Diversity of yeast-like Symbiotaphrina symbionts in the stored product pests Lasioderma serricorne and Stegobium paniceum

The stored product pests Lasioderma serricorne and Stegobium paniceum were described to harbour Symbiotaphrina kochii and Symbiotaphrina buchneri yeast-like symbionts (YLS) respectively, based on axenic cultivation from symbiotic organs. Here we investigate the diversity and stability of the symbiosis in multiple populations.Amplicon sequencing of the fungal internal transcribed spacer (ITS) region from collected and lab-reared populations revealed that the beetle-yeast associations were stable during rearing and populations from different origins were associated with similar yeast strains. However, only one L. serricorne population was associated with Sy. kochii , the others were associated with Sy. buchneri . Further, most S. paniceum samples were associated with a Symbiotaphrina species that could neither be identified as Sy. buchneri , nor Sy. kochii. Yeasts cultivated from both insects were phylogenetically analysed using longer fragments of the rRNA operon (partial 18S rRNA, ITS and 23S rRNA gene) revealing three Symbiotaphrina clades: Sy. kochii , Sy. buchneri and a novel clade. Diagnostic polymerase chain reaction confirmed the exclusive association with Sy. buchneri, Sy. kochii or the novel Symbiotaphrina strain in the individual beetle samples.Our results suggest another, so far overlooked Symbiotaphrina strain or species and a more flexible symbiont association of L. serricorne and St. paniceum .