Heterogeneidade ambiental e diversidade ictiofaunística do trecho de corredeiras do Rio Madeira, Rondônia, Brasil
Several hypotheses and concepts have been employed to explain variations in species richness and ichthyofaunal composition in Neotropical rivers. The present study aimed to analyze the effects of local and regional factors on the species richness and composition of fish assemblages along a 293km str...
| Autor principal: | Torrente -Vilara, Gislene |
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| Grau: | Tese |
| Idioma: | por |
| Publicado em: |
Instituto Nacional de Pesquisas da Amazônia - INPA
2020
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| Acesso em linha: |
https://repositorio.inpa.gov.br/handle/1/11466 http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4790085J9 |
| Resumo: |
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Several hypotheses and concepts have been employed to explain variations in species richness and ichthyofaunal composition in Neotropical rivers. The present study aimed to analyze the effects of local and regional factors on the species richness and composition of fish assemblages along a 293km stretch of the Madeira River near the city of Porto Velho, Rondônia state, Brasil. Ten sampling sites were choosen near the confluence of the main tributaries of the Madeira River in that stretch, where the river is characterized by several rapids zones and waterfalls. An historical account of the knowledge about the fish fauna of Madeira River is presented, gathering the scientific literature dealing with ichthyofaunal inventories and discussing the occurrence of species endemisms in relation to other areas of the Amazon basin. Furthermore, a dataset about 174 fish species obtained by means of standardized sampling effort was employed to test the effects of local and regional factors and the presence of the main waterfalls of the Madeira River on the species richness and assemblages composition. The study was based on 30 samples collected in the flooding season and 30 others obtained in the drying season. Species richness did no respond significantly to any of the environmental factors tested and there was no increase in richness from upstream to dowsnstream areas in the river stretch. Variation in species composition was mainly related to the size of the drainage basin and to the position of the samplig site in relation to the Jirau and Teotônio waterfalls. This study revealed a similar degree of variation in species richness along that stretch of Madeira River that was associated to changes in species composition. These results point out to the existence of a transition zone between the rapids stretch and the downstream sedimentary plains of Madeira River, with the Teotônio waterfall marking the division of fish assemblages and characterizing the existence of an ecological zonation. |