Incidence of Facultative Bacterial Endosymbionts in Spider Mites Associated with Local Environments and Host Plants

Abstract

Spider mites are frequently associated with multiple endosymbionts whose infection patterns often exhibit spatial and temporal variation. However, the association between endosymbiont prevalence and environmental factors remains unclear. Here, we surveyed endosymbionts in natural populations of the spider mite, <i>Tetranychus truncatus</i>, in China, screening 935 spider mites from 21 localities and 12 host plant species. Three facultative endosymbiont lineages, <i>Wolbachia</i>, <i>Cardinium</i>, and <i>Spiroplasma</i>, were detected at different infection frequencies (52.5%, 26.3%, and 8.6%, respectively). Multiple endosymbiont infections were observed in most local populations, and the incidence of individuals with the <i>Wolbachia</i>-<i>Spiroplasma</i> coinfection was higher than expected from the frequency of each infection within a population. Endosymbiont infection frequencies exhibited associations with environmental factors: <i>Wolbachia</i> infection rates increased at localities with higher annual mean temperatures, while <i>Cardinium</i> and <i>Spiroplasma</i> infection rates increased at localities from higher altitudes. <i>Wolbachia</i> was more common in mites from <i>Lycopersicon esculentum</i> and <i>Glycine max</i> compared to those from <i>Zea mays</i> This study highlights that host-endosymbiont interactions may be associated with environmental factors, including climate and other geographically linked factors, as well as the host's food plant.<b>IMPORTANCE</b> The aim of this study was to examine the incidence of endosymbiont distribution and the infection patterns in spider mites. The main findings are that multiple endosymbiont infections were more common than expected and that endosymbiont infection frequencies were associated with environmental factors. This work highlights that host-endosymbiont interactions need to be studied within an environmental and geographic context.