MOLECULAR PHYLOGENY OF THE UPRIGHT ERYTHROPELTIDALES (COMPSOPOGONOPHYCEAE,RHODOPHYTA): MULTIPLE CRYPTIC LINEAGES OF ERYTHROTRICHIA CARNEA1

The phylogeny of morphologically simple algae is problematic due to insufficient morphological characters to aid in distinguishing species and relationships. The problem is further compounded because multiple evolutionary lineages of morphologically similar species occur in most well‐sampled biogeographic locations; therefore, location cannot be used as a proxy for species. The phylogeny of the upright members of the Erythropeltidales is partially clarified by combining molecular data, unialgal culture observations, and worldwide sampling. Our results show that there are several well‐supported lineages within the Erythropeltidales with only two morphologically recognizable taxa at present. The first is the genus Porphyrostromium, with a well‐developed basal crust, which includes two Erythrotrichia species (Porphyrostromium ligulatum comb. nov. and Porphyrostromium pulvinatum comb. nov.). The second is the branched species Erythrotrichia welwitschii (Rupr.) Batters. There are also six strongly supported Erythrotrichia carnea–like lineages. While not completely satisfactory, we propose that one lineage (lineage 2) with samples close to the type locality be designated as E. carnea with a specific isolate as an epitype. The lack of morphology to differentiate the other lineages leads to a taxonomy based solely on gene sequencing and molecular phylogeny, with rbcL sequences differentiating the lineages proposed. We hold off on proposing more species and genera until more data and samples can be gathered.     

TAXONOMY AND MOLECULAR PHYLOGENY OF THE RED ALGAL GENUS LENORMANDIA (RHODOMELACEAE,CERAMIALES)1

The genus Lenormandia Sonder is currently composed of nine species from Australia and New Zealand. Some of these are well known, but others are rare and ill defined. Material of all nine species has been examined and found to fall into three discrete morphological groups forming highly supported clades on analysis of 18S rDNA sequences. The first group contains four Australian‐endemic species and includes the type species L. spectabilis Sonder. Plants have a cleft apex that is not inrolled, a distinctive rhombic surface areolation pattern caused by a one‐ to two‐layered medulla of interlocking cells, lack pseudopericentral cells, and produce their reproductive structures on the blade surfaces. The type species of the genus Lenormandiopsis, L. latifolia (Harvey et Greville) Papenfuss, was found to belong to this group and is thus returned to Lenormandia where it was originally placed. Species falling into the other two groups are removed to new genera that are being described separately. One extremely rare species of Lenormandia from southwestern Australia is transferred to the delesseriacean genus Phitymophora.     

MOLECULAR PHYLOGENY OF THE GENUS KUMANOA (BATRACHOSPERMALES,RHODOPHYTA)1

Species belonging to the newly established genus Kumanoa were sampled from locations worldwide. DNA sequence data from the rbcL gene, cox1 barcode region, and universal plastid amplicon (UPA) were collected. The new sequence data for the rbcL were combined with the extensive batrachospermalean rbcL data available in GenBank. Single gene rbcL results showed the genus Kumanoa to be a well‐supported clade, and there was high statistical support for many of the terminal nodes. However, with this gene alone, there was very little support for any of the internal nodes. Analysis of the concatenated data set (rbcL, cox1, and UPA) provided higher statistical support across the tree. The taxa K. vittata and K. amazonensis formed a basal grade, and both were on relatively long branches. Three new species are proposed, K. holtonii, K. gudjewga, and K. novaecaledonensis; K. procarpa var. americana is raised to species level. In addition, the synonymy of K. capensis and K. breviarticulata is proposed, with K. capensis having precedence. Five new combinations are made, bringing the total number of accepted species in Kumanoa to 31. The phylogenetic analyses did not reveal any interpretable biogeographic patterns within the genus (e.g., K. spermatiophora from the tropical oceanic island Maui, Hawaii, was sister to K. faroensis from temperate midcontinental Ohio in North America). Previously hypothesized relationships among groups of species were not substantiated in the phylogenetic analyses, and no intrageneric classification is recommended based on current knowledge.     

NEW GENERA AND SPECIES OF CERAMIACEAE (RHODOPHYTA) FROM THE SOUTHEASTERN UNITED STATES1

Five Ceramiaceae (Rhodophyta) are reported from the offshore waters of the southeastern, warm temperate coast of the United States. These include two new monotypic genera, Calliclavula trifurcate Schneider in the Griffithsieae and Nwynea grandispora Searles in the Sphondylothamnieae, and three new species, Callithamniella silvae Searles, Ptilothamnion occidentale Searles, and Lejolisia exposita Schneider et Searles.     

TAXONOMY OF THE NEW ZEALAND-ENDEMIC GENUS PLEUROSTICHIDIUM (RHODOMELACEAE, RHODOPHYTA)

A morphological, anatomical, and molecular study of the tribe Pleurostichidieae (Rhodomelaceae, Ceramiales) is presented. New collections of its only member, Pleurostichidium falkenbergii Heydrich, have enabled a thorough re-assessment of this species from a classical-morphological standpoint and have allowed the first photographs to be made of critical features of this little-known obligate epiphyte of the brown alga Xiphophora chondrophylla (Turner) Montagne ex Harvey. The relationship of the tribe to other members of the Rhodomelaceae is considered based on analysis of 18S rDNA sequences from P. falkenbergii , 14 other rhodomelaceous species, and six outgroup taxa. Pleurostichidium falkenbergii is shown to be most closely related to the tribe Polysiphonieae and only distantly related to the Amansieae, with which it was previously associated.     

MOLECULAR SYSTEMATICS OF CERAMIUM AND CENTROCERAS (CERAMIACEAE,RHODOPHYTA) FROM BRAZIL1

Morphological investigations identified 11 Ceramium Roth species, of the 18 previously reported from Brazil. Phylogenetic analyses of sequences of the chloroplast‐encoded rbcL gene confirmed the presence of seven of these species. Three other species are reported from Brazil for the first time. Ceramium affine Setchell & Gardner and C. filicula Harvey ex Womersley were previously known only from the Pacific Ocean (Mexico and Australia, respectively). A new species, C. fujianum Barros‐Barreto et Maggs sp. nov., is described here. Its general habit is similar to that of C. strictum sensu Harvey from Europe but it has one less periaxial cell than C. strictum; its cortical filament arrangement is closest to C. deslongchampsii Chauvin ex Duby, also from Europe, but whorled tetrasporangia partially covered by cortical cells differ strikingly from the naked protruding tetrasporangia of C. deslongchampsii. Ceramium species in which each periaxial cell cuts off transversely only a single basipetal cell formed a robust clade. The genus Ceramium as represented in Brazil is not monophyletic with respect to Centroceras Kützing and Corallophila Weber‐van Bosse; Ceramium nitens, which has axial cells completely covered by rounded cortical cells formed by acropetal and basipetal filaments, did not group with any Ceramium clade but was weakly allied to a species of Corallophila. All three Brazilian Centroceras sequences were attributed to a single species, C. clavulatum.     

MORPHOLOGY,MOLECULAR PHYLOGENY AND TAXONOMY OF TWO NEW SPECIES OF PLEODORINA (VOLVOCEAE,CHLOROPHYCEAE)1

The volvocacean genus Pleodorina has been morphologically characterized as having small somatic cells in spheroidal colonies and anisogamous sexual reproduction with sperm packets. In this study we examined two new species that can be assigned to the genus Pleodorina based on morphology: P. starrii H. Nozaki et al. sp. nov. and P. thompsonii F. D. Ott et al. sp. nov. P. starrii was collected from Japan and had 32‐ or 64‐celled colonies with anterior somatic cells and spheroidal individual cellular sheaths that were weakly attached to each other within the colonial envelope. P. thompsonii from Texas (USA) exhibited four or 12 somatic cells in the anterior pole of 16‐ or 32‐celled colonies, respectively, and had a single large pyrenoid in the chloroplast of mature reproductive cells. The chloroplast multigene phylogeny placed P. starrii and P. indica (Iyenger) H. Nozaki in a clade that was robustly separated from the type species P. californica Shaw and P. japonica H. Nozaki. Pleodorina thompsonii was resolved as a basal branch within a large monophyletic group (Eudorina group) composed of Eudorina, Pleodorina and Volvox (excluding section Volvox). Thus, Pleodorina was found among three separate lineages within the Eudorina group in which Eudorina and Volvox were also resolved as nonmonophyletic. The DNA sequences from additional species/strains as well as recognition of morphological attributes that characterize the monophyletic groups within the Eudorina group are needed to construct a natural generic classification within these members of the Volvocaceae.     

MOLECULAR PHYLOGENY OF SELECTED MEMBERS OF THE ORDER THALASSIOSIRALES (BACILLARIOPHYTA) AND EVOLUTION OF THE FULTOPORTULA1

Recent phylogenetic studies of the diatoms indicate that members of the order Thalassiosirales occupy an interesting position in the diatom evolutionary tree. Despite their radial morphology and scaly auxospores, they are consistently recovered in molecular analyses as a member of subdivision Bacillariophytina and a sister clade to non‐fultoportulate and non‐radial lithodesmioids. This study included 46 species from nine traditionally accepted extant genera, and analyzed 43 nuclear small subunit (SSU) rRNA sequences in parallel with a survey of the variation in fultoportula structure. Three possible scenarios leading to the evolution of the fultoportula are discussed in the context of molecular and morphological similarities between the examined Thalassiosirales and their SSU rRNA sister clade Lithodesmiales. We speculate that the fultoportula might be derived by a modification of either a cribrum in an areola (fultoportula within an areola), or structures similar to marginal ridges now seen in lithodesmioids around a cluster of poroids (fultoportula in a tube), or finally, that the central fultoportula may have an origin different from the marginal fultoportulae. Our data confirm that fultoportula‐bearing diatoms constitute a natural phylogenetic group. The families Thalassiosiraceae, Skeletonemaceae, and Stephanodiscaceae and the genus Thalassiosira Cleve were unexpectedly found to be paraphyletic. Further, Cyclotella Kutz. and Stephanodiscus Ehr. may not be closely related and some species of these genera are more closely allied to other species of Thalassiosira. The generitype, T. nordenskioeldii, is embedded within a large poorly structured cluster of species that includes several members of Thalassiosira, Planktoniella sol, Minidiscus trioculatus, and two members of Stephanodiscus. An emendment of the order Lithodesmiales and the family Lauderiaceae are proposed.     

MOLECULAR PHYLOGENY AND EVOLUTION OF RED ALGAL PARASITES: A CASE STUDY OF BENZAITENIA,JANCZEWSKIA, AND ULULANIA (CERAMIALES)1

A molecular phylogenetic study of red algal parasites commonly found in the Northwestern Pacific and the Hawaiian Islands was undertaken. Four species, Benzaitenia yenoshimensis Yendo, Janczewskia hawaiiana Apt, J. morimotoi Tokida, and Ululania stellata Apt et Schlech (Ceramiales), are parasitic on rhodomelacean species belonging to the tribes Chondrieae and Laurencieae. Although Janczewskia and Ululania are classified in the same tribes as their host species, the taxonomic placement of Benzaitenia has been controversial. To infer the phylogenetic positions of these parasites and to clarify the relationships between the parasites and their hosts, phylogenetic analyses of partial nuclear SSU and LSU rRNA genes and the cox1 gene were performed. The SSU rRNA gene analyses clearly show that both Janczewskia species are positioned within the Laurencia s. str. clade with their host species, while Benzaitenia and Ululania are placed in the Chondrieae clade. According to these analyses, J. hawaiiana and U. stellata are not sister to their current hosts; in contrast, B. yenoshimensis and J. morimotoi are closely related to their current hosts. These data suggest that J. hawaiiana and U. stellata have likely evolved from species other than their current hosts and have switched hosts at some point in their evolutionary history. Likelihood ratio tests do not support the monophyly of J. hawaiiana and J. morimotoi, suggesting multiple origins of parasitism within Laurencia s. str.     

ANALYSIS OF SPATIAL AND TEMPORAL DIVERSITY AND DISTRIBUTION OF PORPHYRA (RHODOPHYTA) IN SOUTHEASTERN NEW ZEALAND SUPPORTED BY THE USE OF MOLECULAR TOOLS1

Molecular studies have shown that New Zealand’s rocky shores are a habitat for >30 species of Porphyra, but little is known of their seasonal and zonal distribution. The spatial and temporal distribution of bladed Porphyra gametophytes at Brighton Beach, southeast New Zealand, were monitored for 32 months. Molecular markers were used for species identification, and a total of nine species was observed as being present during this time. Two species, P. cinnamomea and Porphyra sp. “ROS 54,” were the most common, and both were present for most months, while the remaining seven species were present sporadically, for only a few weeks at a time. P. cinnamomea W. A. Nelson and Porphyra sp. “ROS 54” were most common in the midintertidal, and both showed a similar seasonality with the highest presence during spring. They also showed a similar trend of seasonal dieback resulting in at least 1 month (May) in two consecutive years when they were both absent. This is one of the few studies investigating spatial and temporal distribution within a genus and over a 3‐year period. Our results show no distinct intertidal zonation patterns within the genus, and we conclude that morphologically similar species in a similar habitat rely on physiological mechanisms for survival.     

DEFINING THE MAJOR LINEAGES OF RED ALGAE (RHODOPHYTA)1

Previous phylogenetic studies of the Rhodophyta have provided a framework for understanding red algal phylogeny, but there still exists the need for a comprehensive analysis using a broad sampling of taxa and sufficient phylogenetic information to clearly define the major lineages. In this study, we determined 48 sequences of the PSI P700 chl a apoprotein A1 (psaA) and rbcL coding regions and established a robust red algal phylogeny to identify the major clades. The tree included most of the lineages of the Bangiophyceae (25 genera, 48 taxa). Seven well‐supported lineages were identified with this analysis with the Cyanidiales having the earliest divergence and being distinct from the remaining taxa; i.e. the Porphyridiales 1–3, Bangiales, Florideophyceae, and Compsopogonales. We also analyzed data sets with fewer taxa but using seven proteins or the DNA sequence from nine genes to resolve inter‐clade relationships. Based on all of these analyses, we propose that the Rhodophyta contains two new subphyla, the Cyanidiophytina with a single class, the Cyanidiophyceae, and the Rhodophytina with six classes, the Bangiophyceae, Compsopogonophyceae, Florideophyceae, Porphyridiophyceae classis nov. (which contains Porphyridium, Flintiella, and Erythrolobus), Rhodellophyceae, and Stylonematophyceae classis nov. (which contains Stylonema, Bangiopsis, Chroodactylon, Chroothece, Purpureofilum, Rhodosorus, Rhodospora, and Rufusia). We also describe a new order, Rhodellales, and a new family, Rhodellaceae (with Rhodella, Dixoniella, and Glaucosphaera).     

A MOLECULAR PHYLOGENY OF THE GELIDIALES (RHODOPHYTA) BASED ON ANALYSIS OF PLASTID rbcL NUCLEOTIDE SEQUENCES1

Parsimony analyses of rbcL nucleotide. sequences were used to develop hypotheses of relationships among taxa in the taxonomically difficult order Celidiales including species from seven currently recognized genera: Capreolia, Gelidiella, Gelidium, Onikusa, Pterocladia, Ptilophora, and Suhria. Nucleotide. sequences of rbcL from red algae are variable and provide a large number of informative characters for phylogenetic analysis, yet the absence of insertion/deletion mutations allows for the unambiguous alignment of sequences. Species were resolved into 10 well-.supported major clades representing genera and species complexes. The topological positions of these 10 clades within trees are also well supported and indicate that Gelidium and Pterocladia as currently circumscribed are not monophyletic. These results call for a revision of the classification of the Gelidiales .     

MOLECULAR SYSTEMATICS OF THE FLORIDEOPHYCEAE (RHODOPHYTA) USING NUCLEAR LARGE AND SMALL SUBUNIT rDNA SEQUENCE DATA

Sequence data are presented for approximately 85% of the nuclear large subunit (LSU) rDNA gene for one member of the Bangiophyceae and 47 members of the Florideophyceae, the latter representing all but one of the currently recognized florideophyte orders. Distance, parsimony, and maximum likelihood analyses of these data were used to generate phylogenetic trees, and bootstrap resampling was implemented to infer robustness for distance and parsimony results. LSU phylogenies were congruent with published nuclear small subunit (SSU) rDNA results in that four higher level florideophyte lineages were resolved: lineage 1, containing the order Hildenbrandiales; lineage 2, recovered only under distance analysis, composed of the orders Acrochaetiales, Balliales, Batrachospermales, Corallinales, Nemaliales, Palmariales, and Rhodogorgonales; lineage 3, containing the Ahnfeltiales; and lineage 4, composed of the orders Bonnemaisoniales, Ceramiales, Gelidiales, Gigartinales, Gracilariales, Halymeniales, Plocamiales, and Rhodymeniales. Analyses were also performed on a combined LSU–SSU data set and an SSU-only data set to account for differences in taxon sampling relative to published studies using this latter gene. Combined LSU–SSU analyses resulted in phylogenetic trees of similar topology and support to those obtained from LSU-only analyses. Phylogenetic trees produced from SSU-only analyses differed somewhat in particulars of branching within lineages 2 and 4 but overall were congruent with the LSU-only and combined LSU–SSU results. We close with a discussion of the phylogenetic potential that the LSU has displayed thus far for resolving relationships within the Florideophyceae.     

A PHYLOGENETIC STUDY OF PARASITIC GENERA PLACED IN THE FAMILY CHOREOCOLACACEAE (RHODOPHYTA)1

Red algal parasites are common and have a unique type of development in which parasite nuclei are transferred to host cells and “control” host cell development. Previous phylogenetic studies have concentrated on parasites closely related to their hosts, termed adelphoparasites. A second set of parasites, usually classified in a different family or tribe from their host, termed alloparasites, have not been studied phylogenetically. This study concentrates on the wholly parasitic family, the Choreocolacaceae (Gigartinales). Using small subunit rDNA sequence data, we found that all the parasites studied are within the same family as their host. Our data support the placement of Holmsella, species of which parasitize Gracilaria and Gracilariopsis, in the order Gracilariales and suggest that Holmsella is an old parasitic genus. Most other species of the Choreocolacaceae parasitize species of the Rhodomelaceae. The one exception is the hyperparasitism between Harveyella mirabilis (Reinsch) F. Schmitz et Reinke (Rhodomelaceae) and the parasite Gonimophyllum skottsbergii Setchell (Delesseriaceae). The parasites Bostrychiocolax australis Zuccarello et West and Dawsoniocolax bostrychiae (Joly et Yamaguishi‐Tomita) Joly et Yamaguishi‐Tomita are placed within the tribe Bostrychiae as are their hosts. Harveyella mirabilis has a single origin and has switched hosts several times during its passage between the Atlantic and Pacific Oceans. Evidence does not support the continued recognition of the family Choreocolacaceae. Our results also indicate that the distinction between adelphoparasites and alloparasites is unwarranted, with a continuum between newly evolved parasites closely related to their hosts and parasites less closely related to their hosts.     

TAXONOMY OF THE FLATTENED SOLIERIACEAE (RHODOPHYTA) IN BRAZIL: AGARDHIELLA AND MERISTIELLA1

Taxonomic studies of an extensive collection of flattened members of the Solieriaceae considered by many authors to be species of Agardhiella, Eucheuma, Meristotheca, and Meristiella lead us to conclude that they represent only two genera in Brazil: Agardhiella, including A. ramosissima (Harvey) Kylin and A. floridana (Kylin) Gabrielson ex Guimarães et Oliveira, and Meristiella, with only one species, M. gelidium (J. Agardh) Cheney et Gabrielson. Accordingly, we propose that 1) Meristotheca gigartinoides Joly et Ugadim be synonymized with Agardhiella floridana, and 2) Meristiella echinocarpa (Areschoug) Cheney et Gabrielson and M. schrammii (P. et H. Crouan) Cheney et Gabrielson be synonymized with Meristiella gelidium.     

PSEUDOCODIUM MUCRONATUM,A NEW SPECIES FROM NEW CALEDONIA,AND AN ANALYSIS OF THE EVOLUTION OF CLIMATIC PREFERENCES IN THE GENUS (BRYOPSIDALES,CHLOROPHYTA)1

A new species, Pseudocodium mucronatum, is described from the Chesterfield platform off the west coast of New Caledonia. The species differs from its congeners in having mucronate utricules. A phylogenetic analysis of rbcL and tufA sequences showed that P. mucronatum is most closely associated with P. natalense De Clerck, Coppejans et Verbruggen and P. devriesii Weber Bosse, with which it shares compressed axes, depressed apices, and plastids in the utricles and the medullar siphons. We studied the evolution of climatic and ecological preferences in the genus using an interdisciplinary approach consisting of relaxed molecular clock analysis, extraction of macroecological data from satellite imagery in a geographic information system (GIS) framework, and ancestral character state estimation. It was shown that the genus originated in tropical waters during the Early Mesozoic. Whereas the P. floridanum‐okinawense lineage remained tropical, the lineage including P. natalense, P. devriesii, and P. mucronatum gradually invaded more temperate waters during Cenozoic times. Except for P. devriesii, which occurs in shallow and intertidal habitats, all Pseudocodium species grow in deep‐water habitats, and this ecological preference appears to be ancestral.     

CERAMIUM INKYUII SP. NOV. (CERAMIACEAE,RHODOPHYTA) FROM KOREA: A NEW SPECIES BASED ON MORPHOLOGICAL AND MOLECULAR EVIDENCE1

Ceramium inkyuii sp. nov. is newly described based on samples collected from the east coast of Korea and compared with similar species such as C. paniculatum and C. tenerrimum. The new species is characterized by pseudo‐dichotomously branched thalli with a twist in the upper part, a single row of spines on the abaxial side, strongly inrolled apices, and the presence of gland cells. In contrast, C. paniculatum has alternate branches and lacks gland cells, and C. tenerrimum is spineless and also lacks gland cells. Ceramium inkyuii was observed to be an annual species producing tetrasporangia in the spring to summer and cystocarps in the fall. Plastid‐encoded rbcL and nuclear small subunit (SSU) rDNA sequences were determined in four samples of C. inkyuii from different locations and six samples of four putative relatives. All four C. inkyuii replicates from three different locations had identical sequences of each gene, and the interspecific sequence divergences were enough to warrant its natural entity. The phylogenies of the rbcL and SSU rDNA sequences also indicate the monophyly of C. inkyuii. The spinous C. inkyuii was more closely related to the spineless C. tenerrimum than to the spinous C. paniculatum.     

THE GENUS PIKEA (DUMONTIACEAE,RHODOPHYTA) IN ENGLAND AND THE NORTH PACIFIC: COMPARATIVE MORPHOLOGICAL,LIFE HISTORY,AND MOLECULAR STUDIES1

A Pikea species attributed to Pikea californica Harvey has been established in England since at least 1967. Previously, this species was believed to occur only in Japan and Pacific North America. Comparative morphological studies on field-collected material and cultured isolates from England, California, and Japan and analysis of organellar DNA restriction fragment length polymorphisms, detected using labeled organellar DNA as a non-radioactive probe, showed that English Pikea is conspecific with P. californica from California. Both populations consist of dioecious gametophytes with heteromorphic life histories involving crustose tetrasporophytes; 96% of organellar DNA bands were shared between interoceanic samples. A second dioecious species of Pikea, P. pinnata Setchell in Collins, Holden et Setchell, grows sympatrically with P. californica near San Francisco but can be distinguished by softer texture, more regular branching pattern, and elongate cystocarpic axes. Pikea pinnata and P. californica samples shared 49–50% of organellar DNA bands, consistent with their being distinct species. Herbarium specimens of P. robusta Abbott resemble P. pinnata in some morphological features but axes are much wider; P. robusta may represent a further, strictly sub-tidal species but fertile material is unknown. Pikea thalli from Japan, previously attributed to P. californica and described here as Pikea yoshizakii sp. nov., are monoecious and show a strikingly different type of life history. After fertilization, gonimoblast filaments grow outward through the cortex and form tetrasporangial nemathecia; released tetraspores develop directly into erect thalli. Tetrasporoblastic life histories are characteristic of certain members of the Phyllophoraceae but were previously unknown in the Dumontiaceae. Japanese P. yoshizakii shared 55 and 56% of organellar DNA bands with P. californica and P. pinnata, respectively; phylogenetic analysis indicated equally distant relationships to both species. Pikea yoshizakii or a closely similar species with the same life history occurs in southern California and Mexico.     

SYSTEMATIC REVISION OF THE GENERA LIAGORA AND IZZIELLA (LIAGORACEAE,RHODOPHYTA) FROM TAIWAN BASED ON MOLECULAR ANALYSES AND CARPOSPOROPHYTE DEVELOPMENT,WITH THE DESCRIPTION OF TWO NEW SPECIES1

Some Liagora and Izziella distributed in Taiwan display a wide range of morphological variation and can be difficult to distinguish. To clarify species concepts, we applied DNA sequence analyses and examined carposporophyte development in detail. These studies revealed two new species, which are described herein as Izziella hommersandii sp. nov. and Izziella kuroshioensis sp. nov. I. kuroshioensis superficially resembles Izziella formosana and Izziella orientalis in that its involucral filaments subtend rather than surround the lower portion of the gonimoblast mass (= Izziella type) and a fusion cell is formed from cells of the carpogonial branch, but it can be separated by differences in the cell numbers and branching pattern of the involucral filaments, as well as thallus morphology. In contrast to other species that also bear short lateral branchlets, I. hommersandii is unique in possessing a mixture of short and long involucral filaments, a phenomenon not reported before. The length of the involucral filaments is species specific among species of Izziella and contrasts to the behavior of the involucral filaments after fertilization in species such as “Liagora”setchellii [= Titanophycus setchellii comb. nov.], in which the filaments completely envelop the gonimoblast. In addition, the cells of the carpogonial branch in Titanophycus do not fuse after fertilization to form a fusion cell. Thus, a combination of characters with respect to the behavior of the carpogonial branch and the involucral filaments after fertilization is very useful for delineating species boundaries in Izziella and for separating Titanophycus from Izziella and Liagora.