Phylogenomics and taxon-rich phylogenies of new and historical specimens shed light on the systematics of Hypnea (Cystocloniaceae, Rhodophyta).

Cystocloniacae is a highly diverse family of Rhodophyta, including species of ecological and economic importance, whose phylogeny remains largely unresolved. Species delimitation is unclear, particularly in the most speciose genus, Hypnea, and cryptic diversity has been revealed by recent molecular assessments, especially in the tropics. Here, we carried out the first phylogenomic investigation of Cystocloniaceae, focused on the genus Hypnea, inferred from chloroplast and mitochondrial genomes including taxa sampled from new and historical collections. In this work, molecular synapomorphies (gene losses, InDels and gene inversions) were identified to better characterize clades in our congruent organellar phylogenies. We also present taxon-rich phylogenies based on plastid and mitochondrial markers. Molecular and morphological comparisons of historic collections with contemporary specimens revealed the need for taxonomic updates in Hypnea, the synonymization of H. marchantiae to a later heterotypic synonym of H. cervicornis and the description of three new species: H. davisiana sp. nov., H. djamilae sp. nov. and H. evaristoae sp. nov.

Taxonomic revision of the Peyssonneliales (Rhodophyta): Circumscribing the authentic Peyssonnelia clade and proposing four new genera and seven new species.

The Peyssonneliaceae represents the only family in the order Peyssonneliales, a clade of red encrusting algae distributed worldwide, including 136 species in eleven currently accepted genera. Delineation of genera in the Peyssonneliaceae has mostly been based on vegetative characteristics. Previous molecular phylogenies have shown that some traditionally circumscribed genera are not monophyletic and relationships among them are uncertain. We contribute to the knowledge of the evolutionary history of this clade, presenting a robust rbcL phylogeny that provides new insights on the origin and diversification of the Peyssonneliales. Based on a broad dataset and morphological analyses, we propose a revised taxonomic scheme for the Peyssonneliales resolved as monophyletic with well-supported main lineages. Our results show that Peyssonnelia is polyphyletic, and, therefore, we propose three new genera, Agissea, Olokunia, and Rhodowynnea to accommodate species currently assigned to Peyssonnelia, but distantly related to the clade with the type species of the genus. Additionally, barcoding techniques and analyzed criteria for specific delimitation supported the establishment of one new genus, Brasilophycus, and seven new species, from northeastern Brazil: Agissea amadoi, A. densissima, A. taberniforma, A. villatlantica, A. yemonjasagbae, Brasilophycus similis, and B. roseomarginatus. Our integrative taxonomic approach reveals underestimated diversity of Brazilian Peyssonneliales. Investment in broader sampling along the Brazilian coast and other tropical areas may reveal that its marine biodiversity can be expanded, enlightening our knowledge about this ecologically important group of red algae.

Species-delimitation and phylogenetic analyses of some cosmopolitan species of Hypnea (Rhodophyta) reveal synonyms and misapplied names to H. cervicornis, including a new species from Brazil.

Hypnea has an intricate nomenclatural history due to a wide pantropical distribution and considerable morphological variation. Recent molecular studies have provided further clarification on the systematics of the genus; however, species of uncertain affinities remain due to flawed taxonomic identification. Detailed analyses coupled with literature review indicated a strong relationship among H. aspera, H. cervicornis, H. flexicaulis, and H. tenuis, suggesting a need for further taxonomic studies. Here, we analyzed sequences from two molecular markers (COI-5P and rbcL) and performed several DNA-based delimitation methods (mBGD, ABGD, SPN, PTP and GMYC). These molecular approaches were contrasted with morphological and phylogenetic evidence from type specimens and/or topotype collections of related species under a conservative approach. Our results demonstrate that H. aspera and H. flexicaulis represent heterotypic synonyms of H. cervicornis and indicate the existence of a misidentified Hypnea species, widely distributed on the Brazilian coast, described here as a new species: H. brasiliensis. Finally, inconsistencies observed among our results based on six different species delimitation methods evidence the need for adequate sampling and marker choice for different methods.