Replicated radiation is a type of parallel evolution in which sets of similar forms evolved repeatedly in different regions. The phenomenon is well-documented among animals, but, compelling examples are missing for plants.
Combining DNA sequencing, phylogenetic and biogeographical mapping informed by GBIF-mediated specimen data with morphological analyses, this study explored the possibility of replicated radiation within the Oreinotinus lineage of the angiosperm clade Viburnum.
The authors showed how Oreinotinus moved progressively from eastern Mexico to Central America and from there into the Caribbean and South America over a period of 10–15 million years. They identified areas of endemism in which species formed clades, being more closely related to one another than to those in other regions.
By analysing herbarium sheets and field images, they demonstrated how four distinct leaf forms evolved independently within the lineages in different areas of endemism. These forms did not originate early in Oreinotinus and then spread across the continent, but evolved repeatedly in nine out of 11 areas as lineages diversified.
The authors suggest ecological adaptation as the driver of the observed parallelism as the leaf forms emerged in similar climatic niches within their region. Altogether, they argue that the findings represent perhaps the first well-documented example of replicated radiation among plants.