The interplay between local and landscape scales on the density of pond‐dwelling anurans in subtropical grasslands

Abstract

We investigated the role of local and landscape environmental variables on anurans density classified as habitat specialists and generalists in grassland landscapes, known as South Brazilian grasslands (SBG). In this region, we surveyed 187 ponds distributed over 40 landscape sampling units. For each pond, 31 local environmental variables were measured. Each landscape sampling unit was embedded within a larger regional sampling unit with different landscape properties. For each landscape and regional sampling units, 16 landscape metrics were extracted from a land cover and use map. We recorded 35 species, eleven of which are specialists in the SBG. The specialists were affected by 11 local and 2 landscape environmental variables, while generalists were affected by 14 local and one landscape environmental variable. Thus, specialists and generalists presented different relationships with local and landscape variables, but in general local variables had a greater influence on the density of anurans than the landscape variables. However, the landscape indirectly influenced local variables because higher quality ponds were in landscapes with higher percentages of natural habitat. In conclusion, reproductive sites with higher local quality and located within landscapes with higher percentages of natural grasslands are essential to conserve anurans in this habitat. Effective conservation of such sites would benefit from further studies that assess effects of land use and biotic integrity of ponds, which can help to determine (a) the relative effects of local habitat quality of ponds and (b) the effectiveness of protecting ponds and their local surroundings for anuran conservation in SBG.

Tadpoles Inhabiting Natural and Anthropogenic Temporary Water Bodies: Which Are the Environmental Factors that Affect the Diversity of the Assemblages?

“…In contrast, Eterovick et al (2015) found that developmental rates and fluctuating asymmetries in the larval stage of some anurans were not explained by landscape metrics. This inconsistency of our results pinpoints a major research challenge on the effects of landscape configuration and management practices for the assemblages of anurans in the larval stage inhabiting natural savannas (Iop et al, 2020). In the present study, we showed that some species of anurans oviposit on ponds that are highly affected by the constant presence of cattle (Table 2; Supplementary Material S1).…”

Changes in land use affect anuran helminths in the South Brazilian grasslands

“…Some of these differences were expected (e.g. increase of vegetation in the pond edges, increase in water pH, loss of temporary ponds) due to agricultural practices as suppression of traditional grazing (Erős et al, 2020), relief softening (Iop et al, 2020) and application of lime for the correction of soil acidity. It is known that environmental changes may influence the relationship between host and parasite, especially for helminths with complex life cycles that require multiple hosts for transmission, development and reproduction (King et al, 2010;Koprivnikar et al, 2012a, b).…”

“…This approach was adopted because the importance of habitat descriptors can vary with spatial scale in studies on helminths and/or anuran hosts (e.g. King et al, 2007King et al, , 2010Hartson et al, 2011;Schotthoefer et al, 2011;Koprivnikar & Redfern, 2012;Iop et al, 2012Iop et al, , 2020. Thus, we were interested in identifying which of these descriptor groups better explained the quantitative descriptors of parasitism.…”

“…Thus, we made comparisons on patterns of species richness, abundance, taxonomic composition, prevalence and intensity of parasitic infection, as well as how multiple-scale descriptors change among two contrasting land uses. The extensive livestock on native grasslands is considered a less impactful land-use type in this region (Pillar & Vélez-Martin, 2010), and it was recently highlighted as more compatible with anuran conservation than crops (see Santos et al, 2014;Iop et al, 2020;Moreira et al, 2020). Our hypotheses are:…”

“…The loss of habitat also influences the dynamics and composition of the anuran helminth communities. The structure of the helminth community depends on many factors, including host and helminth life histories (coevolution) (Janovy et al ., 1992; Brooks et al ., 2006; Brunner & Eizaguirre, 2016; Kołodziej-Sobocińska, 2019), diet and habitat (McAlpine & Burt, 1998; Poulin, 1998; Bolek & Coggins, 2003; Zelmer & Arai, 2004; Pinheiro et al ., 2019). It is known that helminth infections cause several negative effects on the development and fitness of anurans.…”