A new genus of Lythraceae emerges from rocky outcrops of the Atlantic Forest in Brazil

Recent collections of Lythraceae from an isolated mountain range in eastern Brazil were found to possess a unique morphology including spurless, weakly actinomorphic floral tubes, two deep red petals, a stipitate ovary and irregularly circumscissile dehiscence of a thickened capsule, characters typically applied to taxon recognition at the generic level. Genomic DNA was extracted from herbarium specimens or silica-dried leaf tissue and subjected to Illumina sequencing, and a phylogenetic analysis was performed based on a combination of plastid trnL-trnF and rpl16 and nuclear ribosomal ITS sequences. Sequences of 22 genera of Lythraceae, including 74 Cuphea spp. representing all recognized sections of the genus and three Pleurophora spp., were included in the analysis; Ludwigia octovalvis (Onagraceae) was used to root the trees. A maximum-likelihood tree was reconstructed based on the concatenated matrix. Strong morphological evidence was found to recognize a new genus and species in Lythraceae: Gyrosphragma latipetala sp. nov., gen. nov. The same characteristics also occur in a little-known species, Cuphea santos-limae, which we transfer to Gyrosphragma. Molecular phylogenetic analysis confirms Gyrosphragma as a monophyletic genus, sister to Cuphea; together these genera form a clade with Pleurophora. The new genus, supported by morphological and molecular evidence, adds new features and extends knowledge on the ecological and geographical diversity within Lythraceae.