title: Co-occurring Synechococcus ecotypes occupy four major oceanic regimes defined by temperature, macronutrients and iron.
abstract: Marine picocyanobacteria, comprised of the genera Synechococcus and Prochlorococcus, are the most abundant and widespread primary producers in the ocean. More than 20 genetically distinct clades of marine Synechococcus have been identified, but their physiology and biogeography are not as thoroughly characterized as those of Prochlorococcus. Using clade-specific qPCR primers, we measured the abundance of 10 Synechococcus clades at 92 locations in surface waters of the Atlantic and Pacific Oceans. We found that Synechococcus partition the ocean into four distinct regimes distinguished by temperature, macronutrients and iron availability. Clades I and IV were prevalent in colder, mesotrophic waters; clades II, III and X dominated in the warm, oligotrophic open ocean; clades CRD1 and CRD2 were restricted to sites with low iron availability; and clades XV and XVI were only found in transitional waters at the edges of the other biomes. Overall, clade II was the most ubiquitous clade investigated and was the dominant clade in the largest biome, the oligotrophic open ocean. Co-occurring clades that occupy the same regime belong to distinct evolutionary lineages within Synechococcus, indicating that multiple ecotypes have evolved independently to occupy similar niches and represent examples of parallel evolution. We speculate that parallel evolution of ecotypes may be a common feature of diverse marine microbial communities that contributes to functional redundancy and the potential for resiliency.
authors.affiliation: Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA.
authors.forename: Jill A
authors.initials: JA
authors.lastname: Sohm
authors.affiliation: Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA.|School of Oceanography, University of Washington, Seattle, WA, USA.
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Ahlgren
authors.affiliation: School of Oceanography, University of Washington, Seattle, WA, USA.
authors.forename: Zachary J
authors.initials: ZJ
authors.lastname: Thomson
authors.affiliation: School of Oceanography, University of Washington, Seattle, WA, USA.
authors.forename: Cheryl
authors.initials: C
authors.lastname: Williams
authors.affiliation: Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA.
authors.forename: James W
authors.initials: JW
authors.lastname: Moffett
authors.affiliation: Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
authors.forename: Mak A
authors.initials: MA
authors.lastname: Saito
authors.affiliation: Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Webb
authors.affiliation: School of Oceanography, University of Washington, Seattle, WA, USA.
authors.forename: Gabrielle
authors.initials: G
authors.lastname: Rocap
mesh_terms: D017931:DNA Primers / Q000235:genetics; D060146:Ecotype; D007501:Iron / Q000032:analysis / Q000378:metabolism*; D009792:Oceans and Seas; D010140:Pacific Ocean; D010802:Phylogeny; D048929:Prochlorococcus / Q000235:genetics / Q000378:metabolism; D012623:Seawater / Q000737:chemistry* / Q000382:microbiology*; D046940:Synechococcus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D013696:Temperature
chemical_list: D017931:DNA Primers; D007501:Iron