title: Contributions of C3and C4plants to higher trophic levels in an Amazonian savanna.
abstract: We studied the energy flow from C3and C4plants 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 C4plants encountered in our study area were grasses and all C3plants 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 C4grasses.
authors.affiliation: Coordenação de Pesquisas em Ecologia, Instituto Nacional de Pesquisas da Amazônia, CP 478, 69011-970 Manaus AM, Brazil e-mail: bill@inpa.gov.br Tel.: +55-92-6431834, Fax: +55-92-6421838, , , , , , BR.
authors.forename: William E
authors.initials: WE
authors.lastname: Magnusson
authors.affiliation: Coordenação de Pesquisas em Ecologia, Instituto Nacional de Pesquisas da Amazônia, CP 478, 69011-970 Manaus AM, Brazil e-mail: bill@inpa.gov.br Tel.: +55-92-6431834, Fax: +55-92-6421838, , , , , , BR.
authors.forename: M
authors.initials: M
authors.lastname: Carmozina de Araújo
authors.affiliation: Coordenação de Pesquisas em Ecologia, Instituto Nacional de Pesquisas da Amazônia, CP 478, 69011-970 Manaus AM, Brazil e-mail: bill@inpa.gov.br Tel.: +55-92-6431834, Fax: +55-92-6421838, , , , , , BR.
authors.forename: Renato
authors.initials: R
authors.lastname: Cintra
authors.affiliation: Coordenação de Pesquisas em Ecologia, Instituto Nacional de Pesquisas da Amazônia, CP 478, 69011-970 Manaus AM, Brazil e-mail: bill@inpa.gov.br Tel.: +55-92-6431834, Fax: +55-92-6421838, , , , , , BR.
authors.forename: Albertina P
authors.initials: AP
authors.lastname: Lima
authors.affiliation: Centro de Energia Nuclear na Agricultura, Av. Centenário 303, 13416-000 Piracicaba SP, Brazil, , , , , , BR.
authors.forename: Luiz A
authors.initials: LA
authors.lastname: Martinelli
authors.affiliation: Coordenação de Pesquisas em Ecologia, Instituto Nacional de Pesquisas da Amazônia, CP 478, 69011-970 Manaus AM, Brazil e-mail: bill@inpa.gov.br Tel.: +55-92-6431834, Fax: +55-92-6421838, , , , , , BR.
authors.forename: Tânia M
authors.initials: TM
authors.lastname: Sanaiotti
authors.affiliation: Coordenação de Pesquisas em Ecologia, Instituto Nacional de Pesquisas da Amazônia, CP 478, 69011-970 Manaus AM, Brazil e-mail: bill@inpa.gov.br Tel.: +55-92-6431834, Fax: +55-92-6421838, , , , , , BR.
authors.forename: Heraldo L
authors.initials: HL
authors.lastname: Vasconcelos
authors.affiliation: Centro de Energia Nuclear na Agricultura, Av. Centenário 303, 13416-000 Piracicaba SP, Brazil, , , , , , BR.
authors.forename: Reynaldo L
authors.initials: RL
authors.lastname: Victoria
keywords: Carbon; Key words Amazonia; Savanna; Stable isotope; Trophic level