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| Author(s): |
Monique Nouailhetas Simon
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB) |
| Defense date: | 2010-08-20 |
| Examining board members: |
José Eduardo de Carvalho;
Denis Otavio Vieira de Andrade;
Gabriel Henrique Marroig Zambonato
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| Advisor: | Carlos Arturo Navas Iannini |
| Abstract | |
The lasting presence of anuran amphibian species in the Caatinga, an environment that has been undergoing a desertification process, raises questions regarding the physiological and evolutionary aspects involved. The argument that phenotypic plasticity allows for the survival of populations in face of environmental changes seems to provide a plausible explanation. Temperature and its variation were elected as representatives of the desertification process. Based on the evidence that the Caatinga was originally a humid forest, correspondent values for the Atlantic forest were used as reference for comparison. The theoretical framework adopted assumes that the thermal sensitivity of differentiation in anuran larvae is higher than growth sensitivity (Smith-Gill and Berven, 1979). Our main hypothesis was that the developmental plasticity of the Caatinga species Rhinella granulosa is greater than those of Atlantic forest species Rhinella ornata and Rhinella icterica. We compared thermal reaction norms of growth rate, development time, metamorphic mass and critical thermal maxima (CTMax) for each species. Larvae were submitted to thermal regimes typical of the Caatinga and the Atlantic forest. A significant interaction between thermal mode and variation was detected for both Rhinella ornata and Rhinella icterica. Forest species appeared very plastic. When submitted to Caatinga thermal regimes, they displayed double growth rate and a third of development time in comparison to when they were submitted to Atlantic forest thermal regimes. The larvae presented individual variation in thermal sensitivity. Indeed, a fraction of the sample did not follow Smith-Gill and Bervens rule and displayed thermal sensitivity of differentiation similar to growth sensitivity. As a consequence, they maintained their metamorphic mass canalized at 0,25g in face of higher temperatures. Although Rhinella granulosa\'s CTMax was higher than for the forest species, it presented less plasticity. The results have not supported our hypothesis as the Atlantic forest species seems more plastic than the Caatinga species. (AU) | |