Abstract:
Red algae (Rhodophyta) are economically useful for their gelling compounds, ecologically critical to marine benthic systems, and evolutionarily poised at the intersection of primary and secondary endosymbiotic lineages. Molecular sequencing has transformed our understanding of red algae, revealing genetic and genomic characteristics that had once been completely unknown. In Grateloupia, a red algal genus that is morphologically simple and notoriously difficult-to-identify, sequencing has greatly assisted in identification of species and phylogenetic placement of troublesome taxonomic groups. However, analysis of DNA has also proven useful for genomic comparisons on a larger scale, in order to resolve deep evolutionary questions in terms of overall genome architecture and gene content. Grateloupia is a prime candidate for genomic research, representing an order that had previously not been explored. In this study, sequencing-based analyses were applied at both levels, examining species of Grateloupia both within the genus and from a greater phylogenetic perspective. Phylogenetic analysis of the rbcL marker revealed the previously unknown species Grateloupia taiwanensis, first reporting this non-native alga from the Gulf of Mexico, and it showed that the species previously known as Grateloupia filicina in the Gulf of Mexico actually includes several species. The organellar genomes of Grateloupia taiwanensis were also sequenced and annotated; both the plastid and mitochondrial genome are typical of florideophyte red algae in size, gene content, and structure. Mauve genome alignments demonstrated a pattern of genomic rearrangements expected given the overall phylogeny of Rhodophyta.
