Mammal ecology in fragmented landscapes: beyond the effects of habitat amount
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Data
2020-09-03
Autores
Regolin, André Luis
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A conversão de áreas naturais para uso antropogênico da terra causa perda, fragmentação e degradação de habitat, as quais são as principais ameaças para a conservação de mamíferos terrestres em todo o mundo. Nesta tese buscamos compreender aspectos sobre a ecologia de mamíferos terrestres em paisagens fragmentadas através de um estudo teórico (capitulo 1) e dois estudos empíricos, sendo um sobre estrutura de comunidades (capítulo 2) e outro sobre modelagem de uso de habitat (capítulo 3). No capítulo 1, elaborado no formato de um ensaio, apresentamos e discutimos potenciais influências da fragmentação de habitat sobre o processo de dispersão de sementes sobre morcegos neotropicais. Identificamos lacunas no conhecimento, sugerimos maneiras de preenchê-las e apresentamos potenciais aplicações relacionadas à conservação. No capítulo 2, avaliamos como assembleias de mamíferos são estruturadas em paisagens fragmentadas heterogêneas, combinando análises da estrutura da paisagem com medidas de heterogeneidade espacial. Especificamente, quantificamos a importância de métricas da paisagem, calculadas a partir de mapas temáticos, e de descritores de heterogeneidade espacial intraclasse, estimados utilizando imagens satélites não classificadas, para explicar a riqueza de espécies e a dissimilaridade da composição de espécies entre paisagens. Descobrimos que, contrário às nossas expectativas, a configuração da paisagem foi o principal fator que afetou a riqueza de espécies, seguido pela heterogeneidade espacial e, por último, pela composição da paisagem. O aninhamento das espécies foi explicado, em ordem de importância, pela heterogeneidade espacial, configuração da paisagem e composição da paisagem. Embora as políticas de conservação tendem a se concentrar principalmente na quantidade de habitat, defendemos que o manejo da paisagem deve incluir estratégias para preservar e melhorar a qualidade do habitat em manchas naturais e a incrementar a complexidade da vegetação na matriz circundante, permitindo que as paisagens abriguem maior diversidade de espécies. Investigamos, no capítulo 3, como o uso de habitat por mamíferos herbívoros e frugívoros é moldado pela interação entre a quantidade e qualidade do habitat no Pantanal. Ainda, avaliamos se a contribuição da qualidade do habitat varia conforme a sensibilidade das espécies à perda de habitat. A qualidade do habitat foi mais importante do que a quantidade de habitat na determinação do uso do habitat pelas espécies. A qualidade do habitat foi a melhor preditora de uso de habitat para quatro das seis espécies, mas o uso de habitat não foi explicado apenas pela quantidade de habitat. A quantidade de habitat influenciou apenas quando considerada em conjunto com covariáveis de qualidade do habitat e apenas para espécies mais sensíveis à modificações do habitat. As espécies menos sensíveis foram melhor modeladas apenas pelas covariáveis de qualidade do habitat. Os programas de conservação devem incorporar tanto a qualidade quanto a quantidade do habitat ao lidar com espécies sensíveis e priorizar o gerenciamento da qualidade do habitat ao focalizar espécies menos sensíveis.
The conversion of natural areas to anthropogenic land use causes habitat loss, fragmentation and degradation, which are the main threats to the conservation of terrestrial mammals worldwide. In this dissertation we aim to understand some aspects of terrestrial mammals ecology in fragmented landscapes through a theoretical study (chapter 1) and two empirical studies, one about community structure (chapter 2) and other regarding habitat use modeling (chapter 3). In chapter 1, a theoretical essay, we present and discuss potential influences of habitat fragmentation on the process of seed dispersal by Neotropical bats. We identify knowledge gaps, suggest ways to advance in this topic and present potential applications related to conservation. In chapter 2, we evaluate how mammal assemblies are structured in fragmented heterogeneous landscapes, combining analyzes of the landscape structure with measures of spatial heterogeneity. Specifically, we quantify the importance of landscape metrics, calculated from thematic maps, and of infraclass spatial heterogeneity descriptors, estimated using unclassified satellite images, to explain species richness and the dissimilarity of species composition between landscapes. We found that, contrary to our expectations, landscape configuration was the main factor affecting species richness, followed by spatial heterogeneity and, finally, landscape composition. Species' nesting was explained, in order of importance, by the spatial heterogeneity, landscape configuration and landscape composition. Although conservation policies tend to focus mainly on the amount of habitat, we argue that landscape management should include strategies to preserve and improve the quality of habitat in natural patches and to increase the complexity of vegetation in the surrounding matrix, allowing landscapes harbor higher diversity of species. In chapter 3, we investigate how the use of habitat by herbivorous and frugivorous mammals is shaped by the interaction between the amount and quality of the habitat in the Pantanal. Furthermore, we evaluate whether the contribution of habitat quality varies according to the sensitivity of species to habitat loss. The quality of the habitat was more important than the amount of habitat in determining habitat use (occupancy) by species. Habitat quality was the best predictor of habitat use for four of the six species, but habitat use was not explained only by the amount of habitat. The amount of habitat influenced habitat use only when considered in conjunction with habitat quality covariates and only for species more sensitive to habitat changes. The least sensitive species were best modeled solely by habitat quality covariates. Conservation programs must incorporate both quality and quantity of habitat when dealing with sensitive species and prioritize habitat quality management when focusing on less sensitive species.
The conversion of natural areas to anthropogenic land use causes habitat loss, fragmentation and degradation, which are the main threats to the conservation of terrestrial mammals worldwide. In this dissertation we aim to understand some aspects of terrestrial mammals ecology in fragmented landscapes through a theoretical study (chapter 1) and two empirical studies, one about community structure (chapter 2) and other regarding habitat use modeling (chapter 3). In chapter 1, a theoretical essay, we present and discuss potential influences of habitat fragmentation on the process of seed dispersal by Neotropical bats. We identify knowledge gaps, suggest ways to advance in this topic and present potential applications related to conservation. In chapter 2, we evaluate how mammal assemblies are structured in fragmented heterogeneous landscapes, combining analyzes of the landscape structure with measures of spatial heterogeneity. Specifically, we quantify the importance of landscape metrics, calculated from thematic maps, and of infraclass spatial heterogeneity descriptors, estimated using unclassified satellite images, to explain species richness and the dissimilarity of species composition between landscapes. We found that, contrary to our expectations, landscape configuration was the main factor affecting species richness, followed by spatial heterogeneity and, finally, landscape composition. Species' nesting was explained, in order of importance, by the spatial heterogeneity, landscape configuration and landscape composition. Although conservation policies tend to focus mainly on the amount of habitat, we argue that landscape management should include strategies to preserve and improve the quality of habitat in natural patches and to increase the complexity of vegetation in the surrounding matrix, allowing landscapes harbor higher diversity of species. In chapter 3, we investigate how the use of habitat by herbivorous and frugivorous mammals is shaped by the interaction between the amount and quality of the habitat in the Pantanal. Furthermore, we evaluate whether the contribution of habitat quality varies according to the sensitivity of species to habitat loss. The quality of the habitat was more important than the amount of habitat in determining habitat use (occupancy) by species. Habitat quality was the best predictor of habitat use for four of the six species, but habitat use was not explained only by the amount of habitat. The amount of habitat influenced habitat use only when considered in conjunction with habitat quality covariates and only for species more sensitive to habitat changes. The least sensitive species were best modeled solely by habitat quality covariates. Conservation programs must incorporate both quality and quantity of habitat when dealing with sensitive species and prioritize habitat quality management when focusing on less sensitive species.
Descrição
Palavras-chave
Dispersão de sementes, Heterogeneidade espacial, Fragmentação de habitat, Qualidade de habitat, Morcegos, Bats, Habitat fragmentation, Habitat quality, Seed dispersal, Spatial heterogeneity