Predatory Spiders Limit Bromeliad-Dwelling Frog Assemblages in the Absence of Habitat Effects

Bromeliads provide key microhabitats for many tropical anurans, offering water reservoirs for reproduction and shelter from predators. We investigated the factors influencing anuran occupancy in bromeliad patches in the Atlantic Forest of northeastern Brazil. Over 13 months, we surveyed 100 bromeliad patches, each consisting of 4–104 individual plants, and recorded eight anuran species, all bromelicolous. Contrary to expectations, morphological traits of bromeliads—including species, size, and spatial arrangement—had no significant effect on anuran richness or abundance. Likewise, canopy cover did not significantly influence anuran richness or abundance, and temperature and humidity were excluded from analysis due to low variation across sampling sites. Despite favorable structural conditions, overall species diversity was low. In contrast, the presence of the predatory theraphosid spider Pachistopelma rufonigrum had a strong negative effect on anuran occupancy, emerging as the most influential factor in our models. This predator–prey interaction may contribute to the apparent absence of bromeligenous frog species in the study area. Our findings highlight the role of biotic interactions—rather than habitat structure—in shaping anuran assemblages in bromeliad microhabitats.