The first complete plastid genomes of Melastomataceae are highly structurally conserved

BACKGROUND: In the past three decades, several studies have predominantly relied on a small sample of the plastome to infer deep phylogenetic relationships in the species-rich Melastomataceae. Here, we report the first full plastid sequences of this family, compare general features of the sampled plastomes to other sequenced Myrtales, and survey the plastomes for highly informative regions for phylogenetics. METHODS: Genome skimming was performed for 16 species spread across the Melastomataceae. Plastomes were assembled, annotated and compared to eight sequenced plastids in the Myrtales. Phylogenetic inference was performed using Maximum Likelihood on six different data sets, where putative biases were taken into account. Summary statistics were generated for all introns and intergenic spacers with suitable size for polymerase chain reaction (PCR) amplification and used to rank the markers by phylogenetic information. RESULTS: The majority of the plastomes sampled are conserved in gene content and order, as well as in sequence length and GC content within plastid regions and sequence classes. Departures include the putative presence of rps16 and rpl2 pseudogenes in some plastomes. Phylogenetic analyses of the majority of the schemes analyzed resulted in the same topology with high values of bootstrap support. Although there is still uncertainty in some relationships, in the highest supported topologies only two nodes received bootstrap values lower than 95%. DISCUSSION: Melastomataceae plastomes are no exception for the general patterns observed in the genomic structure of land plant chloroplasts, being highly conserved and structurally similar to most other Myrtales. Despite the fact that the full plastome phylogeny shares most of the clades with the previously widely used and reduced data set, some changes are still observed and bootstrap support is higher. The plastome data set presented here is a step towards phylogenomic analyses in the Melastomataceae and will be a useful resource for future studies.