A tale of two communities: Neotropical butterfly assemblages show higher beta diversity in the canopy compared to the understory.

Tropical fruit-feeding nymphalid butterflies generally restrict adult foraging exclusively to either the canopy or understory strata. We compared canopy and understory butterfly communities using data from four long-term studies in Central and South America. At all study sites we found little similarity in species composition between canopy and understory, with most species showing a strong affinity for one of the two habitats. There was a consistent phylogenetic signal for canopy and understory association, suggesting a substantial evolutionary history with these habitats. In addition to compositional differences, we found different patterns of beta diversity between canopy and understory communities. Across all study sites, the canopy had greater temporal and spatial beta diversity compared to the understory. Although these two communities are composed of the same feeding guild and separated only by a relatively small vertical space, each has its own stratum-specific species composition and community dynamics.