科研之友
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摘要
We report six complete 18S ribosomal DNA (rDNA) sequences representing five brown algal orders: Sporochnus comosus C. A. Agardh (Sporochnales), Chorda tomentosa Lyngbye (Chordaceae, Laminariales), Saccorhiza polyschides (Lightfoot) Batters (Phyllariaceae, Laminariales), Desmarestia ligulata (Lightfoot) Lamouroux (Desmarestiales), Ectocarpus siliculosus (Dillwyn) Lyngbye (Ectocarpales), and Scytosiphon lomentaria (Lyngbye) J. G. Agardh (Scytosiphonales). These sequences were compared with published laminarialean (Alaria marginata Postel et Ruprecht [Alariaceae] and Macrocystis integrifolia Bory [Lessoniaceae]) and fucalean (Fucus gardneri Silva) rDNA sequences for phylogeny inference using both the distance-matrix and parsimony methods. The inferred 18S phylogenies clustered Sporochnus, Desmarestia, Chorda, Saccorhiza, Alaria, and Macrocystis in an assemblage. This Sporochnales-Desmarestiales-Laminariales (S-D-L) complex was consistently separated from the Ectocarpales, Scytosiphonales, and Fucales by bootstrap analyses. The inferred phylogenies are consistent with several possible evolutionary processes lending to this S-D-L complex. Members in this assemblage lack eyespots in their sperm, and their sperm have the atypical brown algal flagellation: shelter anterior and longer posterior flagella. In addition, they are oogamous with a heteromorphic alternation of generations between a microscopic gametophyte and a macroscopic sporophyte. Members of the S-D-L complex can be separated into different phylogenetic lines based on the presence/absence of eyespots in their meiospores. Our findings support the contention that the Sporochnales, Desmarestiales, and Laminariales are closely related. In addition, our rDNA tree suggests that the Laminariales is paraphyletic.
- 出版日期1996-2
