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A RE‐EVALUATION OF CORALLINE RED ALGAL TAXONOMY USING ULTRA‐STRUCTURAL INFORMATION
Author(s) -
Broadwater S.,
Scott J.
Publication year - 2000
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 - 10.1046/j.1529-8817.1999.00001-20.x
Subject(s) - biology , subfamily , taxonomy (biology) , polyphyly , botany , evolutionary biology , gene , phylogenetics , genetics , clade
Two competing subfamily classification schemes for the red algal family Corallinaceae are in general agreement with respect to the taxonomic value of cell connection type (cell fusions versus secondary pit connections), but differ over the relative weight given to the character of genicular presence/absence. Consequently, Corallinoideae, Melobesioideae and Metagoniolithoideae are recognized as distinct subfamilies. One scheme subsumes the geniculate Amphiroideae into the nongeniculate Lithophylloideae (based on the common presence of secondary pit connections) and the nongeniculate Mastophoroideae into the geniculate Corallinoideae (based on the common presence of cell fusions); the other maintains these subfamilies as four separate lineages. Small subunit r RNA gene sequence data confirms the integrity of Corallinoideae and Melobesioideae and fully supports a revised classification subsuming Amphiroideae into Lithophylloideae. Surprisingly, Mastophoroideae and Metagoniolithoideae (cell fusions) have a closer affinity to the emended Lithophylloideae (secondary pit connections) than with Corallinoideae (cell fusions). These preliminary results cast doubt on the value of using cell connections as a primal character. From ultrastructural investigations of 28 corallinoidean genera, including seven mastophoroidean genera and two lithophylloidian genera, it appears that the presence/absence of an electron‐ dense material (EDM) surrounding nuclei during sporogenesis is a more reliable indicator of subfamily affiliation than cellular connections. Our findings support the revised classification of Lithophylloideae and suggests closer affinity to Lithophylloideae (secondary pit connections, no EDM) than to Corallinoideae (cell fusions, EDM). However, EDM data indicates that Mastophoroideae may be polyphyletic as three genera have EDM and four do not.