The agricultural transformation of Brazil’s Cerrado is influencing the diversity and distribution of tadpoles via lentification

Abstract

More than half of Brazil’s Cerrado has been converted to agricultural land use, threatening its rich biodiversity that includes > 200 anuran species, most of which have aquatic larvae and are thus doubly susceptible to the environmental impacts of agriculture. Past research has largely focused on how land-use change affects adult anurans, which ignores potential impacts on the critical larval stage. We therefore investigated how agricultural land use (250–1000 m scale) and the local pond environment affect the diversity and distribution of tadpole assemblages across the central Cerrado. Tadpole richness declined significantly with increasing cropland within 250 m of ponds and with increasing water pH in permanent ponds. Permanent ponds are more prevalent in agricultural areas where streams are impounded to provide water for irrigation and livestock, and water pH increases with increasing agriculture, likely due to the widespread use of agricultural lime in the Cerrado. Tadpole communities exhibited high beta diversity (81–86% dissimilarity), with species replacement rather than nestedness accounting for 90–97% of species differences between ponds, which was largely driven by hydroperiod. Six species accounted for 70% of the dissimilarity, with most species either more abundant or found only in temporary ponds. Increased lentification, a corollary of agricultural land use, is profoundly altering tadpole assemblages, which has consequences for overall anuran diversity in the Cerrado given that permanent ponds support a different and less-diverse larval assemblage than ephemeral wetlands. Anuran conservation in the Cerrado should therefore additionally consider maintaining or restoring wetland hydrology and native-vegetation buffers around wetlands.