Genetic and phenotypic diversity characterization of natural populations of the parasitoid Parvilucifera sinerae

Abstract

Parasites exert important top-down control of their host populations. The hostpara- site system formed by Alexandrium minutum (Dinophyceae) and Parvilucifera sinerae (Perkinso- zoa) offers an opportunity to advance our knowledge of parasitism in planktonic communities. In this study, DNA extracted from 73 clonal strains of P. sinerae, from 10 different locations along the Atlantic and Mediterranean coasts, was used to genetically characterize this parasitoid at the spe- cies level. All strains showed identical sequences of the small and large subunits and internal tran- scribed spacer of the ribosomal RNA, as well as of the β-tubulin genes. However, the phenotypical characterization showed variability in terms of host invasion, zoospore success, maturation time, half-maximal infection, and infection rate. This characterization grouped the strains within 3 phe- notypic types distinguished by virulence traits. A particular virulence pattern could not be ascribed to host-cell bloom appearance or to the location or year of parasite-strain isolation; rather, some parasitoid strains from the same bloom significantly differed in their virulence traits. Identi- cal markers such as ITS and β-tubulin genes of P. sinerae strains from different geographic areas and from different years precludes their use in assessing intra-specific diversity and could indicate a recent dispersion of this species.