Something is not quite right: effects of two land uses on anuran diversity in subtropical grasslands

Although habitat modification is considered one of the main causes of biodiversity loss, the relative contribution of different rural land uses to biodiversity conservation are far less known. Additionally, the realization of the multidimensionality of biodiversity demands studies integrating variation of functional traits and phylogenetic information as complements to address the effects of land use on the structure of animal communities. Herein, we investigated the effects of land use (i.e., intensive agricultural and extensive livestock rearing) on functional and phylogenetic diversity of anuran communities in farmland ponds from the Uruguayan savanna ecoregion, while considering the effects of local factors (i.e., water depth) on species composition. We surveyed adults and tadpoles in 22 ponds and quantified five traits related to tadpole feeding, habitat use, and predator avoidance. Tadpole identification was corroborated by DNA barcoding based on a fragment of the mitochondrial 16S rRNA gene. We observed a decline in phylogenetic mean nearest taxon distance associated with increase of surrounding agricultural land use. While land use intensification did not affect richness (functional or phylogenetic), ponds in livestock ranches hosted about four times more tadpoles than agricultural ponds. Functional evenness decreased with water depth, although such relationship disappeared when considering phylogenetic non-independence. Our results indicated that specific anuran clades were more sensitive to intensification in land use, reinforcing a recent view of phylogenetic homogenization following habitat conversion. Additionally, our study suggests that extensive cattle grazing over wide native pastures may provide an alternative more compatible with conservation than short-term crops in subtropical grasslands.See attached Read_me.txt for additional information. Funding provided by: Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100002322Award Number: 20132816Funding provided by: Conselho Nacional de Desenvolvimento Científico e TecnológicoCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100003593Award Number: 442987/20In the spring of 2015 (10–16 October), we sampled tadpoles in 22 ponds located 5.5–316 km apart in southern Brazil. In order to ensure that the landscape composition surrounding each pond did not change over different scales, we defined circular areas (1,000 m radius) and measured land-cover data , using Qgis 2.18.16 . We based analysis on Google Earth imagery, using a land-cover classification for 2015 produced within the scope of the MapBiomas initiative. At each pond, we performed eight dip-net sweeps (30 cm diameter, 2mm mesh), each covering approximately 1 m2 and distributed at different pond depths (i.e., four sweeps near the edge of the pond and four sweeps in deep water near the centre of the pond). Sweeps were pooled into one sample per pond (3.5 L plastic bucket), where the collected tadpoles were euthanized with a benzocaine solution and sorted into series based on their morphology (i.e. coloration, body shape, eyes position, tail fin proportion, and mouth position). We also registered the presence of all observed adults, visually or acoustically, during tadpole sampling. In laboratory, each tadpole without tail clip was rinsed in distilled water and then measured for a set of eight morphological traits on an automated stereomicroscope – Leica M205A