O papel das espécies raras na ictiofauna de riachos tropicais em diferentes condições de florestas e escalas
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Data
2017-03-31
Autores
Bordignon, Carolina Rodrigues [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Devido a suas menores abundâncias e/ou apresentarem uma estreita distribuição geográfica, as espécies raras são mais suscetíveis à extinção na ocorrência de eventos estocásticos ou antropogênicos. Elas também podem conter atributos funcionais únicos, associados à realização de papéis importantes para o ecossistema. O desmatamento crescente, principal causa de perda de habitat em riachos, pode levar a um processo de perda de espécies, especialmente das mais raras. Assim, é de suma importância investigar como essas espécies podem responder a diferentes cenários de degradação ambiental e a consequência da perda dessas espécies para comunidades e ecossistemas. Dessa forma, o objetivo desse estudo foi avaliar se a perda de espécies raras influencia a diversidade funcional em comunidades de peixes de riachos florestados e desmatados, em escalas de microbacia e de buffer ripário. Para atingir esse objetivo, foram delimitados quatro grupos de riachos da bacia do rio Machado: FLORESTADO microbacia, FLORESTADO buffer, DESMATADO microbacia e DESMATADO buffer. Para cada grupo, nós usamos 14 riachos, contabilizando uma riqueza total de 97 espécies. As espécies raras foram definidas de acordo com dois critérios: aquelas com abundância menor ou igual a cinco indivíduos dentro de cada grupo de riachos (Rab) ou aquelas com cinco ou menos ocorrências dentro de cada grupo de riachos (Roc). Então, foram utilizados seis atributos ecomorfológicos para calcular a diversidade funcional em cada grupo através o índice FD (Functional Diversity). Posteriormente foi calculada a contribuição de cada espécie para a diversidade funcional das comunidades, para as escalas de microbacia e buffer ripário. A contribuição funcional das espécies raras (Rab e Roc) foi comparada com a contribuição funcional das comuns para cada grupo de riachos e escala analisada. Também foi comparada a contribuição funcional das espécies raras nos ambientes desmatados em relação às raras nos florestados. A contribuição funcional das espécies raras foi significativamente maior do que a das comuns para os riachos desmatados e não houve diferença para os florestados. Quando consideradas apenas as espécies raras, a contribuição funcional foi maior nos riachos desmatados em relação aos florestados. Esse resultado pode estar relacionado com o desmatamento recente da região, onde os riachos desmatados ainda abrigam uma fauna residual de espécies sensíveis, representadas pelas espécies raras com atributos funcionais distintos das espécies comuns. Os riachos florestados apresentam maior heterogeneidade de habitat, propiciando a formação de mesohabitats e ocorrência de espécies com diferentes demandas ecológicas. Portanto, os riachos já florestados devem ser conservados como meio de assegurar a diversidade biológica e o funcionamento do ecossistema. Além disso, esforços devem ser dirigidos à recuperação de áreas desmatadas, como forma de melhorar a qualidade desses ambientes e também proporcionar a ocorrência de mais espécies com atributos funcionais distintos.
Due to their low abundance and/or narrow distribution, rare species are more susceptible to extinctions in consequence of stochastic or anthropogenic events. These species can also have unique functional traits, associated with the performance of important functions to the ecosystem. The growing of deforestation, primary cause of habitat loss in streams, can lead to a species loss process, especially evident to the rare ones. Thus, it is crucial to investigate how rare species can respond to different scenarios of environmental degradation and the consequences of these losses to communities and ecosystems. Therefore, the aim of this study was evaluate if the loss of rare species influences the functional diversity in forested and deforested streams, at watershed and riparian buffer scales. To accomplish this purpose, we delimited four groups of streams from Machado river basin: FORESTED watershed, FORESTED buffer, DEFORESTED watershed and DEFORESTED buffer. For each group, we used 14 streams, for a total richness of 97 species. Rare species were defined according two criteria: the ones with abundance lower than or equal to five individuals per stream group (Rab) and the ones with five or less occurrences (Roc) per stream group. After that, we used six ecomorphological traits to calculate functional diversity for each group through FD index (Functional Diversity). Then, we calculated the contribution of each species for fish communities functional diversity, for watershed and buffer scales. The rare species functional contribution (Rab and Roc) was compared to common species functional contribution for each streams group and scale analyzed. We also analyzed the rare functional contribution at deforested streams compared to forested ones. Rare species functional contribution was significantly higher than the common ones in deforested streams, while forested reaches did not show differences. When only rare species were analyzed, their functional contribution was higher at deforested streams in relation to the forested ones. This result can be associated to the recent deforestation process in the study area, where deforested streams still harbor a residual fauna of sensitive species, composed by rare species with distinct functional traits compared to the common ones. Moreover, forested streams can have a greater habitat heterogeneity, providing different mesohabitats and, consequently the occurrence of species with different ecological needs. Thus, forested streams must be conserved to afford biological diversity and ecosystem functioning. Furthermore, restoration efforts must be concentrated in deforested streams as a measure to improve the quality of these environments and also support the occurrence of more species with distinct functional traits.
Due to their low abundance and/or narrow distribution, rare species are more susceptible to extinctions in consequence of stochastic or anthropogenic events. These species can also have unique functional traits, associated with the performance of important functions to the ecosystem. The growing of deforestation, primary cause of habitat loss in streams, can lead to a species loss process, especially evident to the rare ones. Thus, it is crucial to investigate how rare species can respond to different scenarios of environmental degradation and the consequences of these losses to communities and ecosystems. Therefore, the aim of this study was evaluate if the loss of rare species influences the functional diversity in forested and deforested streams, at watershed and riparian buffer scales. To accomplish this purpose, we delimited four groups of streams from Machado river basin: FORESTED watershed, FORESTED buffer, DEFORESTED watershed and DEFORESTED buffer. For each group, we used 14 streams, for a total richness of 97 species. Rare species were defined according two criteria: the ones with abundance lower than or equal to five individuals per stream group (Rab) and the ones with five or less occurrences (Roc) per stream group. After that, we used six ecomorphological traits to calculate functional diversity for each group through FD index (Functional Diversity). Then, we calculated the contribution of each species for fish communities functional diversity, for watershed and buffer scales. The rare species functional contribution (Rab and Roc) was compared to common species functional contribution for each streams group and scale analyzed. We also analyzed the rare functional contribution at deforested streams compared to forested ones. Rare species functional contribution was significantly higher than the common ones in deforested streams, while forested reaches did not show differences. When only rare species were analyzed, their functional contribution was higher at deforested streams in relation to the forested ones. This result can be associated to the recent deforestation process in the study area, where deforested streams still harbor a residual fauna of sensitive species, composed by rare species with distinct functional traits compared to the common ones. Moreover, forested streams can have a greater habitat heterogeneity, providing different mesohabitats and, consequently the occurrence of species with different ecological needs. Thus, forested streams must be conserved to afford biological diversity and ecosystem functioning. Furthermore, restoration efforts must be concentrated in deforested streams as a measure to improve the quality of these environments and also support the occurrence of more species with distinct functional traits.
Descrição
Palavras-chave
Raridade, Desmatamento, Fauna residual, Riacho amazônicos, Rarity, Deforestation, Residual fauna, Amazon streams