The temporal dynamics of evolutionary diversification in Ipomoea.

Area of Science:

• Evolutionary Biology
• Phylogenetics
• Paleobotany

Background:

• Molecular phylogenies are foundational for macroevolutionary studies.
• Inferences about evolutionary history often require complex methodologies beyond basic phylogeny.
• The genus Ipomoea, including the economically important sweet potato (Ipomoea batatas), serves as a model for exploring these methodological implications.

Purpose of the Study:

• To investigate the impact of methodological assumptions on macroevolutionary inferences within the Ipomoea genus.
• To explore assumptions related to divergence time estimation and diversification parameter inference (speciation, extinction, net diversification).
• To determine the age of Ipomoea, its major clades, diversification rate variations, and the evolutionary timing of the sweet potato storage root.

Main Methods:

• Utilized novel approaches to analyze molecular phylogenies of Ipomoea.
• Assessed sensitivity of divergence time estimates to fossil calibrations and substitution rate variation.
• Examined diversification parameters across different clades within Ipomoea.

Main Results:

• Inferred divergence times for Ipomoea and its clades are highly problematic and sensitive to assumptions.
• Robust inferences were made regarding patterns of diversification rate variation within Ipomoea.
• Evidence suggests the storage root of Ipomoea batatas evolved in pre-human times.

Conclusions:

• Methodological assumptions significantly influence macroevolutionary inferences, particularly divergence times.
• Despite challenges in dating, diversification patterns within Ipomoea can be robustly inferred.
• The study provides valuable insights into tropical plant evolution and the evolutionary history of an important crop.