the analysis of empirical data of long lived taxa such as mammals 6–8. The approach proposed by Royama 9 combines diagnostic tools with the use of phenomenological models, and has increased the predictive power and understanding of the dynamics of intensively studied systems 10–12. In general, for sufficiently long time series, it is possible to use conventional autoregressive models or to apply other analogous methods which aim to determine a clear differentiation between deterministic and random components 13,14. The most common approach 9,15 uses a linear autoregressive model of order k , which relates the logarithm of the population abundance (y t) at different time steps: ∑ β β ε = + +. () = −
The Quaternary history of the mammalian fauna of South America is examined. It is suggested that ... more The Quaternary history of the mammalian fauna of South America is examined. It is suggested that the great interaction of climate and vegetation during the Quaternary profoundly influenced the distributional patterns of South America Recent fauna. In particular, the immense size of the continent allowed for a complex fractioning and reforming of habitats due to climatic fluctuations, leading to a system whereby the geographic ranges of mammals were repeatedly separated and reunited. The influence of these broadscale fluctuations upon selected groups (Primates, marsupials, rodents) is discussed. It is suggested that the model of Pleistocene refugial speciation proposed by Haffer (1969) and Vanzolini and Williams (1970) will be shown to apply to a large number of mammalian groups. Unfortunately, distributional data of Amazonian mammals are not extensive enough to allow for a finely detailed analysis
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