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Max H Hommersand - One of the best experts on this subject based on the ideXlab platform.
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s arcopeltis gen nov Gigartinaceae rhodophyta with s skottsbergii comb nov from southern south america and s antarctica sp nov from the antarctic peninsula
Phytotaxa, 2020Co-Authors: Jeffery R Hughey, Geoffrey L Leister, Paul W Gabrielson, Max H HommersandAbstract:Gigartina skottsbergii is the currently accepted name for the large, peltate species of Gigartinaceae distributed in Argentina, Chile, and along the Antarctic Peninsula. However, phylogenetic analyses of DNA sequences for more than twenty years indicate that two species are passing under the name G. skottsbergii, and both DNA sequences and morpho-anatomy indicate that the species are assignable to an undescribed genus. To formally validate the new genus and species, we performed next generation sequencing (NGS) on the lectotype material of G. skottsbergii to document its genetic identity and obtained its complete mitogenome and partial plastid genome. Phylogenetic analysis of rbcL and cox1 sequences of the lectotype along with recent collections of G. skottsbergii from southern South America and Antarctica, confirmed the generic distinction and the presence of two morphologically similar taxa. We propose Sarcopeltis gen. nov., containing the generitype S. skottsbergii comb. nov. from southern South America, and S. antarctica sp. nov. from the Antarctic Peninsula. Sarcopeltis is characterized by the following suite of features: 1) peg-like secondary haptera that adhere to the substratum, 2) absence of an envelope surrounding each cystocarp, 3) presence of extensive, terminal, tubular gonimoblast filaments that fuse with surrounding vegetative cells, and 4) tetrasporangia formed from secondary filaments entirely in the medulla. This study demonstrates that genetic analysis of type material, together with recently obtained DNA sequences from field collected specimens, can provide clear and objective taxonomic conclusions.
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psilophycus alveatus gen et comb nov a basal taxon in the Gigartinaceae rhodophyta from new zealand
Phycologia, 2011Co-Authors: Wendy A Nelson, Geoffrey L Leister, Max H HommersandAbstract:Abstract Nelson W.A., Leister G.L. and Hommersand M.H. 2011. Psilophycus alveatus gen. et comb. nov., a basal taxon in the Gigartinaceae (Rhodophyta) from New Zealand. Phycologia 50: 219–231. DOI: 10.2216/10.38.1 The red alga Gigartina alveata (Turner) J. Agardh was collected by Joseph Banks in New Zealand in 1769 during Captain Cook's voyage on the Endeavour (1768–1771) and was originally described as Fucus alveatus. This species forms a conspicuous band on rocky outcrops on open sandy beaches of the northern North Island in the mid-intertidal zone. The thallus is narrow, linear, channeled and repeatedly dichotomously branched, with the apices often curled and crowded, giving the plant a bushy appearance. Growth is multiaxial with the formation of parallel files of medullary filaments cross-linked by secondary pit connections in a reticulate manner. Cystocarpic plants greatly outnumber male or tetrasporangial individuals. Tetrasporangia are transformed from inner cortical cells, as in some basal lineages...
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a molecular study of mazzaella Gigartinaceae rhodophyta and morphological investigation of the splendens clade from pacific north america
Phycologia, 2010Co-Authors: Jeffery R Hughey, Max H HommersandAbstract:Abstract Hughey J.R. and Hommmersand M.H. 2010. A molecular study of Mazzaella (Gigartineaceae, Rhodophyta) and morphological investigation of the splendens clade from Pacific North America. Phycologia 49: 113–135. DOI: 10.2216/08-68.1 The delineation of species of Mazzaella remains problematic because of similarities in thallus shape and color. To better define species boundaries, molecular phylogenetic analyses and developmental studies of Mazzaella were performed on one of the more taxonomically challenging clades, the splendens group (Mazzaella flaccida, Mazzaella linearis, Mazzaella sanguinea and Mazzaella splendens). Using an expanded rbcL data set, internal transcribed spacer sequences, and a combined analysis, six clades were identified: splendens, californica, rosea, cobinae, oregona, and South American/African. Morphological examination of members of the splendens clade identified differences in their cystocarpic and tetrasporangial development and supported the recognition of two subspecies, M....
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morphological and molecular systematic study of chondracanthus Gigartinaceae rhodophyta from pacific north america
Phycologia, 2008Co-Authors: Jeffery R Hughey, Max H HommersandAbstract:Abstract Species boundaries in the Gigartinaceae are poorly defined due to the high degree of phenotypic plasticity exhibited by the thallus, with the result that many superfluous taxa have been described. To clarify the taxonomy of species of Chondracanthus Kutzing reported from the Gulf of California and Pacific coast of North America, morphological and molecular phylogenetic studies were performed. Phylogenetic analyses of chloroplast and nuclear DNA yielded nearly congruent hypotheses. DNA from type material was examined from select species to validate the correspondence between modern and historically important collections. Monographic observations on species from Pacific North America were included to clarify species boundaries. Analyses identified two species from the Gulf of California and nine from the Pacific coast. The following statements are supported: (1) Gigartina serrata Gardner is independent of Chondracanthus canaliculatus (Harvey) Guiry, and Chondracanthus serratus (Gardner) comb. nov. ...
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its1 sequences of type specimens of gigartina and sarcothalia and their significance for the classification of south african Gigartinaceae gigartinales rhodophyta
European Journal of Phycology, 2002Co-Authors: Jeffery R Hughey, Paul C Silva, Max H HommersandAbstract:Uncertainties about the identity of type specimens of red algae have frequently led to taxonomic and nomenclatural confusion. A procedure for extracting PCR-amplifiable DNA from formalin-fixed material and herbarium specimens was used to investigate the taxonomic status of several South African Gigartinaceae. We compared nucleotide sequences in the internal transcribed spacer 1 (ITS1) region in type specimens and other historically important collections presently referred to Gigartina bracteata , G. radula and G. stiriata . The following opinions are supported: (1) Fucus bracteatus S.G. Gmelin, Chondrodictyon capense Kutzing and Iridaea clathrata Decaisne represent a single species of South African Gigartina ( G. bracteata (S.G. Gmelin) Setchell & Gardner) in which the disintegration of tetrasporangial sori results in a reticulate thallus. (2) Mastocarpus polycarpus Kutzing, M. incrassatus Kutzing and Iridaea lapathifolia Kutzing represent a single species of South African Gigartina ( G. polycarpa (Kutzing) Setchell & Gardner) that has often, but erroneously, been called G. radula (Esper) J. Agardh. (3) Mastocarpus verrucosus Kutzing is a later heterotypic synonym of Iridaea papillosa Bory ( Sarcothalia papillosa (Bory) Leister) and was based on material that probably came from southern South America rather than from South Africa, the provenance given by Kutzing. (4) Fucus stiriatus Turner and Sphaerococcus burmannii C. Agardh represent a single species of South African Sarcothalia ( S. stiriata (Turner) Leister).
Ricardo A. Scrosati - One of the best experts on this subject based on the ideXlab platform.
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Regeneration and reproduction of Mazzaella cornucopiae (Rhodophyta,
2015Co-Authors: Ricardo A. ScrosatiAbstract:The effects that different intensities of frond harvesting have on frond regeneration and subsequent production of reproductive structures were investigated for the red intertidal alga Mazzaella cornucopiae (Postels & Ruprecht) Hommersand from British Columbia, Canada. Harvesting was done by pruning fronds in the late spring (when stand biomass is highest) of 1993 at two intensities: total and partial collection of fronds, in this second case leaving all frond biomass less than 1 cm high in place. Holdfasts were not damaged. Total percent cover of thalli, frond density, mean frond length, and stand biomass for these experimental quadrats were statistically similar to values for control quadrats in the spring of 1994. These results suggest that one total harvest of fronds per year, done in late spring without damaging holdfasts, may give the highest sustainable yield of biomass. The effects of harvesting intensity on reproduction were variable and difficult to explain. Neither the appearance nor the abundance of cystocarpic fronds were affected by frond pruning, compared with control areas, but pruning did affect the appearance and the abundance of tetrasporic fronds. Partial pruning resulted in a longer presence of tetrasporic fronds, whereas total pruning was associated with their complete absence. Results are compared with those for the few other species of the Gigartinaceae for which experimental harvesting has been done
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effects of elevation wave exposure and year on the proportion of gametophytes and tetrasporophytes in mazzaella parksii rhodophyta Gigartinaceae populations
Hydrobiologia, 2004Co-Authors: Ricardo A. Scrosati, Benita MudgeAbstract:We investigated the effects of elevation, wave exposure, and year on the proportion of gametophytes and tetrasporophytes in populations of the intertidal red seaweed Mazzaella parksii (= M. cornucopiae, Gigartinaceae) from the Pacific coast of Canada. In July 2002, we determined the life-history phase of 864 frond samples from four populations from Barkley Sound, using the resorcinol-acetal test. For these populations, gametophytes were significantly more numerous than tetrasporophytes, and the proportion of gametophytes was significantly higher at higher elevations. The proportion of gametophytes varied directly (although less markedly) with the degree of wave exposure, but significance could not be assessed for this factor. All of these patterns were spatially consistent, as they held for two different rocky points with similar physical characteristics. One of these points had also been surveyed in 1994-1995, which allows us to conclude that the population-wise gametophyte predominance and the positive relationship between elevation and the proportion of gametophytes are stable features of this species in this area. However, the average proportion of gametophytes was similar between the studied levels of wave exposure in 1994–1995; such a difference revealed as non-significant when data were combined with those for 2002. This suggests that wave exposure is not important in determining the proportion of life-history phases for this species. Comparisons with other species are done in search of general patterns for the Gigartinaceae.
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demographic models to simulate the stable ratio between ecologically similar gametophytes and tetrasporophytes in populations of the Gigartinaceae rhodophyta
Phycological Research, 1999Co-Authors: Ricardo A. Scrosati, Robert E. DewreedeAbstract:SUMMARY In populations of the Gigartinaceae (Rhodophyta), gametophytes often predominate numerically over tetrasporophytes. Several hypotheses have been proposed to explain this dominance, based on the usually implicit assumption that the stable ratio between gametophytes and tetrasporophytes (G:T ratio) should be 1 if both reproductive phases are ecologically similar. We developed demographic models to test this assumption, for which we considered that both phases are ecologically similar. Defining ecologic similarity for most demographic rates is relatively straightforward, except for rates of spore output. The first set of models considered the same spore output per thallus of both phases as representing ecologic similarity. Model iterations led to stable G:T ratios of 1 for triennial and for perennial thalli, regardless of the initial G:T ratio, but not for annual thalli with initial G:T ratios different from 1. However, equal spore output may not represent ecologic similarity, due to size differences between carpospores and tetraspores. The second set of models considered the lowest possible spore output for each phase, according to the life history of this family: only one carposporangium, with one carpospore, is produced from every two gametophytes and only one tetrasporangium, with four tetraspores, is produced by every tetrasporophyte. Model iterations led to stable G:T ratios of 2.8 for most cases, a ratio of 1 being obtained only every 2 years for annual thalli with an initial G:T ratio of 1. Increasing absolute spore output, without altering the relative output between phases and incorporating density-independent mortality through a matrix model, given the same mortality rate for both phases, did not modify results. We suggest that the combination of both modeling and field research may uncover more rapidly than otherwise the most relevant ecologic differences between phases, if any, that underlie the G:T ratio observed for a given population.
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Regeneration and reproduction of Mazzaella cornucopiae (Rhodophyta, Gigartinaceae) after frond harvesting
Journal of Applied Phycology, 1998Co-Authors: Ricardo A. ScrosatiAbstract:The effects that different intensities of frond harvesting have on frond regeneration and subsequent production of reproductive structures were investigated for the red intertidal alga Mazzaella cornucopiae (Postels & Ruprecht) Hommersand from British Columbia, Canada. Harvesting was done by pruning fronds in the late spring (when stand biomass is highest) of 1993 at two intensities: total and partial collection of fronds, in this second case leaving all frond biomass less than 1 cm high in place. Holdfasts were not damaged. Total percent cover of thalli, frond density, mean frond length, and stand biomass for these experimental quadrats were statistically similar to values for control quadrats in the spring of 1994. These results suggest that one total harvest of fronds per year, done in late spring without damaging holdfasts, may give the highest sustainable yield of biomass. The effects of harvesting intensity on reproduction were variable and difficult to explain. Neither the appearance nor the abundance of cystocarpic fronds were affected by frond pruning, compared with control areas, but pruning did affect the appearance and the abundance of tetrasporic fronds. Partial pruning resulted in a longer presence of tetrasporic fronds, whereas total pruning was associated with their complete absence. Results are compared with those for the few other species of the Gigartinaceae for which experimental harvesting has been done.
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Mechanisms of recolonization of the clonal intertidal alga Mazzaella cornucopiae (Rhodophyta, Gigartinaceae) after disturbances
Canadian Journal of Botany, 1998Co-Authors: Ricardo A. ScrosatiAbstract:The recolonization of the clonal intertidal alga Mazzaella cornucopiae (Postels et Ruprecht) Hommersand is considered here, as part of a larger project on its population ecology. Recolonization in Barkley Sound, Pacific Canada, started a few months after completely clearing experimental 100-cm 2 quadrats in late spring and occurred both by vegetative growth of perennating holdfasts bordering disturbed quadrats and by recruitment from spores. In terms of percent cover, both mechanisms contributed similarly to recolonization during the first 2 years, although vegetative recolonization was highly variable among quadrats. Great spatial variability prevented the detection of a temporal pattern for recruit density on statistical grounds. However, cohort demography showed some degree of seasonality. Turnover rates of recruits were high; they lived 2.6 months on average. Recruitment was highest between fall or winter and midspring (as might be expected, given that reproductive structures appeared in fall and winter) and null in the first two summer seasons. The highest mortality was recorded in summer, when desiccation and irradiance are highest on an annual basis. Frond density was very variable on a spatial scale and did not follow a clear temporal pattern. The average number of fronds per recruit apparently increased between winter and summer, paralleling frond dynamics in mature stands. By monitoring recolonization in quadrats of the same size cleared previously by other researchers, the time of full recovery of M. cornucopiae was estimated to be 2.7-3.5 years.
Ruth Falshaw - One of the best experts on this subject based on the ideXlab platform.
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Growth and carrageenan composition of two populations of the New Zealand carrageenophyte Sarcothalia lanceata (Gigartinaceae, Rhodophyta)
Journal of Applied Phycology, 2018Co-Authors: Kate Neill, Wendy Nelson, Catriona Hurd, Ruth FalshawAbstract:Sarcothalia lanceata is a broad-bladed, New Zealand red alga. The tetrasporic life stage contains a lambda-carrageenan that has a strong potential for commercial utilisation. The male and female gametophytic life stages contain kappa-II carrageenan that also has commercial potential. However, fundamental information on the growth and variation in carrageenan content of this species in the wild is necessary to underpin possible aquaculture of this species. Therefore, growth in blade length and width was assessed for male and female gametophytes, and tetrasporophytes in two S. lanceata populations in New Zealand’s South Island, and monthly seawater nutrient and tissue nutrients, and carrageenan constituent sugar levels were analysed. Blade length did not vary significantly over time or between life history phases; however, blade width varied significantly for both factors with most temporal variation occurring in male blades. Analysis of seawater and tissue nutrient levels suggested that these populations are nutrient limited year-round. Constituent sugars varied temporally and between life history phases in most cases. Relative 3,6-anhydrogalactitol peracetate (for the males and females) and galactitol peracetate levels (all life stages) were higher in winter than in summer, while glucitol peracetate and xylitol peracetate levels were generally lower in winter than summer. The distinctive morphologies of the male and female plants of this species mean there is potential to cultivate and then separately harvest male and female plants in addition to tetrasporophytic plants. Male blades contain more 3,6-anhydrogalactitol peracetate and galactitol peracetate than female blades, and their morphology may make them less prone to breakage in an aquaculture situation. Experimentation on spore release and growth and the potential effects of nutrient manipulation on early stages are suggested as the direction of future research.
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clump structure population structure and non destructive biomass estimation of the new zealand carrageenophyte sarcothalia lanceata Gigartinaceae rhodophyta
Botanica Marina, 2016Co-Authors: Kate F Neill, Ruth Falshaw, Wendy A Nelson, Catriona L HurdAbstract:Sarcothalia lanceata is a New Zealand carrageenophyte with tetrasporophytic thalli that produce carrageenan very close to the idealised structure of lambda-carrageenan. As such there is interest in its potential for commercial utilisation. There is no information on the biology and ecology of natural populations of this species, but this knowledge is critical for determining whether a species is a suitable candidate for sustainable wild harvest or for aquaculture. Population studies were conducted at two sites in New Zealand’s South Island in order to provide fundamental information on this species. The structure (abundance and composition of male, female, tetrasporophytic and non-reproductive clumps) of the two populations was assessed monthly over a year, and population biomass estimated using regression methods. Seasonal variation was not evident in most of the parameters measured, but differences between sites were found in total population density, the density of different life-history phases, and clump size and structure. The turnover in biomass occurs more frequently at the blade level than at the clump level and the presence of a basal crust in this species promotes population stability.
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chemotaxonomy of new zealand red algae in the family Gigartinaceae rhodophyta based on galactan structures from the tetrasporophyte life stage
Carbohydrate Research, 2009Co-Authors: Ruth Falshaw, Richard H FurneauxAbstract:The identification of the polysaccharides from tetrasporophytic plants of nine endemic New Zealand species belonging to the Gigartinaceae, 'Gigartina' ancistroclada, 'G.' grandifida, Gigartina dilatata, G. divaricata, G. macrocarpa, G. marginifera, G. pachymenioides, G. sp. 'Lindauer 164' and Sarcothalia livida using infra-red spectroscopy in conjunction with constituent sugar and glycosyl linkage/substitution analysis is reported. All nine species contain galactans with structures consistent with lambda-type carrageenans. Differences in the structures of the galactans in these and a further six previously studied species indicate chemotaxonomically distinct groupings that correspond to Sarcothalia, 'Sarcothalia' and Gigartina genera plus some outliers. These distinct, chemotaxonomic groupings are aligned to those determined by rbcL sequence analysis reported in the literature.
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structural analysis of carrageenans from the tetrasporic stages of the red algae gigartina lanceata and gigartina chapmanii Gigartinaceae rhodophyta
Carbohydrate Research, 1998Co-Authors: Ruth Falshaw, Richard H FurneauxAbstract:The use of modern analytical techniques has facilitated the identification of the polysaccharides from tetrasporophytic Gigartina lanceata and Gigartina chapmanii. The G. lanceata polysaccharide corresponds, very closely, to the idealised structure of λ-carrageenan ([G2S-D2S,6S]n). That from G. chapmanii contains predominantly ξ-carrageenan ([G2S-D2S]n), but with about one in seven of the 3-linked units also has a pyruvate acetal group at the 4- and 6-positions, one in four of the 4-linked units is also sulfated at the 6-position, and a small but significant number of 4-linked 3,6-anhydrogalactosyl 2-sulfate units are present.
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carrageenans from the tetrasporic stages of gigartina clavifera and gigartina alveata Gigartinaceae rhodophyta
Carbohydrate Research, 1995Co-Authors: Ruth Falshaw, Richard H FurneauxAbstract:Abstract Modern chemical and spectroscopic techniques have been used to characterise the polysaccharides extracted from the tetrasporic life stages of Gigartina clavifera and Gigartina alveata . Both are predominantly ξ-carrageenans. About one in six of the 3-linked residues in both polysaccharides also have a pyruvate acetal group at the 4- and 6-positions. In addition, a similar proportion of the 4-linked units of each polysaccharide are devoid of sulfate groups, whilst more have sulfate esters on both O-2 and O-6. Some of the 3-linked units contain a sulfate at the 6-position in addition to that at O-2. The polysaccharide from tetrasporophytic G. alveata also contains a small but significant number of 3,6-anhydrogalactosyl units, most of which are naturally sulfated at the 2-position.
Richard H Furneaux - One of the best experts on this subject based on the ideXlab platform.
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chemotaxonomy of new zealand red algae in the family Gigartinaceae rhodophyta based on galactan structures from the tetrasporophyte life stage
Carbohydrate Research, 2009Co-Authors: Ruth Falshaw, Richard H FurneauxAbstract:The identification of the polysaccharides from tetrasporophytic plants of nine endemic New Zealand species belonging to the Gigartinaceae, 'Gigartina' ancistroclada, 'G.' grandifida, Gigartina dilatata, G. divaricata, G. macrocarpa, G. marginifera, G. pachymenioides, G. sp. 'Lindauer 164' and Sarcothalia livida using infra-red spectroscopy in conjunction with constituent sugar and glycosyl linkage/substitution analysis is reported. All nine species contain galactans with structures consistent with lambda-type carrageenans. Differences in the structures of the galactans in these and a further six previously studied species indicate chemotaxonomically distinct groupings that correspond to Sarcothalia, 'Sarcothalia' and Gigartina genera plus some outliers. These distinct, chemotaxonomic groupings are aligned to those determined by rbcL sequence analysis reported in the literature.
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structural analysis of carrageenans from the tetrasporic stages of the red algae gigartina lanceata and gigartina chapmanii Gigartinaceae rhodophyta
Carbohydrate Research, 1998Co-Authors: Ruth Falshaw, Richard H FurneauxAbstract:The use of modern analytical techniques has facilitated the identification of the polysaccharides from tetrasporophytic Gigartina lanceata and Gigartina chapmanii. The G. lanceata polysaccharide corresponds, very closely, to the idealised structure of λ-carrageenan ([G2S-D2S,6S]n). That from G. chapmanii contains predominantly ξ-carrageenan ([G2S-D2S]n), but with about one in seven of the 3-linked units also has a pyruvate acetal group at the 4- and 6-positions, one in four of the 4-linked units is also sulfated at the 6-position, and a small but significant number of 4-linked 3,6-anhydrogalactosyl 2-sulfate units are present.
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carrageenans from the tetrasporic stages of gigartina clavifera and gigartina alveata Gigartinaceae rhodophyta
Carbohydrate Research, 1995Co-Authors: Ruth Falshaw, Richard H FurneauxAbstract:Abstract Modern chemical and spectroscopic techniques have been used to characterise the polysaccharides extracted from the tetrasporic life stages of Gigartina clavifera and Gigartina alveata . Both are predominantly ξ-carrageenans. About one in six of the 3-linked residues in both polysaccharides also have a pyruvate acetal group at the 4- and 6-positions. In addition, a similar proportion of the 4-linked units of each polysaccharide are devoid of sulfate groups, whilst more have sulfate esters on both O-2 and O-6. Some of the 3-linked units contain a sulfate at the 6-position in addition to that at O-2. The polysaccharide from tetrasporophytic G. alveata also contains a small but significant number of 3,6-anhydrogalactosyl units, most of which are naturally sulfated at the 2-position.
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carrageenan from the tetrasporic stage of gigartina decipiens Gigartinaceae rhodophyta
Carbohydrate Research, 1994Co-Authors: Ruth Falshaw, Richard H FurneauxAbstract:The structure of the polysaccharide isolated from tetrasporophytic plants of the New Zealand red alga Gigartina decipiens has been determined by chemical and spectroscopic techniques. It is a linear polymer composed primarily of alternating 3-linked β-d-galactopyranosyl 2-sulphate and 4-linked α-d-galactopyranosyl 2,6-disulphate residues. About 15% of the 3-linked residues have an additional sulphate ester group at the 6-position. Aside from this small extra sulphate substitution, the structure is that of the idealised λ-carrageenan. Good quality solution-state 13C NMR spectra were recorded and interpreted for this carrageenan and for the carrageenans produced from it by solvolytic desulphation and alkali modification.
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carrageenan from the tetrasporic stage of gigartina decipiens Gigartinaceae rhodophyta
Carbohydrate Research, 1994Co-Authors: Ruth Falshaw, Richard H FurneauxAbstract:The structure of the polysaccharide isolated from tetrasporophytic plants of the New Zealand red alga Gigartina decipiens has been determined by chemical and spectroscopic techniques. It is a linear polymer composed primarily of alternating 3-linked beta-D-galactopyranosyl 2-sulphate and 4-linked alpha-D-galactopyranosyl 2,6-disulphate residues. About 15% of the 3-linked residues have an additional sulphate ester group at the 6-position. Aside from this small extra sulphate substitution, the structure is that of the idealised lambda-carrageenan. Good quality solution-state 13C NMR spectra were recorded and interpreted for this carrageenan and for the carrageenans produced from it by solvolytic desulphation and alkali modification.
S Fredericq - One of the best experts on this subject based on the ideXlab platform.
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recent developments in the systematics of the Gigartinaceae gigartinales rhodophyta based on rbcl sequence analysis and morphological evidence
Phycological Research, 1999Co-Authors: Max H Hommersand, S Fredericq, Wilson D Freshwater, Jeffery R HugheyAbstract:The phylogenetic systematics of the Gigartinaceae is discussed for seven genera and three undescribed generic lineages and 65 taxa representing 62 species based on an analysis of rbcL sequences and morphological evidence. An examination of rbcL trees resulting from analyses of these taxa identifies seven lineages: (i) ‘Gigartina’ alveata; (ii) Rhodoglossum/Gigartina; (iii) Chondracanthus; (iv) Ostiophyllum; (v) Sarcothalia; (vi) ‘Gigartina’ skottsbergii; and (vii) a large clade containing Iridaea/‘Sarcothalia’, Mazzaella and Chondrus. These lineages and Chondrus are strongly supported; however, two groups, Iridaea/‘Sarcothalia’ and Mazzaella, receive no bootstrap support. The morphology of the female reproductive system is investigated with the aid of computer-generated, color-coded tracings of photographs of cystocarps seen in cross section at different developmental stages. Seven basic cystocarp types were found which corresponded to species groups seen in rbcL trees. These were: (i) a ‘Gigartina’ alveata group in which the carposporangia-bearing filaments develop apomictically from gametophytic cells; (ii) a Rhodoglossum/Gigartina group in which gonimoblast filaments penetrate the surrounding envelope fusing progessively with envelope cells; (iii) a Chondracanthus group in which gonimoblast filaments penetrate the envelope but fuse with envelope cells only at late developmental stages; (iv) a Sarcothalia group in which the gonimoblast filaments displace an envelope composed mainly of secondary gametophytic filaments and link to envelope cells by terminal tubular gonimoblast cells; (v) an Iridaea group similar to the Sarcothalia group, but with an envelope composed of a mixture of medullary cells and secondary gametophytic filaments; (vi) a Mazzaella group that lacks a true envelope and in which gonimoblast filaments connect to modified gametophytic cells by means of terminal tubular cells; (vii) a Chondrus group in which gonimoblast filaments penetrate the medulla and link to modified medullary cells by means of conjunctor cells forming secondary pit connections. The further separation of these groups into genera is based largely on tetrasporangial characters.
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Observations on the phylogenetic systematics and biogeography of the Solieriaceae (Gigartinales, Rhodophyta) inferred from rbcL sequences and morphological evidence
Hydrobiologia, 1999Co-Authors: S Fredericq, D. Wilson Freshwater, Max H HommersandAbstract:A hypothesis of phylogenetic relationships inferred from analysis of plastid-encoded rbcL sequences is presented for members of the Solieriaceae, an economically important family containing carrageenan-type phycocolloids. Previous studies established that the Solieriaceae sensu lato forms a terminal clade in the Solieriaceae complex, a cluster of families sister to the Gigartinaceae complex (Gigartinaceae and Phyllophoraceae). The family Solieriaceae (including the Areschougiaceae) presently contains about 20 genera that are widely distributed in warm-temperate and tropical waters throughout the world. Molecular rbcL and published morphological evidence are consistent with an Australasian origin for the family and a Tethyan distribution for its tropical representatives from west to east as far as the Pacific coast of North and South America. The austral lineages (Callophycus, Rhabdonia, Areschougia and Erythroclonium) are resolved at the base of the tree. The remaining genera , comprising the tropical and subtropical cluster, form a robust terminal clade (100% bootstrap support). This assemblage can be divided into seven groups, most of which receive strong bootstrap support: (1) Sarconema, (2) a Eucheuma group, (3) an Atlantic Solieria group, (4) an Indo-Pacific Solieria robusta group, (5) a Meristiella/Meristotheca group, (6) Agardhiella and (7) a Sarcodiotheca group that includes 'Eucheuma' uncinatum from the Gulf of California. Four clusters of species are recognized in the Eucheuma group that correspond to the sections: Eucheuma, Gelatiformia (= Betaphycus), Anaxiferae, and Cottoniformia (= Kappaphycus) proposed by Maxwell Doty. No decision is reached regarding the taxonomic rank appropriate to the eucheumoid taxa.
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A gene phylogeny of the red algae (Rhodophyta) based on plastid rbcL
Proceedings of the National Academy of Sciences of the United States of America, 1994Co-Authors: D. W. Freshwater, Max H Hommersand, S Fredericq, B S Butler, M W ChaseAbstract:A phylogeny for the Rhodophyta has been inferred by parsimony analysis of plastid rbcL sequences representing 81 species, 68 genera, 38 families, and 17 orders of red algae; rbcL encodes the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase. Levels of sequence divergence among species, genera, and families are high in red algae, typically much greater than those reported for flowering plants. The Rhodophyta traditionally consists of one class, Rhodophyceae, and two subclasses, Bangiophycidae and Florideophycidae. The Bangiophycidae with three orders (Porphyridiales, Compsopogonales, and Bangiales) appears to be polyphyletic, and the Florideophycidae with 17 orders is monophyletic in this study. The current classification of the Florideophycidae based on ultrastructure of pit connections is supported. With the exception of the Rhodogorgonales, which appears to be misplaced, orders with one or two pit-plug cap layers (Hildenbrandiales, Corallinales, Acrochaetiales, Palmanales, Batrachospermales, and Nemaliales) terminate long branches of basal position within Florideophycidae in the most parsimonious rbcL tree. Orders that lack typical cap layers but possess a cap membrane are resolved as a monophyletic clade sister to the Ahnfeltiales. The large order Gigartinales, which is distributed among five rbcL clades, is polyphyletic. Families that possess typical carrageenan in their cell walls are resolved as a terminal clade containing two family complexes centered around the Solieriaceae and Gigartinaceae.
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phylogenetic systematics and biogeography of the Gigartinaceae gigartinales rhodophyta based on sequence analysis of rbcl
Botanica Marina, 1994Co-Authors: Max H Hommersand, S Fredericq, D. W. FreshwaterAbstract:Recently Hommersand, Guiry, Fredericq and Leister (1993, Hydrobiologia 260/261: 105-120) proposed a revised classification of the marine red algal family Gigartinaceae in which sixty-nine species were classified into four extant (Chondrus Stackhouse, Gigartina Stackhouse, Iridaea Bory, nom. cons., Rhodoglossum J. Agardh) and three reinstated (Chondracanthus Kutzing, Sarcothalia Kutzing, Mazzaella G. de Toni f.) genera based on developmental and morphological criteria. We have undertaken a preliminary study of the phylogenetic systematics and biogeography of the Gigartinaceae based on an independent data set derived from sequence analysis of rbcL, the gene that codes for the large subunit of RuBisCO. The topology of the rbcL tree, which contains 43 species, generally supports our recent systematic revision, while highlighting some taxonomic problems
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new perspectives in the taxonomy of the Gigartinaceae gigartinales rhodophyta
Hydrobiologia, 1993Co-Authors: Max H Hommersand, Michael D. Guiry, S Fredericq, Geoffrey L LeisterAbstract:A revised description of the Gigartinaceae is provided, together with a key and short diagnosis of each genus and a list of the species examined. New combinations have been proposed where appropriate. Distinguishing cystocarp and tetrasporangial characters useful for separating genera are illustrated, and the distribution of the genera is shown on a world map.