The stored product beetles Lasioderma serricorne and Stegobium paniceum are associated with a flexible and hidden diversity of Symbiotaphrina symbionts

The stored product pests Lasioderma serricorne and Stegobium paniceum (Coleoptera: Ptinidae: Anobiinae) have been described to harbour Symbiotaphrina kochii and Symbiotaphrina buchneri yeast-like symbionts (YLS) respectively, based on axenic cultivation from symbiotic organs. While the nutritional benefits provided by the YLS are well characterized, molecular studies focusing on variability or stability in the systems are lacking. Here we address that research gap by investigating the diversity and stability of Anobiid - Symbiotaphrina symbiosis in multiple populations. Amplicon sequencing of the fungal internal transcribed spacer (ITS) from collected and lab-reared populations revealed that populations from different origins were associated with similar YLS strains. These associations remained stable during rearing. However, only one L. serricorne population was associated with Sy. kochii, the others were associated with Sy. buchneri. Most St. paniceum samples were associated with a Symbiotaphrina species that could neither be identified as Sy. buchneri, nor Sy. kochii. Cultivation and subsequent phylogenetic analysis of the partial rRNA operon of YLS revealed a novel Symbiotaphrina clade. Our results indicate more flexible associations than previously assumed, however only with members of the genus Symbiotaphrina. The ecological relevance needs further analyses, but highly variable in vitro growth could indicate extensive differences in YLS capabilities.