Elevational boundaries influence richness patterns at large spatial scales evinced by madicolous insects of the Brazilian Atlantic Forest

1. ‘Biologists have long recognized that elevational and latitudinal species‐richness gradients mirror each other’. With this statement, Stevens (Stevens, The American Naturalist , 140, 893–911, 1992) and other ecologists assumed the same hypotheses to explain richness patterns in latitudinal and altitudinal gradients. However, the monotonic decrease of species toward high altitudes is far from a rule in elevational gradients studies. 2. We analysed the richness pattern of the madicolous insect community along three elevational gradients of the Atlantic Forest, each representing a different altitudinal stratum in the domain (0–1100; 1200–2100; 1600–2800 m a.s.l). This way, we ensured that the complete altitudinal range extant in the Atlantic Forest (0–2800 m a.s.l.) was contemplated. We expected to find repeated patterns of richness variation in the elevational gradients where the elevational boundaries of each mountain constrained species' distribution, causing a mid‐elevation peak of richness in each gradient. 3. Madicolous insects' communities from 70 sampling sites were analysed. Simple and multiple regressions were used to identify significant relations and comparisons between empirical richness data and null models for MDE were made. 4. Each elevational gradient showed a different pattern of richness variation. However, a clear continuity in the richness‐altitude relation was observed in the complete elevational gradient where an intermediate peak was detected. The Rapoport effect was not observed. A significant effect of environmental variables was detected at local scale, while the hard‐elevational boundaries of the Atlantic Forest – sea level and the top of the highest mountaintop – constrained species distribution and contributed to the observed richness pattern.