CONICET | Buscador de Institutos y Recursos Humanos

The seasonality of amphibian activity is a long studied and recognized feature but generally includes only the analysis of adult calling males. In this study, seasonal variation in abundance of a whole assemblage (adults and juvenile), coexistence patterns and phenology was analyzed in a community of sixteen amphibian species inhabiting lowland river floodplain ponds. Species activity period was wider than reproductive phase and assemblage activity concentrated in warm season. The seasonal patterns of abundance and population size structure varied among species but nestedness structure and positive co-occurrence was found for adults and juveniles assemblages. Most adult hylids characterized by prolonged activity periods while bufonids, cycloramphids, leiuperids, leptodactylids and microhylids varied from prolonged to explosive. The recruitment of juveniles was intensive or explosive in nine out of ten evaluated species, generating a seasonal reduction in population size structure. The gathered recruitment indicates that warm season is particularly favourable for ingress of juveniles to populations. River hydrometric level was the best predictor of anuran activity, although seasonality (temperature and photoperiod), humidity, rainfall also were informative. The slight differences in activity patterns respect to other studies could be attributed to variations in local factors and differences in habitat seasonality. Since studied amphibians utilize the same habitat, activity and recruitment differences among species should be the consequence of combined effect of evolutionary fixed life history traits and present ecological interactions. Thus, there is a mixture of profound and proximate factors ruling species activity and seasonal changes in assemblage structure