A test for microbiome-mediated rescue via host phenotypic plasticity inDaphnia

Abstract

AbstractPhenotypic plasticity is a primary mechanism by which organismal phenotypes shift in response to the environment. Host-associated microbiomes often exhibit considerable shifts in response to environmental variation and these shifts could facilitate host phenotypic plasticity, adaptation, or rescue populations from extinction. However, it is unclear how much shifts in microbiome composition contribute to host phenotypic plasticity, limiting our knowledge of the underlying mechanisms of plasticity and, ultimately, the fate of populations inhabiting changing environments. In this study, we examined phenotypic responses and microbiome composition in 20 genetically distinctDaphnia magnaclones exposed to non-toxic and toxic diets containingMicrocystis, a cosmopolitan cyanobacteria and common stressor forDaphnia. Daphniaexhibited significant plasticity in survival, reproduction, and population growth rates in response toMicrocystisexposure. However, the effects ofMicrocystisexposure on theDaphniamicrobiome were limited, with the primary effect being differences in abundance observed across five bacterial families. Moreover, there was no significant correlation between the magnitude of microbiome shifts and host phenotypic plasticity. Our results suggest that microbiome composition played a negligible role in driving host phenotypic plasticity or microbiome-mediated rescue.One sentence summaryDaphniaexhibits considerable plasticity in individual and population-level responses to a cosmopolitan stressor, yet shifts in microbiome composition are not correlated with the magnitude of this plasticity.