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Christian Wiencke - One of the best experts on this subject based on the ideXlab platform.
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Increased CO2 modifies the carbon balance and the photosynthetic yield of two common Arctic brown seaweeds: Desmarestia aculeata and Alaria esculenta
Polar Biology, 2016Co-Authors: Concepción Iñiguez, M. Rosario Lorenzo, Ricardo Carmona, Christian Wiencke, F. Xavier Niell, F. J L GordilloAbstract:Ocean acidification affects with special intensity Arctic ecosystems, being marine photosynthetic organisms a primary target, although the consequences of this process in the carbon fluxes of Arctic algae are still unknown. The alteration of the cellular carbon balance due to physiological acclimation to an increased CO2 concentration (1300 ppm) in the common Arctic brown seaweeds Desmarestia aculeata and Alaria esculenta from Kongsfjorden (Svalbard) was analysed. Growth rate of D. aculeata was negatively affected by CO2 enrichment, while A. esculenta was positively affected, as a result of a different reorganization of the cellular carbon budget in both species. Desmarestia aculeata showed increased respiration, enhanced accumulation of storage biomolecules and elevated release of dissolved organic carbon, whereas A. esculenta showed decreased respiration and lower accumulation of storage biomolecules. Gross photosynthesis (measured both as O2 evolution and 14C fixation) was not affected in any of them, suggesting that photosynthesis was already saturated at normal CO2 conditions and did not participate in the acclimation response. However, electron transport rate changed in both species in opposite directions, indicating different energy requirements between treatments and species specificity. High CO2 levels also affected the N-metabolism, and 13C isotopic discrimination values from algal tissue pointed to a deactivation of carbon concentrating mechanisms. Since increased CO2 has the potential to modify physiological mechanisms in different ways in the species studied, it is expected that this may lead to changes in the Arctic seaweed community, which may propagate to the rest of the food web.
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Increased CO_2 modifies the carbon balance and the photosynthetic yield of two common Arctic brown seaweeds: Desmarestia aculeata and Alaria esculenta
Polar Biology, 2016Co-Authors: Concepción Iñiguez, M. Rosario Lorenzo, Christian Wiencke, Raquel Carmona, F. Xavier Niell, F. J L GordilloAbstract:Ocean acidification affects with special intensity Arctic ecosystems, being marine photosynthetic organisms a primary target, although the consequences of this process in the carbon fluxes of Arctic algae are still unknown. The alteration of the cellular carbon balance due to physiological acclimation to an increased CO_2 concentration (1300 ppm) in the common Arctic brown seaweeds Desmarestia aculeata and Alaria esculenta from Kongsfjorden (Svalbard) was analysed. Growth rate of D. aculeata was negatively affected by CO_2 enrichment, while A. esculenta was positively affected, as a result of a different reorganization of the cellular carbon budget in both species. Desmarestia aculeata showed increased respiration, enhanced accumulation of storage biomolecules and elevated release of dissolved organic carbon, whereas A. esculenta showed decreased respiration and lower accumulation of storage biomolecules. Gross photosynthesis (measured both as O_2 evolution and ^14C fixation) was not affected in any of them, suggesting that photosynthesis was already saturated at normal CO_2 conditions and did not participate in the acclimation response. However, electron transport rate changed in both species in opposite directions, indicating different energy requirements between treatments and species specificity. High CO_2 levels also affected the N-metabolism, and ^13C isotopic discrimination values from algal tissue pointed to a deactivation of carbon concentrating mechanisms. Since increased CO_2 has the potential to modify physiological mechanisms in different ways in the species studied, it is expected that this may lead to changes in the Arctic seaweed community, which may propagate to the rest of the food web.
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Photosynthesis, dark respiration and pigment contents of gametophytes and sporophytes of the Antarctic brown alga Desmarestia menziesii
Botanica Marina, 2009Co-Authors: Iván Gómez, Christian WienckeAbstract:Photosynthetic performance, dark respiration, pigment concentration and fresh : dry weight ratios were measured in different life history stages of the Antarctic brown alga Desmarestia menziesii J. Agardh cultivated under simulated Antarctic conditions. Small gametophytes had the highest pigment concentrations, especially Chi a (1.6 mg g" FW), fucoxanthin (0.8 mg g" FW) and -carotene (0.04 mg g" FW). Young sporophytes had the highest Chi c values (0.4 mg g" FW) and high Chi α contents 1.0 mg g" FW). In general, adult reproductive plants contained the lowest pigment concentrations. Net photosynthetic rates (Pmax), on a fresh weight basis, were significantly higher in gametophytes (20 μηι Ο2 g" FW h"), however, when normalized to Chi a, Pmax was higher in adult reproductive plants (24 μιηοΐ O2 mg" Chi a h"). Dark respiration and photosynthetic efficiency (a), calculated both on a fresh weight and Chi 30 μιηοΐ photons m~ s"). Dry : fresh weight ratios of adult sporophytes were approximately twice those of gametophytes and young sporophytes. These results indicate that small gametophytes and young sporophytes have shade adapted plant characteristics including high pigment content, high α-values, low Ik values and low Chi
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Calcium compartmentation in Antarctic brown algae
Ultramicroscopy, 2002Co-Authors: M. Döpfner, Christian Wiencke, G. O. KirstAbstract:Abstract Calcium localization was studied in conventionally fixed material of Adenocystis utricularis and Desmarestia anceps . Calcium was detected in high quantities in physodes and at lower concentrations in the cell walls. No calcium was found in cytoplasm and chloroplasts. By this way of compartmentation calcium levels are kept at low concentrations in cytoplasm and chloroplasts which is favourable for metabolism. The calcium in the physodes is probably bound to polyphenolic compounds, the dominant component in this compartment. The calcium detected in the cell wall is probably absorbed to acidic polysaccharides and stabilizes the structure of the cell walls.
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Antarctic macroalgae — Sources of volatile halogenated organic compounds
Marine Environmental Research, 1999Co-Authors: Frank Laturnus, Christian Wiencke, Heinz KlöserAbstract:Abstract Twenty-eight different species of Antarctic macroalgae were collected from December 1991 to February 1992 at King George Island, South Shetlands, and investigated for their release of volatile halogenated organic compounds (VHOCs). Dibromomethane, bromoform, dibromochloromethane, bromodichloromethane, diiodomethane and chloroiodomethane were identified and their rates of release determined. For the first time the release of 1,2-dibromoethane from macroalgae is reported. Of all compounds investigated, bromoform is released in very high rates from all species studied, with the highest release rates from the brown algae Desmarestia anceps (3.9 μg g−1 wet algal weight d−1), Desmarestia menziesii (1.3 μg g−1 wet algal weight d−1), Cystosphaera jacquinotii (0.84 μg g−1 wet algal weight d−1) and Himantothallus grandifolius (0.3 μg g−1 wet algal weight d−1). Dibromomethane, diiodomethane, dibromochloromethane and 1,2-dibromoethane were also major compounds, but released at lower rates. Release rates of bromodichloromethane and chloroiodomethane were very low for most species. Release of VHOCs occurred from all parts of the thallus of the macroalga. The highest rates were measured in species with a high surface-to-volume ratio. This indicates the formation of VHOC in photosynthetically and metabolically active cortex (surface located) cells. The biological role of these substances and their input into the Antarctic environment is discussed.
Jeanine L. Olsen - One of the best experts on this subject based on the ideXlab platform.
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Complete mitochondrial genomes of the three brown algae (Heterokonta: Phaeophyceae) Dictyota dichotoma, Fucus vesiculosus and Desmarestia viridis
Current Genetics, 2006Co-Authors: Marie-pierre Oudot-le Secq, Wytze T. Stam, Susan Loiseaux-de Goër, Jeanine L. OlsenAbstract:We report the complete mitochondrial sequences of three brown algae ( Dictyota dichotoma , Fucus vesiculosus and Desmarestia viridis ) belonging to three phaeophycean lineages. They have circular mapping organization and contain almost the same set of mitochondrial genes, despite their size differences (31,617, 36,392 and 39,049 bp, respectively). These include the genes for three rRNAs (23S, 16S and 5S), 25–26 tRNAs, 35 known mitochondrial proteins and 3–4 ORFs. This gene set complements two previously studied brown algal mtDNAs, Pylaiella littoralis and Laminaria digitata . Exceptions to the very similar overall organization include the displacement of orf s, tRNA genes and four protein-coding genes found at different locations in the D. dichotoma mitochondrial genome. We present a phylogenetic analysis based on ten concatenated genes (7,479 nucleotides) and 29 taxa. Stramenopiles were always monophyletic with heterotrophic species at the base. Results support both multiple primary and multiple secondary acquisitions of plastids.
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Phylogeny and historical ecology of the Desmarestiaceae (Phaeophyceae) support a southern hemisphere origin
Journal of Phycology, 1997Co-Authors: A F Peters, Christian Wiencke, M. J. H. Van Oppen, Wytze T. Stam, Jeanine L. OlsenAbstract:Phylogenetic relationships in the Desmarestiales (Phaeophyceae) were inferred among the monotypic Arthrocladia (Arthrocladiaceae) and 27 isolates from Desmarestiaceae, representing 17 taxa of Desmarestia and the monotypic Antarctic genera Himantothallus and Phaeurus. Phaeurus and Arthrocladia were used as outgroups. Parsimony analyses of nuclear ribosomal DNA internal transcribed spacer (ITS1 and ITS2) sequences, in which gaps were both included and excluded yielded well-resolved trees with a consistent general branching pattern. A parallel analysis of nine morphological and life-history characters and three ecological characters yielded a similar tree but provided little resolution in the terminal clades. The position of the monotypic Arthrocladia villosa within the Desmarestiales is consistent with monophyly for the order, but its position as the most primitive Desmarestialean is not resolvable from the molecular data set. The basal position of Phaeurus, the Antarctic Desmarestia species, and Himantothallus is consistent with the hypothesis of a Southern Hemisphere origin for the family Desmarestiaceae. The more recent Northern Hemisphere ''aculeata'' clade evolved from an Antarctic ancestor. A ''D. aculeata-like'' species was ancestral to a lineage characterized by annual sporophytes with high sulfuric acid content, which radiated into many species, widely distributed in both hemispheres. Mapping of morphological and ecological characters onto the molecular tree confirm the informativeness of sulfuric acid-containing vacuoles and unilocular sporangial types. There is good congruence between phylogenetic tree topology and temperature imprints in relation to biogeographic distribution, supporting the theory that temperature tolerance is a conservative trait.
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Arctic-Antarctic disjunctions in the benthic seaweeds Acrosiphonia arcta (Chlorophyta) and Desmarestia viridis/willii (Phaeophyta) are of recent origin
Marine Biology, 1993Co-Authors: M. J. H. Van Oppen, Wytze T. Stam, Jeanine L. Olsen, C. Van Den Hoek, Christian WienckeAbstract:Two examples of the most extreme biogeographic disjunctions in benthic marine algae are found in Acrosiphonia arcta (Chlorophyta) and Desmarestia viridis/willii (Phaeophyta). Both species are members of the Arctic and Antarctic boreal and subboreal marine floras. Although both genera have temperate species, neither genus has subtropical or tropical representative. Comparisons of the fast-evolving ribosomal DNA internal transcribed spacer regions among isolates in each of the two species collected from both hemispheres showed an unexpected near sequence identity suggesting that these biogeographic disjunctions are of recent origin, possibly as recent as the last Pleistocene glacial maximum (18000 yr ago). Paleoclimatic explanations that rely on a much earlier transequatorial passage of cold-adapted species through a narrowed and cooler tropical belt during the Oligocene/Miocene (38 to 7 Ma ago) are unlikely. We hypothesize that despite the separated evolutionary histories of the northern and southern hemisphere coldwater marine floras, deep-water dispersal of microthalli has occurred and probably occurs on a regular basis.
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arctic antarctic disjunctions in the benthic seaweeds acrosiphonia arcta chlorophyta and Desmarestia viridis willii phaeophyta are of recent origin
Marine Biology, 1993Co-Authors: M. J. H. Van Oppen, Wytze T. Stam, Jeanine L. Olsen, C. Van Den Hoek, Christian WienckeAbstract:Two examples of the most extreme biogeographic disjunctions in benthic marine algae are found in Acrosiphonia arcta (Chlorophyta) and Desmarestia viridis/willii (Phaeophyta). Both species are members of the Arctic and Antarctic boreal and subboreal marine floras. Although both genera have temperate species, neither genus has subtropical or tropical representative. Comparisons of the fast-evolving ribosomal DNA internal transcribed spacer regions among isolates in each of the two species collected from both hemispheres showed an unexpected near sequence identity suggesting that these biogeographic disjunctions are of recent origin, possibly as recent as the last Pleistocene glacial maximum (18000 yr ago). Paleoclimatic explanations that rely on a much earlier transequatorial passage of cold-adapted species through a narrowed and cooler tropical belt during the Oligocene/Miocene (38 to 7 Ma ago) are unlikely. We hypothesize that despite the separated evolutionary histories of the northern and southern hemisphere coldwater marine floras, deep-water dispersal of microthalli has occurred and probably occurs on a regular basis.
Wytze T. Stam - One of the best experts on this subject based on the ideXlab platform.
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Complete mitochondrial genomes of the three brown algae (Heterokonta: Phaeophyceae) Dictyota dichotoma, Fucus vesiculosus and Desmarestia viridis
Current Genetics, 2006Co-Authors: Marie-pierre Oudot-le Secq, Wytze T. Stam, Susan Loiseaux-de Goër, Jeanine L. OlsenAbstract:We report the complete mitochondrial sequences of three brown algae ( Dictyota dichotoma , Fucus vesiculosus and Desmarestia viridis ) belonging to three phaeophycean lineages. They have circular mapping organization and contain almost the same set of mitochondrial genes, despite their size differences (31,617, 36,392 and 39,049 bp, respectively). These include the genes for three rRNAs (23S, 16S and 5S), 25–26 tRNAs, 35 known mitochondrial proteins and 3–4 ORFs. This gene set complements two previously studied brown algal mtDNAs, Pylaiella littoralis and Laminaria digitata . Exceptions to the very similar overall organization include the displacement of orf s, tRNA genes and four protein-coding genes found at different locations in the D. dichotoma mitochondrial genome. We present a phylogenetic analysis based on ten concatenated genes (7,479 nucleotides) and 29 taxa. Stramenopiles were always monophyletic with heterotrophic species at the base. Results support both multiple primary and multiple secondary acquisitions of plastids.
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Phylogeny and historical ecology of the Desmarestiaceae (Phaeophyceae) support a southern hemisphere origin
Journal of Phycology, 1997Co-Authors: A F Peters, Christian Wiencke, M. J. H. Van Oppen, Wytze T. Stam, Jeanine L. OlsenAbstract:Phylogenetic relationships in the Desmarestiales (Phaeophyceae) were inferred among the monotypic Arthrocladia (Arthrocladiaceae) and 27 isolates from Desmarestiaceae, representing 17 taxa of Desmarestia and the monotypic Antarctic genera Himantothallus and Phaeurus. Phaeurus and Arthrocladia were used as outgroups. Parsimony analyses of nuclear ribosomal DNA internal transcribed spacer (ITS1 and ITS2) sequences, in which gaps were both included and excluded yielded well-resolved trees with a consistent general branching pattern. A parallel analysis of nine morphological and life-history characters and three ecological characters yielded a similar tree but provided little resolution in the terminal clades. The position of the monotypic Arthrocladia villosa within the Desmarestiales is consistent with monophyly for the order, but its position as the most primitive Desmarestialean is not resolvable from the molecular data set. The basal position of Phaeurus, the Antarctic Desmarestia species, and Himantothallus is consistent with the hypothesis of a Southern Hemisphere origin for the family Desmarestiaceae. The more recent Northern Hemisphere ''aculeata'' clade evolved from an Antarctic ancestor. A ''D. aculeata-like'' species was ancestral to a lineage characterized by annual sporophytes with high sulfuric acid content, which radiated into many species, widely distributed in both hemispheres. Mapping of morphological and ecological characters onto the molecular tree confirm the informativeness of sulfuric acid-containing vacuoles and unilocular sporangial types. There is good congruence between phylogenetic tree topology and temperature imprints in relation to biogeographic distribution, supporting the theory that temperature tolerance is a conservative trait.
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Arctic-Antarctic disjunctions in the benthic seaweeds Acrosiphonia arcta (Chlorophyta) and Desmarestia viridis/willii (Phaeophyta) are of recent origin
Marine Biology, 1993Co-Authors: M. J. H. Van Oppen, Wytze T. Stam, Jeanine L. Olsen, C. Van Den Hoek, Christian WienckeAbstract:Two examples of the most extreme biogeographic disjunctions in benthic marine algae are found in Acrosiphonia arcta (Chlorophyta) and Desmarestia viridis/willii (Phaeophyta). Both species are members of the Arctic and Antarctic boreal and subboreal marine floras. Although both genera have temperate species, neither genus has subtropical or tropical representative. Comparisons of the fast-evolving ribosomal DNA internal transcribed spacer regions among isolates in each of the two species collected from both hemispheres showed an unexpected near sequence identity suggesting that these biogeographic disjunctions are of recent origin, possibly as recent as the last Pleistocene glacial maximum (18000 yr ago). Paleoclimatic explanations that rely on a much earlier transequatorial passage of cold-adapted species through a narrowed and cooler tropical belt during the Oligocene/Miocene (38 to 7 Ma ago) are unlikely. We hypothesize that despite the separated evolutionary histories of the northern and southern hemisphere coldwater marine floras, deep-water dispersal of microthalli has occurred and probably occurs on a regular basis.
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arctic antarctic disjunctions in the benthic seaweeds acrosiphonia arcta chlorophyta and Desmarestia viridis willii phaeophyta are of recent origin
Marine Biology, 1993Co-Authors: M. J. H. Van Oppen, Wytze T. Stam, Jeanine L. Olsen, C. Van Den Hoek, Christian WienckeAbstract:Two examples of the most extreme biogeographic disjunctions in benthic marine algae are found in Acrosiphonia arcta (Chlorophyta) and Desmarestia viridis/willii (Phaeophyta). Both species are members of the Arctic and Antarctic boreal and subboreal marine floras. Although both genera have temperate species, neither genus has subtropical or tropical representative. Comparisons of the fast-evolving ribosomal DNA internal transcribed spacer regions among isolates in each of the two species collected from both hemispheres showed an unexpected near sequence identity suggesting that these biogeographic disjunctions are of recent origin, possibly as recent as the last Pleistocene glacial maximum (18000 yr ago). Paleoclimatic explanations that rely on a much earlier transequatorial passage of cold-adapted species through a narrowed and cooler tropical belt during the Oligocene/Miocene (38 to 7 Ma ago) are unlikely. We hypothesize that despite the separated evolutionary histories of the northern and southern hemisphere coldwater marine floras, deep-water dispersal of microthalli has occurred and probably occurs on a regular basis.
Bill J Baker - One of the best experts on this subject based on the ideXlab platform.
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lack of defense or phlorotannin induction by uv radiation or mesograzers in Desmarestia anceps and d menziesii phaeophyceae 1
Journal of Phycology, 2006Co-Authors: Victoria A Fairhead, Charles D. Amsler, James B. Mcclintock, Bill J BakerAbstract:Phlorotannins are polyphenoloic metabolites occurring only in the Phaeophyceae that have numerous putative primary roles (e.g. cell-wall construction and storage) as well as secondary metabolic roles, which include herbivore feeding deterrence and protection from UV radiation. The proposed role of phlorotannins in the defense against UV radiation is of particular importance in the Antarctic due to depletion of the stratospheric ozone layer in that area. Several studies of brown algae have found evidence of an induction response (the production of defensive metabolites, including phlorotannins) after grazing by various mesograzers, after simulated grazing/wounding, and after exposure to increases in UV radiation. This study aimed to determine if phlorotannin production or other defenses in two dominant, endemic Antarctic species (Desmarestia menziesii Montagne and Desmarestia anceps J. Agardh) could be induced by an increase in exposure to UV radiation or by natural and artificial grazing. An in situ experiment failed to detect any effect of UV radiation on phlorotannin concentrations in either species or on subsequent palatability in feeding bioassays. A laboratory-based experiment did not detect any effect of mesoherbivore grazing or simulated grazing (wounding) on palatability or the concentration of phlorotannins in D. menziesii. Instead, phlorotannin concentrations increased in all treatments in both experiments, consistent with an increase in overall resource availability due to an increase in available PAR compared with the in situ irradiance at the algal collection sites.
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within thallus variation in chemical and physical defences in two species of ecologically dominant brown macroalgae from the antarctic peninsula
Journal of Experimental Marine Biology and Ecology, 2005Co-Authors: Victoria A Fairhead, Charles D. Amsler, James B. Mcclintock, Bill J BakerAbstract:Abstract Macroalgae along the Antarctic Peninsula are generally unpalatable to sympatric herbivores. This is particularly true of the large, brown macroalgae that dominate the communities in terms of cover and biomass. Variation within and between individuals of the ecologically dominant genus Desmarestia has also been detected. In the present study, we examined within thallus variation of both chemical (palatability) and physical (toughness) defences in Desmarestia anceps and Desmarestia menziesii . Each species was divided into the holdfast, the primary stem, and the lateral branches, with tissue fitness values assigned to each component. Lipophilic and hydrophilic extracts were obtained from each thallus component and incorporated into artificial alginate foods. A series of bioassays tested the palatability of these foods to the sympatric, herbivorous amphipod Gondogeneia antarctica . Toughness measurements were also performed on each thallus component. Results from D. anceps , a highly differentiated species, were consistent with the Optimal Defence Theory (ODT) in that the most valuable tissue component (the primary stem) was the most strongly chemically and physically defended. The holdfast, also with a high tissue fitness value, was strongly physically defended. Laterals, which are replaceable and assigned a lower fitness value, were moderately chemically defended. No significant differences were detected in the palatability of the differing thallus parts in D. menziesii , although the holdfast and primary stem were tougher than the lateral branches. These results remain consistent with the ODT as D. menziesii displays less differentiation between the primary stem and the lateral branches and were assigned a similar fitness value.
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Variation in phlorotannin content within two species of brown macroalgae (Desmarestia anceps and D. menziesii) from the Western Antarctic Peninsula
Polar Biology, 2005Co-Authors: Victoria A Fairhead, Charles D. Amsler, James B. Mcclintock, Bill J BakerAbstract:Phlorotannins are metabolites found only in the Phaeophyceae (brown algae) and have a variety of metabolic roles, including both primary (e.g. cell wall construction) and secondary (e.g. herbivore defence and UV protection). This study aimed to establish the level of variation of phlorotannins in two species of dominant Antarctic macroalgae ( Desmarestia anceps and D. menziesii ). Thirteen samples were taken from specific locations throughout the thallus of multiple individuals at two depths at three locations near Anvers Island, Antarctica. Overall average concentrations were 0.117±0.003 g g^−1dwt in D. anceps and 0.052±0.002 g g^−1dwt in D. menziesii . Concentrations varied greatly at the 13 sampling locations in each individual, but not in any consistent manner. Significant variation occurred between locations in both species and between depths in D. anceps .
M. J. H. Van Oppen - One of the best experts on this subject based on the ideXlab platform.
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Phylogeny and historical ecology of the Desmarestiaceae (Phaeophyceae) support a southern hemisphere origin
Journal of Phycology, 1997Co-Authors: A F Peters, Christian Wiencke, M. J. H. Van Oppen, Wytze T. Stam, Jeanine L. OlsenAbstract:Phylogenetic relationships in the Desmarestiales (Phaeophyceae) were inferred among the monotypic Arthrocladia (Arthrocladiaceae) and 27 isolates from Desmarestiaceae, representing 17 taxa of Desmarestia and the monotypic Antarctic genera Himantothallus and Phaeurus. Phaeurus and Arthrocladia were used as outgroups. Parsimony analyses of nuclear ribosomal DNA internal transcribed spacer (ITS1 and ITS2) sequences, in which gaps were both included and excluded yielded well-resolved trees with a consistent general branching pattern. A parallel analysis of nine morphological and life-history characters and three ecological characters yielded a similar tree but provided little resolution in the terminal clades. The position of the monotypic Arthrocladia villosa within the Desmarestiales is consistent with monophyly for the order, but its position as the most primitive Desmarestialean is not resolvable from the molecular data set. The basal position of Phaeurus, the Antarctic Desmarestia species, and Himantothallus is consistent with the hypothesis of a Southern Hemisphere origin for the family Desmarestiaceae. The more recent Northern Hemisphere ''aculeata'' clade evolved from an Antarctic ancestor. A ''D. aculeata-like'' species was ancestral to a lineage characterized by annual sporophytes with high sulfuric acid content, which radiated into many species, widely distributed in both hemispheres. Mapping of morphological and ecological characters onto the molecular tree confirm the informativeness of sulfuric acid-containing vacuoles and unilocular sporangial types. There is good congruence between phylogenetic tree topology and temperature imprints in relation to biogeographic distribution, supporting the theory that temperature tolerance is a conservative trait.
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Arctic-Antarctic disjunctions in the benthic seaweeds Acrosiphonia arcta (Chlorophyta) and Desmarestia viridis/willii (Phaeophyta) are of recent origin
Marine Biology, 1993Co-Authors: M. J. H. Van Oppen, Wytze T. Stam, Jeanine L. Olsen, C. Van Den Hoek, Christian WienckeAbstract:Two examples of the most extreme biogeographic disjunctions in benthic marine algae are found in Acrosiphonia arcta (Chlorophyta) and Desmarestia viridis/willii (Phaeophyta). Both species are members of the Arctic and Antarctic boreal and subboreal marine floras. Although both genera have temperate species, neither genus has subtropical or tropical representative. Comparisons of the fast-evolving ribosomal DNA internal transcribed spacer regions among isolates in each of the two species collected from both hemispheres showed an unexpected near sequence identity suggesting that these biogeographic disjunctions are of recent origin, possibly as recent as the last Pleistocene glacial maximum (18000 yr ago). Paleoclimatic explanations that rely on a much earlier transequatorial passage of cold-adapted species through a narrowed and cooler tropical belt during the Oligocene/Miocene (38 to 7 Ma ago) are unlikely. We hypothesize that despite the separated evolutionary histories of the northern and southern hemisphere coldwater marine floras, deep-water dispersal of microthalli has occurred and probably occurs on a regular basis.
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arctic antarctic disjunctions in the benthic seaweeds acrosiphonia arcta chlorophyta and Desmarestia viridis willii phaeophyta are of recent origin
Marine Biology, 1993Co-Authors: M. J. H. Van Oppen, Wytze T. Stam, Jeanine L. Olsen, C. Van Den Hoek, Christian WienckeAbstract:Two examples of the most extreme biogeographic disjunctions in benthic marine algae are found in Acrosiphonia arcta (Chlorophyta) and Desmarestia viridis/willii (Phaeophyta). Both species are members of the Arctic and Antarctic boreal and subboreal marine floras. Although both genera have temperate species, neither genus has subtropical or tropical representative. Comparisons of the fast-evolving ribosomal DNA internal transcribed spacer regions among isolates in each of the two species collected from both hemispheres showed an unexpected near sequence identity suggesting that these biogeographic disjunctions are of recent origin, possibly as recent as the last Pleistocene glacial maximum (18000 yr ago). Paleoclimatic explanations that rely on a much earlier transequatorial passage of cold-adapted species through a narrowed and cooler tropical belt during the Oligocene/Miocene (38 to 7 Ma ago) are unlikely. We hypothesize that despite the separated evolutionary histories of the northern and southern hemisphere coldwater marine floras, deep-water dispersal of microthalli has occurred and probably occurs on a regular basis.