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The genus Visia is reappraised based on new morphological and molecular data (rbcL and COI-5P sequences), from recently collected and previously studied materials, resulting in the need for several taxonomic changes. Based on our phylogeny and sequence divergence, the genus Visioidea gen. nov. is proposed for two samples from Brazil, forming a distinct clade that is morphologically undistinguishable from the generitype of Visia (V. cayennensis). Two lineages of Visia with high genetic divergences from other species are proposed as new species: 1) V. verviridis sp. nov. from Australia; 2) V. amazonensis sp. nov. from Brazil. Although genetically distinct, both species are morphologically very similar to V. cayennensis. A new record of V. cylindrocellularis was found in Australia, expanding the geographic distribution and the morphometric ranges for this species. The number of species currently recognized in Visia is now six, four with DNA sequence data and two identified based solely on morphology (V. longiarticulata and V. turgida). Cryptic genera within the order Batrachospermales were not recognised until recently with the proposals of Volatus, morphologically indistinct from Kumanoa, and Macrosporophycos undistinguishable from Montagnia and here a third cryptic genus Visioidea is described. [ABSTRACT FROM AUTHOR]

Cryptic diversity is common among marine macroalgae, with molecular tools leading to the discovery of many new species. To assign names to these morphologically similar species, the type and synonyms have to be examined, and if appropriate, new species must be described. The turf‐forming red alga Polysiphonia scopulorum was originally described from Rottnest Island, Australia, and subsequently widely reported in tropical and temperate coasts based on morphological identifications. A recent study of molecular species delineation revealed a complex of 12 species in Australia, South Africa, and Europe. These species are placed in a taxonomically unresolved lineage of the tribe Polysiphonieae. The aim of this study was to resolve the genus‐ and species‐level taxonomy of this complex and related species using molecular and morphological information. Three morphologically indistinguishable species of the complex were found at the type locality of P. scopulorum, preventing a straightforward assignment of the name to any of the molecular lineages. Therefore, we propose a molecularly characterized epitype. Polysiphonia caespitosa is reinstated for the only species found in its type locality in South Africa. We describe seven new species. Only one species of the complex can be morphologically recognized, with the other eight species indistinguishable based on morphometric analysis. The studied complex, together with another seven species currently placed in Polysiphonia and two Bryocladia species, formed a clade distinct from Polysiphonia sensu stricto. Based on observations of Bryocladia cervicornis (the generitype), we describe our seven new species in the genus Bryocladia and transfer another nine species from Polysiphonia to Bryocladia. [ABSTRACT FROM AUTHOR]

Species identification in red algae poses significant challenges when relying solely on morphological characteristics. Consequently, the absence of molecular information often conceals misidentifications, cryptic diversity and introduced cryptic species. Within the genus Lophocladia, species have traditionally been delineated based on subtle morphological traits. Lophocladia trichoclados and Lophocladia lallemandii have been extensively documented in warm and temperate coastal regions, with the latter recognized as an invasive species in the Mediterranean. However, the molecular relationship between these species remains unexplored. To address this gap, a comprehensive taxonomic reevaluation of Lophocladia was conducted in the NE Atlantic, Mediterranean Sea and Red Sea. Through combined molecular and morphological analyses of 75 specimens, two distinct taxa of Lophocladia were identified within the study area. Sequences of the rbcL plastid gene unequivocally demonstrated that L. lallemandii and L. trichoclados are conspecific. Consequently, we propose the synonymization of L. lallemandii with L. trichoclados, which has nomenclatural priority. We report L. kuetzingii, a potentially introduced species from Australia, for the first time in the Macaronesian region of the North Atlantic. This finding underscores the importance of expanding red algal DNA datasets, as such efforts significantly enhance our ability to detect and discern introduced species. Additionally, this research highlights the existence of taxonomic uncertainties surrounding introduced species, even among those already classified as invasive. Molecular tools reveal the synonymy of Lophocladia lallemandii with L. trichoclados. L. trichoclados is a widely distributed species in the Atlantic, Mediterranean and Red Sea. L. kuetzingii is detected as a cryptic introduced species in the Macaronesian region. [ABSTRACT FROM AUTHOR]

Parasitic red algae are an interesting system for investigating the genetic changes that occur in parasites. These parasites have evolved independently multiple times within the red algae. The functional loss of plastid genomes can be investigated in these multiple independent examples, and fine‐scale patterns may be discerned. The only plastid genomes from red algal parasites known so far are highly reduced and missing almost all photosynthetic genes. Our study assembled and annotated plastid genomes from the parasites Janczewskia tasmanica and its two Laurencia host species (Laurencia elata and one unidentified Laurencia sp. A25) from Australia and Janczewskia verruciformis, its host species (Laurencia catarinensis), and the closest known free‐living relative (Laurencia obtusa) from the Canary Islands (Spain). For the first time we show parasitic red algal plastid genomes that are similar in size and gene content to free‐living host species without any gene loss or genome reduction. The only exception was two pseudogenes (moeB and ycf46) found in the plastid genome of both isolates of J. tasmanica, indicating potential for future loss of these genes. Further comparative analyses with the three highly reduced plastid genomes showed possible gene loss patterns, in which photosynthetic gene categories were lost followed by other gene categories. Phylogenetic analyses did not confirm monophyly of Janczewskia, and the genus was subsumed into Laurencia. Further investigations will determine if any convergent small‐scale patterns of gene loss exist in parasitic red algae and how these are applicable to other parasitic systems. [ABSTRACT FROM AUTHOR]

Introduced seaweeds and undescribed species often remain undetected because marine regional floras are as yet poorly understood. DNA sequencing facilitates their detection, but databases are incomplete, so their improvement will continue to lead the discovery of these species. Here we aim to clarify the taxonomy of two turf‐forming red algal Australian species that morphologically resemble the European Aphanocladia stichidiosa. We also aim to elucidate whether either of these species could have been introduced in Europe or Australia. We studied their morphology, analyzed 17 rbcL sequences of European and Australian specimens, examined their generic assignment using a phylogeny based on 24 plastid genomes, and investigated their biogeography using a taxon‐rich phylogeny including 52 rbcL sequences of species in the Pterosiphonieae. The rbcL sequences of one of the Australian species were identical to A. stichidiosa from Europe, considerably expanding its known distribution. Unexpectedly, our phylogenetic analyses resolved this species in the Lophurella clade rather than in Aphanocladia and the new combination L. stichidiosa is proposed. The other Australian species is described as L. pseudocorticata sp. nov. Although L. stichidiosa was originally described in the Mediterranean ca. 70 years ago, our phylogenetic analyses placed it in a lineage restricted to the southern hemisphere, showing that it is native to Australia and introduced to Europe. This study confirms that further work using molecular tools is needed to characterize seaweed diversity, especially among the poorly explored algal turfs, and showcases the usefulness of phylogenetic approaches to uncover introduced species and to determine their native ranges. [ABSTRACT FROM AUTHOR]

Molecular phylogenetic analyses of Hawaiian members of the red algal family Dumontiaceae were used to clarify the species diversity of Dudresnaya and Gibsmithia from Hawaiʻi. Although no new species of Dudresnaya were detected in the analyses, D. babbittiana is newly recorded by Lalo, Manawai, and Oʻahu; however, this record remains tentative until the type material is sequenced. A new species of Gibsmithia, G. punonomaewa A.R. Sherwood, is described here and reported from the mesophotic depths (79–104 m) of the Papahānaumokuākea Marine National Monument, Hawaiʻi. This new species differs from all others in the genus based on the following combination of characters: moderate thallus size (up to 11 cm), smooth and terete gelatinous lobes, presence of a stipe (which is often branched), globose carposporangia, and a non-isodiametric shaped cell subtending the tetrasporangia. This new taxon increases the number of Gibsmithia species recorded from Hawaiʻi to three. Phylogenetically, G. punonomaewa is most closely related to G. dotyi (type locality, Lord Howe Island, Australia) and G. larkumii (type locality, One Tree Island, Queensland, Australia), which are both reportedly widespread in distribution. The relatively dark habitat of the mesophotic in Papahānaumokuākea Marine National Monument contrasts with the surface waters of tropical and subtropical habitats where most Gibsmithia species are found, further highlighting the uniqueness of the species. [ABSTRACT FROM AUTHOR]

Three new species of the red algal genus Asteromenia (Hymenocladiaceae, Rhodophyta) are described based on morphological and molecular analyses. DNA analyses of recent collections of topotype specimens of A. examinans from the Houtman Abrolhos Islands (Western Australia) have revealed that the specimens used in earlier studies were misidentified and represent an undescribed species, herein described as A. juliannae. Two additional new species, A. crenulata and A. praetermissa are described from the Cocos (Keeling) Islands, and Norfolk Island, respectively. For the most part, the new species showed morphological overlap and could not be discriminated based on morphology alone; DNA sequencing is therefore considered essential for accurate species recognition. The potential for misidentification of morphologically similar specimens highlights the need for sequence analyses and reference barcoding to be based on type or topotype specimens. The adoption of molecular methods in alpha taxonomy has led to the recognition of considerable diversity in the Rhodymeniales and it is envisaged that further collecting will add even more taxa to Australia's rich algal flora. [ABSTRACT FROM AUTHOR]

Marine phylogeographic studies have recently shown that historical events, oceanography and ecological factors shape patterns of biodiversity and population connectivity. In southeastern Australia a historical geographic barrier, the Bassian Isthmus, results in deep genetic differentiation between some marine taxa. Using partial mitochondrial cytochrome oxidase subunit I (COI) DNA sequences, we investigated the genetic diversity and phylogeography among 26 populations of the red alga Bostrychia intricata along the southeastern Australian coast. Our genetic data revealed the occurrence of five cryptic B. intricata species (lineages N5, N7, N8, N9 and N10), two of which (N9 and N10) are newly discovered and endemic to Tasmania, while cryptic species N5 and N7 were confined to mainland Australia. Species N8 was more genetically diverse and extensively distributed than the other cryptic species, because it occurred both on mainland Australia and in Tasmania. We also detected a clear east–west phylogeographic break between cryptic species N7 and N5, and between haplotypes of species N8 on either side of Wilsons Promontory (the southernmost tip of mainland Australia). Spatial analysis of molecular variance identified three clusters of populations of species N8 along the south coast of Australia, and the split among these groups corresponded to extensive sandy areas: Coorong dunefield and Ninety Mile Beach. Additionally, our study detected the separation between mainland Australian (species N5 and N7) and Tasmanian species (N9 and N10) across the Bass Strait. We suggest that phylogeographic breaks and genetic differentiation in cryptic B. intricata species likely correlate to the historical Bassian land bridge, present-day habitats and different oceanographic circulation patterns. [ABSTRACT FROM AUTHOR]

Molecular techniques have become important tools to investigate cryptic diversity and phylogeographic patterns. Mitochondrial markers have revealed that the temperate red alga Asparagopsis armata contains two cryptic clades. The A. armata species complex is native to Australia and New Zealand and has been introduced around the world, particularly to Europe. Previous sequencing has focused on A. armata outside of its native range, and there are few sequences available from Australia and New Zealand. Our study investigated cryptic diversity and phylogeographic patterns for over 60 individuals from 7 locations around New Zealand using the mitochondrial cox2-3 spacer and plastid rbcL markers, and found that both cryptic clades within A. armata (L1 and L2) can be found in New Zealand. For the first time, our study has revealed haplotype variation (A and B) within each of the two cryptic A. armata clades. Asparagopsis armata L1A has been found in Australia, Europe and South Africa and is the only invasive lineage currently known, while A. armata haplotype L1B is found throughout New Zealand. In addition, A. armata L2A has been found only in Australia, and A. armata L2B has a southern distribution in New Zealand. The two mitochondrial lineages from New Zealand (L1B and L2B) were found to coexist in several locations. Further work is needed to characterize any differences in the morphology, physiology and biochemistry of the four genetically distinct mitochondrial lineages within the two cryptic clades, as well as their geographic and ecological distributions. [ABSTRACT FROM AUTHOR]

Marine macroalgae have variable carbon-uptake strategies that complicate predicting responses to environmental changes. In seawater, dissolved inorganic carbon availability can affect the underlying physiological mechanisms influencing carbon uptake. We tested the interactive effects of ocean acidification (OA) and warming on two HCO 3 − -users (Lobophora sp. and Amansia rhodantha), a predominately CO2-user (Avrainvillea nigrican s), and a sole CO2-user (Plocamium hamatum) in the Great Barrier Reef, Australia. We examined metabolic rates, growth, and carbon isotope values (δ 13C) in algae at 26, 28, or 30°C under ambient or elevated p CO2 (∼1000 µatm). Under OA, δ 13C values for the HCO 3 − -users decreased, indicating less reliance on HCO 3 − ⁠ , while δ 13C values for CO2-users were unaffected. Both HCO 3 − -users decreased in growth across temperatures under ambient p CO2, but this negative effect was alleviated by OA at 30°C. A. nigricans lost biomass across all treatments and P. hamatum was most sensitive, with reduced survival in all physiological responses. Metabolic rates varied greatly to interacting temperature and OA and indicated a decoupling between the relationship of photosynthesis and growth. Furthermore, our findings suggest HCO 3 − -users are more responsive to future CO2 changes, and highlight examining carbon physiology to infer potential responses to interacting environmental stressors. [ABSTRACT FROM AUTHOR]

Various red algae lack sexual reproduction and propagate by spore recycling, but it is still unknown how apomixis originates. In previous crossing experiments, we obtained an unusual hybrid of Caloglossa monosticha M. Kamiya through the outcrossing between a male from Australia and a female from Indonesia. This hybrid was morphologically identical to a normal tetrasporophyte, but its tetraspores grew into tetrasporophytes and repeated tetraspore recycling. During 5 years of culture, no sexual reproductive structures have formed on the tetrasporelings from this hybrid or its progenies. Further hybridization experiments revealed that all the five female strains from Indonesia successfully crossed with the male strain from the East Alligator River, Australia, and most of the F1 sporophytes demonstrated tetraspore recycling, though the germination rates of these tetraspores were quite low. The ploidy level of the hybrid tetrasporophyte was similar to the normal tetrasporophyte, rather than the parental gametophyte, based on the comparison of relative DNA contents of their nuclei. Single strand conformation polymorphism (SSCP) and sequence analyses of the internal transcribed spacer 1 (ITS1) region indicated that the alleles from both parents were present in all the hybrid tetrasporophytes examined. These results suggest that this hybrid does not carry out meiosis during sporogenesis, and heterozygous diploid sporophytes arose from tetraspores. Therefore, we believe that obligate apomixis was generated through outcrossing between genetically different entities of C. monosticha. [ABSTRACT FROM AUTHOR]

On the basis of comparative morphology and phylogenetic analyses of rbcL and LSU rDNA sequence data, a new genus, Gayliella gen. nov., is proposed to accommodate the Ceramium flaccidum complex ( C. flaccidum, C. byssoideum, C. gracillimum var. byssoideum, and C. taylorii), C. fimbriatum, and a previously undescribed species from Australia. C. transversale is reinstated and recognized as a distinct species. Through this study, G. flaccida (Kützing) comb. nov., G. transversalis (Collins et Hervey) comb. nov., G. fimbriata (Setchell et N. L. Gardner) comb. nov., G. taylorii comb. nov., G. mazoyerae sp. nov., and G. womersleyi sp. nov. are based on detailed comparative morphology. The species referred to as C. flaccidum and C. dawsonii from Brazil also belong to the new genus. Comparison of Gayliella with Ceramium shows that it differs from the latter by having an alternate branching pattern; three cortical initials per periaxial cell, of which the third is directed basipetally and divides horizontally; and unicellular rhizoids produced from periaxial cells. Our phylogenetic analyses of rbcL and LSU rDNA gene sequence data confirm that Gayliella gen. nov. represents a monophyletic clade distinct from most Ceramium species including the type species, C. virgatum. We also transfer C. recticorticum to the new genus Gayliella. [ABSTRACT FROM AUTHOR]

1. Surrogates aim to predict species diversity and to minimize sampling effort. Here the value of surrogates for marine macroalgae is tested. 2. Higher taxonomic levels and dominant taxa were evaluated as surrogates for detecting patterns in macroalgal species diversity (derived from species-level biomass data) in the Recherche Archipelago, Western Australia. 3. Data were stratified by two island groups (inshore and offshore), three depth intervals (<10m, 10–20m, > 20m), and two exposures to wave energy. Correlations between similarity matrices from surrogate and species diversity data matrices were analysed using a modified Spearman rank correlation (rs). The ability of surrogates to detect differences between exposures to wave energy was also investigated using analysis of similarity. Species diversity data were aggregated to higher taxonomic levels and were either fourth-root or presence/absence (richness) transformed. 4. Species richness was the most consistent surrogate (rs-values > 0.69, P = 0.001). Genus-level richness was also strongly correlated to species diversity in the Recherche Archipelago, except in depths < 10m where patterns in diversity were characterized by species turnover. 5. At offshore islands in depths 10–20 m and > 20 m, family- and order-level biomass data were suitable surrogates owing to the abundance of Alariaceae (Order Laminariales) represented by a single genus and species. Surrogates using biomass data from the orders Laminariales, Ceramiales, Dictyotales and Fucales were also successful at offshore islands in middle to deeper depths. 6. At inshore islands in depths 10–20m and > 20m, genera from the orders Gigartinales, Fucales and Ceramiales were strongly correlated to species biomass data. 7. Surrogates, like species richness, that were strongly correlated to species biomass data were also able to distinguish between exposures to wave energy, based on analysis of similarity tests. 8. Sampling effort would be reduced if collecting richness data in species-rich macroalgal assemblages such as those found in temperate Australia. [ABSTRACT FROM AUTHOR]

The characteristics of detached macroalgae (drift) in nearby highly eutrophic and mesotrophic estuaries in south-western Australia are compared to elucidate the magnitude and types of changes that occur in macroalgal drift when estuaries receive excessive nutrient input. Drift characteristics in the large basins of the microtidal, eutrophic Peel-Harvey and mesotrophic Swan-Canning, which is not subjected to large nutrient inputs directly from agricultural land, differed markedly. Biomass (dry weight) in mesotrophic estuary was dominated by rhodophytes (92%), particularly Laurencia and Hypnea , and in eutrophic estuary by opportunistic chlorophytes (68%), especially Chaetomorpha and Ulva. Prevalence and biomass of drift were far greater in the eutrophic estuary, particularly during summer and autumn when macroalgal growth rose sharply. Macroalgal biomass in the eutrophic estuary was positively related to salinity. These results facilitate predictions of how climatic and other anthropogenic changes influence extent of macroalgal growth and thus change the estuarine environment. • Macrophyte drift in nearby microtidal mesotrophic and eutrophic estuaries compared • Rhodophytes dominant in mesotrophic estuary and chlorophytes in eutrophic estuary • Biomass 23 times greater in eutrophic estuary, due to high summer and autumn values • Drift prevalence and dry weight in both estuaries increased from winter to autumn • Biomass positively related to salinity in both mesotrophic and eutrophic estuaries [ABSTRACT FROM AUTHOR]

Systematic studies were undertaken on the Caloglossa continua (Okammura) King et Puttock complex from Japan, Singapore, and Austriala, based on morphology and reproductive compatibility. Specimens from Japan had two to six cell rows derived from a nodel axial cell, at the margin opposite the branch, whereas those from Austraila possessed only a single cell now. Specimens from Singapore formed one to four cell rows per nodal axial cell and always contained at least one single cell row on any one thallus. These differences were maintained in cultural materials over a range of temperagtures or salinities. Type material of C. continua had the same morphology as the Japanese specimens in this study. Carpospores discharged from the Japanese isolate germinated at 10°C, whereas those from Singapore and Australia died at this temperature. In hybridization experiments, the Japanese entity was completely nonfertile with both the Singaporean and Australian isolates. Many pseudocystocarps were produced in the crossing between the make from Australia and the female from Singapore, although the reciprocal combination did not produce any such structures. On the basis of the discontinuous morphology coupled with the complete reproducture isolation, the entiries from Singapore and Australia are described here as C. monosticha sp. nov. The entiries with multiple cell rows likely expanded their geographic range from tropical regions, where the majority of Caloglossa species are now distributed, to high-latitude regions, and such an expansion would be associated with acquining low-temperature tolerance. [ABSTRACT FROM AUTHOR]

Dicroglossum gen nov. (Delesseriaceae, Ceramiales) is a monotypic genus based on Delesseria crispatula, a species originally described by Harvey for plants collected from southwestern Western Australia. Distinctive features of the new genus include exogenous indeterminate branches; growth by means of a single transversely dividing, apical cell; absence of intercalary divisions in the primary, secondary, and tertiary cell rows, lateral pericentral cells not transversely divided; not all cells of the secondary cell rows producing tertiary cell rows; all tertiary initials teaching the thallus margin; midrib present but lateral nerves absent; determinate lateral bladelets arising endogenously; blades monostromatic, except at the midrib; carpogonial branches restricted to primary cell rows on both surfaces of unmodified blades,; procarps produced on both blde surfaces, each procarp conststing of a supporting cell that bears two four-celled carpogonial branches and one sterile-cell groupof three to four cells; and tetrasporangia borne in two layers, separated by a central row of sterile cells. The combination of exogenous indeterminate branching and bicarpogonial procarps is considered to warrant the recongnition of a new tribe, the Dicroglosseae, within the subfamily Delesserioideae. [ABSTRACT FROM AUTHOR]

Dasya roslyniae sp. Nov. (Dasyaceae, Rhodophyta) is described from subtidal habitats at Split solitary Island (30° 14'S, 153° 11'E), New South Wales, Australia. The new species is distinct within the genus due to its strongly compressed and secondarily bilaterally branched axes, differing from the majority of Dasya species that are terete and secondarily redially organized. Pseudolaterals are quickly caduceus on ventral and dorsal (transverse) surfaces but are persistent on laterl surfaces for short distances from the apex, leaving the bulk of the plants flattened and denuded. Its gross morphological characters are thus similar to those displayed by the genera Pogonophorella, Eupogodon (formerly known as Dasyopsis), and Rhodoptilum. Characters used for separating these genera and Dasya are, in some cases, overlapping and in need of critical evaluation. To the primarily radially organized taxa, determined by examination of divisions of the apical cell, are placed species of Dasya, six species now included in Eupogodon, and the type and only species of Pogonophorella californica. Examination of the activity of the apical cells of Eupogodon planum and Rhodoptilum plumosum, the type species of their genera, confirms the primary bilaterality of these two genera, and the traditional defining feature of Eupogodon (lack of discernible pericentral cells in cross-section of indeterminate axes) is shown to be untenable. A secondary character that would separate Ejupogodon and Rhodoptilum is the polyusiphonous bases of otherwise monosiphonous laterals (Pseudolaterals) in Eupogodon and the monosiphonous bases in Rhodoptilum. [ABSTRACT FROM AUTHOR]

The concentrations of mannitol and floridean starch were determined in a 1-year field study of the epiphytic red alga Caloglossa leprieurii (Montagne) J. Agardh from warm temperate waters of eastern Australia. Seasonal environmental data for air and water temperature, day length and rainfall were recorded. The mannitol content and the floridean starch content varied significantly between collections but no seasonal responses were observed, nor were the contents correlated with any of the abiotic factors. A possible function of the starch pool as a supply for respiratory substrates under emergent conditions is discussed. All data indicate that productivity and biomass of C. leprieurii are affected by short-term abiotic and/or biotic conditions rather than controlled directly by seasonally fluctuating environmental factors. In addition, the activity of three highly specific enzymes (mannitol-1-phosphate dehydrogenase, mannitol-1-phosphatase, mannitol-dehydrogenase) and one non-specific enzyme (hexokinase), all of which are involved in the mannitol cycle, were measured in cell-free extracts every 2 weeks. All enzymes showed marked changes in activity over the year, but again no clear patterns emerged, neither with season nor in relationship to one another. On the basis of the results here, C. leprieurii is considered to be a 'season responder' rather than a 'season anticipator'. [ABSTRACT FROM AUTHOR]

Morphological and hybridization experiments were performed on Caloglossa leprieurii (Montagne) J. Agardh collected from Japan, Singapore and Australia in order to evaluate taxonomic characters of this species. Within C. leprieurii at least four mating groups were recognized from the Indo-Pacific region. These mating groups could be characterized by the blade width at the internode and the cell-row numbers on the opposite side derived from the first axial cell at the main axis, though these properties showed a certain variability even in the same plant under both field and culture conditions. The phylogenetic relationship and geographic distribution of the four mating groups are discussed. [ABSTRACT FROM AUTHOR]

The new propagule-forming red algae from southern Australia, Deucalion levirnii(Lindauer) gen. Et comb. Nov. and Anisoschizus propaguli gen. Et sp. nov., are described and defined largely on their development in laboratory culture. Deucalion is included in the tribe Comp-sothamnieae on the basis of its subapical procarp and alternate disticlous branching. It differs from the other genera included in that tribe in that it produces 3-celled propagules, polysporangia, a subapical cell of the fertile axis which bears 3-pericentral cells, and an apparently post-fertilization involucre which develops from the hypogenous and sub-hypogenous cells of the fertile axis. Its gametophyle morphology has been elucidated in culture, as only sporophytes are known from the field. Gametophytes do not appear to produce propagules. Anisoschizus is provisionally included in the tribe Spermothamnieae on the basis of its subdichotomous branching, possession of a prostrate system and the of a prostrate system and the production of polysporangia. It differs from the other genera of the tribe in the production of 2-celled propagules. Observation on the germination of the "monosporangia" of Mazoyerella arachnoidea and Monosporus spp. Indicate that they are analagous to the propagules of Deucalion and Anisoschizus. The mature of these propagules and their role in recycling the parent plant are discussed and contrasted with true monosporangia It is recommended that Monosporus be maintained as a from genus containing representalives from more than one tribe, as exemplified by plants from Lord Howe I, provisionally identified as M. indicus Boergesen which have both prostrate and erect, as opposed to only erect, axes. [ABSTRACT FROM AUTHOR]

• Maximum entropy species distribution modelling methods were compared for 8 seaweeds • Suitability for farming novel species was predicted in existing aquaculture zones • Forward selection models were most parsimonious and had good predictive accuracy • A Cauchy prior approach can be used when maximum likelihood fails due to separation Maximum entropy (maxent) modelling is a widely used method for developing species distribution models (SDMs), but default maxent modelling methods can result in overly complex models with poor transferability. Methods suggested to reduce overfitting include increasing regularisation, using only linear and quadratic features, or applying forward selection of predictors using maximum likelihood (ML) methods. We built models using these options to determine environmental suitability within existing aquaculture zones for eight seaweed species, four red (Rhodophyta: Florideophyceae) and four brown (Ochrophyta: Phaeophyceae), that are being investigated for aquaculture in southern Australia. Forward selection models were the most parsimonious, but we encountered failure of ML methods for Pterocladia lucida (Rhodophyta) due to separation. Separation is a known issue for logistic regression and has recently been recognised in maxent models. Separation occurs where a variable, or combination of variables, is a perfect predictor for a binary response, here, species occurrence, and results in ML parameter estimates tending to infinity. One method for obtaining finite parameter estimates under separation is to apply a Cauchy prior distribution for coefficients. We therefore also built models for each species using a Cauchy-prior version of the forward selection method, and found that these models performed similarly to those built with ML methods. Default models achieved marginally higher predictive performance than other options based on training data metrics, but simpler models performed equivalently to, or better than, default models at predicting independent presence-absence test data. Predictive performance using test data varied considerably between species, but the difference in performance between models within each species was generally small. Our results confirm the concern that default maxent models may suffer from over-fitting and poor transferability. Model transferability and interpretability were important for our purpose, hence, based on the principle of parsimony, forward selection models were preferred. We also found that forward selection models retained similar predictive performance to the best model as assessed by each metric, further supporting use of these models. Where ML methods failed due to separation, the use of the Cauchy-prior method was a viable alternative. Predictions for the region of interest (Spencer Gulf, South Australia) were generated using the most parsimonious models, and Solieria robusta (Rhodophyta) showed the highest predicted suitability of the eight candidate species within existing aquaculture zones, especially in northern Spencer Gulf. Predicted suitability was low for the other Rhodophyta considered, while each of the Phaeophyceae showed moderate to high suitability in at least some southern Spencer Gulf aquaculture zones. These model results help to inform selection of the best candidate species and suitable farming areas for future research. Image, graphical abstract [ABSTRACT FROM AUTHOR]