Phylogenetic Relationships and Character Evolution in Neotropical Phyllanthus (Phyllanthaceae), with a Focus on the Cuban and Caribbean Taxa

Premise of research. The Caribbean is an important area of species diversity within the large pantropical genus Phyllanthus. With the goal of illuminating the evolutionary origins of Caribbean Phyllanthus, we undertook a phylogenetic analysis significantly increasing previous samplings of the genus in the Neotropics. We reconstructed the evolution of selected morphological characters and evaluated the implications of our results in light of the representation of Caribbean and Neotropical species in the infrageneric classification of the genus. Methodology. We estimated phylogentic trees using parsimony, Bayesian, and likelihood approaches based on plastid and nuclear sequence data sets. These represented 78 taxa from the Neotropics, most of which were generated for this study, as well as most other subgenera and sections of Phyllanthus and other genera of Phyllanthaceae. Four vegetative and four floral morphological characters were assessed for the whole study group. Ancestral character states were reconstructed using BayesTraits. Pivotal results. Plastid and nuclear partitions agree on a highly supported Caribbean clade that contains the vast majority of the species from this region as being part of a large Neotropical clade. Another small Caribbean clade is found nested among African linages. Although morphological characters exhibit some level of homoplasy, some trends are evident, for example, in the large Neotropical clade. Conclusions. The majority of species in the Caribbean belong to a single clade that has evolved from Neotropical ancestors. This is well circumscribed with morphology and corresponds to subgenus Xylophylla, the concept of which is adjusted here to be monophyletic. The existence of a small Caribbean clade related to African species marks a noteworthy case of Caribbean plant origin. Although phyllanthoid branching is not a synapomorphy for Phyllanthus s.l. (including Breynia, Glochidion, and Sauropus), combinations of vegetative and floral characters allow a clear assignment to the Phyllanthus s.l. clade.