Habitat loss, cattle, and community-level patterns
Species richness increased with both forest patch area (Fig. 2B) and habitat amount (Fig. 2D) and decreased with cattle intrusion (Fig. 2C). The effect of cattle is likely to be underestimated when species detection is not taken into account: when using occupancy models, cattle presence was estimated to locally extirpate an average of 26 ant species, whereas a naïve species count would estimate a reduction of only 14 species.
Due to the relatively high number of missing species due to sampling effects (low detection), pairs of patches were estimated to be more similar to each other in species composition than a naïve measure of species similarity (Fig. S14). Unexpectedly, the pairwise similarity in species composition was positively associated with geographic distance (Fig. 4A), and differences in patch size (Fig. 4B) and habitat amount (Fig. 4C). We did not find evidence that differences in cattle intrusion affected the similarity in species composition (Fig. 4D). When using raw (uncorrected) similarities, the effect of geographic distance was qualitatively similar, whereas no effects of patch size and habitat amount could be detected (Fig. S15). Cattle was only weakly associated with species similarity when the Jaccard index was measured using raw data (r2 = 0.04 for the turnover component; Fig. S15).