title: Divergence time estimates and the evolution of major lineages in the florideophyte red algae.
abstract: The Florideophyceae is the most abundant and taxonomically diverse class of red algae (Rhodophyta). However, many aspects of the systematics and divergence times of the group remain unresolved. Using a seven-gene concatenated dataset (nuclear EF2, LSU and SSU rRNAs, mitochondrial cox1, and plastid rbcL, psaA and psbA genes), we generated a robust phylogeny of red algae to provide an evolutionary timeline for florideophyte diversification. Our relaxed molecular clock analysis suggests that the Florideophyceae diverged approximately 943 (817-1,049) million years ago (Ma). The major divergences in this class involved the emergence of Hildenbrandiophycidae [ca. 781 (681-879) Ma], Nemaliophycidae [ca. 661 (597-736) Ma], Corallinophycidae [ca. 579 (543-617) Ma], and the split of Ahnfeltiophycidae and Rhodymeniophycidae [ca. 508 (442-580) Ma]. Within these clades, extant diversity reflects largely Phanerozoic diversification. Divergences within Florideophyceae were accompanied by evolutionary changes in the carposporophyte stage, leading to a successful strategy for maximizing spore production from each fertilization event. Our research provides robust estimates for the divergence times of major lineages within the Florideophyceae. This timeline was used to interpret the emergence of key morphological innovations that characterize these multicellular red algae.
authors.affiliation: Marine Ecosystem Research Division, Korea Institute of Ocean Science &Technology, Ansan 15627, Korea.|Department of Marine Biology, Korea University of Science and Technology, Daejeon 34113, Korea.
authors.forename: Eun Chan
authors.initials: EC
authors.lastname: Yang
authors.affiliation: Department of Biology, Chungnam National University, Daejeon 305-764, Korea.
authors.forename: Sung Min
authors.initials: SM
authors.lastname: Boo
authors.affiliation: Department of Ecology, Evolution and Natural Resources, Rutgers University, New Brunswick, NJ 08901, USA.
authors.forename: Debashish
authors.initials: D
authors.lastname: Bhattacharya
authors.affiliation: Department of Biology, University of New Brunswick, Fredericton, NB E3B 5A3 Canada.
authors.forename: Gary W
authors.initials: GW
authors.lastname: Saunders
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Knoll
authors.affiliation: Department of Biology, University of Louisiana at Lafayette, Lafayette, LA 70504-3602, USA.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Fredericq
authors.affiliation: Department of Biological Sciences, Sungkyunkwan University, Suwon 16419, Korea.
authors.forename: Louis
authors.initials: L
authors.lastname: Graf
authors.affiliation: Department of Biological Sciences, Sungkyunkwan University, Suwon 16419, Korea.
authors.forename: Hwan Su
authors.initials: HS
authors.lastname: Yoon
mesh_terms: D005075:Biological Evolution; D019143:Evolution, Molecular; D005580:Fossils; D010802:Phylogeny; D000461:Rhodophyta / Q000145:classification* / Q000235:genetics*