A new order of red algae based on the Peyssonneliaceae, with an evaluation of the ordinal classification of the Florideophyceae (Rhodophyta)

The Peyssonneliaceae Denizot comprises a worldwide group of non-calcified or calcified, crust-forming red algae found in diverse, intertidal to deep subtidal marine habitats. Eight genera have been recognized in the family, with Peyssonnelia Decaisne having the largest number of species. Both comparative morphology and rbcL and nuclear LSU rDNA sequence data support the monophyly of the family and show that it cannot be maintained in the order Gigartinales Schmitz. A new order, Peyssonneliales, is herein proposed to accommodate the Peysonneliaceae, with only two of the genera (i.e., Peyssonnelia and Sonderopelta), and its relationship to the other red algal orders is discussed. We also propose the transfer of one species, Peyssonnelia capensis Montagne to Sonderopelta Womersley & Sinkora.