Towards a species-level phylogeny for Neotropical Myrtaceae: Notes on topology and resources for future studies.

PREMISE: Increasingly complete phylogenies underpin studies in systematics, ecology, and evolution. Myrteae (Myrtaceae), with ~2700 species, is a key component of the exceptionally diverse Neotropical flora, but given its complicated taxonomy, automated assembling of molecular supermatrices from public databases often lead to unreliable topologies due to poor species identification. METHODS: Here, we build a taxonomically verified molecular supermatrix of Neotropical Myrteae by assembling 3909 published and 1004 unpublished sequences from two nuclear and seven plastid molecular markers. We infer a time-calibrated phylogenetic tree that covers 712 species of Myrteae (~28% of the total diversity in the clade) and evaluate geographic and taxonomic gaps in sampling. RESULTS: The tree inferred from the fully concatenated matrix mostly reflects the topology of the plastid data set and there is a moderate to strong incongruence between trees inferred from nuclear and plastid partitions. Large, species-rich genera are still the poorest sampled within the group. Eastern South America is the best-represented area in proportion to its species diversity, while Western Amazon, Mesoamerica, and the Caribbean are the least represented. CONCLUSIONS: We provide a time-calibrated tree that can be more reliably used to address finer-scale eco-evolutionary questions that involve this group in the Neotropics. Gaps to be filled by future studies include improving representation of taxa and areas that remain poorly sampled, investigating causes of conflict between nuclear and plastid partitions, and the role of hybridization and incomplete lineage sorting in relationships that are poorly supported.

Diversity, phylogeny and evolution of the rapidly evolving genus Psidium L. (Myrtaceae, Myrteae).

BACKGROUND AND AIMS: Psidium is the fourthth largest genus of Myrtaceae in the Neotropics. Psidium guajava is widely cultivated in the tropics for its edible fruit. It is commercially under threat due to the disease guava decline. Psidium cattleyanum is one of the 100 most invasive organisms in the world. Knowledge of the phylogenetic relationships within Psidium is poor. We aim to provide a review of the biology, morphology and ecology of Psidium, a phylogenetic tree, an infrageneric classification and a list of species. METHODS: Morphological and geographic data were obtained by studying Psidium in herbaria and in the field between 1988 and 2020. Forty-six herbaria were visited personally. A database of approx. 6000 specimens was constructed, and the literature was reviewed. Thirty species (about a third of the species in the genus) were sampled for molecular phylogenetic inference. Two chloroplast (psbA-trnH and ndhF) and two nuclear (external transcribed spacer and internal transcribed spacer) regions were targeted. Phylogenetic trees were constructed using maximum likelihood (ML; RaxML) and Bayesian inference (BI; MrBayes). KEY RESULTS: Psidium is a monophyletic genus with four major clades recognized as sections. Section Psidium (ten species), to which P. guajava belongs, is sister to the rest of the genus; it is widespread across the Neotropics. Section Obversifolia (six species; restricted to the Brazilian Atlantic Forest), which includes P. cattleyanum, is sister to the innermost clade composed of sister sections Apertiflora (31 species; widespread but most diverse in the Brazilian Atlantic Forest) + Mitranthes (26 species; widespread in dry forests and probably diverse in the Caribbean). Characters associated with diversification within Psidium are discussed. CONCLUSIONS: Research on pre-foliation, colleters, leaf anatomy, leaf physiology, staminal development, placentation and germination associated with the anatomy of the opercular plug is desirable. Studies are biased towards sections Psidium and Obversifolia, with other sections poorly known.