Speciation across the Earth driven by global cooling in terrestrial orchids

Area of Science:

• Evolutionary Biology
• Paleoclimatology
• Botany

Background:

• Climate change is a known driver of species diversification.
• Previous research suggests localized climate and time are more influential than global climate shifts.
• Highly speciose clades require focused analysis to understand diversification drivers.

Purpose of the Study:

• To investigate the impact of global cooling on terrestrial orchid biodiversity.
• To disentangle the roles of climate change, geography, and time in orchid speciation.
• To determine if terrestrial orchids are a prime example of temperature-driven speciation.

Main Methods:

• Phylogenetic analysis of 1,475 species within the Orchidoideae subfamily.
• Comparative modeling to assess speciation rate drivers (global cooling vs. time).
• Analysis of over 2.5 million georeferenced records to map diversification patterns.

Main Results:

• Speciation rate in terrestrial orchids is primarily dependent on historic global cooling.
• Models of cooling-driven speciation are over 700 times more likely than time-based accumulation.
• Terrestrial orchids show one of the strongest cases for temperature-spurred speciation.
• Global cooling contemporaneously drove diversification across all seven major orchid bioregions.

Conclusions:

• Historic global cooling is a significant, quantifiable driver of terrestrial orchid biodiversity.
• Terrestrial orchids provide a robust model for understanding long-term climate change impacts on speciation.
• Findings contrast with the prevailing view that global climate change effects are inconsistent.