Effects of Grazer Presence on Genetic Structure of a Phenotypically Diverse Diatom Population

Abstract

Studies of predator-prey systems in both aquatic and terrestrial environments have shown that grazers structure the intraspecific diversity of prey species, given that the prey populations are phenotypically variable. Populations of phytoplankton have traditionally considered comprising only low intraspecific variation, hence selective grazing as a potentially structuring factor of both genetic and phenotypic diversity has not been comprehensively studied. In this study, we compared strain specific growth rates, production of polyunsaturated aldehydes, and chain length of the marine diatom Skeletonema marinoi in both grazer and non-grazer conditions by conducting monoclonal experiments. Additionally, a mesocosm experiment was performed with multiclonal experimental S. marinoi populations exposed to grazers at different levels of copepod concentration to test effects of grazer presence on diatom diversity in close to natural conditions. Our results show that distinct genotypes of a geographically restricted population exhibit variable phenotypic traits relevant to grazing interactions such as chain length and growth rates. Grazer presence affected clonal richness and evenness of multiclonal Skeletonema populations in the mesocosms, likely in conjunction with intrinsic interactions among the diatom strains. Only the production of polyunsaturated aldehydes was not affected by grazer presence. Our findings suggest that grazing can be an important factor structuring diatom population diversity in the sea and emphasize the importance of considering clonal differences when characterizing species and their role in nature.

How to value biodiversity in environmental management?

“…Another, more recent study examined the functional diversity of the marine diatom Skeletonema marinoi by observing the potential effects of grazing pressure (reflected by different grazer levels) (Sjöqvist et al, 2013). The study confirmed that genetically distinct individuals of S. marinoi are functionally more diverse.…”

Genetic diversity affects ecological performance and stress response of marine diatom populations

“…Baltic low-salinity-adapted populations of the species are genotypically diverse and display considerable phenotypic diversity (Sjöqvist et al, 2014(Sjöqvist et al, , 2015. Using microsatellite-based genotyping methods we were able to monitor and confirm true clonal diversity in experimental mixtures.…”

“…For example, blooms of S. marinoi consist of genetically distinct clones that differ largely in growth characteristics and cell chain morphology (Sjöqvist et al, 2014). Other phytoplankton species vary intraspecifically in environmental tolerances (Gsell et al, 2012;Ribeiro et al, 2013;Skjelbred et al, 2013) and cellular toxicity (Suikkanen et al, 2013).…”

Different Nutritional Histories Affect the Susceptibility of Algae to Grazing

“…Copepods of the genus Acartia , instead, have been reported to be able to discern their prey by detecting cell composition (e.g., Poulet and Marsot , Sjöqvist et al. ); the experimental evidences in support of this, however, are quite indirect (as argued in the introduction of this paper) and less ambiguous results would be required to demonstrate the ability of copepods to select algae based on their cell content.…”