Synergistic effect of habitat loss and chronic anthropogenic disturbances on ant species richness

Habitat loss is an important factor in global biodiversity loss, but categorizing human-modified landscapes as fragments of natural or anthropogenic habitats may underestimate our impact on biodiversity since most natural fragments suffer from chronic anthropogenic disturbances. Here, we tested the synergistic effect between habitat loss and chronic anthropogenic disturbances on ant communities of the Caatinga, a seasonally dry tropical forest in South America. From online sources and published material, we built a data-set containing information on habitat loss and chronic anthropogenic disturbance index, as well as its vectors (i.e., human population density, infrastructure, logging, fire, and grazing), for 23 Caatinga localities containing information on ant community composition. Generalized linear models demonstrated that habitat loss interacts with chronic anthropogenic disturbance to determine total ant richness and the richness of habitat specialist ants. Furthermore, habitat loss interacts synergistically with several vectors of chronic anthropogenic disturbances to determine ant richness. In general, the effect of habitat loss is exacerbated by human population density, infrastructures, logging, and grazing. The proportion of habitat specialists in the communities did not respond to habitat loss or chronic anthropogenic vectors, suggesting that both ant groups were equally affected by habitat alterations. Although habitat amount is an important predictor of the integrity of the local biodiversity, it tends to underestimate our impact on biological communities. The incorporation of estimates of habitat quality can help us build better models to predict our impact on Earth.