The evolution of insular woodiness

Area of Science:

• Evolutionary biology
• Island biogeography
• Plant sciences

Background:

• Insular woodiness (IW) is a prominent evolutionary phenomenon observed in island plant species.
• Previous hypotheses suggest drivers like competition for light, drought, favorable climates, and reduced herbivory.
• Fragmented data has hindered comprehensive testing of these proposed drivers.

Purpose of the Study:

• To identify the key drivers of insular woodiness (IW).
• To analyze the evolutionary transitions toward woodiness on islands globally.
• To test proposed hypotheses regarding the factors influencing IW.

Main Methods:

• Identified 1,097 insular woody species across 375 islands.
• Inferred at least 175 evolutionary transitions on 31 archipelagos.
• Utilized structural equation models to analyze correlations between environmental factors and IW.

Main Results:

• On oceanic islands, IW richness correlates with aseasonal climate, drought, and isolation.
• On continental islands, reduced herbivory, drought, and isolation are the most significant factors.
• Convergent evolution towards IW is driven by diverse pathways across different archipelagos.

Conclusions:

• Island archipelagos serve as natural laboratories for studying convergent evolution.
• Specific abiotic and biotic conditions on islands can repeatedly drive the evolution of similar traits.
• Understanding IW drivers provides insights into island ecosystem dynamics and evolutionary processes.