PHYLOGENYAND HISTORICAL ECOLOGY OF THE DESMARESTIACEAE (PHAEOPHYCEAE) SUPPORT A SOUTHERN HEMISPHERE ORIGIN¹

Abstract

Phylogenetic relationships in the Desmarestiales (Phaect phy ceae) were infmed among the monotypic Arthrocladia {Arthrocladiaceae) and 2 7 isolates j-om 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 transm'bed 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 morphologzcal and life-histoly characters and three ecolopcal characters yielded a similar tree but provided little resolution in the terminal clades. The position of the monotypic Arthrocladia villosa within the Desmarestiaks is consistent with monophyly for the order, but its position as the most primitive desmarestialean is not resoluable from the molecular data set. The basal position of Phaeurus, the Antarctic Desmarestia species, and Himantothallus is consistent with the hypothesis of a Suuthern Hemisphere origin for the family Desmarestiaceae. The more recent Nmthern H~i s p h e r e "aculeata" clade evoluedj-om an Antarctic ancestor. A "D. aculeatalike" 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 sporangzal types. There is good congruence between phylogenetic tree topology and temperature impints in relation to biogeographic distribution, supporting the the09 that temperature tolerance is a conservative trait.

A study of sexual and asexual populations ofScytosiphon lomentaria(Scytosiphonaceae, Phaeophyceae) in Hokkaido, northern Japan, using molecular markers

“…Intraspecific variation in DNA sequences has been reported for macroalgae in the ITS regions of nrRNA genes, a chloroplast-encoded Rubisco spacer and mitochondrial genes (Peters et al, 1997;Kamiya et al, 1999;Serra˜o et al, 1999;Zuccarello et al, 1999;Fama´et al, 2000;Coyer et al, 2002;Gabrielsen et al, 2002;Zuccarello & West, 2002). In our preliminary survey of S. lomentaria, ITS2 sequences differed between gamete-releasing and asexual zoid-releasing thalli, suggesting that the asexual zoid-releasing thalli may be derived from asexual populations.…”

“…In the ITS2 analyses, gaps were counted as single events regardless of gap length (Peters et al, 1997), and a gap matrix was added to the end of the alignment. Nucleotide differences among haplotypes were calculated with the 'pair-wise distances' command in PAUP.…”

Life strategy, ecophysiology and ecology of seaweeds in polar waters

“…In P. antarcticus, sporangia are catenate and develop in rows in adjacent cells as filamentous outgrowths of the cortex, interspersed with club-shaped sterile hairs. These phylogenetic relationships have been confirmed meanwhile by molecular data (Peters et al 1997). Ascoseira mirabilis, whose exact phylogenetic relationships are still unresolved, has a fucalean type of life history (Clayton 1987).…”

“…This order is ecologically replaced by the Desmarestiales. According to phylogenetic and morphological analyses and studies on ecophysiological traits this order is considered to have originated in the Southern Ocean and subsequently radiated into the Northern Hemisphere (Peters et al 1997). A conspicuous character of the Antarctic seaweed flora is the scarcity of small macroalgal epiphytes compared to temperate regions.…”

Molecular systematics, historical ecology, and phylogeography of Halimeda (Bryopsidales)

“…The Indo-Pacific representatives share the habitat with several other Halimeda species (H. distorta, H. hederacea, H. micronesica, H. minima) and do not cover reefs to the same extent as their Caribbean relatives. Only a few other seaweed phylogeographic studies have elucidated dispersal directionality (Bakker et al, 1995b;Peters et al, 1997;Van Oppen et al, 1995).…”