Habitat use, trophic structure and functional diversity of fish in karst streams in the brazilian midwest
Carregando...
Data
2021-10-27
Autores
Neto, Francisco de Paula Severo da Costa
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Sistemas cársticos constituem ambientes único no mundo. Sua geomorfologia se baseia em rochas carbonáticas que agem como um filtro natural na hidrologia, resultando em ambientes aquáticos de alta transparência e beleza cênica extraordinária. Além de seu apelo visual, contribuem diretamente com o consumo de água por uma grande parcela da população mundial. Apesar destes fatores, ambientes cársticos são ameaçados pela ação humana, seja diretamente através da modificação do ambiente ou contaminação dos leitos por agentes defensivos e fertilizantes provindos do sistema agropecuário, ou indiretamente pelo aquecimento global. No Brasil, ambientes cársticos estão representados em sua maior parte na região Nordeste e Sudeste. Na região Centro-Oeste, próximo à fronteira com o Paraguai encontra-se o único sistema cárstico no estado de Mato Grosso do Sul, a Serra da Bodoquena, que consiste de um platô inserido na borda sul da bacia do Alto Paraguai, cujos tributários drenam para a planície do Pantanal Brasileiro. Trata-se de uma região mundialmente conhecida pelo turismo ecológico, especialmente para as atividades envolvendo seus rios cristalinos e a fauna de peixes residente. Embora a riqueza de espécies de peixes da região tenha seu consequente apelo no turismo e na manutenção da biodiversidade como um todo, informações básicas sobre sua biologia ainda são incipientes. Mais ainda, a região tem passado por mudanças quanto às atividades econômicas principais, com a substituição de pastagens por lavouras, porém, o consequente impacto dessas mudanças sobre peixes ainda é desconhecido. Sendo assim, o objetivo geral dessa Tese foi compreender como as espécies utilizam o ambiente (Capítulo 1), os recursos alimentares (Capítulo 2) e o efeito da paisagem na composição das comunidades (Capítulo 3). Para atingir esses objetivos, lançamos mão da classificação das espécies em grupos tróficos funcionais, que permitem a compreensão do uso da dimensão espacial pelos peixes dentro dos córregos e como e onde os recursos são obtidos por eles (Capítulo 1). Conhecendo o uso do espaço pelos peixes, determinamos quais itens fazem parte da dieta das espécies e como elas se relacionam na teia trófica regional (Capítulo 2). Encerramos investigando como a elevação e uso do solo atua sob a substituição de espécies e/ou atributos funcionais (Capítulo 3). Em suma, encontramos que: (1.) a maior parcela de peixes da região é de pequeno porte e contribui diretamente na riqueza de grupos funcionais tróficos; (2.) a dieta das espécies consiste basicamente de itens provenientes de fora do ambiente aquático e a rede trófica da comunidade apresenta alto grau de especialização, aninhamento e modularidade. Em outras palavras, um mesmo recurso pode ser partilhado entre várias espécies; entretanto, há aquelas que se especializam em determinado item, o que resulta na compartimentalização da comunidade com relação ao tipo de recurso consumido; (3.) A substituição de espécies/atributos funcionais não se relacionou com o uso do solo, mas sim com a altitude, mostrando que, no primeiro caso, fatores estocásticos estão envolvidos e no segundo, ambientais. Em conclusão, o conjunto de espécies de peixes da Serra da Bodoquena apresenta únicos padrões de uso de habitat, um reflexo da imposição ambiental da região, como uso de corredeiras; peixes pequenos usam principalmente margens e representam a maior parcela da riqueza da comunidade, evidenciando um padrão Neotropical; a partilha de recursos é alta e dependente de itens alóctones; e, no contexto da bacia do Alto Paraguai, o padrão singular de altitude da região é um fator fundamental na manutenção da diversidade de peixes.
Karst systems constitute unique environments in the world. Its geomorphology is based on carbonate rocks that act as a natural filter in the hydrology, resulting in highly transparent aquatic environments and extraordinary scenic beauty. In addition to their visual appeal, they directly contribute to water consumption by a large portion of the world's population. Despite these factors, karst environments are threatened by human action, either directly through the modification of the environment or contamination of beds by defensive agents and fertilizers from the agricultural system, or indirectly by global warming. In Brazil, karst environments are mostly represented in the Northeast and Southeast regions. In the Center-West region, close to the border with Paraguay, the only karst system in the state of Mato Grosso do Sul is the Serra da Bodoquena which consists of a plateau inserted in the southern edge of the Upper Paraguay River basin, whose tributaries drain into the plain of the Brazilian Pantanal. It is a region known worldwide for ecological tourism, especially for activities involving its crystalline rivers and resident fish fauna. Although the richness of fish species in the region has its consequent appeal for tourism and the maintenance of biodiversity as a whole, basic information about their biology still incipient. Furthermore, the region has undergone changes in terms of its main economic activities, with the replacement of pastures by crops, but the consequent impact of these changes on fish is still unknown. Therefore, the general objective of this Thesis was to understand how species use the environment (Chapter 1), the feeding resources (Chapter 2), and the effect of landscape on community composition (Chapter 3). To achieve these goals, we use the classification of species into functional trophic groups, which allow us to understand the use of the spatial dimension by fish within streams and how and where resources are obtained by them (Chapter 1). Knowing the use of space by fish, we determine which items are part of the species' diet and how they are related in the regional food web (Chapter 2). We close by investigating how elevation and land use act under the replacement of species and/or functional attributes (Chapter 3). In summary, we found that: (1.) the largest portion of fish in the region is small and contributes directly to the richness of trophic functional groups; (2.) the species' diet basically consists of items from outside the aquatic environment and the trophic network of the community presents a high degree of specialization, nestedness and modularity. In other words, the same resource can be shared among several species, although there are those that specialize in a certain item, which results in the compartmentalization of the community in relation to the type of resource consumed; (3.) The replacement of species/functional attributes was not related to land use, but rather to altitude, showing that, in the first case, stochastic factors are involved and, in the second, environmental ones. In conclusion, the set of fish species in Serra da Bodoquena presents unique patterns of habitat use, a reflection of the environmental imposition of the region; small fish mainly use margins and represent the largest portion of the richness of the community, evidencing a Neotropical pattern; resource sharing is high and dependent on allochthonous items; and, in the context of the Upper Paraguay basin, the region's unique altitude pattern is a fundamental factor in maintaining fish diversity.
Karst systems constitute unique environments in the world. Its geomorphology is based on carbonate rocks that act as a natural filter in the hydrology, resulting in highly transparent aquatic environments and extraordinary scenic beauty. In addition to their visual appeal, they directly contribute to water consumption by a large portion of the world's population. Despite these factors, karst environments are threatened by human action, either directly through the modification of the environment or contamination of beds by defensive agents and fertilizers from the agricultural system, or indirectly by global warming. In Brazil, karst environments are mostly represented in the Northeast and Southeast regions. In the Center-West region, close to the border with Paraguay, the only karst system in the state of Mato Grosso do Sul is the Serra da Bodoquena which consists of a plateau inserted in the southern edge of the Upper Paraguay River basin, whose tributaries drain into the plain of the Brazilian Pantanal. It is a region known worldwide for ecological tourism, especially for activities involving its crystalline rivers and resident fish fauna. Although the richness of fish species in the region has its consequent appeal for tourism and the maintenance of biodiversity as a whole, basic information about their biology still incipient. Furthermore, the region has undergone changes in terms of its main economic activities, with the replacement of pastures by crops, but the consequent impact of these changes on fish is still unknown. Therefore, the general objective of this Thesis was to understand how species use the environment (Chapter 1), the feeding resources (Chapter 2), and the effect of landscape on community composition (Chapter 3). To achieve these goals, we use the classification of species into functional trophic groups, which allow us to understand the use of the spatial dimension by fish within streams and how and where resources are obtained by them (Chapter 1). Knowing the use of space by fish, we determine which items are part of the species' diet and how they are related in the regional food web (Chapter 2). We close by investigating how elevation and land use act under the replacement of species and/or functional attributes (Chapter 3). In summary, we found that: (1.) the largest portion of fish in the region is small and contributes directly to the richness of trophic functional groups; (2.) the species' diet basically consists of items from outside the aquatic environment and the trophic network of the community presents a high degree of specialization, nestedness and modularity. In other words, the same resource can be shared among several species, although there are those that specialize in a certain item, which results in the compartmentalization of the community in relation to the type of resource consumed; (3.) The replacement of species/functional attributes was not related to land use, but rather to altitude, showing that, in the first case, stochastic factors are involved and, in the second, environmental ones. In conclusion, the set of fish species in Serra da Bodoquena presents unique patterns of habitat use, a reflection of the environmental imposition of the region; small fish mainly use margins and represent the largest portion of the richness of the community, evidencing a Neotropical pattern; resource sharing is high and dependent on allochthonous items; and, in the context of the Upper Paraguay basin, the region's unique altitude pattern is a fundamental factor in maintaining fish diversity.
Descrição
Palavras-chave
Ictiologia, Comunidades, Água doce, Interações tróficas, Ecomorfologia, Diversidade Beta, Bacia do Alto Rio Paraguai, Serra da Bodoquena, Ichthyology, Communities, Freshwater, Ecomorfology, Beta diversity, Upper Paraguay River basin