Horizontal transmission of Wolbachia in Hylyphantes graminicola is more likely via intraspecies than interspecies transfer

Bacterial endosymbionts, such as Wolbachia , are widespread in arthropods, with vertical transmission (from mother to offspring) deemed to be the dominant route. Although horizontal transmission of Wolbachia is considered possible as a conveyance route for infections to be introduced to new individuals, evidence for such transmission remains limited. Thus, to elucidate the horizontal transmission of Wolbachia among hosts, we conducted parasitism, predation, cannibalism, and mating experiments in small spider species Hylyphantes graminicola . While no direct evidence was found for horizontal transmission via parasitism or predation, cannibalism and mating behavior were shown to be potential Wolbachia transmission pathways, with copulatory transmission identified from Wolbachia -positive females to Wolbachia -negative males (and vice versa). Based on these findings, our study suggests that horizontal transmission of Wolbachia is more likely to occur within species than between species.