Resumo
Spiders are generalist predators and present a high diversity of capturing and foraging, as well as considerable species richness in tropical habitats. Although, generally, not presenting specific relations to the host plant, they can be influenced by its phenology, structure and resource availability. So, this study analyzed temporal variation on the structure and composition of Araneae assemblage in Callisthene fasciculata (Spr.) Mart. (Vochysiaceae) canopies, in an area of monodominant vegetation, in the periods of high water, receding water, dry season and rising water in Pantanal of Mato Grosso, Brazil. The collection was performed on 24 individuals of C. fasciculata, six in each seasonal period, in 2010 and 2011, making use of canopy fogging with insecticide. For that, ten nylon funnels were distributed under each canopy of C. fasciculata individuals, in a total of 240 m² of sampled canopies. In all, 3,610 spiders were collected and distributed in 24 families and 55 species. Anyphaenidae (43.3%; 6.5 ind./m2), Pisauridae (16.2%; 2.4 ind./m2), Araneidae (12.7%; 1.9 ind./m2) and Salticidae (12.4%; 1.9 ind./m2) were the most representative. Osoriella tahela Brescovit, 1998 was the most abundant species (12.2%). The nocturnal aerial runners of foliage (45.6%; 6.9 ind./m2), nocturnal aerial ambushers of foliage (17.3%; 2.6 ind./m2), aerial orb weavers (13.3%; 2.0 ind./m2) and the diurnal aerial runners of foliage (12.5%; 1.9 ind./m2) spiders represented the most abundant guilds. Significant differences were observed in the composition of families and behavioral guilds, as well as abundance and richness among seasonal periods. The assemblage showed the highest abundance in receding water and highest species richness in high water period, probably related to the hydrologic cycle of the area and its influence on C. fasciculata phenology, indicating the importance of this plant species for spiders diversity maintenance in the Pantanal.
Aranhas são predadoras, generalistas e apresentam elevada diversidade de estratégias de captura e forrageamento, bem como considerável riqueza de espécies em habitats tropicais. Apesar de, geralmente, não apresentarem relações específicas com hospedeiros vegetais, suas assembleias podem ser influenciadas pela fenologia, estrutura e disponibilidade de recursos sobre o hospedeiro. Assim, este estudo analisou a variação temporal na estrutura e composição da assembleia de aranhas em copas de Callisthene fasciculata (Spr.) Mart. (Vochysiaceae) em área de vegetação monodominante, ao longo dos períodos de cheia, vazante, seca e enchente na região norte do Pantanal de Mato Grosso, Brasil. As coletas foram realizadas sobre 24 exemplares de C. fasciculata, seis em cada período sazonal, em 2010 e 2011, empregando-se a termonebulização de copas com inseticida. Para a coleta, 10 funis de nylon foram distribuídos debaixo da copa de cada indivíduo de C. fasciculata, totalizando 240 m² de copas amostradas. Ao todo foram coletadas 3.610 aranhas e distribuídas em 24 famílias e 55 espécies. Anyphaenidae (43,3%), Pisauridae (16,2%), Araneidae (12,7%) e Salticidae (12,4%) predominaram. Osoriella tahela Brescovit, 1998 foi a espécie mais abundante (12,2% do total). As aranhas corredoras aéreas noturnas de folhagens (45,6%), emboscadeiras noturnas de folhagens (17,3%), tecelãs orbiculares aéreas (13,3%) e as corredoras aéreas diurnas de folhagens (12,6%) representaram as guildas mais abundantes. Diferenças significativas foram observadas na composição de famílias e agrupamentos em guildas comportamentais, bem como para a abundância e riqueza de aranhas entre os períodos sazonais. A assembleia apresentou maior abundância na vazante e maior riqueza de espécies no período de cheia, provavelmente relacionadas com o ciclo hidrológico da região e sua influência sobre a fenologia de C. fasciculata [...]
Assuntos
Animais , Aranhas , Biodiversidade , Áreas AlagadasResumo
ABSTRACT Spiders are generalist predators and present a high diversity of capturing and foraging, as well as considerable species richness in tropical habitats. Although, generally, not presenting specific relations to the host plant, they can be influenced by its phenology, structure and resource availability. So, this study analyzed temporal variation on the structure and composition of Araneae assemblage in Callisthene fasciculata (Spr.) Mart. (Vochysiaceae) canopies, in an area of monodominant vegetation, in the periods of high water, receding water, dry season and rising water in Pantanal of Mato Grosso, Brazil. The collection was performed on 24 individuals of C. fasciculata, six in each seasonal period, in 2010 and 2011, making use of canopy fogging with insecticide. For that, ten nylon funnels were distributed under each canopy of C. fasciculata individuals, in a total of 240 m² of sampled canopies. In all, 3,610 spiders were collected and distributed in 24 families and 55 species. Anyphaenidae (43.3%; 6.5 ind./m2), Pisauridae (16.2%; 2.4 ind./m2), Araneidae (12.7%; 1.9 ind./m2) and Salticidae (12.4%; 1.9 ind./m2) were the most representative. Osoriella tahela Brescovit, 1998 was the most abundant species (12.2%). The nocturnal aerial runners of foliage (45.6%; 6.9 ind./m2), nocturnal aerial ambushers of foliage (17.3%; 2.6 ind./m2), aerial orb weavers (13.3%; 2.0 ind./m2) and the diurnal aerial runners of foliage (12.5%; 1.9 ind./m2) spiders represented the most abundant guilds. Significant differences were observed in the composition of families and behavioral guilds, as well as abundance and richness among seasonal periods. The assemblage showed the highest abundance in receding water and highest species richness in high water period, probably related to the hydrologic cycle of the area and its influence on C. fasciculata phenology, indicating the importance of this plant species for spiders diversity maintenance in the Pantanal.
RESUMO Aranhas são predadoras, generalistas e apresentam elevada diversidade de estratégias de captura e forrageamento, bem como considerável riqueza de espécies em habitats tropicais. Apesar de, geralmente, não apresentarem relações específicas com hospedeiros vegetais, suas assembleias podem ser influenciadas pela fenologia, estrutura e disponibilidade de recursos sobre o hospedeiro. Assim, este estudo analisou a variação temporal na estrutura e composição da assembleia de aranhas em copas de Callisthene fasciculata (Spr.) Mart. (Vochysiaceae) em área de vegetação monodominante, ao longo dos períodos de cheia, vazante, seca e enchente na região norte do Pantanal de Mato Grosso, Brasil. As coletas foram realizadas sobre 24 exemplares de C. fasciculata, seis em cada período sazonal, em 2010 e 2011, empregando-se a termonebulização de copas com inseticida. Para a coleta, 10 funis de nylon foram distribuídos debaixo da copa de cada indivíduo de C. fasciculata, totalizando 240 m² de copas amostradas. Ao todo foram coletadas 3.610 aranhas e distribuídas em 24 famílias e 55 espécies. Anyphaenidae (43,3%), Pisauridae (16,2%), Araneidae (12,7%) e Salticidae (12,4%) predominaram. Osoriella tahela Brescovit, 1998 foi a espécie mais abundante (12,2% do total). As aranhas corredoras aéreas noturnas de folhagens (45,6%), emboscadeiras noturnas de folhagens (17,3%), tecelãs orbiculares aéreas (13,3%) e as corredoras aéreas diurnas de folhagens (12,6%) representaram as guildas mais abundantes. Diferenças significativas foram observadas na composição de famílias e agrupamentos em guildas comportamentais, bem como para a abundância e riqueza de aranhas entre os períodos sazonais. A assembleia apresentou maior abundância na vazante e maior riqueza de espécies no período de cheia, provavelmente relacionadas com o ciclo hidrológico da região e sua influência sobre a fenologia de C. fasciculata, indicando a importância desta espécie vegetal para a manutenção da diversidade de aranhas no Pantanal.
Resumo
Spiders are generalist predators and present a high diversity of capturing and foraging, as well as considerable species richness in tropical habitats. Although, generally, not presenting specific relations to the host plant, they can be influenced by its phenology, structure and resource availability. So, this study analyzed temporal variation on the structure and composition of Araneae assemblage in Callisthene fasciculata (Spr.) Mart. (Vochysiaceae) canopies, in an area of monodominant vegetation, in the periods of high water, receding water, dry season and rising water in Pantanal of Mato Grosso, Brazil. The collection was performed on 24 individuals of C. fasciculata, six in each seasonal period, in 2010 and 2011, making use of canopy fogging with insecticide. For that, ten nylon funnels were distributed under each canopy of C. fasciculata individuals, in a total of 240 m² of sampled canopies. In all, 3,610 spiders were collected and distributed in 24 families and 55 species. Anyphaenidae (43.3%; 6.5 ind./m2), Pisauridae (16.2%; 2.4 ind./m2), Araneidae (12.7%; 1.9 ind./m2) and Salticidae (12.4%; 1.9 ind./m2) were the most representative. Osoriella tahela Brescovit, 1998 was the most abundant species (12.2%). The nocturnal aerial runners of foliage (45.6%; 6.9 ind./m2), nocturnal aerial ambushers of foliage (17.3%; 2.6 ind./m2), aerial orb weavers (13.3%; 2.0 ind./m2) and the diurnal aerial runners of foliage (12.5%; 1.9 ind./m2) spiders represented the most abundant guilds. Significant differences were observed in the composition of families and behavioral guilds, as well as abundance and richness among seasonal periods. The assemblage showed the highest abundance in receding water and highest species richness in high water period, probably related to the hydrologic cycle of the area and its influence on C. fasciculata phenology, indicating the importance of this plant species for spiders diversity maintenance in the Pantanal.(AU)
Aranhas são predadoras, generalistas e apresentam elevada diversidade de estratégias de captura e forrageamento, bem como considerável riqueza de espécies em habitats tropicais. Apesar de, geralmente, não apresentarem relações específicas com hospedeiros vegetais, suas assembleias podem ser influenciadas pela fenologia, estrutura e disponibilidade de recursos sobre o hospedeiro. Assim, este estudo analisou a variação temporal na estrutura e composição da assembleia de aranhas em copas de Callisthene fasciculata (Spr.) Mart. (Vochysiaceae) em área de vegetação monodominante, ao longo dos períodos de cheia, vazante, seca e enchente na região norte do Pantanal de Mato Grosso, Brasil. As coletas foram realizadas sobre 24 exemplares de C. fasciculata, seis em cada período sazonal, em 2010 e 2011, empregando-se a termonebulização de copas com inseticida. Para a coleta, 10 funis de nylon foram distribuídos debaixo da copa de cada indivíduo de C. fasciculata, totalizando 240 m² de copas amostradas. Ao todo foram coletadas 3.610 aranhas e distribuídas em 24 famílias e 55 espécies. Anyphaenidae (43,3%), Pisauridae (16,2%), Araneidae (12,7%) e Salticidae (12,4%) predominaram. Osoriella tahela Brescovit, 1998 foi a espécie mais abundante (12,2% do total). As aranhas corredoras aéreas noturnas de folhagens (45,6%), emboscadeiras noturnas de folhagens (17,3%), tecelãs orbiculares aéreas (13,3%) e as corredoras aéreas diurnas de folhagens (12,6%) representaram as guildas mais abundantes. Diferenças significativas foram observadas na composição de famílias e agrupamentos em guildas comportamentais, bem como para a abundância e riqueza de aranhas entre os períodos sazonais. A assembleia apresentou maior abundância na vazante e maior riqueza de espécies no período de cheia, provavelmente relacionadas com o ciclo hidrológico da região e sua influência sobre a fenologia de C. fasciculata [...](AU)
Assuntos
Animais , Aranhas , Biodiversidade , Áreas AlagadasResumo
The composition of the spider fauna of riparian forests is insufficiently known. These forests, adjacent to both aquatic and terrestrial environments, are recognised as having important ecosystem functions. We compare the composition of spider assemblages of four riparian forests in different drainage basins, along with their microhabitats (edges and forest interior), in the state of Rio Grande do Sul, southern Brazil. Sampling was carried out in the riparian forests of the following rivers: Piratini, municipality of Arroio Grande; Camaquã, municipality of Cristal; Sinos, municipality of Parobé, and Maquiné, municipality of Maquiné. Two samples per season were collected in two years, by sampling the tree-shrub strata with a beating tray, following fixed transects. There were six transects per drainage basin, two per microhabitat: grassland edge, forest interior and river edge. Overall, 42,057 spiders were sampled (juveniles: 79%; adults: 21%). Among the adults (8,851 individuals), we identified 440 species. Similarity analyses (ANOSIM) indicated that the araneofauna composition of the four drainage basins differ in their quantitative (Morisita) and qualitative (Simpson) similarity indexes. There were no differences in composition among microhabitats. The composition of the Maquiné River basin was the most distinct, possibly due to a greater influence of the Atlantic forest on it and a greater dominance of the Linyphiidae Sphecozone personata (Simon, 1894) (SIMPER analysis, contribution to dissimilarity: 12.15%). Differences in spider composition on large spatial scales most likely reflect regional variations in a number of environmental factors, and result in each area having in increased importance in terms of conservation.
Assuntos
Animais , Aranhas/classificação , Fauna/análise , Fauna/classificação , Florestas , Bacias FluviaisResumo
The composition of the spider fauna of riparian forests is insufficiently known. These forests, adjacent to both aquatic and terrestrial environments, are recognised as having important ecosystem functions. We compare the composition of spider assemblages of four riparian forests in different drainage basins, along with their microhabitats (edges and forest interior), in the state of Rio Grande do Sul, southern Brazil. Sampling was carried out in the riparian forests of the following rivers: Piratini, municipality of Arroio Grande; Camaquã, municipality of Cristal; Sinos, municipality of Parobé, and Maquiné, municipality of Maquiné. Two samples per season were collected in two years, by sampling the tree-shrub strata with a beating tray, following fixed transects. There were six transects per drainage basin, two per microhabitat: grassland edge, forest interior and river edge. Overall, 42,057 spiders were sampled (juveniles: 79%; adults: 21%). Among the adults (8,851 individuals), we identified 440 species. Similarity analyses (ANOSIM) indicated that the araneofauna composition of the four drainage basins differ in their quantitative (Morisita) and qualitative (Simpson) similarity indexes. There were no differences in composition among microhabitats. The composition of the Maquiné River basin was the most distinct, possibly due to a greater influence of the Atlantic forest on it and a greater dominance of the Linyphiidae Sphecozone personata (Simon, 1894) (SIMPER analysis, contribution to dissimilarity: 12.15%). Differences in spider composition on large spatial scales most likely reflect regional variations in a number of environmental factors, and result in each area having in increased importance in terms of conservation.(AU)
Assuntos
Animais , Aranhas/classificação , Florestas , Fauna/análise , Fauna/classificação , Bacias FluviaisResumo
This study describes the composition and temporal variation of the spider assemblage (Arachnida: Araneae) associated with canopies of Vochysia divergens Pohl. (Vochysiaceae) in the northern region of the Brazilian Pantanal. Three V. divergens plants were sampled in 2004, at each seasonal period of the northern Pantanal (high water, receding water, dry season and rising water), using thermonebulization of the canopies with insecticide, totaling 396 m2 of sampled canopies. Analysis of abundance and richness of spider families were based on Non-Metric Multidimensional Scaling (NMDS) and Variance Analysis (ANOVA and MANOVA). A total of 7,193 spiders were collected (6,330 immatures; 88.0%; 863 adults, 12.0%) distributed in 30 families. Araneidae (1,676 individuals), Anyphaenidae (1,631 individuals), Salticidae (1,542 individuals) and Pisauridae (906 individuals), were predominant, representing 80.0% of the sample. Ten different guilds were registered: aerial hunters, orb-weavers, nocturnal aerial runners and diurnal space web weavers dominated, sharing most ecological niches. The spider assemblage is affected by changes in the habitat structure, especially by the seasonal hydrological regime and variations in the phenology of V. divergens . The assemblage is composed of different groups of spiders. The dominant taxa and behavioral guilds differ in the different seasonal periods. Spiders were more abundant during the dry and rising water seasons, most likely reflecting a greater supply of potential prey, associated with new foliage and flowering at the canopy. The displacement of soil dwelling spiders to the trunks and canopies before and during the seasonal floods can change the structure and composition of the canopy assemblages. Oonopidae, Gnaphosidae and Caponiidae, were more frequent during the rising and high water seasons, which indicates that these taxa use the canopies of V. divergens as a refuge during the seasonal flooding in the Pantanal.
Assuntos
Animais , Aranhas/classificação , Estações do Ano , Grupos de População Animal/classificação , Áreas Alagadas , Comportamento Animal , FaunaResumo
This study describes the composition and temporal variation of the spider assemblage (Arachnida: Araneae) associated with canopies of Vochysia divergens Pohl. (Vochysiaceae) in the northern region of the Brazilian Pantanal. Three V. divergens plants were sampled in 2004, at each seasonal period of the northern Pantanal (high water, receding water, dry season and rising water), using thermonebulization of the canopies with insecticide, totaling 396 m2 of sampled canopies. Analysis of abundance and richness of spider families were based on Non-Metric Multidimensional Scaling (NMDS) and Variance Analysis (ANOVA and MANOVA). A total of 7,193 spiders were collected (6,330 immatures; 88.0%; 863 adults, 12.0%) distributed in 30 families. Araneidae (1,676 individuals), Anyphaenidae (1,631 individuals), Salticidae (1,542 individuals) and Pisauridae (906 individuals), were predominant, representing 80.0% of the sample. Ten different guilds were registered: aerial hunters, orb-weavers, nocturnal aerial runners and diurnal space web weavers dominated, sharing most ecological niches. The spider assemblage is affected by changes in the habitat structure, especially by the seasonal hydrological regime and variations in the phenology of V. divergens . The assemblage is composed of different groups of spiders. The dominant taxa and behavioral guilds differ in the different seasonal periods. Spiders were more abundant during the dry and rising water seasons, most likely reflecting a greater supply of potential prey, associated with new foliage and flowering at the canopy. The displacement of soil dwelling spiders to the trunks and canopies before and during the seasonal floods can change the structure and composition of the canopy assemblages. Oonopidae, Gnaphosidae and Caponiidae, were more frequent during the rising and high water seasons, which indicates that these taxa use the canopies of V. divergens as a refuge during the seasonal flooding in the Pantanal.(AU)
Assuntos
Animais , Aranhas/classificação , Estações do Ano , Grupos de População Animal/classificação , Áreas Alagadas , Fauna , Comportamento AnimalResumo
Assemblages of spiders of the herbaceous vegetation were sampled by sweeping method in two sweet orange orchards (Citrus sinensis) in the south of Brazil. Each sampled orchard is characterized by receiving a different handling type: "traditional" or "ecological". In addition it was sampled the assemblage of spiders of the orange trees of the orchard with the "ecological" handling with the beating method. A total of 3,876 spiders were collected, 2,379 in the orange trees and 1,497 in the herbaceous vegetation; 17 families and 99 species were registered; Oxyopes salticus Hentz, 1845 (Oxyopidae) was the most abundant spider in herbaceous vegetation and Sphecozone cristata Millidge, 1991 (Linyphiidae) the most abundant in the orange trees. Cursorial spiders were the most abundant guild at both herbaceous vegetation and orange trees. The araneofauna of herbaceous vegetation in the different handling orchards did not present significant differences in diversity (H'= 2.13 "ecological"; 2.24 "traditional"); the diversity was smaller in the orange trees (H'=1.95). Perhaps because of different sampling methods at different microhabitats, the Jaccard's Index indicates low similarity between assemblages (17.5%).
Assembléias de aranhas da vegetação herbácea foram amostradas com rede-de-varredura em dois pomares de laranja doce (Citrus sinensis) no sul do Brasil. Cada pomar amostrado é caracterizado por receber um diferente tipo de manejo: "tradicional" ou "ecológico". Adicionalmente, foi amostrada a assembléia de aranhas das laranjeiras do pomar com manejo "ecológico" através do uso de guarda-chuva japonês. No total foram coletadas 3.876 aranhas, 2.379 nas laranjeiras do pomar de manejo "ecológico" e 1.497 junto à vegetação herbácea de ambos pomares; foram registradas 99 espécies de 17 famílias de aranhas; Oxyopes salticus Hentz, 1845 (Oxyopidae) foi a aranha mais abundante na vegetação herbácea e Sphecozone cristata Millidge, 1991 (Linyphiidae) a mais abundante nas laranjeiras. Aranhas errantes foram mais abundantes em ambos tipos de vegetação. A araneofauna da vegetação herbácea nos pomares com diferentes manejos não apresentou diferenças significativas na diversidade (H'= 2,13 - "ecológico"; 2,24 - "tradicional"); a diversidade foi menor nas laranjeiras (H'=1,95). Em razão de terem sido utilizados diferentes métodos de coleta nas amostragens entre os microhabitats, o índice de Jaccard (17,5%) indicou baixa similaridade entre as assembléias.
Resumo
Assemblages of spiders of the herbaceous vegetation were sampled by sweeping method in two sweet orange orchards (Citrus sinensis) in the south of Brazil. Each sampled orchard is characterized by receiving a different handling type: "traditional" or "ecological". In addition it was sampled the assemblage of spiders of the orange trees of the orchard with the "ecological" handling with the beating method. A total of 3,876 spiders were collected, 2,379 in the orange trees and 1,497 in the herbaceous vegetation; 17 families and 99 species were registered; Oxyopes salticus Hentz, 1845 (Oxyopidae) was the most abundant spider in herbaceous vegetation and Sphecozone cristata Millidge, 1991 (Linyphiidae) the most abundant in the orange trees. Cursorial spiders were the most abundant guild at both herbaceous vegetation and orange trees. The araneofauna of herbaceous vegetation in the different handling orchards did not present significant differences in diversity (H'= 2.13 "ecological"; 2.24 "traditional"); the diversity was smaller in the orange trees (H'=1.95). Perhaps because of different sampling methods at different microhabitats, the Jaccard's Index indicates low similarity between assemblages (17.5%).
Assembléias de aranhas da vegetação herbácea foram amostradas com rede-de-varredura em dois pomares de laranja doce (Citrus sinensis) no sul do Brasil. Cada pomar amostrado é caracterizado por receber um diferente tipo de manejo: "tradicional" ou "ecológico". Adicionalmente, foi amostrada a assembléia de aranhas das laranjeiras do pomar com manejo "ecológico" através do uso de guarda-chuva japonês. No total foram coletadas 3.876 aranhas, 2.379 nas laranjeiras do pomar de manejo "ecológico" e 1.497 junto à vegetação herbácea de ambos pomares; foram registradas 99 espécies de 17 famílias de aranhas; Oxyopes salticus Hentz, 1845 (Oxyopidae) foi a aranha mais abundante na vegetação herbácea e Sphecozone cristata Millidge, 1991 (Linyphiidae) a mais abundante nas laranjeiras. Aranhas errantes foram mais abundantes em ambos tipos de vegetação. A araneofauna da vegetação herbácea nos pomares com diferentes manejos não apresentou diferenças significativas na diversidade (H'= 2,13 - "ecológico"; 2,24 - "tradicional"); a diversidade foi menor nas laranjeiras (H'=1,95). Em razão de terem sido utilizados diferentes métodos de coleta nas amostragens entre os microhabitats, o índice de Jaccard (17,5%) indicou baixa similaridade entre as assembléias.
Resumo
We investigated the impact of swarm-hunting army ants of the species Eciton burchelli on the ground spider assemblage in an Amazonian "terra firme" rain forest. Spiders were collected from 20 quadrat litter samples taken in front of 7 hunting swarms and 20 samples taken in the same areas after army ants had passed, and were identified to genus or species level. Observed significant effects on the abundance of several spider groups are discussed on the base of the prey-spider spectrum of the ants, known from a study in the same forest. We discuss several difficulties and chances of misinterpretation of the results, due to the high natural variability of arthropod abundance in the habitat and the restriction of the method under the conditions of the field study.
Investigamos o efeito do forrageamento de formigas de correição da espécie Eciton burchelli, a qual caça em forma de enxame, sobre a comunidade de aranhas de liteira em uma floresta tropical de terra firme na Amazônia Central. O método usado foi a amostragem de aranhas por triagem manual de liteira, coletando-se 20 quadrados na frente de 7 enxames de caça das formigas e 20 quadrados logo após a passagem das formigas. As aranhas foram identificadas ao nível de gênero ou espécie e efeitos significativos foram avaliados levando-se em conta o espectro de aranhas-presa destas formigas, conhecido por um estudo na mesma área. Discutem-se as dificuldades e possíveis erros na avaliação do efeito das formigas sobre artrópodos causados pela variância natural de abundâncias e pela restrição da metodologia sob as circunstâncias estudadas.
Resumo
We investigated the impact of swarm-hunting army ants of the species Eciton burchelli on the ground spider assemblage in an Amazonian "terra firme" rain forest. Spiders were collected from 20 quadrat litter samples taken in front of 7 hunting swarms and 20 samples taken in the same areas after army ants had passed, and were identified to genus or species level. Observed significant effects on the abundance of several spider groups are discussed on the base of the prey-spider spectrum of the ants, known from a study in the same forest. We discuss several difficulties and chances of misinterpretation of the results, due to the high natural variability of arthropod abundance in the habitat and the restriction of the method under the conditions of the field study.
Investigamos o efeito do forrageamento de formigas de correição da espécie Eciton burchelli, a qual caça em forma de enxame, sobre a comunidade de aranhas de liteira em uma floresta tropical de terra firme na Amazônia Central. O método usado foi a amostragem de aranhas por triagem manual de liteira, coletando-se 20 quadrados na frente de 7 enxames de caça das formigas e 20 quadrados logo após a passagem das formigas. As aranhas foram identificadas ao nível de gênero ou espécie e efeitos significativos foram avaliados levando-se em conta o espectro de aranhas-presa destas formigas, conhecido por um estudo na mesma área. Discutem-se as dificuldades e possíveis erros na avaliação do efeito das formigas sobre artrópodos causados pela variância natural de abundâncias e pela restrição da metodologia sob as circunstâncias estudadas.