Based on morphology and molecular data, Palisada rigida comb. nov. and Laurencia decussata comb. et stat. nov. (Rhodophyta, Rhodomelaceae) are proposed

Abstract

Inspecting herbaria collections of Laurencia rigida highlighted frequent misidentifications between L. rigida and L.heteroclada f. decussata, two poorly studied taxa from Australia. Recent collections of DNA material, including from topotypematerial, allowed for re-examination of these two taxa using molecular techniques. Detailed morphological andmolecular analyses based on two markers (rbcL and COI-5P) strongly supported these two taxa as being distinct fromeach other and requiring nomenclatural changes. Comprehensive morphological analyses highlighted features useful foraccurate identifications. Interestingly, L. rigida was found to belong to the genus Palisada with evidence from both themorphology and molecular data. Therefore, this study proposed recognizing L. rigida as Palisada rigida comb. nov. Moleculardata for L. heteroclada f. decussata on the other hand supported its separation from L. heteroclada, with too greata molecular distance to be considered a variety. Morphological characters that best separated P. rigida from L. decussataincluded seven characters; number of pericentral cells per vegetative axial segment, the presence of secondary pit connections,the presence of lenticular thickenings, tetrasporangia alignment, the presence of corps en cerise, holdfast morphology,and overall plant shape. Morphologically, L. heteroclada f. decussata was also separated from L. heteroclada,particularly by the following characteristics; ultimate branchlets morphologies, lower order branch lengths, primary axisand holdfast morphologies. Therefore, it was proposed that L. heteroclada f. decussata is recognized at a species level asL. decussata comb. et stat. nov.