IS IT FASTER TO MOVE OR EVOLVE? COMPARING EFFECTS OF NICHE CONSERVATISM AND NICHE EVOLUTION ON DIVERSIFICATION RATE IN THE NEOTROPICAL PLANT GENUS CITHAREXYLUM (VERBENACEAE)

FROST, L.; O'LEARY, NATALY; OLMSTEAD, RICHARD

Quito

Congreso; XII Congreso latinoamericano de Botánica; 2018

ALB

Much of our understanding of Neotropical diversification relates to recent, rapid radiations in a single biome (e.g. the paramo or cloud forests). We sought to investigate patterns of biogeography and diversification in an older lineage inhabiting multiple biomes in order to understand relative contributions of niche conservatism and niche evolution on diversification in a lineage of Neotropical origin. Citharexylum comprises ca. 60 species of flowering trees and shrubs distributed from northern Mexico to southern Brazil and Argentina in low-elevation tropical moist forest, high alpine biomes, tropical dry forests and deserts. The genus originated in Central America in the Oligocene, during a period of global cooling and aridification. Early diversification occurred in seasonal, semi-arid environments. Dispersal to South America was followed by separate radiations in high alpine biomes and low to mid-elevation forest. A subsequent dispersal to Central America resulted in the largest radiation of the genus into arid, seasonal, and moist forest biomes. Each major radiation comprises a seasonal or dry adapted clade sister to a predominantly moist forest clade, and a moist forest ancestor is inferred for each radiation. Diversification rates are higher in moist forest clades. Niche evolution is a common pattern in the evolutionary history of Citharexylum?there seem to be few barriers to adaptation to different biomes?but niche conservatism is the greater contributor to diversification.