Understanding the relative roles of diversification and dispersal is key to explaining large-scale biogeographic patterns. Although both processes are known to shape biodiversity, their relative contributions remain understudied in many systems. Here, we examine how these processes have jointly contributed to the exceptional diversity and endemism of Nymphalidae butterflies in South America’s Atlantic Forest, a global biodiversity hotspot. We obtained DNA sequences for 68 Nymphalidae species (43 missing from major phylogenies) and integrated them into published time-calibrated phylogenies. We used Dispersal-extinction-cladogenesis models and Biogeographical Stochastic Mapping to infer historical biogeographic patterns over time, and ClaDS to estimate region-specific diversification rates. We further evaluate whether regional patterns of diversification are associated with occurrence in montane environments or across the north–south biogeographic break within the Atlantic Forest. Our results show that butterfly diversity in the region was driven primarily by recurrent dispersal from Amazonia and the Andes, rather than by elevated in situ diversification, which remained low and stable through time. Although dispersal increased progressively during the Cenozoic, we found no evidence that the Diagonal of open formations acted as a major barrier, indicating that forest corridors probably allowed extensive exchanges between the Atlantic Forest and other Neotropical regions. Southern lineages exhibited slightly higher diversification rates, especially among montane generalist species, but overall diversification contributed little compared to the sustained input of dispersing lineages. Together, these findings highlight the central role of biome connectivity in shaping Atlantic Forest Nymphalidae diversity, while underscoring the importance of jointly considering diversification and dispersal processes to better understand the macroevolutionary dynamics underlying current biodiversity patterns.

Understanding the relative roles of diversification and dispersal is key to explaining large-scale biogeographic patterns. Although both processes are known to shape biodiversity, their relative contributions remain understudied in many systems. Here, we examine how these processes have jointly contributed to the exceptional diversity and endemism of Nymphalidae butterflies in South America’s Atlantic Forest, a global biodiversity hotspot. We obtained DNA sequences for 68 Nymphalidae species (43 missing from major phylogenies) and integrated them into published time-calibrated phylogenies. We used Dispersal-extinction-cladogenesis models and Biogeographical Stochastic Mapping to infer historical biogeographic patterns over time, and ClaDS to estimate region-specific diversification rates. We further evaluate whether regional patterns of diversification are associated with occurrence in montane environments or across the north–south biogeographic break within the Atlantic Forest. Our results show that butterfly diversity in the region was driven primarily by recurrent dispersal from Amazonia and the Andes, rather than by elevated in situ diversification, which remained low and stable through time. Although dispersal increased progressively during the Cenozoic, we found no evidence that the Diagonal of open formations acted as a major barrier, indicating that forest corridors probably allowed extensive exchanges between the Atlantic Forest and other Neotropical regions. Southern lineages exhibited slightly higher diversification rates, especially among montane generalist species, but overall diversification contributed little compared to the sustained input of dispersing lineages. Together, these findings highlight the central role of biome connectivity in shaping Atlantic Forest Nymphalidae diversity, while underscoring the importance of jointly considering diversification and dispersal processes to better understand the macroevolutionary dynamics underlying current biodiversity patterns.