Climatic Niche Dynamics of Three Widespread Cardiospermum (Paullinieae, Sapindaceae) Species Revealed Possible Dispersal Pathways

The genus Cardiospermum comprises eight species distributed in the American continent, from central-eastern United States of America to central Argentina, Uruguay, and Chile; C. corindum, C. grandiflorum, and C. halicacabum are distributed worldwide. Howthese species spread to the African continent from the Americas and from Africa to the rest of theworld remains to be understood. Two hypotheses were tested in this study: the species would have colonized the African continent either naturally, through extreme long-distance dispersal, or via human activities. Our work considers the niche conservatism principle, which states that a species tends to retain aspects of its fundamental niche over space and time; however, a deviation (i.e. niche shift) may be detected, indicating that the ecological and evolutionary traits of the species change in response to environmental modifications. We compared the niche of each of the three species based on their known occurrences, both in the Americas and in the rest of the world, and on climatic variables. We performed an environmental niche modelling analysis for three periods: Holocene, Last Glacial Maximum, and the present. In addition, a Principal Components Analysis of climatic variables associated with known occurrences was performed through the COUE scheme. Our results suggest an early migration of C. corindum and C. halicacabum from the Americas to Africa; therefore, these two species would be native to these ranges, as proposed in previous studies. In addition, a recent introduction event of C. grandiflorum to Africa, and from Africa to India, Asia, and Oceania, was detected, which confirms the invasive status of this species outside the Americas.