William Magnusson | Instituto Nacional de Pesquisas da Amazônia (original) (raw)
Papers by William Magnusson
The high diversity of amphibians in rhe central Amawn Rain Forest alIowed us to exarnine rhe inHu... more The high diversity of amphibians in rhe central Amawn Rain Forest alIowed us to exarnine rhe inHuence of tadpole antipredator defenses on assemblage structure and composition wirhin bodies of water (a diversity) and among aquatic sites (~ diversity) at a local scale. During a rhree-year stUdy of tadpole assemblage composition, we found rhat rhe anuran community used a variety ofbodies of water for reproduction; rhese ranged from streams and streamside ponds to isolated forest ponds. The distribution of several tadpole species was negatively related to fish density. while orher species coexisted wirh high densities of fish. Tadpole size did not ensure survival against fish, and few tadpoles avoided fish by hiding in rhe leaf litter. Controlled predation experiments using a single tadpole species in a no-choice situation were conducted over 24-to 48-hour periods. Nearly alI species of tadpoles rhat occurred in habitats wirh high fish densities were unpalatable to fish (except Centro/ene/Ja oyampimsis), indicating that unpalatability is a major adaptation alIowing tadpoles and fish to coexist in rhis system. Unpalatability (to fish). however, was not an effective antipredator defense against OOonate larvae, rhe orher major tadpole predator in rhis system. The combination of predation pressure and rhe anti-predator traits exhibited by individual species largely determined rhe composition of tadpole assemblages in individual bodies of water (a diversity). The heterogeneous distribution of predators among bodies water and rhe diversity of antipredator defenses exhibited by larval amphibians facilitated high diversity in rhis community (~ diversity). RESUMO A elevada diversidade de anflbios na floresta Amazônica central nos perrniriu examinar a influência das defesas anripre-dadores de girinos na esrrututa e na composição das comunidades nos corpos d'água (diversidade alfa) e enrre corpos d'água (diversidade beta) em uma escala local. Durante um estudo de três anos da composição da comunidade de girinos nós enconrrarnos que a comunidade de anuros usa urna variedade de corpos d'água para a reprodução; estes variaram de córregos e de poças ao lado de córregos a poças isoladas na floresta. A distribuição de várias espécies de girinos estava negativamente relacionada à densidade de peixes enquanto ourras espécies coexisriram com elevadas densidades de peixes. O tamanho do girino não assegurou a sobrevivência no encontro com peixes, e poucos girinos evitaram os peixes abrigando-se na camada de folhiço. Experiências controladas de predação utilizando uma única espécie de girino em uma situação sem-escolha foram conduzidas dUtante perlodos de 24-48 hotas. Quase todas as espécies de girinos que ocorreram em habitats com elevadas densidades de peixes eram impalatáveis para peixes (exceto Centrolenella oyampiensis), indicando que a impalatabilidade é a principal adaptação permitindo a coexixtência de girinos e peixes neste sistema. Enrretanto, a impalatabilidade (aos peixes) não foi uma defesa anripredador eficaz contra larvas de odonata, o outro principal predador de girinos neste sistema. A combinação da pressão de predação e das caracterlsticas anripredador exibidos por cada espécie individualmente determinou em grande parte a composição da comunidade de girinos em corpos d'água individuais (diversidade aifa). A distribuição heterogênea dos predadores enrre corpos d'água e a diversidade de defesas conrra pre-dadores exibidas por larvas de anflbios facilitou a elevada diversidade nesta comunidade (diversidade beta).
Journal of Natural History, 2012
Trends in Ecology & Evolution, 2010
Biotropica, 2008
Ferraz et al. (2008) indicated the need for planning in biological monitoring in the Amazon, and ... more Ferraz et al. (2008) indicated the need for planning in biological monitoring in the Amazon, and reviewed what they considered recent progress. The problems and solutions they discuss are well known, and it is unlikely that many biologists would disagree with most of them. ...
Ecological Indicators, 2012
We present a synthesis of the first 10 years of Long Term Ecological Research project in Amazonia... more We present a synthesis of the first 10 years of Long Term Ecological Research project in Amazonian Forest. We elucidate the natural dynamics of forest ecosystem processes and associated biota, and its changes caused by distinct pressures of selective timber extraction and forest fragmentation. We found that, for both plants and animals, densities of individ- uals and distribution of species assemblages are spatially heterogeneous at the mesoscale, even in relatively undisturbed forests, and that associations with topo-edaphic variables allow prediction of a considerable part of this variation. For biological groups whose dynam- ics were studied in the short-term, levels of change in species composition and densities were relatively high, and these changes were generally in tune with spatial environmen- tal variation. The impact of selective logging on assemblages and ecosystem processes was normally moderate, and around 19 years were needed for recovering forest biomass and tree size distribution. Continued studies are needed to determine the time required for recuper- ation of timber stocks and pre-logging floristic composition. Selective logging appears to be compatible with the biodiversity conservation, but reduction and better planning of road access may be more important than planned logging intensities. Habitat-loss’ impact on organisms and ecosystem processes is large and long-lasting, since it induces the loss of many taxonomic groups and species, higher tree mortality and accelerated forest dynamics. There was a negative synergy between the impacts of habitat loss and climatic changes, and a better understanding of these processes can only be obtained through long-term research.
Biological Conservation, 2011
The Herpetological …, 2005
The Herpetological …, 2006
The high diversity of amphibians in rhe central Amawn Rain Forest alIowed us to exarnine rhe inHu... more The high diversity of amphibians in rhe central Amawn Rain Forest alIowed us to exarnine rhe inHuence of tadpole antipredator defenses on assemblage structure and composition wirhin bodies of water (a diversity) and among aquatic sites (~ diversity) at a local scale. During a rhree-year stUdy of tadpole assemblage composition, we found rhat rhe anuran community used a variety ofbodies of water for reproduction; rhese ranged from streams and streamside ponds to isolated forest ponds. The distribution of several tadpole species was negatively related to fish density. while orher species coexisted wirh high densities of fish. Tadpole size did not ensure survival against fish, and few tadpoles avoided fish by hiding in rhe leaf litter. Controlled predation experiments using a single tadpole species in a no-choice situation were conducted over 24-to 48-hour periods. Nearly alI species of tadpoles rhat occurred in habitats wirh high fish densities were unpalatable to fish (except Centro/ene/Ja oyampimsis), indicating that unpalatability is a major adaptation alIowing tadpoles and fish to coexist in rhis system. Unpalatability (to fish). however, was not an effective antipredator defense against OOonate larvae, rhe orher major tadpole predator in rhis system. The combination of predation pressure and rhe anti-predator traits exhibited by individual species largely determined rhe composition of tadpole assemblages in individual bodies of water (a diversity). The heterogeneous distribution of predators among bodies water and rhe diversity of antipredator defenses exhibited by larval amphibians facilitated high diversity in rhis community (~ diversity). RESUMO A elevada diversidade de anflbios na floresta Amazônica central nos perrniriu examinar a influência das defesas anripre-dadores de girinos na esrrututa e na composição das comunidades nos corpos d'água (diversidade alfa) e enrre corpos d'água (diversidade beta) em uma escala local. Durante um estudo de três anos da composição da comunidade de girinos nós enconrrarnos que a comunidade de anuros usa urna variedade de corpos d'água para a reprodução; estes variaram de córregos e de poças ao lado de córregos a poças isoladas na floresta. A distribuição de várias espécies de girinos estava negativamente relacionada à densidade de peixes enquanto ourras espécies coexisriram com elevadas densidades de peixes. O tamanho do girino não assegurou a sobrevivência no encontro com peixes, e poucos girinos evitaram os peixes abrigando-se na camada de folhiço. Experiências controladas de predação utilizando uma única espécie de girino em uma situação sem-escolha foram conduzidas dUtante perlodos de 24-48 hotas. Quase todas as espécies de girinos que ocorreram em habitats com elevadas densidades de peixes eram impalatáveis para peixes (exceto Centrolenella oyampiensis), indicando que a impalatabilidade é a principal adaptação permitindo a coexixtência de girinos e peixes neste sistema. Enrretanto, a impalatabilidade (aos peixes) não foi uma defesa anripredador eficaz contra larvas de odonata, o outro principal predador de girinos neste sistema. A combinação da pressão de predação e das caracterlsticas anripredador exibidos por cada espécie individualmente determinou em grande parte a composição da comunidade de girinos em corpos d'água individuais (diversidade aifa). A distribuição heterogênea dos predadores enrre corpos d'água e a diversidade de defesas conrra pre-dadores exibidas por larvas de anflbios facilitou a elevada diversidade nesta comunidade (diversidade beta).
Journal of Natural History, 2012
Trends in Ecology & Evolution, 2010
Biotropica, 2008
Ferraz et al. (2008) indicated the need for planning in biological monitoring in the Amazon, and ... more Ferraz et al. (2008) indicated the need for planning in biological monitoring in the Amazon, and reviewed what they considered recent progress. The problems and solutions they discuss are well known, and it is unlikely that many biologists would disagree with most of them. ...
Ecological Indicators, 2012
We present a synthesis of the first 10 years of Long Term Ecological Research project in Amazonia... more We present a synthesis of the first 10 years of Long Term Ecological Research project in Amazonian Forest. We elucidate the natural dynamics of forest ecosystem processes and associated biota, and its changes caused by distinct pressures of selective timber extraction and forest fragmentation. We found that, for both plants and animals, densities of individ- uals and distribution of species assemblages are spatially heterogeneous at the mesoscale, even in relatively undisturbed forests, and that associations with topo-edaphic variables allow prediction of a considerable part of this variation. For biological groups whose dynam- ics were studied in the short-term, levels of change in species composition and densities were relatively high, and these changes were generally in tune with spatial environmen- tal variation. The impact of selective logging on assemblages and ecosystem processes was normally moderate, and around 19 years were needed for recovering forest biomass and tree size distribution. Continued studies are needed to determine the time required for recuper- ation of timber stocks and pre-logging floristic composition. Selective logging appears to be compatible with the biodiversity conservation, but reduction and better planning of road access may be more important than planned logging intensities. Habitat-loss’ impact on organisms and ecosystem processes is large and long-lasting, since it induces the loss of many taxonomic groups and species, higher tree mortality and accelerated forest dynamics. There was a negative synergy between the impacts of habitat loss and climatic changes, and a better understanding of these processes can only be obtained through long-term research.
Biological Conservation, 2011
The Herpetological …, 2005
The Herpetological …, 2006