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

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 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 (1) the relative effects of local habitat quality of
ponds, and (2) the effectiveness of protecting ponds and their local
surroundings for anuran conservation in SBG.