title: A century-long genetic record reveals that protist effective population sizes are comparable to those of macroscopic species.
abstract: Effective population size (Ne) determines the rate of genetic drift and the relative influence of selection over random genetic changes. While free-living protist populations characteristically consist of huge numbers of cells (N), the absence of any estimates of contemporary Ne raises the question whether protist effective population sizes are comparably large. Using microsatellite genotype data of strains derived from revived cysts of the marine dinoflagellate Pentapharsodinium dalei from sections of a sediment record that spanned some 100 years, we present the first estimates of contemporary Ne for a local population in a free-living protist. The estimates of Ne are relatively small, of the order of a few 100 individuals, and thus are similar in magnitude to values of Ne reported for multicellular animals: the implications are that Ne of P. dalei is of many orders of magnitude lower than the number of cells present (Ne/N ∼ 10(-12)) and that stochastic genetic processes may be more prevalent in protist populations than previously anticipated.
authors.affiliation: Institute of Integrative Biology, University of Liverpool, , Biosciences Building, Liverpool L69 7ZB, UK.
authors.forename: Phillip C
authors.initials: PC
authors.lastname: Watts
authors.forename: Nina
authors.initials: N
authors.lastname: Lundholm
authors.forename: Sofia
authors.initials: S
authors.lastname: Ribeiro
authors.forename: Marianne
authors.initials: M
authors.lastname: Ellegaard
mesh_terms: D000818:Animals; D004141:Dinoflagellida / Q000235:genetics*; D004463:Ecology; D014644:Genetic Variation; D005828:Genetics, Population; D005838:Genotype; D016013:Likelihood Functions; D018895:Microsatellite Repeats / Q000235:genetics; D011156:Population Density; D011157:Population Dynamics; D013269:Stochastic Processes; D013997:Time Factors
keywords: dinoflagellate; drift; effective population size; palaeogenetics