Phylogenetic Relationships of Cuban and Caribbean Plumeria (apocynaceae) Based on the Plastid Genome

Plumeria L. (Apocynaceae) is a Neotropical genus mostly restricted to the Caribbean, which is cultivated in tropical gardens worldwide. Almost all similar to 27 species are endemic to the Caribbean Islands, except for four (Plumeria inodora Jacq., Plumeria obtusa L., Plumeria pudica Jacq., and Plumeria rubra L.) that are native to Central America and northern South America. Cuba harbours the largest diversity of the genus, with 13 endemic species. We present the first molecular phylogeny of the genus based on the nucleotide sequences of the complete plastid genome. Partial plastid genomes of 11 Plumeria species and one closely related species (Himatanthus sp.) were sequenced using long-PCR and next-generation sequencing. The recovered clades mostly grouped by single islands or closely neighboring islands. The phylogenetic relationships indicate patterns of adaptive radiation, with ecological shifts within these island-based clades and a west-to-east colonization route in the region. Plumeria rubra and Himatanthus sp. were resolved as sister to the rest of the genus. One unexpected finding was that P. pudica, a species restricted to the southern Caribbean Basin mainland, was recovered within the clade containing the Caribbean Island endemics, rendering the endemic group polyphyletic. Our study provides a phylogenetic framework for future studies that will need to include nuclear molecular markers and a more extensive sampling.