Order Batrachospermales Research Articles

Reappraisal of the genus Visia (Batrachospermales, Rhodophyta) and proposal for a new genus and species

ABSTRACT 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.

A New Species of Kumanoa (Batrachospermales, Rhodophyta) from Baiyun Mountain, Guangdong, China

Kumanoa belonging to the order Batrachospermales is the most species-rich and widely distributed genus of freshwater red algae in China. In this study, a new Kumanoa species is described and illustrated from Baiyun Mountain, Guangdong, China, based on morphological observations and phylogenetic analysis. Kumanoa baiyunensis sp. nov is morphologically distinguished from other species by presenting a small habit (0.5–1 cm tall) with abundant branching in upper part of the thallus; carposporophytes spherical and one per whorl; club-shaped trichogynes with distinct stalk; spermatangia sparse and single-grown, terminal on primary fascicles. Phylogenetic analysis based on the concatenated rbcL+COI-5P+UPA alignment places Kumanoa baiyunensis in a well-supported clade (98/0.96, bootstrap proportion/posterior probability) sister to K. faroensis (from USA) and K. spermatiophora (from Hawaii) with high divergence (rbcL: 4.9%–5.0%, COI-5P: 10.1%–10.5%, UPA: 2.3%). In addition, K. baiyunensis can be easily distinguished from ten Kumanoa species reported in China through morphological features such as small thallus size, abundant branching in upper parts of the thallus, and spermatangia sparse, single-grown, and terminal on primary fascicles. The description of this new species expands the diversity of genus Kumanoa in the world.

Revision of the Genus Sirodotia Kylin (Batrachospermales, Rhodophyta) with Description of Four New Species

Most genera of the freshwater red algal order Batrachospermales have been systematically revised using molecular and morphological data, but Sirodotia Kylin remains to be thoroughly reviewed. In this investigation, DNA sequence data for the rbcL, COI-5P and LSU markers of specimens collected worldwide were combined with morphological observations to assess their specific diversity, infer their relationships and evaluate the morphological characters relevant for species identification. Phylogenetic analyses showed the genus to be a monophyletic lineage with high support. Inter- and intra-specific divergence values were well-delineated with higher interspecific (2.1-7% and 4.4-10.5%) and lower intraspecific (0-2.4% and 0-3.8%) variations for rbcL and COI-5P sequences, respectively. LSU sequences revealed lower interspecific divergence values than the COI-5P sequences (0.7-3.3%) indicating less resolution as a barcode marker. Nine species are recognized based on DNA sequence data, morphological characters and geographic distribution. Five species were previously described (S. assamica Necchi, Rossignolo, Yasmin, J.A.West & Ganesan, S. delicatula Skuja, S. huillensis (Welwitsch ex West & GSWest) Skuja, S. kennedyi A.L.Szinte, J.C.Taylor & M.L.Vis and S. suecica Kylin) and four new species are proposed (S. amazonica Necchi, N.L.Rossignolo & M.O.Paiano, sp. nov., S. aquiloamericana Necchi, N.L.Rossignolo & M.L.Vis, sp. nov., S. cryptica Necchi, N.L.Rossignolo & M.O.Paiano, sp. nov. and S. delicatuliformis Necchi, N.L.Rossignolo & M.O.Paiano, sp. nov.). Diagnostic characters for the genus are confirmed to be carpogonia asymmetric with a basal protuberance and carposporophytes diffuse with indeterminant prostrate filaments producing determinate erect branches terminating in carposporangia. The following morphological characters were applied to distinguish species: primary fascicle cell number, spermatangial arrangement, origin of gonimoblast filament and size of carposporangia. Based on morphology, S. sinica, S. segawae and S. yutakae are proposed as synonyms of S. suecica and S. ateleia Skuja of S. delicatula. The status of three species (S. cirrhosa Skuja ex M.S.Balakr. & B.B.Chaugule, S. gardneri Skuja ex Flint and S. huangshanensis Z.X.Shi & S.L.Xie) could not be confirmed due to lack of type specimens and published information on informative diagnostic characters.

Paludicola gen. nov. and Revision of the Species Formerly in Batrachospermum Section Turfosa (Batrachospermales, Rhodophyta)

Since the first phylogenetic study of the order Batrachospermales, Batrachospermum was shown to be paraphyletic. Subsequently, sections of the genus have been methodically investigated using DNA sequences and morphology in order to propose new genera and delineate species. Batrachospermum section Turfosa is the last section with multiple species yet to be examined. New sequence data of specimens from Europe and the United States were combined with the sparse sequence data already available. Phylogenetic analyses using rbcL and COI-5P sequences showed this section to be a well-supported clade, distinct from Batrachospermum section Batrachospermum and its segregate genera. SectionTurfosa is raised to the generic rank as Paludicola gen. nov. Substantial genetic variation within the genus was discovered and 12 species are recognized based on DNA sequence data as well as morphological characters and geographic distribution. The following morphological characters were applied to distinguish species: branching pattern (pseudodichotomous or irregular), whorl size (reduced or well developed), primary fascicles (curved or straight), spermatangia origin (primary or secondary fascicles), and carposporophyte arrangement (loose or dense). Previously published species were transferred to the new genus: P.turfosa, P.keratophyta, P.orthosticha, P.phangiae, and P.periploca. Seven new species are proposed as follows: P.groenbladii from Europe; P.communis, P.johnhallii, and P.leafensis from North America; and P.aquanigra, P.diamantinensis, and P.turfosiformis from Brazil. In addition, three unsequenced species in the section, P.bakarensis, P.gombakensis, and P.tapirensis, were transferred to the new genus.

<p><strong>Affinities of four freshwater putative “Chantransia” stages (Rhodophyta) in Southern China from molecular and morphological data</strong></p>

Four putative “Chantransia” isolates were collected from four locations in Hubei and Yunnan Provinces, China. Morphological analyses were conducted on all isolates. Two specimens (HB26 and YN2) fit the morphological description of A. pygmaea, while the other two isolates (YN1 and YN3) varied in morphology, but were within the circumscription of Audouinella hermannii. Due to the fact that the morphological characters of the “Chantransia” stages of order Batrachospermales and the species of genus Audouinella are too similar to be distinguished, a molecular analysis was performed to clarify the phylogenetic position of these four isolates based on rbcL and psbA sequences. Two “pygmaea” specimens collected from Jiugong Mountain, Hubei Province (HB26) and Shimen Gorge, Yunnan Province (YN2), such as S. jiugongshanensis and S. shimenxiaensis, are proposed primarily based on the DNA sequence data generated in this study. The description of these two new species provides more molecular data for phylogenetic analysis of the genus Sheathia. In addition to these newly described species, the results strongly support that those “hermannii” isolates (YN1 and YN3) collected from Yunnan Province were the “Chantransia” of S. arcuata. However, their gametophyte stages have not been found, meaning that critical diagnostic morphological features were unavailable and molecular methods were the only means for ascertaining their phylogenetic position. Considering the extensive application of the rbcL and psbA genes in phylogenetic analyses of freshwater red algae, we recommend using these two genes to identify species when no morphological characteristics are available.

Relative expression analysis of light-harvesting genes in the freshwater alga Lympha mucosa (Batrachospermales, Rhodophyta).

Members of the freshwater red algal order Batrachospermales are often described as shade‐adapted. Nevertheless, recent ecophysiological studies have demonstrated species‐level differences in acclimation to a range of irradiances. Lympha mucosa occurs in open and shaded portions of temperate streams and is abundant during summer months, suggesting it tolerates high and low irradiances. Specimens of L. mucosa were collected from open (sun‐acclimated) or shaded (shade‐acclimated) sites and exposed to low (<20 μmol photons · m−2 · s−1) or high (220 μmol photon · m−2 · s−1) light for 72 h to examine mechanisms of photoacclimation at the transcriptional level. High‐throughput sequence data were used to design specific primers for genes involved with light harvesting and these were quantified with qPCR. The greatest significant difference in transcript abundances was observed in the psaA gene (Photosystem I P700 apoprotein), and site‐type had an effect on these responses. Shade‐acclimated thalli were 22‐fold down‐regulated at high light, whereas sun‐acclimated thalli were only 5‐fold down‐regulated. Another gene involved with Photosystem I (petF ferredoxin) was down‐regulated at high light, but only individuals from the shaded site were significantly different (4‐fold). In thalli from both sites, cpeA (Phycoerythrin alpha chain) was down‐regulated at high light. Although not statistically significant, patterns consistent with previous physiological and transcriptomic studies were uncovered, namely the inverse response of transcriptional activity in genes that encode phycobiliproteins. In support of previous ecophysiological studies of freshwater red algae, these data indicate significant transcriptional changes involving Photosystem I and phycobiliprotein synthesis are required to tolerate and grow at various irradiances.

Survey of Freshwater Red Algae from the Batrachospermales (Rhodophyta) in South Carolina

Freshwater red algae are important components of the algal flora in streams and rivers with high water quality. The order Batrachospermales is the most species-rich portion of the red algal taxa reported throughout North America. We investigated 30 stream segments in South Carolina for the presence of freshwater red algae classified within the Batrachospermales. We collected a total of 50 specimens representing 7 genera and 9 species. We documented Batrachospermum gelatinosum, B. turfosum, Kumanoa skujana, Montagnia australis, Sheathia americana, S. heterocortica, Sirodotia suecica, Tuomeya americana, and Virescentia viride-americana. We observed M. australis and T. americana from the greatest number of streams and in multiple years from the same site. We observed V. viride-americana in 3 streams; our specimens represent the only new record for the state. We generated DNA sequence data of the rbcL gene or gleaned it from the literature for 8 of the 9 taxa identified in the study and confirmed their morphological identification. We collected stream temperature, pH, and conductivity data from sites where we collected 6 of the taxa (Batrachospermum gelatinosum, B. turfosum, M. australis, Sheathia americana, T. americana, and V. viride-americana). Our records were within previously reported ranges for these taxa, although water temperatures tended to be higher than those in previous reports. Present data for the diversity of Batrachospermales in South Carolina represent 64% of the generic/infrageneric and 20% of the species diversity known for North America. This diversity may still be an underestimation of what might be detected by future studies that target more specialized habitats; taxa that are known from neighboring states but not yet reported from South Carolina might be discovered.

Temperature effects on photosynthesis in gametophytic and sporophytic stages of the freshwater red alga Sirodotia delicatula (Rhodophyta, Batrachospermales) under a global warming perspective

SUMMARYThe increase in Earth's global mean temperature due to human influence has become a major concern, with ecological consequences already being reported around the world. In tropical streams, benthic red algae belonging to the order Batrachospermales contribute to a large fraction of the community energy input and play an important role in sustaining autotrophic food webs. The Batrachospermales also have a unique life history, with heteromorphic life stages (gametophytes and sporophytes) occurring seasonally and with distinct ecological roles. Through “in vivo” chlorophyll fluorescence and dissolved oxygen evolution techniques, we evaluated the effects of projected temperature increases of two future scenarios (RCP 4.5 and RCP 8.5) on the photosynthetic response of Sirodotia delicatula gametophytes and sporophytes. In general, both chlorophyll fluorescence and dissolved oxygen showed that the RCP 8.5 scenario could severely jeopardize the photosynthetic performance of the sporophytes during the summer while also providing a stressful physiological situation to the gametophytes. Due to the crucial role of sporophytes in the development of this species, results indicate that this predicted scenario could affect this species. Given the position of these organisms at the base of the food web in tropical lotic environments, especially in shaded low‐order streams, such impact could generate unforeseen cascade effects on higher trophic levels.

Complete mitochondrial genomes of six species of the freshwater red algal order Batrachospermales (Rhodophyta)

Only two mitochondrial (mt) genomes had been reported in members of the red algal order Batrachospermales, which are confined to freshwater habitats. Additional mt genomes of six representative members (Batrachospermum macrosporum, Kumanoa ambigua, K. mahlacensis, Paralemanea sp., Sheathia arcuata, and Sirodotia delicatula) were sequenced aiming to gain insights on the evolution of their mt genomes from a comparative analysis with other red algal groups. Mt genomes sequenced had the following characteristics: lengths ranging between 24,864 nt and 29,785 nt, 22 to 26 protein-coding genes, G + C contents of 21.3 to 30.7%, number of tRNA of 16 to 37, non-coding DNA from 3.8% to 14.8%. Comparative analysis revealed that mt genomes in Batrachospermales are highly conserved in terms of genome size and gene content and synteny. Phylogenetic analyses based on COI nucleotide data revealed high bootstrap support only for the genera usually recovered in the phylogenetic analyses but no support for supra-generic groups. The insertion of a group II intron carrying an ORF coding for the corresponding intron maturase interrupting the COI gene was observed in Paralamenea sp. and accounted for its larger genome in comparison to the other Batrachospermales mt genomes.

Organization of plastid genomes in the freshwater red algal order Batrachospermales (Rhodophyta).

Little is known about genome organization in members of the order Batrachospermales, and the infra-ordinal relationship remains unresolved. Plastid (cp) genomes of seven members of the freshwater red algal order Batrachospermales were sequenced, with the following aims: (i) to describe the characteristics of cp genomes and compare these with other red algal groups; (ii) to infer the phylogenetic relationships among these members to better understand the infra-ordinal classification. Cp genomes of Batrachospermales are large, with several cases of gene loss, they are gene-dense (high gene content for the genome size and short intergenic regions) and have highly conserved gene order. Phylogenetic analyses based on concatenated nucleotide genome data roughly supports the current taxonomic system for the order. Comparative analyses confirm data for members of the class Florideophyceae that cp genomes in Batrachospermales is highly conserved, with little variation in gene composition. However, relevant new features were revealed in our study: genome sizes in members of Batrachospermales are close to the lowest values reported for Florideophyceae; differences in cp genome size within the order are large in comparison with other orders (Ceramiales, Gelidiales, Gracilariales, Hildenbrandiales, and Nemaliales); and members of Batrachospermales have the lowest number of protein-coding genes among the Florideophyceae. In terms of gene loss, apcF, which encodes the allophycocyanin beta subunit, is absent in all sequenced taxa of Batrachospermales. We reinforce that the interordinal relationships between the freshwater orders Batrachospermales and Thoreales within the Nemaliophycidae is not well resolved due to limited taxon sampling.

Complete mitochondrial genome of the freshwater red alga Lympha mucosa (Rhodophyta)

We present the complete mitochondrial genome of a newly described freshwater red alga Lympha mucosa. The genome was sequenced using the Illumina MiSeq platform. The circular mitochondrial genome is 25,191 bp, contains 46 genes (24 CDS, 20 tRNA, and 2 rRNA), and has an overall GC content of 27.5%. Phylogenetic analyses of the cox1 gene show the placement of Lympha mucosa within the strictly freshwater order Batrachospermales. The four mitochondrial genomes within the subclass Nemaliophycidae sequenced to date are highly conserved in terms of genome size, gene content, and gene synteny.

A New Record of the Rare Freshwater Red AlgaTuomeya americana(Batrachospermaceae, Rhodophyta) from Connecticut

Members of the freshwater red algal order Batrachospermales are widely distributed across the northeastern US. Among them, the monotypic Tuomeya is the least reported genus, showing a sporadic distribution and being documented by decreasingly frequent reports. This study presents a new find of T. americana from Connecticut and is the first published Connecticut record of the species since 1890. I conducted an extensive literature search and review of herbarium records in order to summarize the known occurrence data for T. americana in New England. From my compilation it appears that the species has been reported with decreasing frequency, but it cannot be determined whether the sparse records reflect a true rarity and decline of T. americana or dwindling floristic efforts in New England. The present study underscores the importance of continuous floristic work aiming to better understand the distributions of algal species.

Phylogeography of the freshwater red alga Sirodotia (Batrachospermales, Rhodophyta) in Brazil

SummaryConsidering the lack of knowledge on genetic variation on members of the freshwater red algal of the order Batrachospermales in tropical regions, phylogeographic patterns in Sirodotia populations were investigated using two mitochondrial regions: the cox2‐3 spacer and partial cox1 gene (barcode). Individuals identified as Sirodotia delicatula were analyzed from 14 stream segments across its distribution in Brazil. Phylogenetic analyses based on the ribulose‐1,5‐bisphosphate carboxylase/oxygenase large sub‐unit gene showed three clades, one representing S. delicatula, from all locations in southeastern Brazil and other regions from Brazil. The remaining samples formed two clades, which were highly divergent and distantly positioned from those of S. delicatula: 2.5–2.7% and 3.4–3.7%. This level of variation would warrant the species split of these taxa from mid‐western Brazil. A total of eight cox2‐3 spacer and nine cox1 haplotypes were observed among the 122 individuals studied. One location had two cox2‐3 haplotypes and three locations had two cox1 haplotypes; all others had a single dominant haplotype each. The existence of high intraspecific genetic variation among individuals of distinct locations (several haplotypes), but little variation within a location seems to be a pattern for the Batrachospermales. Haplotype networks showed low variation among the haplotypes from southeastern Brazil (10 locations with divergence of 0.3–1.1% for cox2‐3, 0.1–0.3% for cox1) and high variation among the haplotypes from the mid‐west region (four locations, 4.0–9.3% for cox2‐3, 6.2–8.4% for cox1). Thus, the present data clearly suggest the existence of cryptic species in Sirodotia in Brazil.

Contrasting intra versus interspecies DNA sequence variation for representatives of the Batrachospermales (Rhodophyta): Insights from a DNA barcoding approach

SUMMARYSixty‐five accessions of the species‐rich freshwater red algal order Batrachospermales were characterized through DNA sequencing of two regions: the mitochondrial cox1 gene (664 bp), which is proposed as the DNA barcode for red algae, and the UPA (universal plastid amplicon) marker (370 bp), which has been recently identified as a universally amplifying region of the plastid genome. upgma phenograms of both markers were consistent in their species‐level relationships, although levels of sequence divergence were very different. Intraspecific variation of morphologically identified accessions for the cox1 gene ranged from 0 to 67 bp (divergences were highest for the two taxa with the greatest number of accessions; Batrachospermum helminthosum and Batrachospermum macrosporum); while in contrast, the more conserved universal plastid amplicon exhibited much lower intraspecific variation (generally 0–3 bp). Comparisons to previously published mitochondrial cox2–3 spacer sequences for B. helminthosum indicated that the cox1 gene and cox2–3 spacer were characterized by similar levels of sequence divergence, and phylogeographic patterns based on these two markers were consistent. The two taxa represented by the largest numbers of specimens (B. helminthosum and B. macrosporum) have cox1 intraspecific divergence values that are substantially higher than previously reported, but no morphological differences can be discerned at this time among the intraspecific groups revealed in the analyses. DNA barcode data, which are based on a short fragment of an organellar genome, need to be interpreted in conjunction with other taxonomic characters, and additional batrachospermalean taxa need to be analyzed in detail to be able to draw generalities regarding intraspecific variation in this order. Nevertheless, these analyses reveal a number of batrachospermalean taxa worthy of more detailed DNA barcode study, and it is predicted that such research will have a substantial effect on the taxonomy of species within the Batrachospermales in the future.

AUTHORSHIP OF THE FRESHWATER RED ALGAL SPECIES TUOMEYA AMERICANA (BATRACHOSPERMACEAE)

Tuomeya Harvey (1858) is recognized as a genus of freshwater red algae of the order Batrachospermales (Kumano 2002; Vis et al. 1998). Tuomeya americana was originally described and reported from the eastern half of North America (Bailey 1848; Flint 1948; Harvey 1858; Kaczmarczyk et al. 1993; Kutzing 1857; Prescott 1951; Sheath and Hymes 1980; Smith 1950). Although Sheath (2003) referred to T. americana as unique to North America, the species now is known also from South Africa (Borge 1928), Finland (Eloranta and Kwandrans 1996), India (Babu and Baluswami 2005), and China (Feng et al. 2007). The record of T. americana from Australia (from a Master’s thesis and reported by Day et al. 1995) is based on a misidentification (T. Entwisle, Royal Botanic Gardens Sydney, pers. comm.). A second species reported from North America, T. grandis (Wolle) Wolle (Wolle 1887), was transferred to Paralemanea (Kumano 2002). An additional species, T. gibberosa Kumano (1978), was described from Malaysia but later transferred to Batrachospermum (Kumano 1986). Necchi and Entwisle’s (1990) proposal to relegate Tuomeya to the status of a section within Batrachospermum was opposed by Kaczmarczyk et al. (1993) and has not been subsequently followed (Vis et al. 1998). Ever since Papenfuss (1958) proposed the binomial Tuomeya americana (Kutz.) Papenf. to replace the taxonomic synonym T. fluviatilis Harv., the authorship of the former name has persisted in the literature, including contemporary publications and on-line resources (Bourrelly 1970; Entwisle 1984; Guiry and Guiry 2007; Kaczmarczyk et al. 1993; Kapraun et al. 2007; Kumano 2002; Sheath 2003; Vis and Entwisle 2000; Vis et al. 1998, 2005). Papenfuss (1958) pointed out that Kutzing’s (1857) Baileya americana predated RHODORA, Vol. 109, No. 940, pp. 464–467, 2007 E Copyright 2007 by the New England Botanical Club

Nuclear rDNA sequences from Ballia prieurii support recognition of Balliopsis gen. nov. in the Batrachospermales (Florideophyceae, Rhodophyta)

Nuclear small-subunit and partial large-subunit rDNA sequences were determined for the freshwater rhodophyte species Ballia prieurii, from northern Brazil, to assess its relationship to the marine species that have recently been transferred to a new order, Balliales, in the Florideophyceae. Ballia prieurii unequivocally associated with species of the freshwater order Batrachospermales, rather than with the marine Balliales, in all molecular analyses. In addition to habitat, asexual reproduction by monosporangia in the freshwater species of Ballia is consistent with inclusion in the Batrachospermales and has not been reported for any marine Ballia species, which reproduce exclusively by asexual tetrasporangia. As B. prieurii is distinct in morphological and molecular features from all other members of Batrachospermales, a new genus Balliopsis G.W. Saunders & Necchi gen. nov. is proposed to accommodate this species, which becomes Balliopsis prieurii (Kützing) G.W. Saunders & Necchi comb. nov. Previously published morphological and anatomical observations indicate that a second freshwater species of Ballia, B. pinnulata, is clearly related to Balliopsis prieurii and it too is transferred to the new genus. The familial affinities of Balliopsis are discussed, but Balliopsis is left as a genus Incertae sedis within the Batrachospermales.

INSIGHTS INTO THE PHYLOGENY OF THE BATRACHOSPERMALES (RHODOPHYTA) FROM rbcL SEQUENCE DATA OF AUSTRALIAN TAXA

Thirteen representatives of the freshwater red algal order Batrachospermales from Australia were analyzed with previously published sequences in a phylogenetic analysis of RUBISCO large subunit (rbcL) gene sequence data. The newly sequenced taxa represented putative endemics to the Australia–New Zealand region (Batrachospermum antipodites, B. deminutum, B. discors, B. kraftsii, B. theaquum, B. wattsii, and Nothocladus lindaueri) and more cosmopolitan species (B. ambiguum, B. atrum, B. cayennense, B. gelatinosum[two samples], and Sirodotia suecica). From parsimony, distance, and maximum likelihood analyses, three clades of batrachospermalean taxa were suggested: a “mixed” clade composed of taxa sampled from Australia and North America, a clade of primarily Australian collections, and a clade of predominantly North American samples. The latter two clades appeared to be more closely related to each other than to the mixed clade. It is hypothesized that the Australian clade may be of Gondwanic origin, but more sampling of other continents is needed to confirm this statement. The collections of B. gelatinosum from Australia did not form a monophyletic clade with B. gelatinosum from North America, and a new species, B. pseudogelatinosum, is proposed for the Australian collections. Unlike the B. gelatinosum results, B. atrum and S. suecica samples from Australia were very closely related to collections of the same species from other continents. With the addition of B. deminutum and B. ambiguum to the analysis, Batrachospermum section Contorta is shown to be monophyletic if section Hybrida is included. The expansion of the description for section Contorta is proposed to accommodate species from section Hybrida. The validity of Batrachospermum section Aristata is questioned based on the distant relationship of B. macrosporum and B. cayennense.

PHYLOGENY OF THE BATRACHOSPERMALES (RHODOPHYTA) INFERRED FROM rbcL AND 18S RIBOSOMAL DNA GENE SEQUENCES

The sequence data from the large subunit of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (rbcL) gene and 18S ribosomal DNA (small subunit) of taxa in the freshwater rhodophyte order Batrachospermales were used to construct phylogenetic hypotheses. Taxa examined in this study represent four families, eight genera, and six sections of the genus Batrachospermum. In addition, Rhododraparnaldia oregonica Sheath, Whittick et Cole, was included in the analysis because it shares particular ultrastructural, reproductive, and morphological characteristics with members of the Batrachospermales and Acrochaetiales. The trees generated from each gene, as well as a combined data set, were largely congruent. Rhododraparnaldia consistently occurs on an early branch within the Acrochaetiales–Palmariales clade and does not appear to be a member of the Batrachospermales. In addition,Thorea violacea Bory de St. Vincent was not closely related to the other taxa of the Batrachospermales in all trees and hence the family Thoreaceae does not appear to be a natural grouping within this order. All other taxa analyzed, which are presently classified within this order, formed a monophyletic clade in most analyses. Psilosiphon scoparium Entwisle was not closely allied with the taxa of the Lemaneaceae, lending support to the newly proposed family Psilosiphonaceae. Sequence data from the remaining taxa of the Lemaneaceae support the concept of a derived monophyletic clade. The genus Batrachospermum appears to comprise many morphologically similar but distantly related taxa, which will need further investigation to resolve their taxonomic status. Tuomeya, Sirodotia and Nothocladus are retained at the generic level until further data are obtained.