What drives diversification in a pantropical plant lineage with extraordinary capacity for long-distance dispersal and colonization?

Aim Colonization of new areas may entail shifts in diversification rates linked to biogeographical movement (dispersification), which may involve niche evolution if species were not exapted to new environments.Scleria(Cyperaceae) includesc. 250 species and has a pantropical distribution suggesting an extraordinary capacity for long-distance dispersal and colonization. We investigate patterns of diversification inScleria, and whether they are coupled with colonization events, climate niche shifts or both. Location Tropics and subtropics. Taxon NutrushesScleria(Cyperaceae). Methods We used molecular data from three DNA regions sequenced for 278 accessions representing 140Scleriataxa (53% of species) to develop a chronogram, model ancestral ranges and measure rates of diversification. Integrating data from 12,978 digitized and georeferenced herbarium records, we investigated niche evolution. Results High dispersal rates inScleria, a genus with multiple dispersal syndromes, make reconstruction of ancestral ranges at deep nodes in the phylogeny highly equivocal. Main dispersal and colonization events involve movements from South to Central America (c. 19), from Africa to Madagascar (c. 12), from Asia to Oceania (c. 7), from Africa to South America (c. 7) and Central America to South America (c. 6). The two main shifts in diversification rates happened during the warm period of the Miocene. Main conclusions Dispersification from South America to Africa without climate niche shift seems to explain the diversification shift in sectionHypoporumimplying that species were exapted. Shifts in climate niche evolution predate the second shift in diversification rates suggesting lineages were exapted prior to biogeographical movements. Within subgenusScleria, colonizations of Asia and Madagascar by sectionsElataeandAbortivae, respectively, are coupled with niche shifts suggesting that these colonizations involved climate niche adaptation.