Macroevolutionary dynamics in the transition of angiosperms to aquatic environments

Area of Science:

• Evolutionary biology
• Plant science
• Ecology

Background:

• Angiosperms show high diversity in terrestrial environments but lower diversity in aquatic habitats.
• Understanding the macroevolutionary drivers of aquatic angiosperm diversity is a long-standing evolutionary question.

Purpose of the Study:

• To investigate the macroevolutionary dynamics of angiosperm transitions from terrestrial to aquatic environments.
• To identify factors contributing to the low diversity of aquatic angiosperms compared to their terrestrial relatives.

Main Methods:

• Utilized diversification models and ancestral state reconstruction.
• Employed a comprehensive angiosperm phylogeny with over 10,000 genera.
• Analyzed macroevolutionary rates of speciation, extinction, and habitat transitions.

Main Results:

• Net diversification rates are significantly lower in aquatic angiosperms, driven by reduced speciation and elevated extinction.
• While early angiosperm evolution saw some aquatic transitions, most occurred in the last 25 million years.
• Reversals to terrestrial habitats occurred at higher rates than transitions to water, with gradual lineage accumulation in aquatic environments.

Conclusions:

• Low diversification rates and infrequent transitions to water, coupled with frequent reversals to land, explain the limited diversity of aquatic angiosperms.
• Stressful aquatic conditions and limited available habitat surface are hypothesized factors contributing to lower diversification.
• These findings provide insights into the macroevolutionary history and ecological constraints shaping aquatic plant life.