Linking South American dry regions by the Gran Chaco: Insights from the evolutionary history and ecological diversification of Gomphrena s.str. (Gomphrenoideae, Amaranthaceae)

BENA, M.J.; BARANZELLI, M.C.; COSTAS, S.M.; COSACOV, A.; ACOSTA, M. C.; MOREIRA-MUÑOZ, A.; SÉRSIC, A. N.

JOURNAL OF SYSTEMATICS AND EVOLUTION

SCIENCE PRESS

Lugar: Marrickville NSW; Año: 2023

0529-1526

Geoclimatic events driving South American aridization have generated biota differentiation due tobarriers and new environment formation. New environments allow species climatic niche evolution, or thegeographical expansion of an existing one. Understanding the role these processes play may clarify theevolution of South American biota. Gomphrena L. ranges across almost all the continent´s arid environments.We tested whether South American drylands are biogeographically connected through the Gran Chaco but, dueto different aridity levels, lineage diversification could have also been associated with the evolution of climaticniches and morphological or physiological traits. With available data, we generated a dated phylogeny,estimated ancestral ranges, performed diversification analyses, reconstructed ancestral states of twocharacters, and examined if niches have changed between lineages. Results showed that Gomphrenadiversified throughout the easternmost South American drylands ~15.4 Ma, and subsequently threeindependent clades colonized the western arid regions during the last Andean pulse, and after the marinetransgressions (~4.8–0.4 Ma) via the Gran Chaco. The colonization implied an increase in the diversification rateof annuals over perennials and the progressive east–west differentiation of the occupied climatic niche. Thisdiversification was influenced by C4 photosynthesis, which could have acted as a niche opener to conquer newenvironments after the Paranaean Sea withdrew. Spatiotemporal patterns found in Gomphrena suggest thatgeographical expansion and evolution of climatic niches played a common but decoupled role in promotingdiversification. These results show that the Gran Chaco may have acted as a historical connection linking SouthAmerican drylands.