Taxonomic Reappraisal of Sphacelaria rigidula and S. fusca (Sphacelariales, Phaeophyceae) Based on Morphology and Molecular Data with Special Reference to S. didichotoma

doi:2005.20.1.1

Algae > Volume 20(1); 2005 > Article

Algae 2005;20(1): 1-13. doi: https://doi.org/10.4490/algae.2005.20.1.001

Yeon-Shim Keum, Jung Hyun Oak, Stefano G.A. Draisma², Willem F. Prud’homme van Reine² and In Kyu Lee¹

Division of Life Science, Gyeongsang National University, Jinju 660-701,
¹School of Biological Sciences, Seoul National University, Seoul 151-742, Korea and
²Universiteit Leiden Branch, Nationaal Herbarium Nederland, P.O. Box 9514, 2300 RA Leiden, The Netherlands

ABSTRACT

The taxonomic status of three closely related species of the genus Sphacelaria, S. rigidula Kutzing, S. fusca (Hudson) C.F Gray and S. didichotoma Saunders was reassessed on the basis of morphological observations from herbarium specimens and phylogenetic analysis of RUBISCO spacer sequences. Sphacelaria rigidula was characterized by having only 2-armed propagules and somewhat slender filaments. Culture experiments revealed that its propagules commonly formed secondary arms, even though they were rarely produced in the field. It is concluded that S. divaricata Montagne characterized by dichotomously branched arms in propagules shoud be synonymized with S. rigidula, based on propagule morphology and measurements. Sphacelaria fusca clearly be separated from S. rigidula by having 2-4 armed propagules. These morphological differences were highly supported by the differences in the RUBISCO spacer sequences. S. didichotoma resembles S. rigidula in having propagules with two dichotomously branched arms. However, it commonly produces the secondary arms in the field. Additionally, this species has shorter primary arms than S. rigidula. Phylogenetic analyses supported the distinction of S. didichotoma from S. rigidula. The northwestern Pacific plants, previously recorded as S. divaricata, were recognized as S. didichotoma.

Key words: phylogenetic analysis, propagule morphology, RUBISCO spacer sequences, Sphacelaria didichotoma, S.