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 species with this evolutionary adaptation belong to the grass family (Poaceae).

In a study from 2018, 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 analyze the transistion of species between climates and photosynthethic types, finding that C₄ origins are more common in tropical regions, and that reversal from C₃ to C₄ 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 photosynthesys, 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.