Low Molecular Weight Carbohydrate Patterns in Geographically Different Isolates of the Eulittoral Red Alga Bostrychia tenuissima from Australia

Sixteen isolates of the red alga, Bostrychia tenuissima King et Puttock, from New South Wales, Victoria and South Australia were cultured in the laboratory and analysed for low molecular weight carbohydrates using ¹³C-NMR and HPLC techniques. All populations south of 34 °S contain D-sorbitol in combination with the heteroside digeneaside. The isolates north of 34° S lack digeneaside, but contain D-sorbitol and, in addition, an isomeric form D-dulcitol. Moreover, the ¹³C-NMR spectra showed an unknown metabolite which was only measured in combination with digeneaside. While in the strains south of 34 °S digeneaside and the unknown compound occur in small quantities and remained unchanged with increasing salinities (5–60 ppt), the relatively high D-sorbitol contents strongly increased under hypersaline conditions. In the populations north of 34 °S both the concentrations of D-sorbitol and D-dulcitol increased with increasing salinity. These data demonstrate the important role of polyols in the osmotic acclimation of B. tenuissima. The ecological and/or biological factors controlling this geographical pattern of metabolite content are not known. However, the different carbohydrate patterns within B. tenuissima are considered as indicators of the development of physiological ecotypes.     

Non‐monophyly of Bostrychia simpliciuscula (Ceramiales,Rhodophyta): Multiple species with very similar morphologies,a revised taxonomy of cryptic species

The discovery of a plethora of cryptic species in many algal groups has led to speculation as to the causes of this observation and has affected taxonomy, with reluctance to give names to species that look identical. While this is defensible for monophyletic cryptic species complexes, both our understanding of similar morphologies (crypsis) and nomenclature is challenged when we encounter non‐monophyletic ‘cryptic’ species. Bostrychia simpliciuscula is a wide‐ranging species in which multiple cryptic species are known. Our increased sampling shows that this species consists of four lineages that do not form a clade, but lineages are sister to species with different morphologies. Careful morphological examination shows that characters, especially branched monosiphonous laterals and rhizoid morphology in haptera, are able to distinguish these four lineages into two groups, that are still not monophyletic. The similar morphologies in these lineages could be due to convergence, but not developmental constraints or lack of time to diverge morphologically; or possibly maintenance of a generalized body plan. These lineages appear to have specific biogeographic patterns and these will be used to propose a new taxonomy. B. simpliciuscula is now confined to the tropics. Another of these lineages matches a previously described species, B. tenuissima, that was synonymized with B. simpliciuscula and is from cold temperate Australasia, and is resurrected. Another lineage is found in Japan in which a previous name is also available, B. hamana‐tokidae; the last lineage is found in central New South Wales, morphologically it resembles B. tenuissima, with which it overlaps in distribution around Sydney, and is named as a new species, B. kingii sp. nov.     

Biogeography of sexual and asexual populations in Bostrychia moritziana (Rhodomelaceae, Rhodophyta)

Bostrychia moritziana (Sonder ex Kützing) J. Agardh is recorded from many regions around the world. Our laboratory culture investigations have verified a sexual life cycle in isolates from Australia, Venezuela, Colombia, South Africa, Fiji, New Zealand and Indonesia. By contrast, asexual isolates producing successive generations of tetrasporophytes in laboratory culture and, presumably, in the field, are known from Australia. New Caledonia and Japan. In Australia, asexual reproduction is absent only in Victoria. In Western Australia, Northern Territory and Queensland, 99% of the isolates have asexual reproduction. In New South Wales (NSW), asexual and sexual populations are often intermixed. Of the 176 worldwide field collections, 58% were vegetative, 39% were tetrasporic, 2% were female and 1% were male. After several years of observations on the asexual isolates in culture, at least 30 successive asexual tetrasporophytic generations have developed. Only two asexual isolates (3558 and 3575) from NSW have formed a single male and female gametophyte in culture. In a self-cross of 3568, the carpospores developed into tetrasporophytes that recycled asexually. All outcrosses done with normal sexual isolates produced normal carposporophytes and the carpospores developed into tetrasporophytes that also recycled asexually. Asexual populations may arise repeatedly by loss of meiosis in tetrasporangia of sexual populations. Asexual reproduction apparently does not diminish the overall dispersal and abundance in the field. Our present bio-geographic data show that sexually reproducing popuiations of B. moritziana occur worldwide, while asexuaily reproducing populations are confined to the western Pacific. Bostrychia bispora West et Zuccarello, initially described on the basis of its asexual reproduction to distinguish it from B, moritziana, is now reduced to synonymy with B. moritziana.     

Hybridization studies in Bostrychia. 1: B. radicans (Rhodomelaceae, Rhodophyta) from Pacific and Atlantic North America

Bostrychia radicans(Montagne) Montagne is a pantropical/temperate red alga associated with mangroves and saltmarsh plants. Collections were made from a similar north-south geographic distribution along both the Pacific and Atlantic coasts of North America. Hybridization studies were performed with cultured isolates to assess the extent of interfertility and reproductive isolation along these two coastlines. All male and female gametophytes derived from single tetrasporophytes were intercompatible. Almost all isolates extending over 1500 km of coast line from northern Pacific Mexico are compatible, forming cystocarps that released viable carpospores. Even isolates which morphologically would be placed in two species [B. radicans and B. moritziana(Sender ex Kützing) J. Agardh], based on the presence or absence of monosiphonous branches, were capable of hybridizing. Crosses of isolates from the Atlantic USA showed a greater amount of incompatibility. Certain isolates were not compatible with any other isolates including isolates collected in close proximity (North Carolina isolates), while other isolates from the same locality were compatible (South Carolina). An isolate from South Carolina formed tetrasporophytes with isolates from Pacific Mexico but tetraspores were not viable. Certain incompatible crosses formed ‘pseudocystocarps’ but viable carposporophytes did not develop. Generalizations about reproductive isolation within a species must also consider differences between populations from different biogeographic regions that may reflect different paleoclimatological histories, founder effects and unique dispersal events.     

Comparative physiological studies on the growth of cryptic species of Bostrychia intricata (Rhodomelaceae,Rhodophyta) in various salinity and temperature conditions

Inter‐ and intra‐specific physiological variations of intertidal macroalgae have been well investigated. However, studies on physiological responses of cryptic algal species have been poorly documented. Bostrychia intricata is a widespread marine red alga in the Southern Hemisphere, and has many cryptic species. We investigated the effect of different salinities and temperatures on the specific growth rate of three cryptic species (N2, N4 and N5) of B. intricata from New Zealand. Our data indicated that all cryptic species grew at the full range of salinities and temperatures tested, but exhibited a significant difference in their specific growth rates. Cryptic species N4 had a higher growth rate than the other two cryptic species under all experimental conditions, whereas cryptic species N2 occasionally showed a higher growth rate than cryptic species N5 at high salinities and lower temperatures. The distinct physiological properties of these cryptic species may explain their distribution pattern (a wider distribution of cryptic species N4 than N2 and N5) in New Zealand. The physiological divergence between the cryptic species could be related to their levels of evolutionary divergence, with more similar physiology between cryptic species, which share a more recent common ancestor (N2 and N5). Our findings underline that morphologically indistinguishable cryptic algal species are different in many other aspects and are truly independent entities.     

Climate and the range dynamics of species with imperfect detection

Reliable predictions for species range changes require a mechanistic understanding of range dynamics in relation to environmental variation. One obstacle is that most current models are static and confound occurrence with the probability of detecting a species if it occurs at a site. Here we draw attention to recently developed occupancy models, which can be used to examine colonization and local extinction or changes in occupancy over time. These models further account for detection probabilities, which are likely to vary spatially and temporally in many datasets. Occupancy models require repeated presence/absence surveys, for example checklists used in bird atlas projects. As an example, we examine the recent range expansion of hadeda ibises (Bostrychia hagedash) in South African protected areas. Colonization exceeded local extinction in most biomes, and the probability of occurrence was related to local climate. Extensions of the basic occupancy models can estimate abundance or species richness. Occupancy models are an appealing additional tool for studying species' responses to global change.     

The cell wall chemistry of Bangia atropurpurea (Bangiales, Rhodophyta) and Bostrychia moritziana (Ceramiales, Rhodophyta) from marine and freshwater environments

The cell wall polysaccharides of two species of red algae, which are adapted to both freshwater and marine environments, were analysed to determine the effect of these widely different environments on their commercially important agarocolloids and to investigate the possible role of the cell wall in environmental adaptation. Cell wall polymers of freshwater isolates of Bangia atropurpurea (Roth) C. Agardh and cultured freshwater and marine Bostrychia moritziana (Sonder ex Kützing) J. Agardh were isolated and the polysaccharides chemically fractionated and characterized. Wall polysaccharides of freshwater B. atropurpurea were similar to those previously reported for marine isolates with repeating disac-charide units of agarose and porphyran predominant in the hot water extracts. In the insoluble residues, 3-iinked galactosyl and 4-linked mannosyl residues were predominant. Bostrychia moritziana wall polysaccharides included agarocolloids with various patterns of methyl ether substitution similar to those previously described for other Ceramiales. Differences in the position of methyl ether substituents were detected in the hot water extracts of the freshwater and marine specimens. Polymers of freshwater ß. moritziana cultures were composed of a complex mixture of repeating disaccharide units including 2′-O-methyl agarose, 6-O-methyI agarose and 2′-O-methyl porphyran. Polymers of marine isolates of ß. moritziana differ in that they contain only trace amounts of 2-O-methyl saccharides and increased amounts of 6-O-amethyl saccharides. The hot water insoluble residues of both freshwater and marine isolates of ß. moritziana contain a mixture of 3-linked galactosyl and 4-linked glucosyl residues. These results indicate that the adaptive response of B. moritziana to changing osmotic and ionic conditions may include changes in cell wall chemistry: notably, the pattern of methyl ether substitution.     

COMPARATIVE DEVELOPMENT OF THE RED ALGAL PARASITES BOSTRYCHIOCOLAX AUSTRALIS GEN. ET SP. NOV. AND DAWSONIOCOLAX BOSTRYCHIAE (CHOREOCOLACACEAE,RHODOPHYTA)1

The development of two red algal parasites was examined in laboratory culture. The red algal parasite Bostrychiocolax australis gen. et sp. nov., from Australia, originally misidentified as Dawsoniocolax bostrychiae (Joly et Yamaguishi-Tomita) Joly et Yamaguishi-Tomita, completes its life history in 6 weeks on its host Bostrychia radicans (Montagne) Montagne. Initially the spores divide to form a small lenticular cell, and then a germ tube grows from the opposite pole. Upon contact with the host cuticle, the germ tube penetrates the host cell wall. The tip of the germ tube expands, and the spore cytoplasm moves into this expanded tip. The expanded germ tube tip becomes the first endophytic cell from which a parasite cell is cut off that fuses with a host tier cell. The nuclei of this infected host cell enlarge. As parasite development continues, other host-parasite cell fusions are formed, transferring more parasite nuclei into host cells. The erumpent colorless multicellular parasite develops externally on the host, and reproductive structures are visible within 2 weeks. Tetrasporangia are superficial and cruciately or tetra-hedrally divided. Spermatia are formed in clusters. The carpogonial branches are four-celled, and the carpogonium fuses directly with the auxiliary (support) cell. The mature carposporophyte has a large central fusion cell and sympodially branched gonimoblast filaments. Early stages of development differ markedly in Dawsoniocolax bostrychiae from Brazil. Upon contact with the host, the spore undergoes a nearly equal division, and a germ tube elongates from the more basal of the two spore cells, penetrates the host cell wall, and fuses with a host tier cell. Subsequent development involves enlargement of the original spore body and division to form a multicellular cushion, from which descending rhizoidal filaments form that fuse with underlying host cells. This radically different development is in marked contrast to the final reproductive morphology, which is similar to B. australis and has lead to taxonomic confusion between these two entities. The different spore germination patterns and early germ-ling development of B. australis and D. bostrychiae warrant the formation of a new genus for the Australian parasite.     

Spore discharge in the red algae Bostrychia tenella and Caloglossa leprieurii from the Godavari estuary,India

Bostrychia tenella (Vohl.) J. Ag. and Caloglossa leprieurii (Mont.) J. Ag., two examples of species important for human consumption from estuaries in Asia, were studied with respect to spore formation and release with a long-term view to their mass cultivation. Plants were collected between January and December 1987 from three different regions of the Gautami Godavari estuary, India. Both species behaved rather similarly. Tetrasporophytic plants were present throughout the year, whereas carposporophytic plants were found only in certain months. Shedding of tetraspores was observed throughout the year, but with seasonal difference in their output. Carpospores were liberated from October to May when the material was available. Maximum shedding of carpospores and tetraspores was observed in December and January and the minimum number of tetraspores in August and carpospores in May. The maximum number of spores was liberated, when plants were submerged at 20% salinity.     

INCREASED SAMPLING FOR INFERRING PHYLOGEOGRAPHIC PATTERNS IN BOSTRYCHIA RADICANS/B. MORITZIANA (RHODOMELACEAE,RHODOPHYTA) IN THE EASTERN USA1

Zuccarello and West (2003) reported on the phylogenetic diversity of algae identified as Bostrychia radicans (Montagne) Montagne and B. moritziana (Sonder ex Kützing) J. Agardh from around the world. They showed that the species complex consisted of seven distinct lineages, of which two lineages were common on the East Coast of the USA and eastern Gulf of Mexico. The distribution of haplotypes within these lineages on the East Coast of the USA showed a general north–south distribution. One haplotype of lineage 5 (B) was mostly collected in northern areas, while the other common haplotype (C) was more southerly in distribution. Samples in lineage 6 (haplotype D) were not found north of Sapelo Island, Georgia. Increased sampling from the eastern USA over 5 years later has revealed an altered pattern. Haplotype D is distributed in North Carolina and is common in some populations. Haplotype C is rare or absent in many sampled populations. Haplotype B is only observed in the northern sampled sites on both sides of the Florida peninsula. This disjunct distribution agrees with geological scenarios for a strait between the western Gulf of Mexico and southern Georgia in the Miocene/Pliocene, which closed in the late Pliocene. This paper highlights the importance of increased sampling to determine phylogeographic patterns and hypotheses of dispersal scenarios in algae.