Tracking the xeric biomes of South America: The spatiotemporal diversification of Mandacaru cactus

Aim The interconnectedness and biotic interchange among Neotropical biomes are thought to play an important role in driving adaptation and diversification. However, how these processes are in synteny to trait evolution in species of open and xeric areas is poorly studied. Here, we investigate the spatial and temporal dimensions of evolution and candidate traits associated with biome shifts in xeric vegetation, focusing on the family Cactaceae. Location Xeric and open areas of South America. Taxon Genus Cereus Mill. (Cactaceae, Cereeae). Methods We applied biogeographical reconstructions on a time-calibrated phylogeny inferred from multilocus data (ddRAD-Seq) using Bayesian analyses on BEAST2, species distribution modelling in Maxent, the reconstruction of biome affinities and niche shift analyses based on abiotic traits (climate and soil) using Mk-model in BioGeoBEARS, and phenotypic trait-based analysis in Mesquite. Results The Cerrado domain is the ancestral area of Cereus, with most diversification events occurring in a time of intense orogenesis, climatic changes, and marine regressions within the last 5 Mya. Events of biome transition from the seasonally dry tropical forest (SDTF) were also associated with trait and niche shifts. Main conclusions The diversification of the xerophyte genus Cereus is associated with the climatic and geomorphological instabilities of the Pliocene and Pleistocene epochs. The Cerrado domain states an important region of dispersal for the genus. Some geographical range movements involved biome shifts associated with niche evolution while others were restricted to a simple biogeographical transition without niche change. Particular clades that experienced biome shifts displayed some phenotypic state changes, suggesting a role of biotic traits for environment transition. The results observed in Cereus may be a biogeographical pattern that should be tested with other cactus species, such as Pilosocereus spp., or species of xeric habitats, such as Annonaceae and Vochysiaceae.

Automated summary

The study found that the diversification of Cereus genus in xeric vegetation is associated with the climatic and geomorphological instabilities of the Pliocene and Pleistocene epochs, with the Cerrado domain in Brazil being an important region for the dispersal of this genus. Some geographical range movements involved in environmental transitions were associated with niche evolution, while others were limited to simple biogeographical transitions without changes in niche.