Neotropical niche evolution of Otoba trees in the context of global biogeography of the nutmeg family

Aim Plant distributions are influenced by species’ ability to colonize new areas via long-distance dispersal and propensity to adapt to new environments via niche evolution. We use otobas, a clade of ecologically dominant trees found in low-to mid-elevation wet forests, as a system to understand the relative importance of these processes within the Neotropics. Location Neotropics and global. Taxon Otoba and entire Myristicaceae. Methods We resolve the first phylogeny of Otoba the Angiosperms353 loci and plastome sequences from 13 accessions representing seven species. We pair this with the most densely sampled phylogeny of Myristicaceae to date, inferred using publicly available plastid data. We then use environmental niche modelling, biogeographical reconstruction, phylogenetic principle components analysis and Ornstein–Uhlenbeck models to infer biogeography and examine patterns of niche evolution. Results Myristicaceae has an Old World origin, with a single expansion into the Americas. Divergence dates, fossil evidence and a notable lack of long-distance dispersal are consistent with a Boreotropical origin of Neotropical Myristicaceae. Mirroring the rarity of dispersal at the family level, Otoba’s biogeography is marked by few biogeographical events: two expansions into Central America from a South American ancestor and a single dispersal event across the Andes. This limited movement contrasts with rapid climatic niche evolution, typically occurring across geographically proximate habitats. Main conclusion Contrasting with previous studies, long-distance dispersal does not need to be invoked to explain the pantropical distribution of Myristicaceae, nor the biogeography of Otoba. This likely results from the family’s relatively large seeds that are dispersed by large-bodied vertebrates. Instead, rapid niche evolution in Otoba has facilitated its occurrence throughout mesic habitats of the northern Neotropics, including the Amazon rainforest and Andean montane forests. Otoba adds to a growing group of Neotropical plant clades in which climate adaptation following local migration is common, implying an important role of niche evolution in the assembly of the Neotropical flora.