Measuring the difference between biological communities is an important step in understanding how and why biodiversity is distributed. Such differences are expressed as beta diversity, which gauges the turnover of taxa or functional groups between communities. Beta diversity patterns can also be used to understand the consequences of habitat loss and fragmentation, which represent a major threat to the maintenance of biodiversity and ecosystem function. Today it is recognized that habitat loss and fragmentation are different things. However, for this work we assume that these processes act together, so from now on we will call these processes of landscape transformation. Competing but not mutually exclusive process have been advanced to describe beta diversity patterns among landscape transformation: homogenization and stochastic based. Homogenization based, such as environmental filtering and biological interactions between species, posit that only species that can tolerate landscape transformation change can persist in disturbed environments. Such biotic homogenization would lead to a decrease in beta diversity between the habitat patches. Stochastic based, propose that the reduction and isolation of populations in habitat patches may increase the importance of ecological drift, leading to an increase in beta diversity among communities of different patches. Beta diversity can be evaluated by taxonomic diversity (ie differences in species composition among sample units) or by functional attributes of species. Functional beta diversity aims to gauge patterns of spatial dissimilarity in the distribution and abundances of attributes of species and expresses aspects of the functionality of the environment that can not be determined when only the species composition is investigated. Another important factor to be understood is the relative importance of turnover and nestedness from beta diversity in patches. The turnover component of beta diversity has been defined as changes caused by the loss or gain of species over space or time. This is the sole component of beta diversity component that is expected by the stochastic process. Nestedness occurs when the set of species of areas with fewer species is a subset of fauna in the richest areas, reflecting a non-random process of species loss as a consequence of any factor that promotes orderly disaggregation of communities. Thus nesting can be caused by deterministic environmental filters, which select species that persist only in limited range of an environmental continuum. Our objective is investigate the patterns of organization of taxonomic and functional beta diversity (turnover and/or nestedness) communities of anurans in landscape transformation of the South Brazilian Grassland. By investigating how predictable are the effects of landscape change on the organization of the anuran communities in the grasslands the project seeks to contribute to a central debate in community ecology: the importance of homogenization and stochastic processes in community structuring. Besides this, quantifying the proportion of each component of beta diversity in this highly landscape transformation bioregion is also crucial for the planning of conservation strategies in landscape change in general and in subtropical grasslands in particular.
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