The influence of floral variation and geographic disjunction on the evolutionary dynamics of Ronnbergia and Wittmackia (Bromeliaceae: Bromelioideae)

Abstract

The Ronnbergia alliance is a lineage of two genera, Ronnbergia and Wittmackia, which diversified in three centres of distribution; the Pacific Forest, the Atlantic Forest and the Caribbean. In this study, we reconstructed the most plausible biogeographic scenario that explain the disjunct evolution of the Ronnbergia alliance in these centres of diversity. We also compared the evolutionary rate dynamics of lineage diversification and floral evolution in each of these areas. Our results suggested that the Ronnbergia alliance originated in the Atlantic Forest c. 5.2 Mya. Ronnbergia originated c. 3.5 Mya after a long-distance dispersal event to the Pacific Forest. The diversification of Wittmackia started in the Atlantic Forest, c. 3.2 Mya, and experienced more heterogeneous evolutionary rate dynamics than Ronnbergia during its radiation. In Wittmackia a long-distance dispersal from the Atlantic Forest to Jamaica gave rise to the Caribbean clade, which diversified rapidly and experienced significantly higher rates of floral evolution. This study helped in understanding how bromeliad diversification occurs differently among major centres of biodiversity. In our case, we found how the Caribbean is a much more dynamic area of diversification than the Atlantic Forest or the Pacific Forest.