Deforestation is principally induced by land use change as a consequence of human activities, causing biodiversity loss. Thus, it is urgent to understand how ecological communities respond to these changes. We studied the response of dung beetle communities to the transformation of temperate pine-oak forest to pastures used for sheep grazing in the Mexican Transition Zone, where small sheep herds are guided through pastures surrounded by pine-oak forests, this extensive pastoral activity is a traditional practice in the area. We used baited pitfall traps in 10 localities, and two sampling sites per locality: one forest and one grazing pasture. In each site we measured some environmental variables and the composition of land uses surrounding the 20 sampling sites using aerial photographs taken with a drone, and measured land use heterogeneity with a diversity index (1D). We used generalized linear mixed models (GLMMs) to test for differences in species richness, abundance and diversity (response variables) between the studied habitat types (forest and pasture), with habitat type as a fixed factor and localities as a random factor. We evaluated differences in species composition with a two-factor PERMANOVA analysis (habitat and locality), and used generalized linear models (GLMs) to explore relations between environmental variables and response variables.
Results/Conclusions
We captured 24 species, 14 species (1,075 beetles) in forests and 20 species (2,702 beetles) in pastures, and 10 species are shared between habitats. Although the number of species is similar in both habitat types, a high turnover of clearly differentiated species and communities was found. The PERMANOVA showed significant statistical differences in species composition between habitats, and also between localities. Regarding the heterogeneity of land uses surrounding the sample sites; we obtained a higher value of ¹D diversity in pasture sites (more diverse in land uses) than in forest sites. Results from the GLMMs showed statistically significant differences in species richness, diversity and abundance between habitats. With the GLMs we found a significant relationship between species richness and elevation, species abundance with elevation, dung availability and soil hardness, and diversity measures 1D y 2D with percentage of forest coverage. Documenting how traditional sheep grazing activity, land use heterogeneity and environmental variables shape the structure of current dung beetle communities is critical for understanding the impact of the human influenced habitats in the biodiversity of the Mexican Transition Zone.