title: Pseudo-cryptic speciation in coccolithophores.
abstract: Coccolithophores are a group of calcifying unicellular algae that constitute a major fraction of oceanic primary productivity, play an important role in the global carbon cycle, and are key biostratigraphic marker fossils. Their taxonomy is primarily based on the morphology of the minute calcite plates, or coccoliths, covering the cell. These are diverse and include widespread fine scale variation, of which the biological/taxonomic significance is unknown. Do they represent phenotypic plasticity, genetic polymorphisms, or species-specific characters? Our research on five commonly occurring coccolithophores supports the hypothesis that such variation represents pseudocryptic speciation events, occurring between 0.3 and 12.9 million years ago from a molecular clock estimation. This finding suggests strong stabilizing selection acting on coccolithophorid phenotypes. Our results also provide strong support for the use of fine scale morphological characters of coccoliths in the fossil record to improve biostratigraphic resolution and paleoceanographic data retrieval.
authors.affiliation: Alfred Wegener Institute for Polar and Marine Biology, Department of Biological Oceanography, Am Handelshafen 12, D-27570 Bremerhaven, Germany. a.saez@imperial.ac.uk
authors.forename: Alberto G
authors.initials: AG
authors.lastname: Saez
authors.forename: Ian
authors.initials: I
authors.lastname: Probert
authors.forename: Markus
authors.initials: M
authors.lastname: Geisen
authors.forename: Patrick
authors.initials: P
authors.lastname: Quinn
authors.forename: Jeremy R
authors.initials: JR
authors.lastname: Young
authors.forename: Linda K
authors.initials: LK
authors.lastname: Medlin
mesh_terms: D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D004247:DNA / Q000235:genetics; D056890:Eukaryota / Q000145:classification* / Q000166:cytology / Q000235:genetics*; D005580:Fossils; D014644:Genetic Variation; D008969:Molecular Sequence Data; D010802:Phylogeny; D010839:Phytoplankton / Q000145:classification / Q000166:cytology / Q000235:genetics; D013045:Species Specificity
chemical_list: D004247:DNA