The Organellar Genomes of Melanthalia abscissa and Polyopes polyideoides (Rhodophyta, Florideophyceae).

Florideophyceae is the most species rich red algal class, including large numbers of well-studied, economically important species and lesser-known clades. We present the complete plastid and mitocondrial genome assemblies of two Florideophycean species, Melanthalia abscissa (Gracilariaceae) and Polyopes polyideoides (Halymeniaceae). We identified more large-scale rearrangements within the plastid genomes of Gracilariales than within Halymeniales. Maximum likelihood phylogenies using rbcL data support the placement of both M. abscissa and P. polyideoides samples in monophyletic genera. However, not all genera within Halymeniales were recovered as monophyletic. Sequences that appear to be derived from red algal plasmids were identified within the plastid genome of M. abscissa. Determining the presence or absence of plasmid-derived sequences in the P. polyideoides plastome is more difficult due to a lack of publicly available data for Halymeniaceae. The addition of the sequences produced by this study will support further phylogenetic and systematic research on these Rhodophytan genera and orders.