Macro-climatic niche limits and the evolution of C4 photosynthesis in Gomphrenoideae (Amaranthaceae s.s.)

M. JULIA BENA; ACOSTA, JUAN MANUEL; LONE AAGESEN

BOTANICAL JOURNAL OF THE LINNEAN SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2017 vol. 184 p. 283 - 297

0024-4074

During the evolution of vascular plants, C4 photosynthesis has developed more than 60 times. Most studies concerning the evolution and the ecophysiological advantages of the C4 syndrome have been carried out in grasses. However, among eudicots C4 photosynthesis has developed in lineages that are morphologically more diverse than the relatively homogenous grasses, and conclusions about C4 evolution based on grasses may or may not apply to eudicots. Very little is known about the origin of C4 photosynthesis in Amaranthaceae s.s., one of the most C4 species rich lineages within eudicots. Among the subfamily Gomphrenoideae, both C3 and C4 species are found in arid regions, but highAndean species display the C4 pathway. In this study we aimed to compare the climatic extremes between C3 and C4 species within Gomphrenoideae. In particular, we evaluated the upper and lower extremes of three climatic variables among closely related C3 and C4 lineages, using Phylogenetic Generalized Least Squares (PGLS). PGLS were appliedon four topologies: Maximum Parsimony, Bayesian, Maximum Likelihood (ML) including species with available DNA sequences, and a ML topology that also included unsequenced species with available climate data. We testedwhether the evolution of C4 photosynthesis correlates with a niche specialization where both the upper and lower extremes change position, or a niche expansion where only a single extreme changes position. PGLS results showed that C4 Gomphrenoideae species have specialized to dryer regions and expanded into colder ones, compared to their C3 relatives. However the niche expansion into colder climates only includes areas with low temperatures during winter ? not during the growing period. Finally, we found no evidence for a niche change into warmer climates. Therefore, the model for the evolution of C4 photosynthesis in Gomphrenoideae may differ from the one supported inChenopodiaceae and seems to be more similar to the one found in grasses, where the C4 pathway appears to have evolved in humid habitats but facilitated an expansion into arid ones. However, we found no support for the commonexpectation that C4 species reach warmer climates than their C3 relatives, contrasting previous results on grasses.