Non-equilibrium dynamics and floral trait interactions shape extant angiosperm diversity.

Area of Science:

• Evolutionary biology
• Phylogenetics
• Trait evolution

Background:

• Trait distribution across the tree of life varies, with some combinations common and others rare.
• Understanding trait diversity requires considering ancestral states, evolution rates, and diversification dynamics.
• Angiosperms exhibit notable patterns of common and rare trait combinations.

Purpose of the Study:

• To investigate the influence of transition rates, differential diversification, and non-equilibrium dynamics on angiosperm evolutionary history.
• To identify key innovations driving trait abundance and rarity in angiosperms.

Main Methods:

• Analysis of transition rates and diversification (speciation minus extinction) across angiosperm lineages.
• Examination of non-equilibrium dynamics in trait evolution.
• Simulations to predict future trait state frequencies.

Main Results:

• A synergistic combination of three character states (corolla present, bilateral symmetry, reduced stamen number) acts as a key innovation.
• This key innovation doubles diversification rates in lineages where it occurs.
• The combination is currently less common than predicted at equilibrium due to infrequent individual character evolution.
• Angiosperms are predicted to remain far from equilibrium frequencies for trait states in the future.

Conclusions:

• Rarely evolving major innovations can lead to long-term non-equilibrium dynamics in trait distributions.
• Lineages with ancestral traits can persist and even outnumber those with diversification-enhancing states for millions of years.
• Non-equilibrium dynamics are significant in shaping the evolutionary history of angiosperms and potentially other clades.