John M. Huisman

On the identity and origin of the Mediterranean invasive Caulerpa racemosa(Caulerpales, Chlorophyta)

Recent morphological and genetic studies on the Caulerpa racemosa (Forsskål) J. Agardh complex have demonstrated that three taxa occur in the Mediterranean Sea. One of them, the ‘invasive variety’, provisionally regarded as close to C. racemosa var. occidentalis J. Agardh, is currently spreading spectacularly throughout the Mediterranean. On the basis of new morphological and molecular studies (rDNA ITS1, 5.8S and ITS2 sequences), we confirm here that this invasion is the result of a recent introduction and we identify the invasive variety as Caulerpa cylindracea Sonder, endemic to south-west Australia, and currently known as C. racemosa var. laetevirens f. cylindracea (Sonder) Weber-van Bosse. C. cylindracea differs from the tropical north Australian C. laetevirens Montagne by its slender thallus, lack of large rhizoidal pillars, the slight inflation of the basal part of the upright axes immediately above the attachment to the stolon, by the range of morphological variations (branchlets clavate to cylindrical but never trumpet-like or shield-like) and by the rDNA ITS sequence data. The new combination C. racemosa var. cylindracea (Sonder) Verlaque, Huisman et Boudouresque is therefore proposed.

Culture of the astaxanthin-producing green algaHaematococcus pluvialis 1. Effects of nutrients on growth and cell type

The freshwater green algaHaematococcus pluvialis (Strain Vischer 1923/2) grows best at high nitrate concentrations (about 0.5 to 1.0 g 1−1 KNO3), intermediate phosphate concentration (about 0.1 g 1−1 K2HPO4) and over a wide range of Fe concentrations. Low nitrate or high phosphate induce the formation of reddish palmella cells and aplanospores. Mixotrophic growth with acetate improves growth rate and final cell yield, and also stimulates the formation of the astaxanthin-containing palmella cells and aplanospores.H. pluvialis cannot grow above about 28 °C, or above a salinity of approximately 1% w/v NaCl. An increase in temperature or the addition of NaCl also stimulates the formation of palmella cells and aplanospores.

Resolving phenotypic plasticity and species designation in the morphologically challenging Caulerpa racemosa–peltata complex (Chlorophyta, Caulerpaceae)

Although recent molecular studies have indicated the presence of a number of distinct species within the Caulerpa racemosa–peltata complex, due to the difficulties presented by high levels of phenotypic plasticity and the large number of synonyms, infra‐specific taxa, and names of uncertain affinity, taxonomic proposals are yet to be made. In this study, we aimed to resolve the taxonomy of the complex and provide an example of how historical nomenclature can best be integrated into molecular based taxonomies. We accomplished this by first determining the number of genetic species within our globally sampled data set through a combination of phylogenetic and species‐delimitation approaches of partial elongation factor TU and RUBISCO large subunit gene sequences. Guided by these results, comparative morphological examinations were then undertaken to gauge the extent of phenotypic plasticity within each species, as well as any morphological overlap between them. Our results revealed the presence of 11 distinct species within the complex, five of which showed high levels of phenotypic plasticity and partial overlap with other species. On the basis of observations of a large number of specimens, including type specimens/descriptions, and geographic inferences, we were able to confidently designate names for the lineages. Caulerpa peltata, C. imbricata and C. racemosa vars. laetevirens, occidentalis and turbinata were found to represent environmentally induced forms of a single species, for which the earlier‐described C. chemnitzia, previously regarded as a synonym of C. racemosa var. turbinata, is reinstated. C. cylindracea, C. lamourouxii, C. macrodisca, C. nummularia and C. oligophylla are also reinstated and two new species, C. macra stat. nov. and C. megadisca sp. nov., are proposed.

Benthic Macroalgae of Shark Bay, Western Australia

One hundred and sixty one taxa of benthic macro-algae are reported from Shark Bay, Western Australia, growing either on subtidal rock platforms, on the extensive sandflats that dominate the bay, or as epiphytes on seagrasses and other algae. In addition many species survive as drift algae amongst the seagrass beds. Tropical taxa predominate. The Rhodophyta are represented by the greatest number of taxa, but these tend to be inconspicuous epiphytes. Members of the Chlorophyta are the most conspicuous in most areas, with Penicillus nodulosus and Polyphysa peniculus the most common species. Polyphysa peniculus dominates the high salinity areas south of the Faure Sill. The brown algae Hormophysa cuneiformis and Dictyota furcellata were also common in high salinity areas. Benthic algal species richness was lower in areas of high salinity.

Phylogenetic study of the Nemaliales (Rhodophyta) based on large-subunit ribosomal DNA sequences supports segregation of the Scinaiaceae fam. nov. and resurrection of Dichotomaria Lamarck

Gene sequence data have been newly obtained for 18 species in 13 genera of the order Nemaliales (Rhodophyta), allowing for the first time a relatively comprehensive molecular phylogenetic appraisal of the order. The phylogenetic trees generated from these data support the recognition of three families: (i) the Liagoraceae as presently constituted; (ii) a reduced Galaxauraceae including Actinotrichia, Galaxaura (sensu lato), and Tricleocarpa; and (iii) a new family, Scinaiaceae, segregated from the Galaxauraceae and including the genera Scinaia, Gloiophloea, Nothogenia, and probably Whidbeyella. The four genera of the Scinaiaceae differ from the newly circumscribed Galaxauraceae in being uncalcified, and having heteromorphic life histories in which the tetrasporophyte is much reduced and filamentous or crustose. This type of life history is found in only Tricleocarpa of the Galaxauraceae. The results also show Galaxaura to be para/polyphyletic if Actinotrichia and Tricleocarpa are recognized. To remedy this, the Galaxaura marginata species complex, Galaxaura diesingiana, and Galaxaura obtusata are removed from the genus and placed in the resurrected Dichotomaria Lamarck. Galaxaura marginata, presently thought to be wide‐ranging and morphologically variable, is shown to comprise several species. As a consequence, Galaxaura tenera Kjellman and Brachycladia australis Sonder are removed from the synonymy of G. marginata and restored as independent species in Dichotomaria for South African and Australian isolates, respectively. The Liagoraceae is shown to encompass genera previously placed in the segregate families Nemaliaceae and Dermonemataceae, and the value of the reproductive characters used to define those taxa is discussed.

The type and Australian species of the red algal genera Liagora and Ganonema (Liagoraceae, Nemaliales)

The type and Australian species of the liagoraceous genera Liagora and Ganonema (Rhodophyta: Nemaliales) are described. Twenty-one species are included, comprising 15 of Liagora and six of Ganonema. Five new species, Liagora walkerae, L. kraftii, L. izziae, L. delicatula and Ganonema borowitzkae are described. The new combinations Ganonema pinnatum (Harv.) Huisman, Ganonema samaense (Tseng) Huisman, Ganonema clavatum (Yamada) Huisman and Ganonema megagynum (Borgesen) Huisman are proposed. Liagora cladonioides Borgesen is shown to be a member of the genus Stenopeltis Itono & Yoshizaki. A key to the worlds species of Liagora and Ganonema is provided.

ASTEROMENIA (RHODYMENIACEAE, RHODYMENIALES), A NEW RED ALGAL GENUS BASED ON FAUCHEA PELTATA

Asteromenia gen. nov. (Rhodymeniales, Rhodophyta) is proposed with a single species, Asteromenia peltata (W. R. Taylor) comb. nov. (basionym: Fauchea peltata W. R. Taylor). Thalli of the proposed new genus are stipitate with dorsiventral, peltate blades that are initially circular in shape but with age become stellate with ligulate arms. Internally, the blades have a polystromatic medulla of large, hyaline cells, grading into a cortex of smaller, pigmented cells. Clusters of translucent cells occur on the dorsal surface of the blade. Tetrasporangia are formed by transformations of intercalary midcortical cells. Mature tetrasporangia have cruciately arranged spores and are densely aggregated in the cortex, mostly on the ventral surface, but occasional tetrasporangia also arise on the dorsal surface. Carpogonial branches are four‐celled and arise on inner cortical cells. Auxiliary cells are borne on auxiliary mother cells attached to supporting cells of the carpogonial branches. Cystocarps are protuberant, with well‐developed, ostiolate pericarps that often have extended, proboscis‐like necks. The new genus differs from the previously described peltate or dorsiventral taxa in the Rhodymeniaceae by its polystromatic medulla (Maripelta and Sciadophycus have a monostromatic medulla), intercalary tetrasporangia formed in an unmodified cortex, and four‐celled carpogonial branches (Halichrysis, as typified by H. depressa (J. Agardh) F. Schmitz, has terminal tetrasporangia in nemathecia and three‐celled carpogonial branches).

New species, observations, and a list of new records of brown algae (Phaeophyceae) from the Hawaiian Islands

Two new species of brown algae (Phaeophyceae), Padina moffittiana Abbott et Huisman, sp. nov. and Cutleria irregularis Abbott et Huisman, sp. nov., are described from the Hawaiian Islands (between 19°04′N, 155°35′W and 28°25′N, 178°20′W). In addition, the new combination Cutleria canariensis is proposed for Aglaozonia canariensis. New observations are presented on Nereia intricata Yamada, a species described 67 years ago and known only from its type specimen. New records of a further 14 species are given for the Hawaiian Islands. These 17 taxa bring the total number of species of brown algae recorded for the Hawaiian Islands to 55, an increase of 28%. Of the 15 new records, two are recent ‘accidental’ introductions: Dictyota flabellata (Collins) Setchell et Gardner and Sargassum muticum (Yendo) Fensholt from California. Six records are notable because of their great distances from previously known collections: Nereia intricata Yamada from the Ryukyu Is., Japan; Discosporangium mesarthrocarpum (Meneghini) Hauck, from the Adriatic, Mediterranean, warm Atlantic and southern Australia; Distromium flabellatum Womersley, Spatoglossum macrodontum J. Agardh, and Sporochnus moorei Harvey, from Australia; Desmarestia ligulata (Lightfoot) Lamouroux from temperate and colder waters in the Pacific and Atlantic. A comparison with some Japanese species of Padina confirms that Padina japonica Yamada should be subsumed with Padina sanctae‐crucis Børgesen, as proposed earlier.

Studies of the Liagoraceae (Rhodophyta) of Western Australia: Gloiotrichus fractalis gen. et sp. nov. and Ganonema helminthaxis sp. nov.

Two new taxa of Liagoraceae (Nemaliales) are described from Western Australia. Gloiotrichus fractalis gen. et sp. nov. has been collected from 3–20 m depths at the Houtman Abrolhos, Western Australia. Plants are calcified, extremely lubricous, and grow to 17 cm in length. Carpogonial branches are straight, 6 or 7 cells in length, arise from the basal or lower cells of cortical fascicles, and are occasionally compound. Branched sterile filaments of narrow elongate cells arise on the lower cells of the carpogonial branch prior to gonimoblast initiation, at first on the basal cells, then on progressively more distal cells. Following presumed fertilisation the carpogonium divides transversely, with both cells giving rise to gonimoblast filaments. The distal cells of the carpogonial branch then begin to fuse, with fusion progressing proximally until most of the cells of the carpogonial branch are included. As fusion extends, the filaments on the carpogonial branch are reduced to the basal 2 or 3 cells. The gonimoblast is compact and bears terminal carposporangia. Spermatangial clusters arise on subterminal cells of the cortex, eventually displacing the terminal cells. The sequence of pre- and post-fertilisation events occurring in the new genus separates it from all others included in the Liagoraceae, although it appears to have close affinities with the uncalcified genus Nemalion. Ganonema helminthaxis sp. nov. was collected from 12 m depths at Rottnest Island, Western Australia. Plants are uncalcified and mucilaginous, the axes consisting of a few (< 10) primary medullary filaments, each cell of which gives rise to a cortical fascicle at alternate forks of the pseudodichotomies borne on successive medullary cells. Subsidiary (adventitious) filaments and rhizoids comprise the bulk of the thallus. Carpogonial branches are straight, (3-)4(-6) cells in length, arise on the basal 1–4 cells of the cortical fascicles, and are frequently compound. Carposporophytes develop from the upper of two daughter cells formed by a transverse division of the fertilised carpogonium. Ascending and descending sterile filaments girdle the carpogonial branch cells and arise mostly on the supporting cell prior to fertilisation. Ganonema helminthaxis is the first completely non-calcified member of the genus, and its reproductive and vegetative morphology supports the recognition of Ganonema as a genus independent from Liagora. Liagora codii Womersley is a southern Australian species displaying features of Ganonema, to which it is transferred.

Identity and origin of a slender Caulerpa taxifolia strain introduced into the Mediterranean Sea

Abstract On the basis of morphological and molecular studies, we identified the Australian endemic green alga known as Caulerpa distichophylla along the coasts of Sicily (Italy, Mediterranean Sea). The slender Caulerpa previously reported as C. taxifolia from southeastern Turkey (Gulf of Iskenderun) also belongs to C. distichophylla. Morphologically, C. distichophylla clearly differs from C. taxifolia in its slender thallus and the lack of large rhizoidal pillars. However, genetic data do not provide undisputed evidence that the species are distinct. Sequences of the tufA cpDNA gene and of the cp 16S rDNA intron-2 sequences separated the two taxa by only one single nucleotide mutation, whereas ITS rDNA sequences did not clearly distinguish them. The new combination Caulerpa taxifolia var. distichophylla is therefore proposed. Western and eastern Mediterranean populations of C. taxifolia var. distichophylla are probably the result of introduction events from southwestern Australia. Although the vector of primary introductions remains unknown (aquarium trade or shipping), maritime traffic appears to be the most likely vector of secondary dispersal. C. taxifolia var. distichophylla is closely related to C. taxifolia, hence interbreeding with the other C. taxifolia strains in the Mediterranean Sea might be expected to occur.