title: Persistent Intra-Specific Variation in Genetic and Behavioral Traits in the Raphidophyte, Heterosigma akashiwo.
abstract: Motility is a key trait that phytoplankton utilize to navigate the heterogeneous marine environment. Quantifying both intra- and inter-specific variability in trait distributions is key to utilizing traits to distinguish groups of organisms and assess their ecological function. Because examinations of intra-specific variability are rare, here we measured three-dimensional movement behaviors and distribution patterns of seven genetically distinct strains of the ichthyotoxic raphidophyte, Heterosigma akashiwo. Strains were collected from different ocean basins but geographic distance between isolates was a poor predictor of genetic relatedness among strains. Observed behaviors were significantly different among all strains examined, with swimming speed and turning rate ranging from 33-115 μm s(-1) and 41-110° s(-1), respectively. Movement behaviors were consistent over at least 12 h, and in one case identical when measured several years apart. Movement behaviors were not associated with a specific cell size, carbon content, genetic relatedness, or geographic distance. These strain-specific behaviors resulted in algal populations that had distinct vertical distributions in the experimental tank. This study demonstrates that the traits of genetic identity and motility can provide resolution to distinguish strains of species, where variations in size or biomass are insufficient characteristics.
authors.affiliation: Skidaway Institute of Oceanography, University of Georgia, Savannah GA, USA.
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Harvey
authors.affiliation: Graduate School of Oceanography, University of Rhode Island, Narragansett RI, USA.
authors.forename: Susanne
authors.initials: S
authors.lastname: Menden-Deuer
authors.affiliation: Graduate School of Oceanography, University of Rhode Island, Narragansett RI, USA.
authors.forename: Tatiana A
authors.initials: TA
authors.lastname: Rynearson
keywords: Heterosigma akashiwo; behavior; intra-specific variability; microsatellites; phytoplankton