Land use around protected areas affects functional diversity of anuran assemblages in ponds of Southern Brazilian Highland Grasslands

Abstract

Anthropogenic land-use change drives biodiversity loss by altering habitat structure, reducing connectivity, and reshaping ecological processes, even within protected areas. Although protected areas are key for biodiversity conservation, their effectiveness may depend on the surrounding landscape context. This study evaluates the effects of land use around and within protected areas on species richness and functional diversity in amphibian assemblage. Data were collected during 12 monthly expeditions between January 2013 and December 2014, sampling 81 ponds across eight protected areas and surrounding landscapes in southern Brazil. We measured species richness, abundance, and 21 ecomorphological traits, using phylogenetic eigenvector regression to control phylogenetic autocorrelation. Functional diversity was estimated as the total branch length of functional dendrograms. Structural equation modelling was used to assess the effects of spatial, landscape, land use, and habitat variables on species richness, abundance, and functional diversity. Land use, hydroperiod, and spatial configuration shaped amphibian assemblages through different mechanisms. Species richness was mainly driven by vegetation heterogeneity in ponds, abundance and pond connectivity, whereas functional diversity responded to land use, native landscape and hydroperiod. Anthropogenic land use (e.g., agriculture and reforestation) was positively associated with functional diversity, likely reflecting shifts toward generalist and disturbance-tolerant species rather than improved environmental conditions. Overall, our results show that different diversity dimensions respond to distinct drivers, and that land-use change can reorganize functional structure. We highlight the importance of conserving interconnected ponds with diverse hydroperiods and high vegetation heterogeneity within and around protected areas to maintain amphibian diversity and avoid long-term functional homogenization.

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