C₄ photosynthesis presents no barrier to colonization of temperate climates

Warm climate adaptation evolved in the tropics but promotes migration to cooler climates

Data resources used via GBIF : 14.8 million species occurrences
Phragmites australis
Common reed (Phragmites australis) by Mr. Quindlen's 5th grade class from Bethel Springs Elementary School–via iNaturalist. Photo licensed under CC BY-NC 4.0.

In the hot climates of tropical and subtropical regions, plants have developed the specialized C₄ photosynthetic pathway, optimized for increased photorespiration under high temperatures. More than half of the species with this evolutionary adaptation belong to the grass family (Poaceae).

In this study, researchers used all GBIF-mediated Poaceae occurrences combined with WorldClim climate data to derive temperature ranges for more than 2,000 grass species–about half of which are C₄.

They analyse the transition of species between climates and photosynthetic types, finding that C₄ origins are more common in tropical regions, and that reversal from C₄ to C₃ almost never happens in grasses. However, transitions from tropical to temperate climates is more common for C₄ than C₃ taxa.

While increases in the upper bounds of plant temperature niches are associated with C₄ photosynthesis, the lower bounds did not differ significantly between C₃ and C₄. Taken together, these findings suggest that C₄ presents no physiological barrier to colonization of temperate climates.

Link to original article

Watcharamongkol T, Christin P-A and Osborne CP (2018) C4 photosynthesis evolved in warm climates but promoted migration to cooler ones. Ecology Letters. Wiley 21(3): 376–383. Available at: https://doi.org/10.1111/ele.12905.