The red alga Chrysymenia saccata was first discussed by J.Agardh in 1876, and described in 1877. In subsequent publications there has been confusion about the type material, as well as the identity, and correct taxonomic placement of this species, currently referred to the genus Gloioderma. We consider the nomenclatural and taxonomic history of this species, and conclude that Chrysymenia saccata was based on poorly preserved material of Hymenocladia sanguinea. The species that was documented in detail by Sparling (1957), and is currently known as Gloioderma saccatum, is described as G. sparlingiae sp.nov.

We analyzed both mitochondrial cox1 and plastid rbcL sequences from specimens of Pterocladiella from Madagascar and compared their morphologies with previously described species in the genus. Both molecular and morphological datasets demonstrated the presence of five species in Madagascar: P. australafricanensis, P. bartlettii, P. caerulescens, and two new species, P. feldmannii and P. hamelii, described here. Pterocladiella feldmannii is distinguished by plants with a size of about 6 cm with narrow axes and opposite to irregular branches, rhizines congested in medulla, tetrasporangial branchlets constricted at base of branches, tetrasporangial sori without sterile margins, and irregular arrangement of tetrasporangia. Pterocladiella hamelii is characterized by plants with a size of about 3 cm with flattened and thin erect axes and irregular branches, radial arrangement of subapical cells at tips of main axes, tetrasporangial sori with sterile margins and horizontal to irregular arrangement of tetrasporangia. Phylogenetic analyses based on cox1 and rbcL sequences revealed the sister relationship between P. feldmannii and P. hamelii, and their distant relationships to P. australafricanensis, P. bartlettii, and P. caerulescens. The Madagascan Pterocladiella is composed of two geographical elements: Madagascan endemic (P. feldmannii and P. hamelii) and species with wide distributions (P. australafricanensis, P. bartlettii and P. caerulescens).

The Pacific Island region is an ideal setting for case studies on the invasion history of macroalgae in tropical coastal waters. Many textbook examples of algal invasions in this region demonstrate their significant ecological impacts on native reef communities. In light of increased maritime traffic as a potential anthropogenic dispersal mechanism for nonindigenous marine algae between tropical North Pacific Islands, a risk assessment was conducted to (1) quantify floristic disparities between marine ecoregions based on three subsets of species inventories, (2) evaluate the environmental and spatial distribution characteristics of island floras that are conducive to new introductions, and (3) establish a baseline with which future risk assessments based on a molecularly-assisted alpha taxonomy concept may be compared. The results of the environmental and floristic analyses showed that the “potentially invasive species” (i.e., species belonging to genera with known invasive representatives) constitute the best taxonomic subset for future risk assessments of marine macroalgae as this group (1) consists of an adequate—yet manageable—number of species, (2) is characterized by environmental and distribution parameters similar to that of the entire flora, (3) alleviates the deficit of non-indigenous species detection in tropical waters due to a historical bias toward temperate waters, and (4) closely mimics proportional differences in species composition between entire floras.

The red alga Schmitzia hiscockiana Maggs & Guiry is reported for Brittany for the first time. Our finding point to the southernmost limit of geographic distribution of this species. Molecular sequences (COI-5P, psbA, rbcL and LSU) are provided for the species and molecular phylogeny resolved Schmitzia hiscockiana along with two unidentified australian species of Schmitzia as sister to the lineage encompassing the Acrosymphytales and the Ceramiales.