Towards a global perspective for Salvia L.: Phylogeny, diversification and floral evolution

Area of Science:

• Botany and Evolutionary Biology
• Plant Systematics and Phylogenetics
• Macroevolutionary Studies

Background:

• Salvia is a globally distributed, species-rich genus within the Lamiaceae family, with approximately 1000 known species.
• Previous evolutionary studies have not fully explored the diversification patterns and drivers within Salvia, particularly concerning floral traits.
• Understanding the evolutionary history of Salvia is crucial for comprehending plant speciation and adaptation.

Purpose of the Study:

• To investigate the tempo and mode of diversification in the genus Salvia using macroevolutionary analyses.
• To model and explore the evolutionary dynamics of corolla length and the lever-mechanism pollination system in Salvia.
• To reconstruct a comprehensive phylogeny for Salvia, including underrepresented Iranian species, to enhance phylogenetic resolution.

Main Methods:

• Reconstruction of a multigene phylogeny for 366 Salvia species, incorporating 50 species from Iran.
• Application of macroevolutionary models, including disparity tests, BAMM (Bayesian Analysis of Molecular Mixtures and Clades), and HiSSE (Hidden State Speciation and Extinction) models.
• Analysis of divergence time estimates to correlate with the evolution of corolla length, habit (woody vs. herbaceous), and pollination mechanism.

Main Results:

• A medium corolla length (15-18 mm) was inferred as the ancestral state for Salvia, with subsequent evolution showing multiple shifts to shorter and longer corollas.
• Macroevolutionary analyses revealed high corolla length disparity throughout Salvia's evolution, significantly deviating from Brownian motion expectations over the last 28 million years.
• Diversification rates of corolla length were found to be higher in some Andean Salvia species; however, the lever-mechanism pollination system was not supported as a significant driver of diversification.

Conclusions:

• Corolla length has evolved with significant disparity in Salvia, indicating complex evolutionary dynamics beyond simple trait accumulation.
• The lever-mechanism pollination system is unlikely to be a primary driver of speciation across the Salvia genus.
• Further research should focus on other potential factors influencing Salvia diversification, rather than solely on the lever-mechanism pollination system.