Abstract Detail

Macroevolution

Santoro, Julian Aguirre [1], Michelangeli, Fabian A. [2], Stevenson, Dennis [3].

The Geographically Disjunct Evolution of Ronnbergia and Wittmackia (Bromeliaceae) Across Three Neotropical Biodiversity Hotspots.

The genera Ronnbergia and Wittmackia encompass a monophyletic group nested within the adaptive radiation of the tank-epiphytic clade of berry-fruited bromeliads. The ca. 70 species that compose these genera diversified within three Neotropical hotspots of biodiversity: 1) the Tumbes-Chocó-Magdalena and adjacent forests (Pacific Forest), 2) the Atlantic Forest, and 3) the Caribbean. The species within these genera exhibit a highly heterogeneous floral diversity, suggesting a possible role of floral evolution as a modulator in the radiation of lineages. In this study, we estimated the most plausible scenarios that explain the disjunct evolution of lineages within Ronnbergia and Wittmackia and compared their evolutionary dynamics of lineage diversification and floral evolution. Our results suggest that the radiation started with the geographic split of Ronnbergia and Wittmackia between Pacific Forest and the Atlantic Forest, respectively, ca. 3.6 mya. The rates of speciation and floral evolution remained constant with a tendency to slowdown in the evolution of Ronnbergia within the Pacific Forest, despite the large floral variation observed in this genus. This pattern suggests an early-burst process followed by a possible effect of interspecific competition in the radiation Ronnbergia. On the other hand, the evolutionary dynamics within Wittmackia are more heterogeneous. The early stages of the radiation in Wittmackia showed the same evolutionary rate regime observed for Ronnbergia; however, this pattern was disrupted in the most derived lineages by a significant acceleration in speciation rates. This rate shift occurred during the diversification of Wittmackia in the Atlantic Forest, ca. 1.8 mya, in lineages that inhabit areas previously subjected to climatic fluctuation during the Pleistocene glaciations. A second major geographic range shift occurred within Wittmackia with the long-distance dispersal from the Atlantic Forest to Jamaica, followed by a rapid diversification in the Caribbean. This radiation is characterized by exhibiting much faster speciation rates than Ronnbergia and the Brazilian-centered lineages of Wittmackia, coupled with a significant increase in the rates of evolution of floral traits related to floral protection (e.g. floral compression and enlarged floral bracts). This pattern suggests that the radiation in the Caribbean is an episode of a nested adaptive radiation occurring within the adaptive evolution of the tank-epyphitic, berry-fruited bromeliads. Although our study only explored a limited set of evolutionary processes, it demonstrates how species-level phylogenetic studies combined with ecological, geographic, and morphological data can help understand fine-scale processes that shaped the biodiversity within the most strategic biodiversity hotspots of the Neotropics.

1 - Universidad Nacional de Colombia, Instituto de Ciencias Naturales, Carrera 30 No. 45-03, edificio 425, Oficina 304, Bogota, Colombia
2 - The New York Botanical Garden, Institute Of Systematic Botany, 2900 Southern Blvd., Bronx, NY, 10458, USA
3 - THE NY BOTANICAL GARDEN, 2900 SOUTHERN BLVD, BRONX, NY, 10458-5126, USA

Keywords:
Bromeliaceae
Diversification
neotropical species
Hotspots of biodiversity
Ronnbergia
Wittmackia.

Presentation Type: Oral Paper
Session: 2, Macroevolution
Location: Fort Worth Ballroom 5/Omni Hotel
Date: Monday, June 26th, 2017
Time: 11:15 AM
Number: 2012
Abstract ID:543
Candidate for Awards:None