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PHYLOGENY OF SPIROGYRA AND SIROGONIUM (ZYGNEMATOPHYCEAE) BASED ON RBC L SEQUENCE DATA 1
Author(s) -
Drummond Christopher S.,
Hall John,
Karol Kenneth G.,
Delwiche Charles F.,
McCourt Richard M.
Publication year - 2005
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.1529-8817.2005.00130.x
Subject(s) - spirogyra , biology , monophyly , botany , clade , phylogenetics , maximum parsimony , evolutionary biology , zoology , algae , genetics , gene
DNA sequence data were obtained for the gene encoding the large subunit of RUBISCO ( rbc L) from 26 strains of Spirogyra and seven of Sirogonium , using as outgroups 10 genera in the Zygnematales and Desmidiales ( Closterium , Cosmarium , Cylindrocystis , Gonatozygon , Mesotaenium , Netrium , Penium , Zygnema , Zygnemopsis , Zygogonium ). Sequence data were analyzed using maximum parsimony (MP), maximum likelihood (ML), and Bayesian inference (BI), with bootstrap replication (MP, ML) and posterior probabilities (BI) as measures of support. MP, ML, and BI analyses of the rbc L data strongly support a single clade containing Spirogyra and Sirogonium . The Spirogyra taxa are monophyletic, with the exception of Spirogyra maxima (Hassall) Wittrock, which is nested within a clade with Sirogonium and shares with them the characters of loosely spiraled chloroplasts (<1 complete turn per cell) and anisogamy of gametangial cells; S. maxima differs from Sirogonium in displaying well‐defined conjugation tubes rather than a tubeless connection involving bending (genuflection) of filaments. The ML and BI analyses place this Sirogonium / Spirogyra maxima clade sister to the remaining Spirogyra . Morphological differences among strains of Spirogyra grouped together on the basis of rbc L data, including laboratory strains derived from clonal cultures ( Spirogyra communis , S. pratensis ), indicate that some characters (filament width, chloroplast number) used in the traditional taxonomy of this group are poor measures of species identity. However, some characters such as replicate end walls and loose spiraling of chloroplasts may be synapomorphies for Spirogyra clades.