Anfíbios dos campos da Mata Atlântica: influência relativa de gradientes ambientais e espaciais nos padrões de diversidade e estrutura filogenética
Carregando...
Data
2016-06-30
Autores
Crivellari, Lucas Batista [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Com intuito de compreender os processos que determinam a composição e distribuição da diversidade de anfíbios em paisagens subtropicais, nós (1) inventariamos a composição dos anfíbios em áreas de campos naturais entremeados a formações florestais da Mata Atlântica, (2) avaliamos como características da paisagem (i.e., cobertura e uso do solo) e dos habitats (i.e., área, hidroperíodo, cobertura de dossel dos corpos d’água) influenciam os padrões de distribuição da diversidade taxonômica e filogenética e (3) avaliamos quais e como gradientes ambientais e espaciais influenciam a estrutura filogenética da metacomunidade regional. Empregamos três métodos de amostragem (transecção, amostragem em sítio de reprodução e busca ativa) em 12 unidades de conservação e entorno, distribuídas nos Estados do Paraná e de Santa Catarina. As amostragens foram realizadas em diferentes períodos entre 2004 e 2014. Nós registramos 63 espécies de 11 famílias de anfíbios, das quais 20 espécies foram associadas aos campos, 19 às áreas florestais e ecótonos e 21 espécies foram generalistas. Espécies com um único indivíduo registrado não foram avaliadas quanto ao uso de habitat. Para avaliar a influência das características estruturais do habitat e da paisagem sobre os padrões de distribuição dos anfíbios, nós selecionamos oito das unidades de conservação e amostramos mensalmente, ao longo de um ano, entre oito e 14 corpos d’água em cada unidade, totalizando 81 corpos d’água (poças temporárias, lagoas permanentes, banhados e açudes). Em cada corpo d’água nós determinamos 10 variáveis estruturais do habitat e 11 da paisagem. As variáveis da paisagem foram mensuradas em múltiplas escalas espaciais através de buffers com diferentes comprimentos de raio (250 m, 500 m e 1.000 m) a partir de cada corpo d’água. A diversidade taxonômica foi representada pela riqueza de espécies e abundância de indivíduos, e a diversidade filogenética foi calculada pelo índice de entropia quadrática de rao. Nós utilizamos modelos lineares generalizados mistos, com as variáveis ambientais estruturais inseridas como variáveis de efeito fixo e as localidades (i.e., unidades de conservação) como covariáveis de efeito aleatório. Os modelos só foram validados após checados quanto a presença de autocorrelação espacial nos resíduos. Os resultados evidenciaram que a heterogeneidade da vegetação nas margens e no interior do corpo d’água, a distância entre os corpos d’água e a equitabilidade na proporção de campos naturais e floresta com araucária em um raio de 1.000 m explicam 43% da variação na riqueza de espécies. Em relação a abundância total de indivíduos, o modelo de melhor ajuste indicou que a área e a heterogeneidade da vegetação nas margens e no interior do corpo d’água explicam 44% da variação da abundância acumulada. Já em relação a diversidade filogenética, a heterogeneidade da vegetação no interior dos corpos d’água, hidroperíodo intermediário (termo quadrático) e grau de distúrbio antrópico em uma escala de 250 m explicaram 46% da variação total da diversidade filogenética nos corpos d’água. Para determinar a influência de gradientes ambientais e espaciais na estrutura filogenética da metacomunidade, utilizamos o método de ponderação filogenética difusa seguido por análise de coordenadas principais da estrutura filogenética. Com esta análise são gerados autovetores que correspondem a eixos independentes que contemplam a variação filogenética (gradientes filogenéticos). Com isso, é possível comparar as comunidades em relação a composição filogenética e identificar quais clados estão associados a cada gradiente filogenético, além de possibilitar a investigação destes gradientes filogenéticos em relação a diferentes gradientes ambientais e espaciais. Os gradientes ambientais foram representados pelas variáveis de cobertura e tipo de uso do solo e de heterogeneidade estrutural dos habitats de reprodução. Os gradientes espaciais foram representados pelos autovetores obtidos por análise de coordenadas principais de matrizes de vizinhas (PCNMS). Nós utilizamos a análise de redundância parcial e partição da variância para avaliar relações entre os gradientes filogenéticos (variáveis resposta) e os gradientes ambientais e espaciais (variáveis preditoras). Verificamos que os gradientes ambientais e espaciais juntos explicaram 27% da variabilidade na composição filogenética, sendo que o componente ambiental (heterogeneidade estrutural do corpo d’água + paisagem) explicou a maior parte da variação (13%). Adicionalmente, o espaço teve um papel fundamental na estruturação da composição filogenética, principalmente pela sua associação significativa com as variáveis da paisagem. Nossos resultados indicaram a existência de associações significativas entre os gradientes ambientais de cobertura e tipo de uso do solo e gradientes espaciais, tanto em escalas amplas (regional) quanto em escalas finas (entre corpos d’água) e a estrutura filogenética desta metacomunidade regional. As variáveis locais não apresentaram associação com os gradientes espaciais, ou seja, não possuem estrutura espacial em nenhuma escala. Nossos resultados sugerem que a influência de filtros espaciais PCNMS sobre a estrutura filogenética de anfíbios está mais relacionada aos gradientes ambientais do que a limitação por dispersão pelas linhagens filogenéticas. Assim, processos espaciais através de dinâmicas neutras, parecem exercer uma influência menor do que processos determinísticos relacionados ao nicho na distribuição de clados filogenéticos dos anfíbios dos campos naturais da Mata Atlântica. Adicionalmente, a forte associação de alguns clados com determinados gradientes ambientais corroboram com nossa expectativa de que caraterísticas dos corpos d’água e de cobertura e tipo de uso do solo atuam como filtro influenciando a estrutura filogenética da metacomunidade. Nós verificamos que as variáveis hidroperíodo e alteração antrópica em um raio de 250 m do corpo d’água foram importantes estruturadores filogenéticos, influenciando a variação filogenética contemplada pelo primeiro gradiente filogenético, que foi associado ao clado Microhylidae, separando este clado dos demais. O hidroperíodo também foi um importante estruturador filogenético associado ao segundo gradiente filogenético, que corresponde à ocorrência dos hilídeos do clado Hypsiboas. Nossos resultados demonstram que a influência destes gradientes ambientais na composição de espécies é dependente das relações filogenéticas entre as espécies que co-ocorrem. Nós também encontramos uma relação significativa e positiva entre a variação filogenética contemplada pelo quinto gradiente filogenético, que foi associado aos hilídeos do clado Dendropsophus, com a heterogeneidade da vegetação no interior do corpo d’água e com menor área de cobertura de campos nativos em um raio de 1.000 m do corpo d’água. Com este estudo fomos capazes de avaliar variações na estrutura filogenética de uma metacomunidade regional de anfíbios subtropicais e concomitantemente detectar quais os principais gradientes ambientais e espaciais que influenciam a distribuição de clados distintos. O conjunto de informações obtidas indicam quais variáveis ambientais e quais processos determinam a composição e distribuição da diversidade de espécies de anfíbios nos campos naturais da Mata Atlântica. Essas informações são, também, fundamentais para formulação e aplicação de estratégias de conservação.
In order to understand wich processes determine the composition and distribution of amphibian diversity in subtropical landscapes, the goals of this work was (1) inventorying the composition of amphibians in areas of natural grasslands associated with Atlantic Forest, (2) assess how land coverage (i.e., land cover and use) and breeding habitats features (i.e., area, depth) influence the distribution patterns of taxonomic and phylogenetic diversity, (3) evaluate how environmental and spatial gradients influence the phylogenetic structure regional metacommunity. We employ three sampling methods (transect sampling, survey at breeding site and active search) in 12 conservation units, distributed in the states of Paraná and Santa Catarina. Samples were taken at different periods between 2004 and 2014. We recorded 63 species of amphibians distributed in 11 families. In relation to use of habitat by amphibians, 20 species were preferably associated with grasslands, 19 were preferably forest and forest edge, 21 generalist (recorded on forest, edge and grasslands environments). Species with a single individual recorded were not evaluated for their habitat use. In order to assess how land coverage and breeding habitats features influence the distribution patterns of taxonomic and phylogenetic diversity, we selected eight conservation units and sampled monthly, over a year, a minimum of 8 and a maximum of 14 water bodies in each unit, totaling 81 water bodies (i.e., pools, permanent ponds and mashes). We measured 10 structural variables of breeding habitats and 11 variables on the level of landscape features. Landscape variables were measured at multiple spatial scales through buffers with different radius lengths (250m, 500m and 1.000m) from each water body. The taxonomic diversity was represented by the species richness and abundance of individuals, and phylogenetic diversity was calculated using the quadratic entropy index rao. We used generalized linear mixed models with environmental variables as fixed effect variables and locations (i.e., conservation units) as random effect co–variables. The models validated only after checked for residuals spatial autocorrelation. The results showed that the heterogeneity of vegetation (edges and inside of breeding sites), distance between water bodies and evenness of natural grasslands and araucaria forest in 1.000 meters of adjacency of breeding sites explain 43% of the variation in species richness. In relation to total abundance of individuals, the best fit model indicated the area (m²) and heterogeneity of vegetation types in edges and inside explaining 44% of the accumulated variation of abundance. Phylogenetic diversity was associated with heterogeneity of vegetation within the water bodies, intermediate hydroperiod (quadratic term) and anthropogenic disturbance in a range of 250 meters explaining 46% of the total variation of the phylogenetic diversity among all water bodies. Finally, we assess how environmental and spatial gradients influence the phylogenetic structure of regional metacommunity. Phylogenetic structure of the metacommunity was characterized using phylogenetic fuzzy weighting method followed by principal coordinate analysis of phylogenetic structure (PCPS). This proceedings analysis generated eigenvectors (phylogenetic gradients), that correspond to independent orthogonal axes which include the phylogenetic variation through which we can compare the communities on phylogenetic composition and enable us the investigation about the influence of environmental and space gradients. The land coverage and breeding habitats features represented environmental gradients. The spatial gradients were represented by the eigenvectors (PCNMs) obtained by principal coordinate analysis of neighborhood’s. Through analysis of variance partition, we found that the environmental and spatial gradients together explained 27% of the variability in the phylogenetic composition and the environmental component explained most of the variation 13% (breeding habitats features and landscape together). In addition, the space had a key role in structuring the phylogenetic composition, mainly for its significant association with the landscape variables. Our results indicated the existence of significant associations between environmental gradients of land coverage at broad and fine spatial scales influencing the phylogenetic structure of regional metacommunity. Local variables of breeding habitats were not associated with any spatial gradients, indicating variation in breeding habitats features is not related to any particular spatial scale. Our results suggest that the influence of spatial filters on the phylogenetic structure of amphibians in grasslands from Atlantic Forest biome is more related to environmental gradients captured by PCNM variables than to dispersal limitation of phylogenetic lineages. Thus, neutral dynamics are expected to exert a minor influence in the distribution of phylogenetic clades in this scale of regional metacommunity. In addition, some clades were strongly associated with environmental gradients corroborate our expectation that characteristics of water bodies and land coverage act as phylogenetic filtering. We found that hydroperiod (HID) and anthropogenic disturbance in 250 meters from the water body (ANT250m) were important phylogenetic drivers influencing the variation contemplated by the first PCPS1, this phylogenetic gradient were associated with the clade of Microhylidae. Moreover, hydroperiod was also an important phylogenetic driver influencing the variation contemplated in PCPS2, which split Hylidae clade from the other clades. We also found a significant relationship between phylogenetic variation contemplated by the PCPS5, associated Dendropsophus clade with the heterogeneity of vegetation within the water body (HVI) and less coverage of native grasslands at scale of 1.000 meters from the water body. With this study, we were able to evaluate variations in the phylogenetic structure of a regional metacommunity of sub-tropical amphibians and simultaneously detect which key environmental and spatial gradients that influence the distribution of distinct clades. The set of information obtained indicate which environmental variables and processes determine the composition and distribution of species diversity of amphibians in grasslands from Atlantic Forest. This information is also essential for the formulation and implementation of conservation strategies.
In order to understand wich processes determine the composition and distribution of amphibian diversity in subtropical landscapes, the goals of this work was (1) inventorying the composition of amphibians in areas of natural grasslands associated with Atlantic Forest, (2) assess how land coverage (i.e., land cover and use) and breeding habitats features (i.e., area, depth) influence the distribution patterns of taxonomic and phylogenetic diversity, (3) evaluate how environmental and spatial gradients influence the phylogenetic structure regional metacommunity. We employ three sampling methods (transect sampling, survey at breeding site and active search) in 12 conservation units, distributed in the states of Paraná and Santa Catarina. Samples were taken at different periods between 2004 and 2014. We recorded 63 species of amphibians distributed in 11 families. In relation to use of habitat by amphibians, 20 species were preferably associated with grasslands, 19 were preferably forest and forest edge, 21 generalist (recorded on forest, edge and grasslands environments). Species with a single individual recorded were not evaluated for their habitat use. In order to assess how land coverage and breeding habitats features influence the distribution patterns of taxonomic and phylogenetic diversity, we selected eight conservation units and sampled monthly, over a year, a minimum of 8 and a maximum of 14 water bodies in each unit, totaling 81 water bodies (i.e., pools, permanent ponds and mashes). We measured 10 structural variables of breeding habitats and 11 variables on the level of landscape features. Landscape variables were measured at multiple spatial scales through buffers with different radius lengths (250m, 500m and 1.000m) from each water body. The taxonomic diversity was represented by the species richness and abundance of individuals, and phylogenetic diversity was calculated using the quadratic entropy index rao. We used generalized linear mixed models with environmental variables as fixed effect variables and locations (i.e., conservation units) as random effect co–variables. The models validated only after checked for residuals spatial autocorrelation. The results showed that the heterogeneity of vegetation (edges and inside of breeding sites), distance between water bodies and evenness of natural grasslands and araucaria forest in 1.000 meters of adjacency of breeding sites explain 43% of the variation in species richness. In relation to total abundance of individuals, the best fit model indicated the area (m²) and heterogeneity of vegetation types in edges and inside explaining 44% of the accumulated variation of abundance. Phylogenetic diversity was associated with heterogeneity of vegetation within the water bodies, intermediate hydroperiod (quadratic term) and anthropogenic disturbance in a range of 250 meters explaining 46% of the total variation of the phylogenetic diversity among all water bodies. Finally, we assess how environmental and spatial gradients influence the phylogenetic structure of regional metacommunity. Phylogenetic structure of the metacommunity was characterized using phylogenetic fuzzy weighting method followed by principal coordinate analysis of phylogenetic structure (PCPS). This proceedings analysis generated eigenvectors (phylogenetic gradients), that correspond to independent orthogonal axes which include the phylogenetic variation through which we can compare the communities on phylogenetic composition and enable us the investigation about the influence of environmental and space gradients. The land coverage and breeding habitats features represented environmental gradients. The spatial gradients were represented by the eigenvectors (PCNMs) obtained by principal coordinate analysis of neighborhood’s. Through analysis of variance partition, we found that the environmental and spatial gradients together explained 27% of the variability in the phylogenetic composition and the environmental component explained most of the variation 13% (breeding habitats features and landscape together). In addition, the space had a key role in structuring the phylogenetic composition, mainly for its significant association with the landscape variables. Our results indicated the existence of significant associations between environmental gradients of land coverage at broad and fine spatial scales influencing the phylogenetic structure of regional metacommunity. Local variables of breeding habitats were not associated with any spatial gradients, indicating variation in breeding habitats features is not related to any particular spatial scale. Our results suggest that the influence of spatial filters on the phylogenetic structure of amphibians in grasslands from Atlantic Forest biome is more related to environmental gradients captured by PCNM variables than to dispersal limitation of phylogenetic lineages. Thus, neutral dynamics are expected to exert a minor influence in the distribution of phylogenetic clades in this scale of regional metacommunity. In addition, some clades were strongly associated with environmental gradients corroborate our expectation that characteristics of water bodies and land coverage act as phylogenetic filtering. We found that hydroperiod (HID) and anthropogenic disturbance in 250 meters from the water body (ANT250m) were important phylogenetic drivers influencing the variation contemplated by the first PCPS1, this phylogenetic gradient were associated with the clade of Microhylidae. Moreover, hydroperiod was also an important phylogenetic driver influencing the variation contemplated in PCPS2, which split Hylidae clade from the other clades. We also found a significant relationship between phylogenetic variation contemplated by the PCPS5, associated Dendropsophus clade with the heterogeneity of vegetation within the water body (HVI) and less coverage of native grasslands at scale of 1.000 meters from the water body. With this study, we were able to evaluate variations in the phylogenetic structure of a regional metacommunity of sub-tropical amphibians and simultaneously detect which key environmental and spatial gradients that influence the distribution of distinct clades. The set of information obtained indicate which environmental variables and processes determine the composition and distribution of species diversity of amphibians in grasslands from Atlantic Forest. This information is also essential for the formulation and implementation of conservation strategies.
Descrição
Palavras-chave
Anfíbios, Metacomunidade, Uso de Solo, Estrutura Filogenética, Campos da Mata Atlântica, Amphibians, Metacommunity, Land use, Phylogenetic Structure, Grasslands of Atlantic Forest