Contribuição de processos determinísticos e estocásticos na estrutura de metacomunidades de girinos do Pantanal
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Data
2021-11-09
Autores
Marques, Ynaiá Yamanaka
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Universidade Estadual Paulista (Unesp)
Resumo
Um dos principais adventos da ecologia de comunidades nas últimas décadas foi o reconhecimento de que a estrutura de uma comunidade local é influenciada por interações locais e processos regionais. Esse avanço foi possível com o desenvolvimento do conceito de metacomunidade, que incluiu o papel da dispersão nos padrões de diversidade. Diversos estudos indicam que variáveis ambientais e espaciais são fortes estruturadores de comunidades de anuros. Entretanto, dois estudos recentes detectaram uma fraca influência desses dois conjuntos de variáveis em comunidades de anuros do Pantanal brasileiro, sugerindo que processos estocásticos constituem a principal força influenciando a diversidade nesse sistema. Neste estudo, avaliamos a influência de variáveis ambientais (processos determinísticos) e da probabilidade de imigração (processos estocásticos) em metacomunidades de girinos do Pantanal. Analisamos o conjunto de dados proveniente da amostragem de 74 corpos d’água lênticos em escala espacial ampla e em três escalas espaciais restritas. Para isso, empregamos uma abordagem analítica integrativa de estudo de metacomunidades proposta recentemente e um parâmetro estimado com base na Teoria Neutra da Biodiversidade e Biogeografia. Testamos a hipótese de que as metacomunidades estão sob forte influência de processos estocásticos devido à constante redistribuição de indivíduos pela paisagem, em decorrência do pulso de inundação. Esse fenômeno, associado ao hábito habitat-generalista dos indivíduos adultos das espécies levaria a ocupação de habitats de forma estocástica. Contrariando nossa predição, verificamos que as metacomunidades de girinos do Pantanal estão sob influência principalmente de fatores determinísticos, mas também de fatores estocásticos. Detectamos fraca, mas significativa influência do ambiente e do espaço, indicando a atuação de processos determinísticos relacionados ao nicho e fraca ou ausência de restrição à dispersão, que por sua vez é reforçada pela correlação com a probabilidade de imigração. Também encontramos evidências de que a estrutura das metacomunidades resulta da associação de diferentes processos que atuam diferentemente sobre as fases larval e adulta. O evento de inundação do Pantanal em associação com características de história de vida das espécies parecem ser as principais forças que estruturam as metacomunidades de girinos nessa região, promovendo uma redistribuição massiva de indivíduos pela paisagem e possibilitando que eles alcancem habitats com características adequadas ao longo do gradiente ambiental.
One of the major advances in community ecology in recent decades was the recognition that local interactions and regional processes affect the structure of a local community. This advance was possible with the development of the metacommunity concept, which included the role of dispersal in diversity patterns. Several studies indicate that environmental and spatial variables are strong structuring factors of anuran communities. However, two recent studies detected a weak influence of these two sets of variables on anuran communities in the Brazilian Pantanal, suggesting that stochastic processes are the main force influencing diversity in this system. In this study, we evaluated the influence of environmental variables (deterministic processes) and immigration probability (stochastic processes) on tadpole metacommunities in the Pantanal. We analyzed the dataset from 74 lentic water bodies sampled at a broad and at three fine spatial scales. We employed a recently proposed integrative analytical approach to study metacommunities and an estimated parameter based on the Neutral Theory of Biodiversity and Biogeography. Our hypothesis was that the metacommunities are under strong influence of stochastic processes due to the constant redistribution of individuals across the landscape because of the flood pulse. This phenomenon, associated with the habitat-generalist habit of adult individuals of the species, would lead to stochastic occupation of habitats. Contrary to our prediction, we found that the Pantanal tadpole metacommunities are under the influence mainly of deterministic factors, but also of stochastic factors. We detected weak but significant influence of environment and space, indicating the action of deterministic niche-based processes, and weak or absence of dispersal limitation, reinforced by the correlation with immigration probability. We also found evidences that the metacommunities structure results from the association of different processes acting differently on adults and tadpoles. The Pantanal flood event in association with life history characteristics of the species seems to be the main forces structuring tadpole metacommunities in this region, promoting a massive redistribution of individuals across the landscape and allowing them to reach habitats with suitable characteristics along the environmental gradient.
One of the major advances in community ecology in recent decades was the recognition that local interactions and regional processes affect the structure of a local community. This advance was possible with the development of the metacommunity concept, which included the role of dispersal in diversity patterns. Several studies indicate that environmental and spatial variables are strong structuring factors of anuran communities. However, two recent studies detected a weak influence of these two sets of variables on anuran communities in the Brazilian Pantanal, suggesting that stochastic processes are the main force influencing diversity in this system. In this study, we evaluated the influence of environmental variables (deterministic processes) and immigration probability (stochastic processes) on tadpole metacommunities in the Pantanal. We analyzed the dataset from 74 lentic water bodies sampled at a broad and at three fine spatial scales. We employed a recently proposed integrative analytical approach to study metacommunities and an estimated parameter based on the Neutral Theory of Biodiversity and Biogeography. Our hypothesis was that the metacommunities are under strong influence of stochastic processes due to the constant redistribution of individuals across the landscape because of the flood pulse. This phenomenon, associated with the habitat-generalist habit of adult individuals of the species, would lead to stochastic occupation of habitats. Contrary to our prediction, we found that the Pantanal tadpole metacommunities are under the influence mainly of deterministic factors, but also of stochastic factors. We detected weak but significant influence of environment and space, indicating the action of deterministic niche-based processes, and weak or absence of dispersal limitation, reinforced by the correlation with immigration probability. We also found evidences that the metacommunities structure results from the association of different processes acting differently on adults and tadpoles. The Pantanal flood event in association with life history characteristics of the species seems to be the main forces structuring tadpole metacommunities in this region, promoting a massive redistribution of individuals across the landscape and allowing them to reach habitats with suitable characteristics along the environmental gradient.
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Palavras-chave
Anura, Ecologia da paisagem, História natural, Nicho (Ecologia), Processo estocástico, Landscape ecology, Natural history, Niche (Ecology), Stochastic process